摘要:

THE QUARTERLY JOURNAL OF THE CHEMICAL SOCIETY 1.-On Some Points in the Composition of Wheat-Grak its Products in the Milt and Bread. BY J. B. LAWES,F.R.S. F.C.S. AND J. H. GILBERT PH. D. F.C.S. THEcomposition of the grain yielding the most important article of human food in temperate climates its yield of valuable products and the varying composition either of the grain itself or of these products according to the conditions of growth or the circum- stances of after preparation are subjects worthy the attention equally of states and of men of science. Accordingly we find that a chemical examination of wheat-grain and its products has from time to time been undertaken by chemists of repute; sometimes as a matter of private investigation and at others of public inquiry ; and almost as numerous as the names of the experimenters are the special lines of research which they have selected.We are indebted to Beccaria for the first notice more than a century ago of the gluten in wheat. Among the earlier investi- gators of the subsequent period are Pro u s t V au g u e1in De Saussure and Vogel who have examined the proximate principles and some of the changes to which they are subject in various descriptions of wheat>of flour or of bread. M. I3 ous-sin ga ult has somewkat elaborately studied various branches of the subject more recently; and we are indebted to Dumas R Payen Johnston and Dr. R. D. Thomson for original as well as a considmable amount of collected information.The most recent OII some points the most detailed and from advance in method8 php~ nil some also the most reliable are the results of M. Pcligot in 1849 on the proximate constitution of various kinds of whcat and of M. Millon in 18$9 and I%%,on some- what similar points. Lastly in 1853 M. Poggiale and in 1855 Dr. Maclagan have given the results of their investigations on the characters and composition of bread. Besides these more general investigations we have had in recent times many special inquiries corinccted with our subject. Thus M. Boussingault has given us analyses of the ashes oi wheat; and many other such analyses have been made in Ger-many and elsewlicre since the first appetirancc in 1840 of Baron Lie b i g’s work on ‘I Chemistry in its Applications to Agriculture and Physiology.” In this country Mr.Way has given us the most extensive series of wheat-grain-ash analyses his list including those of 26 specimens or descriptions. The plan of our own investigation which unfortunately has been much less perfectly filled up than we at first intended was entered upon more than a dozen years ago and was devised with reference to the following points :-1st. The influence of varying characters of season and of vari-ous manuring upon the organic and mineral composition of wheat grain. Rndlp. The characters of varieties especially in relation to their adaptation and the qualities they then develop under the influence of broader distinctions as to locality altitude latitude and vary-ing climatic circumstances generally.It is in the second branch of the inquiry that we have fallen the furthest short of our intentions. With a view to its prosecution a journey through the chief corn growing districts of Europe com- mencing at the northernmost point at which wheat is grown suc-cessfully was about to be undertaken in 1848; but the social dis- turbances on the continent at that period necessarily prevented it. The plan proposed mas-to collect information as to the geological and meteorological characters of the various localities as to the mode of culture and as to the general acreage yield both in straw and grain ; and lastly to procure characteristic specimens for chemical examination at home. Failing entircly in tlie esccution of this &sign the Exhibition of 1851 was loolted forward to as an oppor- ON THE COMPOSITION OF WHEAT-GRAIN QEC.tunity for procuring specimens not only of wheat but of other vegetable products and perhaps also important par+kdarsof their growth from various countries and climates. Su& Itowever was the division of authority and such the alleged pw&rlrcduae given to public institutions in such matters that whethar the Latter bene-fited or not the collection which we as private individuals were enabled to make was entirely inadequate to our object. From these difficulties it is that our second main object of inquiry was necessarily to a great extent abandoned; and chiefly for this rea- son but partly owing to the pressure of other subjects; the first or more limited or local branch of the investigation has in recent years been but imperfectly followed up.And as it is probable that it must for some time remain so it has been thought desirable thus to put on record the results already obtained; hoping that they may serve the double purpose of confirming or adding to previously existing knowledge and of indicating to others the points most requiring further study. The following is a brief outline of the plan of investigation which has yielded the results which we have now to lay before the Sockty. From the season 1843-4 up to the present time wteat has been growing in the same field continuously both without manure by ordinary and by various chemical manures. As a general rule the same description of manure has succeeded year after year on the same plot of land.The amount of produce corn straw and chaff and its characters as to weight per bushel &c. have in every case been carefully ascertained and recorded. Samples from each plot-both grain and straw-have also been collected every year. Of each of these samples two weighed por- tions are coarsely ground ;the dry matter determined at a tempera-ture of 212'; and the ash by burning on sheets of platinum in cast iron muffles arranged for that purpose.* Other weighed por- tions of grain and straw are partially dried so as to prevent their decomposition ;and in this state they are preserved for any exami- nation of their organic constituents. By this course of procedure a vast mass of results has been obtaiiued illustrating the influence of season and manuring upon the percentage of dry substance and of mineral constituents in the produce.In selected cases the nitrogen in the grain and in the straw has been determined. * The dry matter and ash were not determined in such complete aeries in the earlier years as in the later. 1 2 LAWES AND GILBERT A summary table of these dry matter ash and nitrogen results will be givcn below. In from twenty to thirty cases complete analyses of the grain-ashes have been made and the results of these will be given in full. Besides the experiments above described in selected cases chiefly from the produce of the earlier years of the field experi- ments it was sought to ascertain the comparative yield of $our and also the characters of the flour of grain grown by different manures in the same season or by the produce of different sea- sons.The colonist’s steel handmill was first had recourse to for this purpose. But it was soon found that it was extremely diffi- cult so to regulate the machine as to secure uniform action upon the different grains; and it was further found that the grain and especially the bran was cut up rather than crushed so as to leave too much of flour in the portion separated as bran and too much of bran in that separated as flour ; and hence the results were not sufficiently comparable with those of the ordinary mill. Arrange-ments were therefore made for prosecuting the inquiry at a flour mill in the neighbourhood worked by water power.Weighed quantities of the selected samples (from 125 to 250 lbs. each) were passed through the stones and the f‘mea2” thus obtained through the dressing machine under our own personal superintendence ; great care being taken to clear from the different parts of the apparatus the whole of one lot before another was commenced upon. The yield in the dressing machine of each of the different products was ascertained and its percentage in relation to the total grain or its ‘(meal,” has becn calculated. Portions of each of these products have had their dry matter (at 212O) and their mineral matter (by burning on platinum) determined. The per- centage of nitrogen in a few selected series-from the finest flour down to the coarsest bran-has also been estimated; and in the same cases the amounts of one or two of the more important constituents of the ash have also been determined.The results of these dry matter ash nitrogen and constituent of ash deter- minations in the series of different products obtained in the mill will be given in tables further on. The original design was to complete the examination of the mill products by determining in several series of them the per- centage of each of their proximate organic principles; and also the amount and composition of mineral matters associated with ON THE COMPOSITION OF WHEAT-GRAIN &C. them respectively. It was hoped by this latter inquiry to obtain important collateral information bearing upon the influence of various constituents upon the healthy and special development of the plant.Although however specimens of the flour we pre- served for this purpose as well as the ashes of eaeh crude pro-duct it is feared that this subject cannot be proceeded with at least for a considerable time to come. Portions of the different products of the dressing machine (including more or less of the finest flour of the more granular or of the more branny particles respectively) from grains of somewhat various history of growth have been experimented upon to ascertain their comparative bread-making qualities ; and these results togcther with a few examinations of baker’s bread and a discussion of the results of other experimenters as to the yield of bread from a given amount of flour and the percentage of water and of nitrogen in the former will be given below.With this short outline of the plan of investigation which has been pursued we proceed now to a discussion of the results which have been obtained. In Table I. are given in the first four columns certain pro-minent characters of the produce of each of ten years of the suc- cessive growth of wheat as above described. The items are :-The total produce per acre (corn and straw) in lbs. ; The per cent. of corn in the total produce; The per cent. of dressed corn in the total corn; and The weight per bushel of dressed corn in lbs. The figure given for each year generally represents the average of about 40 cases; and the characters enumerated are the best which can be given in a summary and numerical form to indicate the more or less favourable condition of the respec- tive seasons for the healthy development of the crop and the perfect maturation of the grain.In the second set of three columns are given side by side with the general characters just described the percentages in the grain of each year- Of dry substance; Of ash in dry substance; and Of nitrogen in dry substance ; the two former items being in most cases the average of 30 to 40 cases in each year; but the per cent. of nitrogen is in each instance the mean of a few selected cases only. LAWES AND GILBERT In the third set of three columns are given similar particu- lars relating h the composition of the straw.The percentages of dry snlbtzmce and of ash in the straw are however not the averages of SQ many cases in each year as are those for the corn ; and the Betmmhtttions of nitrogen in the straw have also been made in fewer cases than in the grain. It will thus be seen that the table affords n summary view of a really enormous amount of experimental result and we ought to be able by its means to discover at least the broad and characteristic effects of varying seasons upon the compo- sition of the crop.* This indeed is all we could hope to attain in such a mere outline and general treatment of the subject as is appropriate to our present purpose. TABLE I. GENERAL SUMMABY CON osition of Corn osition of Particulars of the Produce.&*LIN. 8T)TBAW. Total 'er cent. Weight )rn and ?er cent. Irewed Per 'cr cent 'er cent Jercent er cent 'er cent. Ter cent. Harvest straw corn in :orn in )ushe1o dry ash in nitroger dry ash in iitrogen ser acre total total dressed .n lbs. ?rodace. corn. corn in (2120.) dry. in dry. [.2120.) dry. in dry. lbs. q_ I_ 1845 554 5 33'1 90'1 56.7 80.8 1'91 2.25 .. 7.06 0-92 1846 4114 43'1 93.2 63'1 84.3 1.96 2-15 .. 6.02 0.6i 1847 5221 36'4 93'6 62'0 .. .. 2-30 .. 5.56 0.73 1848 4517 36'7 89'0 58.5 80.3 2 02 2-39 .. 7-24 0.18 1849 5321 40 9 95.5 63'5 83'1 1'84 1-94 82.6 6.1 7 0.82 1850 5496 33-6 94.3 60.9 84.4 1-99 2.15 84-4 5.88 0.87 1851 5279 38-2 92.1 62.6 84'2 1-89 1-98 84.7 5.58 0.78 1852 4299 31% 92.1 56.7 83-2 2%0 2.38 82'6 6-53 0.79 1853 3932 25-1 85 9 50.2 60's 2-24 2.35 81.0 6-27 1.20 1854 6803 35.8 95'6 6 1.4 84.9 1.93 2'14 83.7 5.08 0.69 _I l!e:lIls 5353 35.4 92.1 59% 829 1.98 2.20 839 0.82 Leaving then out of view all minor points and confining our- selves to our already defined object-namely that of ascertaining the general direction of the influence of variation of season upon the composition of the wheat crop-we cannot fail to see that wherever the three items indicating the quality of the produce * It shou!tl I)c staid tllal up to 1848 inclusive the description of wheat was the Old Red Lammas; froin 15-19 to 1852 inclusive it was the Red Cluster and since that time the Robtoclr.'l'he variations according to 3eaJoii. both in the characters and composition of tlie prodii~~, are however very marked within the period of growth of cxch scparcltc dcvclopxnciit.ON THE COMPOSITION OF WHEAT-GRAIN &C. markedly distinguish the crop as favourably developed we have a general tendency to a high percentage of dry substance and to a low percentage both of mineral matter and of aihgcn in that dry substmce. This generalization is more especiallg applicable to the grain; but with some exceptions mostly explicable on a detailed consideration of the circumstances and degree of its deve- lopment it applies to a great extent to the straw also. Let us take in illustration the extreme cases in the table. The seasons of 1846 1849 and 1851 with in the cases of the two latter large produce also give us the best proportion of corn in total produce more than the average proportion of dressed corn in total corn and the highest weight per bushel-a very significant character.With this cumulative evidence as to the relatively favourable development and maturation of these crops we find the grain in two of the cases to be among the highest in percentage of dry matter ; and in the third (1849) though not so high as we should have expected it is still above the average. The per- centages of mineral matter and of nitrogen in the dry substance of the grain are at the same time in these three cases the lowest in the series. The seasons of 1850 and 1854 again with large amounts of produce yielded also very fairly developed grain; and coincidently they aiTord a high percentage of dry substance and lower percentages both of mineral matter and of nitrogen in that dry substance than the cases of obviously inferior maturation With some exceptions it will be seen that the straws also of these 5 better years give a tendency to low percentages both of mineral matter and of nitrogen in their dry substance.Turning now to the converse aspect the seasoif of 1853 shows itself in the general characters of the produce to have been in every respect the least favourable to the crop ; and it should be added that in this instance (as well as in 1845 to which we shall next refer) the seed was not sown until the spring. In 1853 the produce of grain was small as well as very bad in quality; and with these characters we have in the grain nearly the lowest per- centage of dry matter and the highest percentage of ash and of nitrogen in that dry matter.In the straw too the dry matter is low the ash somewhat high and the nitrogen much the highest in the series. In 1845 another year of spring-sowing and at the same time of very bad quality of produce we have nevertheless a large amount of growth; a fact which tends to explain some of the differences in composition as compared with 1853. Thus 1845 LAWES AND GILBERT gives us low percentage of dry matter but not very high either ash or nitrogen in the grain. The straw however gives high per- centages both of ash and of nitrogen; it being in the latter point next in order to 1853. The seasons of 1848 and 1852 again show low characters of produce.The former has coincidently the lowest percentage of dry matter in the grain in the series; and both have high percentage of ash and nitrogen in the dry sub-stance of the grain. In the straw the ash is in 1848 the highest and in 1852 above the average; the nitrogen in dry matter of straw being however in neither instance high. In several of the cases here cited there are deviations from our general assumption on one point or other. But an examination in greater detail would in most or all of them clear up the appa- rent discrepancy. When indeed we bear in mind how infinitely varied was the mutual adaptation of climatic circumstances to stage of growth of the plant in almost every case it would indeed be anomalous did we not find a corresponding variation on some point or other in the characters or composition of the crop.Still we have the fact broadly marked that within the range of our own locality and climate high maturation of the wheat crop is other things being equal generally associated with a high percentage of dry substance and a low percentage of both mineral and nitro- genous constituents. Were we however extending the period of our review and going into detail as to varying climatic circum- stances interesting exceptions could be pointed out. It may be observed in passing that owing to the general rela- tionships of the amounts of corn to straw and the generally coin- cident variations in the percentages of nitrogen in each the tendency of all these variations is in a degree so to neutralize each other as to give a comparatively limited range of difference in the figures representing for each year the percentage of nitrogen in the dry substance of the total produce-corn and straw together.The tendency of maturation to reduce the percentages of mineral matter and frequently of nitrogen also is not observable in corn crops alone. We have fully illustrated it in the case of the turnip; and our unpublished evidence in regard to some other Crops goes in the same direction. The fact is indeed very important to bear in mind; for it constitutes an important item in our study of the variations which are found to exist in the composition both of the organic substance and of the ash of one and the same crop grown undcr different circumstances.We may particularly observe ON THE COMPOSITION OF WHEAT-GRAIN &C. that the obvious reduction in the percentage of nitrogen in wheat- grain the more within certain climatic limits the seed is perfected is in itself a fact of the highest interest; and it is the more so when we consider how exceedingly dependent for full growth is this crop upon a liberal supply of available nitrogen within the soil. Bearing in mind then the general points of relationship which have been established between the characters of' the crop as to development and maturation on the one hand and the percentage amounts of certain constituents on the other let us now see-what is the general influence of characteristic constituents of manure upon the characters and composition of our wheat crop which is allowed to remain on the land until the plant has fulfilled its highest function-namely that of producing a ripened seed ? In illustrat,ion of this point we have arranged in Table 111,the same particulars as to general character of the crop and as to the composition of the produce from several individual plots during the ten years; instead of the average of the series in each year as in Table I.The cases selected for the comparison are :-1. A continuously unmanured plot ; 2. A plot having an excess of ammoniacal salts alone every year ; 3. The average of several plots each having the same amount of ammoniacal salts as the plot just mentioned but with it a more or less perfect provision by manure of the mineral con-stituents also.It would be impossible to give the detail supplying all the results collected in this Table 111 ; but perhaps it is only proper that we should do so so far at least as the percentage of nitro- gen in the dry substance of the grain is concerned. LAWES AND GILBERT TABLE I1. Determinations of Nitrogen per Cent.in the Dry Matter of Wheat Grain grown at Rothamsted. EXPERIMENTS . Harvests Mean. 3 1 12 Unmanured. I . . 1845 .... 2 -28 2 -21 2 33 2 *30 .. 2*28 1846 .... 2 -11 2 .12 .. .. 2*11 1847 .. *. 2 *11 2 -08 2'.22 2 -22 .. 2 .16 1848 .... 2 '33 2.34 2 32 2 *37 .. 2.34 1849 .... 1-85 1-83 1.91 ..1.86 1850 .... 2.07 .. 2 10 i.07 .. 2.08 1851 .... 1*80 1.74 1-89 1*76 .. 1.80 1852 .... 2 -31 2 23 2 .38 2 .31 .. 231 1853 .... 2 *26 2 *33 2 -38 .. 232 1854 .... 2 *06 2'*b6 1*98 1*96 .. 201 -. I_L I__u Manured with Ammoniacal Salts only. . .-1845 .... 2 .18 2.29 2.22 2 *23 .. 2.23 1846 .... 2.18 2 -12 2 .29 2 19 .. 2'19 1847 .... 2 '35 2 -29 2.42 2 .32 .. 2*34 1848 .... 2 -39 2 .41 2 39 2.49 .. 2-42 1849 .... 1-89 .. 2 .04 1.92 .. 1*95 1850 .... 2 .13 .. 2 '08 2 -19 .. 2.13 1851 .... 2.15 2 12 2 -09 2 .25 .. 2.15 1852 .... 2.41 2 .50 2 *44 2.55 .. 248 1853 .... 2 -43 2 -48 2.37 2 .44 .. 2-43 1854 .... 2 31 2 -22 2 .31 2 37 .. 2.30 I-Manured with Ammoniacal Salts and Nineral Manure.(Mixed Plots.) 1845 .... .. .. ..1846 .... 216 1847 .... 2*40 1848 .... 2 *36 2-41 1849 .... 1-96 1-97 2.10 2.07 .. 2.02 1850 .... 2.16 2.28 2.25 2 25 .. 2 23 1851 .... 2 00 1.98 2.02 1 92 .. 1*98 1852 .... 2.43 2.34 2.31 2.40 2 32 2.36 1853 .... 2 .30 2.34 2.29 1 .. 2.30 1854 .... 2-16 .. 2.12 .. 212 ON THE CORIPOSITION OF WHEAT-GRAIN &C. It is necessary to make a few remarks in reference to this Table of more than one hundred nitrogen determinations. They were made by the method of burning with soda-lime and collecting and weighing as platinum salt in the ordinary way. Few perhaps who have only made a limited number of such determinations then only on pure and uniform substances and who have not attempted to control their work at another period with fresh re-agents or by the work of another operator will imagine the range of variation which is to be expected when all these adverse elements are to have their influence.It is freely granted that the variations shown in the Table between one determination and another on one and the same substance are sometimes more than could be desired. The following however are the circumstances under which they have been obtained. Experiments 1and 2were pretty uniformly made by the same operator but not all consecutively or with the same batch of re-agents. It mas thought therefore that inde- pendently of any variations between the two determinations it would be desirable to have results so important in their bearings verified by others. Accordingly samples of each of the ground grains were given under arbitrary numbers to two other operators and their results are recorded respectively in columns 3 and 4; and where a fifth determination is given it is a repetition by one or other of the experimenters last referrcd to.We should observe that we have found it almost impossible to procure a soda-lime that will not give more or less indication of nitrogen when burnt with an organic substance not containing it; and hence we have at length adopted the plan of mixing 1-2 per cent. of non-nitro-genous substance intimately with the bulk of soda-lime igniting it in a muffle moistening and reheating it gently. After this treatment the soda-lime is free from ammonia yielding matter. It should further be remembered that a ground wheat-grain is by no means an uniform substance.Indeed as we shall show further on some of the particles of which such a powder is com- posed may contain half as much again of nitrogen as others; and thus any inefficiency in the grinding or error in taking the por- tion for analysis may materially affect the result. Notwithstand-ing all these circumstances and the admittcdly undesirable range of difference in the several determinatioiis in some cases it will be observed that generally three at least of the numbers agree sufficiently closely arid in some cases the fourth also. In fact after all a stdy of the detailed table inust give considerable confidence at least in the dircction of the variations between the mew results given in Table 111 and in their sufficiency for the arguments fomded upon them.With tliesc remarks on the data let us proceed with the discussion of Table PI1 itself which next follows LAWES AND GILBERT H H E 5! E ON THE COMPOSITION QF.WHEAT-GRAIN &C. 13 A glance at this Table 111 shows that the quantity of produce varies very much indeed in om arid the same season according to the manuring. With these great differences in the yuantities dependent on manuring me have far less marked differences in the quality of this ripened crop dependent on the same causes; and this with some few exceptions is the same whether we look to the columns indicating the general characters only or the cornposition of the produce.That is to say the same general distinctions between the pmduce of one season and anothcr are observable under the several varying conditions of manuring in each as have been exhibited in the Table I of averages alone. In fact season or climatic variations are seen to have much more influence than manuring upon the character and composition of the crop. We have said that other things being c'qual the percentage of nitrogen in our wheat-grain was the lowcr the more the seed mas perfected; and we have also s~id,that nitrogecous maiiures greatly aid the development of the crop. Bat an inspection of the columns of Table 111which give the percentages of nitrogen in the dry substance of the grains produced under the three different conditions of manuring specified shons us that there is almost invariably a higher percent age of nitmgen where ammo-uiacal salts alone liavc been employed than where the crop was unmanured.Vt'e also sec that almost invariably there is a higher percentage of nitrogen where mineral mammy as well as ammo-niacal salts have been used than in tlie produce of the corm-spondiiig unmanured plots. A closer examination shows however though the indication is not uliifool'ilz that there is nevertldess an obvious tendency to a lower percentage of iiitrogen where the mineral constituents also have been eraployed than wlierc the ammoniacal salts have been used ahe; and with this there is 011 the average a someii-hat higher weight per bashel indicatirig higher degree of maturation. Tku again what are the circunl-stances of these experiments under which an increased percentage of nitrogen in the fixed substance of the produce is obtained by a supply of it in manure? The unmanured plot with its lorn per-centage of nitrogen in produce is shown by the field experiments to be greatly exhausted of the annually availabk rritrogen relatively to the annually available mkxd constituents required by the ivbeat crop.The plot with the amrnoniztcal salts alone is showll by the field results to be defective in the requisite and available minerals it4atively to the avnilahle nitrogen aid hcrice the crop LAWES AND GILREET is grown under a relative excess of the latter. Again the plots with mineral manures and amrnoniacal salts together received so far an excess of the latter as to yield with the minerals a larger crop than the average of the locality under rotation and larger also than the average of seasons would ripen healthily.It is then under these artificial and abnormal circumstances of the somewhat unnaturally low percentage of nitrogen from obvious defect of it in relation to the developing and maturing capabilities of the season on the one hand and the obviously relative excess of it on the other that we got an increased percentage of nitrogen in wheat- grain by the use of it in manure. Even under these extreme conditions the range of variation by manuring is very small; and there is nothing in the evidence that justifies the opinion that within the range of full crops and healthy maturation the per-centage of nitrogen in wheat grain can be increased at pleasiire by the use of it in manure.That very opposite extremes of condition of soil-supply may directly influence the composition even of wheat-grain is however illustrated in the percentages of mineral matter as well as those of nitrogen given in the table. Thus taking the mean results only ve have with the relative excess of mineral constituents on tlie unmanured plot the highest per cent. in the produce; with the greatest relntivc defect on the plot with arnmuniacal salts only the lowest per cent. in the grain; and with the medium relation in the other plots the medium per cent in the produce. Excepting however abnoriz~alconditions as already remarked variation in climatic circumstances has much greater influence on tlie percentage-composition of wheat-grain than variation in maouring.Let us now turn to the composition of the ash of wheat-grain. Independently of the defect of a sufficient number of published analyses of wheat-grain ash a dozen years ago when we took up the subject it mas then generally believed that the composition of the ash of vegetable produce would vary considerably with the supplies of the different constituents in the soil; it was thought indeed that according to the abundance of their presence one base might substitute another as for instance soda potash and SO on. About the same time that me undertook a series of wheat-ash analyses the ashes of various succulent vegetables werc also analysed.This latter investigation led us to conclude that the fixity of the composition of thc ash of such substances depended ve1-y much upon the degree of imCar.:ttion of thc produce; and in ON THE COMPOSITION OF WHEAT-GRAIN &C. fact that some constituents-soda and chlorine for instance-occurred in much larger quantities in the more succulent and unripe than in the more elaborated specimens. It seemed to be perfectly consistent with this experience to find in the ash of a comparatively perfected vegetable product like wheat-grain a con-siderable uniformity of composition-such indeed as the analyses now to be recorded will indicate. These analyses were made ten years ago by Mr. Dugnld Campbell and the late Mr. Ashford.And as since that time the methods of ash-analysis have in some points been improved upon it will be well to give an outline of the plan then adopted especially as it is by a consideration of the tendencies to error on some points that we must interpret the bearings of the actual figures given On this point we need only add that Mr. Camp-bell fully concurs in the tenor of our remarks. Method of Analysis :-Three portions of ash were taken. No. 1. In this the saizd silica and charcoal phosphate of iron phosphoric acid lime and magnesia were determined. The ash mas dissolved in dilute hydrochloric acid evaporated to perfect dryness moistened with hydrochloric acid boiled with water and the insoluble matter collected and weighed as-sand silica and charcoal.To the filtrate acetate of ammonia mas added and after digestion the precipitate separated dried ignited and weighed -asphosphate ofiron. To the filtrate now obtained a solution of a weighed portion of pure iron dissolved in nitro-hydrochloric acid was added then acetate of ammonia and the mixture digested until the whole of the iron was precipitated as phosphate of the peroxide with excess of peroxide from which was calculated thephosphoric acid. From the solution filtered from the phos-phate of iron and oxide of iron the Zime was separated as oxalate and ignited as earhonate; and from this last filtrate the mnagnesia by phosphate of soda and ammonia. No. 2. A second portion of ash was put into a carbonic acid apparatus the acid if any evolved by means of nitric acid and determined by the loss.The solution being filtered sulphuric acid was separated by nitrate of baryta; and afterwards chlorine By nitrate of silver. No. 3. To a solution of a weighed portion of the ash in hydrochloric acid caustic baryta was added in excess and the precipitate separated by filtration ;the excess of baryta was then removed by carbonate of ammonia and the filtered solution evaporated to dryness the residue heated to redness and weighed ; water added any insoluble matter deducted and the remainder taken as chlorides of potassium and sodium; a solution of' chloride of platinum wits now added to separate the potash; the soda being calculated from the loss. It is now admitted that the separation of phosphate of iron from the earthy phosphates by acetate of ammonia as above described is unsatisfactory; and it is probable t.he amounts given in the tables as phosphate of iron are too high and if so part of the difference should obviously go to the earthy bases For a similar reason it is possible that the phosphoric acid determinations may be somewhat too high-also at the expense of the earthy bases.Then again it is well-known that in. practice the process for potash and soda is one of Some delicacy; ad that the tendency of manipulative error is to give the soda somewhat too high. We conclude upon the whole that our phosphoric acid determinations may be somewhat high; our phosphate of iron pretty certainly so; and probably the soda also; the other bases being on this supposition given somewhat too low.The wheat-grain ash-analyses 23 in number and referring to the produce of three separate seasons and of very various manu-ing are given in the following Tables-numbered IV V and VI respectively. ON THE COMPOSITION OF WHEAT-GRAIN &C. I I .. ........ A. ........ ........ ........ 3 .............o '3 TABLE V. Analyses of Wheat-Grain Ash. HARVEST, 1845. I I Plot Numbers ,. .. .. .. 2 3 15 17 -I Superphospliatc Lime Superphosphate Lime in Bone-ash 224 Ibs. Sulpliate and $~~~$~~ 214 lbr. Farm-yard 1643-44. 112 Ibs. IIvdrochlorii Iluiiatc Ammoiii:i each Manuring per acre . . .. ?rlanure Unmanured 324 lbs 112 Ibs.Rape Cakc Means. Sulphate 280 11,s 19tons. Anlmonia 224 lbs. _l_.ll -I_ Characters of the produce :-Per Cent. Corn in Total Produce .. 33 -4 34-7 34.8 32.5 33.9 34 -2 35 -4 34 -13 Weight per bushel of Dremed Corn (lbs.) . 56 -7 56 *5 57.5 57.2 57.7 57 ‘5 55 .’ 56 -97 Per Cent. Dry Substance in Corn (at 2l2.) 80 +O 81 -2 81-1 80.9 81.7 80.9 80 .F 80 891 Per Cent. Ash in Dry Substance .. 1 *89 1.93 1.88 1-98 1.92 1 -91 1-92 I .92 ---.-_-,--I-Coiivtituentsof Ash :-1. Phosphoric Acid .. .* 47.08 48.69 45 -69 47.81 51 *56 50 26 51.34 50 41 49.05 Phosphate of Iron .. .. .. 1-97 2 -31 3 ‘66 4.58 1-21 1 *07 -80 1’20 2 -10 Potass .. .. .. .. 25 .I6 28 *53 29 -06 28.87 31-75 32.27 30 -20 30 *47 29.54 Soda .. *. .. .. 8.01 -00 6.19 5 .01 -00 40 968 -00 2 -49 Magnesia .... .. .. 11.06 11*58 9 -57 8.98 10.14 10 -00 10 -G5 9 -98 10 -24 Lime .. .. .. .. 3 $6 3 *57 3 -39 2.02 3.20 3 -36 3 *06 3 *16 3 *18 ~ Chlorine .. .. .. .. .00 .20 -00 -00 Trace Tracc *40 -23 *lo Silica Sand and Charcoal .. .. 3 -29 3.39 1-45 1-68 2 *36 2 21 2.61 1 5.40 2 -55 -I_I__ --I--_-Totals .. .. 100 93 98 -27 99 *01 98.95 100.22 99 -17 .I 214 Ibs. Earm-pard R one-ash Sulphate and Hydrochloric Muriate Acid 224 11)s. TABLE VI. Analyses of Wheat-Grain Ash. HARVEST, 1846. .I .I Plot Numbem .. .. -311 2 Bone-ash Bone-ash, Boile-ash 224 lhs. 224!bs. Manuring per acre .. *. .! Unmanured. Sulphuric Acid 234 lbs. Manure 14tons. 224lbs. Sulphate Ammonia Sul hate and Animonio each Ammonh, Ruriate 112 1h3.22k ills. each 112 Ibs. Character of the produce ;-~-I---I Per Cent. Corn in Total Produce .. 42 -7 44-4 43 .6 Weight per bnshel of Dressed Corn (Ibe.) . 63 *O 63.7 62 .6 Per Cent. Dry Substancein Corn (at 212') . 84*I 84 -0 a3 -3 Per Cent. Ash in Dry Substance .. 2 a07 2.03 2 -04 Constituents of Ash :-Phosphoric Acid . .. .. 50 *01 49 *89 50 -62 49*47 48 *73 50 -08 Phosphate of Iron .. .. .. I .65 1-66 3 .I0 2 52 2.62 3 *06 Potass .. .. .. .. 30 -03 30 -60 27.93 29 -58 31 *00 29.18 I. Soda .. .. .. a35 *25 .oo *oo -00 -00 Magnesia _. .. .. .. 1193 10.97 10 -79 11 *13 10*43 10 *34 b Lime .. .. .. 2.98* 2 '89" 4 94 4.63 4.31 4 .22 c Chlorine .. .. *. ,. *I2 .09 *30 34 Traces -17 ~3 Silica Sand and Charcoal .. .. 1 *88 -2 -17 -2 -18 2 *54 2 -62 3 *oo TotaIs .. .. 98-05 08-52 98 -96 100 -21 99 *71 100 -05 a. * It would seem probable that in these two cases the Lime is given too low; but as the analyst Mr. Ashford is dead no reference can bc made and we have unfortnnately + not had time to repeat the anaiysea prior to publication ne we hdd intended. cd rli\wx ANT) GILBERT It is at once seen that this ash may be reckoned to contain neither sulphuric acid carbonic acid nor chlorine. The latter at least occurred only occasionally and then in such small quantities as to lead us to the supposition that its presence is accidental or at any rate not essential in the ash of a perfectly-ripened grain. From the frequent absence of soda again and from the uncertainty in its determinations as above alluded to we are led to look at it as an equally unessential ingredient in the grain-ash of perfectly ripened wheat.Excluding then the chlorine the soda the iron of the phosphate of iron and that portion of the matter collected as insoluble which may have been soluble silica-the whole of these on the average amounting to a very few per cent.-the ash of wheat-grain is seen to consist essentially of phosphates only ;the bases being potash magnesia and lime. The potash amounts to nearly one-third of the whole ash; the magnesia to rather more than one-third of the potash; and the lime to about one-third of the magnesia. If we now compare with one another the analyses of the eight different ashes in 1844 those of the seven in 1845 or of the six in 1846 having regard to the manures by which the crops were grown it is impossible to say that these have had any direct and well-defined influence upon the composition of the ash of the grain.Thus we find looking at the Table for 1844 that several of the plots manured with superphosphate of lime yield a grain-ash having no higher percentage of phosphoric acid than that of the unmanured plot. Again where potash is added (plots 15 16 and 18) the percentage of it in the ash is not greater than the average of the cases where it was not employed. And again in the only case where soda was employed (plot 16) there is none of it found in the ash; nor lastly is the percentage of magnesia obvioiisly increased by the use of it in maiiure.A similar detailed consi- deration of the composition of the ashes of the seasons of 1845 and 1846 would as already intimated lead to a similar conclusion. In fact the variations in the composition of the ash of this supposed ripened product according to the manure by which it is grown seem to be scarcely beyond the limits of error in the manipulation of the analysis; though one case at least of the duplicate analysis of the same ash-namely that of No. 9 184214-indicatesthe range of variation from this cause to have been but small; in the other (No. 17 1845) it was somewhat greater. Although the accuracy of the analyses may not he such as to ON THE CO~IPOSZTION OF WHE~LT-GKBLN &C.show the difference in composition if any dependent on manure yet it is found to be quite adequate to indicate the marked diffe- rences in the degree of development and maturation of the grains dependent upon season. Before calling attention to the figures illustrating this point it should be remarked that the season of 1845 was the worst but one and that of 1846 nearly the best for ripening the grain during the thirteen years of our continuous growth of wheat. And me shall find consistently with this and with the conclusions arrived at in connection with Tables I and 111 that the variation in the composition of the ash is comparing one year with another much the greatest in the produce of the bad ripening season 1845 and much the least in the good ripening season 1846.This point and some others are illustrated in the following Summary Table No. VII. h3 TABLE VII. ra Composition of Wheat-Grain Ash. ~ Variation in pcr Cent. in Mean for each Season. 3feans according to Manuring. General Means. each Season. Other 23 Unma-'arm-yard Famires Cases 26 1844 1845 1846 1844 1845 1846 nured Manure Cases 3 years). :S years). 3 years) totham-Mr. Way. ' Cases. iCases. Cases I Cases. 3 Cases. 6 Cases. 17 Cases. sted. -I_ -7 Chuiacters of the producc :-F Per Cent. Corn in Total Produce .. .. .. 46 .2 34 -1 43 -3 41 *4 40 -8 41 -3 41 *2 +-Weight per bushel of Dressed Corn (lbs.) .. .. .. 60 *4 57 .o 63.3 59 *6 59 *6 60 -1 60 *O b ------M m Pcr Ccnt. Dry Substance in Corn (at 212") .... .. 80.9 84 .1 82 *3 82 -3 82 -5 82 *4 + Pc:. Cent. Ash in Dry Substance *. .. .. 2 -05 1-92 1-98 2 *04 2 01 1.97 1*99 1.69 5 V -_I C_'oniposittionof Lisli:-E Phosplioric Acid .. .. 3 *30 5 -87 1-89 50 16 49 -05 49.80 49 -81 48 -41 49 -88 49 -68 45.01 3 Phosphate of Iron .. .. *90 3 -87 1.45 2.54 2 .lo 2 .43 2 -14 2 *06 2 -45 2 -36 0 -82 2 Potnss . . .. .. 2 *82 7.11 3 97 28 -93 29.54 29 -72 29.78 28.03 29 *50 29.35 31.44 Soda .. .. .. 2'10 8 -01 .35 -57 2 *49 -10 '08 3 -04 *95 1.12 2 *71 Magnesia .. .. .. 1 74 2 $0 .79 11.07 10 -24 10'78 11'20 11-31 10.51 10 TO 12 -36 Lime .. .. *. 1-06 1*64 1'74 3 *30 3 *18 3 *84 3 -15 3 -47 3 *43 3 -40 3 -52 Sulphuric Acid .. .. .. .. .. .. .. .. .. .. .. 0 -34 Carbonic Acid .. .. .. .. .. .. .... .. *. ... 0 *02 Chlorine . . .. .. .. .. *. -13 -10 -17 -14 *04 *14 *13 .13 Silica Sand and Charcoal .. .. .. .. 2 -45 2 -55 2 *40 2 "76 2 -60 2 *41 2 -47 3 -67* -. Totals . . .. .. .. .. 99 *15 99 -25 99 *24 99.06 98 *96 99 -27 99 -21 100 *03 I * M r. Way gives this as soluhle silica exclusive of the sand and cliarcoal included with it in our own analyses. ON THE COMPOSITLON OF WHEAT-GltAIN &C. Looking at the first Division of this Table VII it is seer1 that in the item of phosphoric acid the variation in the percentage among the several cases in each year is the greatest in 1845 and the least in 1846; in the phosphute of iron it is the greatest in 1845; in the potush it is the greatest in 1845 much less and about equal in 1814 and 1846; in the soda it is much the greatest in 1845 and much tlic least in 1846; in the magnesia it is again far thc greatest in 1815 and it is the least in 1846.In the case of the Zime we have an exception to this general indica- tion dependent on the two low amounts of it given for Nos. 2 and 3 1846; but if these are really in error in the direction suggested at the foot of Table V1 the indication would be the same as for the other constituents. We have then in the circum-stances of the seasons arid in the comparative characters of the produce coincident with these variations the evidence that for one and the same description of grain in a perfectly matured condition the composition of the ash will be within certain narrow limits constant.So far as the constituents of the ash of the entire grain of wheat is concerned we have only further to call attention to the three other Divisions of this Summary Table No. VII. In these are shown side by side :-In the second Division of the Table the mean composition of the ashes for each of the three separate years; In the third Division thc mean composition for the three years together (a) of the grain-ash from the unmantired plot-(6) of that from the farm-yard manured-plot -(c) of the grain-ashes from all the other manures during the three years including 17 cases; and In the fourth and last Division the mean composition of all. our own wheat grain-ashes analyzed 23 in number by the side of the mean of 26 analyses of the grain-ashes of wheat of diffcrent descriptions or grown in different localities published by Mr.Way.We will go into very little detail discussions of these mean results as the points they illustrate have most of them already been alluded to. We may first remark as a point to which we shall recur further on that the mean percentage of lime is thc least in the bad year 1845 and the grcatest in the good year 18-46. Again it is greater in the avcragc from the manured plots than in that from tlic unnianurcd. We may perhaps here anticipate hy saying that this is at any rat(. coiisistent with what we shall LAWES AND GILBERT afterwards have to record namely that the ash of the finer flour -of which there is a greater proportion in the grain of the seasons of best maturation-contains more lime than that of the coarser and more branny portions of the grain.Lastly in reference to this Summary Table we modd call attention to the mean composition of wheat grain-ash yielded by the 26 analyses given by Mr. Way b=j- the side of that of the 23 specimens grown at Rothamsted. Mr. Way’s analyses equally with our own show that wheat grain-ash essentially consists of phosphates of potash magnesia and lime. He however if we exclude silica gives higher percentages of base and a lower one of acid than our own analyses indicate. Mr. Way’s average amount of phosphoric acid is indeed nearly 5 per cent. less in the ash than ours. His series however included many descriptions of wheat and our own only one-the Old Red Lammas.In several of his cases too we observe that the percentage of this acid very closely approximates to our own average. We have now given a summary view of some points of the composition of the entire wheat-grain and of its ash as affected by varying season and various manuring. WTe next turn to an equally summary statement of a large number of experiments made in reference to the yield and composition of the various products separated in the milling process. The grains operated upon with this view were of the same dcscription of whcat but grown experimentally in different seasons and under different conditions of manuring. There have been many observations recorded as to the percent- age of flour obtained in practice from 100 parts of grain and in a subsequent Table some of these will be adduced.We are also indebted to M. Boussingault for the determination of the flour and of the bran yielded by 24 different descriptions of wheat all grown side by side in the Jardin des Plantes at Paris. His method was to powder the grains in a mortar and separate the flour and bran by means of a silken sieve. Results of this kind can perhaps scarcely be compared with those of the ordinary mill. The differences exhibited between the different specimens were indeed very great ;but the comparisons afforded within the series itself are interesting and very curious. In our own experiments the so-called Colonist’s steel hand-mill was first had recourse to; as it was thought that by its use rather ON THE COMPOSITION OF W HEAT-GRAIN &C.than that of an ordinary flour-mill much smaller quantities of grain might be submitted to experiment and that uniformity of working would also be more within our control. It was soon found however that in all cases the grain was in this steel-mill rather cut up than crushed and rubbed down as between ordinary mill-stones. It was also found that the action in this respect varied considerably according to the speed of the operator and to the precise set of the mill which required to be varied according to the character of the grain. From these causes a statement of the amount of the yield of the various products obtained from the steel hand-mill would be of little value. Though further on we shall have to call attention to some interesting points connected with the comparative composition of the several products of the grains mechanically separated in this way We next determined to submit a series of the experimentally grown grains to careful and as far as possible uniform treatment between the stones and in the dressing apparatus of an ordinary flour-mill.The mill in question was worked by water-power. From 125 to 250 lbs. of the several grains were submitted to the experiment ; the whole of the apparatus being carefully cleared of the products of one specimen before another was commenced upon. The weights and samples of the “meals” as furnished by the stones and of the several products separated in the dressing- machine were taken under our own personal superintendence.Even here and although every possible precaution was taken considerable irregularities in the action of the apparatus were manifest depending partly on the varying characters of the grain. Indeed it was clear that to obtain results as to comparative yield of flow strictly referable to the practical qualities of the respective grains it would be necessary to operate on much larger quantities of each than those even now taken in order that. the miller might so re-adjust the set of his stones as the work proceeded according to the character of the grain and of the meal which it afforded as to get from each its largest yield as he would do in working upon considerable quantities. In all twenty-eight lots of grain were operated upon in this way; and although as above implied and as will be pointed out further on the results might in some points have been somewhat different with larger quantities yet the miller after a careful examination of all the products decided that their general bearings were to be fully trusted.Iu some cases the meal obtaiued from the stones was separated LAWES AND GILBERT in the dressing apparatus into nine products and in others the products of the first three wires were taken together constituting the bulk of the Jine flour obtainable arid amounting to only about 70 per cent. of the grain. In practice however the fourth product of the dressing machine ‘‘ Tails,” is generally redressed and the fifth “Fine Sharps” or “Middlings,” reground and redressed together raising the amount of good bread-flour to about 80 per cent.or sometimes more. The sixth product is called ‘‘ Coarse Sharps ;”the seventh ‘‘Fine Pollard ;”the eighth Coarse Pollard;” and the ninth Long Bran.” It should be stated however that mills vary very much in the arrangement of their dressing machines in different localities and even in the same locality; so that the exact division of the products here given will not apply invariably. In Table VIII are given- 1st. In the upper division of the Table the percentage yield in 100 meal of each of the mill products 7 or 9 as the case may be; each figure being the mean of several experiments. 2nd. (In the middle division of the Table)-The mean per cent. of dry substance (at 212O) in each flour bran &c.And 3rd. The mean per cent. of mineral matter (ash) iu each of the same mill products. As will be seen seven of the specimens were grown in 1846 nineteen in 1847 and two in 1848; and in order to give some idea of the general character of the produce yielding the results in each of the separate columns there is given at thc head the mean bushels per acre the mean weight per bushel and the mean per cent. of corn in total produce of the specimens to which the column refers ON THE COMPOSITION OF WHEAT-GRAIN &C. TABLE VIII. Showing the yield of the different Mill Products from 100 of Grain ;and their Per-cenfagesof Dry Substance and Mineral Matter. MEANRESULTS. Products of Wires 1,2 and 3.Means of all in each year. 1846 1846 1847 1 1848 7 19 2 %a. ctlaes. cases General Characters of Produce :-MfXm buahelsperacre ...... 28 31) 314 Yean weight per bushel (111s.)... 63.4 62.1 59.1 MWI p. c. corn in total produce. 43.0 36.0 37.1 1-0. Yield of Flour Bran &c. in 100 Meal. 1. Wire1 ............ 4.40 2. Wire 2 ............ 17.9 3. Wire 3 ............ 8-7 I_ Products 1 2 and 3 together. 70.6 4. Tails 4 -6 5. Fine Sharps or Mr'ddlinz : 8.7 6. Coarse Sharps ........ 3 -1 7. Fine Pollard ........ 1.8 8 Coarse Pollard ........ El *6 9. Long Bran ........ 4 -3 Per Cent. Dry Substance (at 212" F.) in each Flour Bran &c. -1. Wire 1 ...........' 85.4 84 -4 84.3 2. Wire 2 ........... 85 2 84 *5 83.7 85-2 84 'S 3. Wire 3 ........... ' 85.2 84.5 83.9 85.2 84 -4 I Products 1 2 and 3 togetlier. ... l-... 83 8 85.3 04J.1 ~ 4. Tails 84.4 85 5 85.0 86.5 85 *O 5. Fine Shar; ar Middlings : 83.1 85.3 84.5 85.3 84 -5 6 Cmrseqha s 86.5 85 -7 85.3 85.4 85 -4 7. E'ine ~oiar2' 1: :: :: 87 3 86 '1 84.8 86.7 85 -3 8. Coarse Pollard ......... 86.4 85.5 85.3 86.2 85.4 9. Long Bran ......... 86.3 85.8 86.1 85.7 85 -3 Per Cent. Mineral Mat,ter (Ash) in each Flour Bran &c. 0.69 984 10.71 *132 -- 0%d '0617 Produets 1 9 and 3 together. 1 ... 1 0.71 1 ... 4.Td6 ... 1.03 -054 5. Fine Sharps or ?&dlin$ ... 2.12 -186 G Coarse Sha s ... 4.18 *142 7 Fine Pollai% :: :: ...5 65 -138 8. Coarse Pollard ......... 6 47 420 9. Long Uran ......... ,7 11 -213 -Tutal ... ... ... ... ... 1.634 LAWEX AND GILBERT After the remarks already made little need be said in detail regarding the comparative yield of the various products by 100 parts of the different meals. It was decided by the miller that pretty uniformly there was too much flour left in the fourth but particularly in the fifth product; and this as an inspection of the Table will show was obviated in the later experiments namely those on the grain of the harvest 1848. So far then the variation of the result is more due to the management of the miller than to the intrinsic character of the grain. It is more interesting to observe that a very careful examination of all the products led to the conclusion that the grains grown by the more nitrogenous manuring and consequently in the larger crops,provided they were well developedmd matured,* allowed abetter separation of the flour and less cuttingup and intermixtureof branny particles with it; and hence yielded a cleaner bran than the grain of the poorer crops.This was not the case however unless the highly-manured crops were at the same time well developed. It is consistent with this character of the grain of the more highly- manured crops that the produce of the heavier and ricber wheat- lands is generally admitted to yield a larger proportion of flour. The fact that the grain of richly-manured crops is frequently coarse and not the good miller’s sample arises from the circum- stance not of the direct effect of rich manuring in depreciating the quality of the grain but because the larger crops are more subject to injury due to climatic circumstances and are conse- quently frequently less favourably developed and matured.It will be observed that the amount of long bran is always more than 2 and in the yenr of badly-ripened grain (1843),it is nearly 6 per cent. of the total meal. This ninth product together with the three or four immediately before it in the list yield us nearly 20 per cent. of the total meal of such a branny character as seldom to be used for human food. Some of the more recent expe- rimenters MM. Millon and Peligot for example have concluded that the amount of actual woody fibre in wheat-grain is seldom more than from 2to 3per cent.On this supposition the nearly 20 per cent. of the grain generally not applied directly as human food would contain but a small proportion of necessarily indigestible woody matter; and it would appear that there was very great room for improvement in the modes of preparation of the grain if It would appear that in a good ripening season this condition is best attained when the crop iE cut before the grain is perfectly ripc. OM THE COMPOSITION OF WHEAT-GRAIN &C. it were desirable to separate as human food in the first instance a larger proportion of its nutritious matters. M. Poggiale on the other hand maintains that the quantity of moody fibre refractory to the digestive organs though not to chemical agents out of the body is really very considerable.* But of some points of the composition of the various products we shall have to speak more in detail presently.In the second or middle division of Table VIII we have the average percentage of dry matter in the different products. In reference to these results it may be noticed that as might be expected the percentage of dry matter is rather higher in the mill products than it was in the entire grains which yielded them. This is particiilarly the case in regard to the two specimens of the harvest 1848 the mill products of which give on the average a higher per cent. of dry matter than the samples of either of the other two years although the dry matter of the entire grain of that season (1848j was very low.The differences are therefore obviously wore due to the circumstances of preservation and after- treatment than to distinctions in the character of the respective grains. The only other remark which need be made regarding the varying percentages of dry matter is that the branny or more external portions of the grain have pretty uniformly a higher percentage of dry matter than the more farina1 internal portions. The widely differing percentages of mineral mutter in the several mill-products of the same grain and the variations in ‘this respect even between the corresponding products in the different speci- mens in the same or in different seasons are both more striking and of greater interest.It is seen that we have about ten times as high a percentage of ash in the ninth product or bran as in the first three or purer flours. The percentage increases rapidly from the fourth to the ninth-that is to say the greater the proportion of branny par- ticles. A careful examination of the more detailed Tables also showed that the variations in the percentage of mineral matter in the corresponding products of different specimens of grain had a direct relation to the percentage or relative position of the respective products in the 100 of meal; in other words to the * Since the above was written a very favourable report has appeared in the (‘Comptes Rendus ” (January 12,1857’),by MM. Dumas Pelouze Payen Peligot and Chevreul -the Commission appointed by the Academy of Sciences to inquire into the matter -on a new process of M.MBge Nourii?s which claims to yield a perfectly white wholesome and agreeable bread employing 86-85 per cent. of the entire grain. LAWES AND GILBERT proportions of flour or of bran which they respcctivelp contained. Although however the percentage of mineral matter is so very much greater in those portions of the grain which we not gene-rally used in the first instance as human food yet an inspection of the last column of the Table shoving the distribution of the mineral matter in the several products of 100 of meal according to the amount of each of these mill show that even in our first three products we have nearly one-third of the whole mineral matter of the grain; and adding to these a certain portion of that in the fourth and fifth products which frequently contribute to the bread-flour we shall have more than one-third of it in the currently edible portion of the grain.Further information as to the composition of the respective mill-products and of their ashes will be found in Tables IX X XI and XII. In Table IX are given the individual nitrogen determinations in each of the several mill-products; those in the first three columns being by one experimenter and those in the fourth column by another. In Table X is given a collective view of the composition of the same products in regard to some other consti- tuents as far as they have been determined; including also the mean results of Table IX TABLE IX.Determinations of Nitrogen per Cent. in Mill Products of Wheat-Grain. HARVEST 1846; GROUND 1848. In natural state of dryness. Description of Mill Products. Experiments. I ________ Mean. 1. 2. 3. 4. 1. Wire 1 .. .. 1.69 1-62 .. 1.63 2. , 2 .. .. .. 1.73 1-69 .. 1.69 3. , 3 .. .. .. 1.78 1.79 .. 1TS 4 Tails .. .. .. 1.86 1.84 .. 1-86 5. Fine Sharps or Middlings .. 2.20 2.22 2.22 2 .21 -___ -~ 6. Coarse Sharps .. .. 2.52 2-59 2.62 2 -58 7. Fine Pollard .. .. 3 37 2.48 2.48 2 -44 8. Coarse Pollard .. *. 2.32 2.47 2.46 2.42 9. Long Bran.. .. .. 2.37" .. 2 a42 2 *39 * By a third experiiucntcr. TABLE X. Composition of Mill-products of Wheat Grain.n HARVEST 1846; GROUSD 1848. In 100 of each Product. In 100 each Ash. Distribution of Constituents in Mill Products of 100 Grain. Flours &c. 1 Description of Mill from 100 ! II In the Bsh. Products. Dry Mineral Insoluble Phosphoric Grain. Substance Matter Nitrogen. in acid. Acid. [at 212"F.) (Ash). I-I I 1. Wire 1 .. 51 02 44 -3 0 -36 I 0 ,83 1 0.022 1 0.161 2. ) 2 . . 24 -8 45.5 0.18 (I:.:0.010 0.083 3. , 3 . . .. -1*'I 48 -1 0 *01 0.000 0.007 4. Tails . . .. 1*5 85 *2 1 .04 1.86 2 -18 48 *4 0.02 >0'03 0.000 0.008 5. Fine Sharps or I 1 1 1 1 1 Middlings . . 3 -3 85 *5 2-19 2.21 3.04 51 -3 0.07 0.07 0.002 0.037 ~~ 6. Coarse Sharps .. 3.3 49 *6 0 .13 0 *08 0.005 0.064 7. Fine Pollard .. 1.8 52 *3 0 *lo 0.04 0.001 0.051 8. Coarsg Pollard .. 6.7 55 -2 0 *44 0 *242 1 :': 1 1 9. Long Bran .. 5.0 54 -8 0 -36 1 0.195 I 1 Totals .. 99 -4 *. 1.67 1-78 0,044 0.850 LAWES AND GILBERT The grain to which Tables IX and X refer was an equal mixture of the produce from four different plots very variously manured arid grown in the season 1845-6; the harvest of which yielded one of the best-matured grains throughout our series of field experi- ments. The wheat in question was however not ground until 1848; and we have in the percentage-yield of the respective pro- ducts confirmation of the general opinion that other things being equal old wheat yields up its flour better than new. Thus whilst in the average of the cases already recorded we have little more than 70 per cent.of flour through the first three wires we have from this old wheat 772 per cent. The products 4 and 5 from which a further yield of bread-flour is obtained were correspondingly small; but Nos. 8 and 9 were on thc other hand somewhat large. The particulars given in Table X are the percentages of Dry Mutter of Ash and of Nitrogen in the respective mill-products of this niised grain. There are also given the percentages of Matter insoluble in Acid and of phosphoric acid in each of the nine ashes; and in the last four columns we have the distribution of the total mineral matter of the nitrogen and also of the insoluble matter and phosphoric acid of the ash in each of the nine products according to the proportion of the latter in 100 of the grain or meal.The percentage of Dry ilhtter in the several products from this old grain is as would be expected somewhat higher than the average from the grains of the same year which had not been so long stored. As before the percentage of Dry Matter shows a tendency to incrcase as we proceed to the outer portions of the grain. The percentages of ash also show the same relations as already pointed out. Referring to the column of the percentage of nitrogen in each of thc nine separated products we find that it is lowest in the products at the head of the dressing machine-that is in the flours; and it is half as high again in the more branny portions. It is seen however to be the highest of all in the product No.6; and somewhat lower in the coarser brans. It may be remarked that the indications of the figures in this respect are at any rate consistent with such observations as have been recorded regarding the structural composition of wheat-grain ;it being stated that the greatest concentration of nitrogenous compounds is imme- diately below the pericarp itself; and we should expect that the ON THE COMPOSITION OF WHEAT-GRAIN &C. longer bran would have less of the more internal matters adherent to it. The higher percentage of nitrogen in bran than in fine flour has frequently led to the recommendation of the coarser breads as more nutritious than the finer. We have already seen that the more branny portions of the grain also contain a much larger percentage of mineral matter.And further it is in the bran that thelargest proportion offatty matter-the non-nitrogenous substance of highest respiratory capacity which the wheat contains-is found. It is however we think very questionable whether upon such data alone a valid opinion can be formed of the comparative values as food of bread made from the finer or coarser flours from one and the same grain. The published evidence at command leads to the conclusion that of the nitrogenous constituents of bran a much larger proportion is soluble in water than of those in the finer flours. That is to say there is in the bran probably a larger proportion of the more universal vegetable compound albumen and less of those more special to the grain of wheat; and hence we may perhaps conclude that it exists in a less elaborated and probably therefore less assimilable condition .* It is stated on the other hand by Poggiale that a large proportion of the insoluble nitrogenous constituents of bran occurs in a form only in an inferior degree digestible.Again it is an indisputable fact that branny particles when admitted into the flour in the degree of imperfect division in which our ordinary milling processes leave them very considerably increase the peristaltic action ; and hence the alimentary canal is cleared much more rapidly of its contents. It is also well known that the poorer classes almost invariab€y prefer the whiter bread; and among some of them who work the hardest and who consequently would soonest appreciate a diffe- rence in nutritive quality (navies for example) it is distinctly stated that their preference for ;he whiter bread is founded on the fact that the browner passes through them too rapidly; con-sequently before their systems have extracted from it as much nutritious matter as it ought to yield them.* According to M. MBge Nouri&s before referred to a portion of the soluble nitrogenoqs matter of bran exists as a peculiar body Cerealine which when dissolved up from bran in water at a given temperatiire effects the solution of the adherent starch also. His process of extracting from the bran an additional amount of the bread-material which the grain contains consists in fermenting after the addition of some glucose an infusion of the finer Lrans straining of€' the woody matter and using the fluid in making up the dough with the finer flour.D LAWES AND OITABERT It is freely granted that much useful nutritious matter is iii the first instance lost as human food in the abandonment of 15 to 20 per cent. of our wheat-grain to the lower animals. It should be remembered however that the aniouiit of food SO applied is by no means entirely wasted. And further we think it more than doubtful even admitting that an increased propor- tion of mineral and nitrogenous constituents would be an advan- tage whether unless the branny particles could be either excluded or so reduced as to prevent the clearing action above alluded to more nutriment would not be lost to the system by this action than would be gained by the introduction into the body coinci- dentally with it of a larger actual amount of supposed nutritious matters.In fact all experience tends to show that the state as well as the chemical composition of our food must be consi-dered; in other words that its digcstibility and aptitude for assimilation are not less important qualities than its ultimate composition. Observation also tends to show that elaboration or maturation have their influence in determining the digestibility or the assimilability of our food-both the vegetable and animal. But to this point we shall refer again presently. Returning to the experimental results in Table X the next point of remark is as to the amount of matter insoluble in acid in the ash of the respective mill-products.It is seen that the percentage of such matter is very much greater-indeed in this particular case ten times greater-in the ash of the finest flour than in that of the coarsest bran. It was at first thought that this must be an error. Some repetitions were therefore made and the products of the steel-hand-mill were also examined ; when it was found that the result in question mas fully confirmed. It would be interesting to examine the series to determine what proportion of this insoluble matter is really proper mineral consti- tuent of the respective products avid how much adventitious merely. On consideration it will however be clear that the process of dressing the meal would tend to shake and clean the bran from a11 adherent matters; which if silicious as well 8s the particles arising from the abrasion of tlic mill-stones would natu- rally be found among the heavier products at the head of the machine.That is to say they would be found in larger propor-tion in the flour whilst tlie bran by the mechanical methods of its separation would he almost entirely freed from them. Accord-ing to published analyses it wo~ildappear however that silica as ON THE COMPOSITION OF WHEAT-GRAIN &C. distinguished from merely insoluble sandy matter does exist to a considerable though variable extent in the ash of entire wheat- grain. And from the results now given it may perhaps be concluded that this constituent found to exist so constantly in some animal substances does really occur in larger amount in those portions of wheat-grain which are best adapted as food? Phosphoric acid on the other hand is seen to be in smallest proportion in the ash of the flour at the head of the dressing machine; and the percentage pretty gradually augments as we proceed from the finer to the coarser and more branny portions the ash of the latter being far the richest in this essential acid.* It may further be remarked in reference to the varying compo- sition.of the ash of the different mill-products that in several series we have found the magnesia greatly to increase as we pro- ceed from that of the finer to that of the coarser products. The percentage of lime is on the other hand greatest in the ash of the flours and less in that of the brans.This latter point is consistent with a tendency discernible to an increase in the percentage of lime in the ash of those grains most matured in one and the same season or in the ash of the grains grown in a season of higher maturing character. RTe may further conclude from the great increase in the percentages both of the phosphoric acid and of the magnesia as we proceed from the ash of the flours to that of the brans and also from the very slight compensation from the decrease in that of the lime (the total amount of lime being relatively small) that the chief complementary constituent of wheat-grain ash-namely potash-will occur in larger proportion in the ash of the flours than in that of the brans; hence its larger amount will be coincident with the larger amount of silica.In the last Division of Table X is shown the distribution in the respective products from 100 of grain or its meal-of the nitrogen of the total mineral matter axid of the insoluble substance and phosphoric acid of the latter-which the entire grain contained. It will be seen that notwithstanding the percentage of nitrogen is so much greater in the branny products yet owing to the smaller amount of these by far the larger proportion of the total nitrogen of the grain is accumulated in the flours. In fact in the case * Probably a portion of the phosphoric acid existing in wheat-grain-aph is due to the oxidation during incineration of pliosphorus found by Profcssor Toel cker to exist in siich large amount associated with the nitrogenous bodies.See also Profcssor H. Rose on this subject-Poggendorffs Annalen vol. Ixxvi. p. 305. D2 LAWES AND UILBERT before us about three-fourths of the nitrogen would be accumu- lated in those of the products which would be ordinarily used for bread or for human food in other forms. On the other hand only about two-fifths of the total mineral matter would be found with this three-fourths of the nitrogen. Of the phosphoric acid again the larger amount is distributed in the branny portions; only about one-third of it being obtained in the bread flours. At the foot of these columns of the distribution of the constituents the percentage in the entire grain or meal of the items as determined by aualysis in each separate product is given by the addition of these items so obtained; and the percentage so calculated agrees very closely with that which the analysis of the entire wheat-grain or its ash would indicate.Thus we may mention that according to the sum of the phosphoric acid distributed in the different products we have 50.7 per cent. of it in the ash of 100 of grain or meal; whilst the average percentage obtained in the analyses of the six ashes of the produce of the same season was 49.8 an approxima- tion sufficiently near to give some confidence at least in the relative accuracy of the numerous analytical results involved in such an estimate. Before leaving the question of the comparative chemical compo- sition of the different products obtained by means of mechanical separation from wheat-grain attention may bc called to some results of this kind in connection with the products of the Colonial steel-hand-mill which was first employed in these experiments.As will be seen the results now to be recorded agree in general tendency with those already given ; yet they have some special and curious points of interest. The individual nitrogen determinations are given in Table XI and the collected results of the examination of the various products in Table XII. ON THE COMPOSITION OF WHEAT-GRAIN &C. TABLE XI. Nitrogen per Cent. in the Products of Wheat-Grain from the Colonial Steel-hand-mill. (In natural State of Dryness.) Wheat-Grain Harvest 1846.Unmanured. Manured. Products from Experiments. Experiments. First Grinding :-Wire 1 .. .. l. I 2. Mean. 1 .91 1. I 2. Mean. Wire 2 .. .. 1 .58 Second Grinding :-Wire 1 .. .. 1060 1.61 1 *60 Wire 2 .. .. 1.53 1 65 1-59 Wire 3 .. .. 1.58 1-49 1.54 Bran .. .. 1-69 1-79 1.74 TABLE XII. Composition of the Products of Wheat-Grain from the Colonial Steel-hand-mill. Wheat-Grain Harvest 1846. Unmanured. Manured. Mean of 5. Products from In 100 of each Product. In 100 of each Ash. In 100 of each Product. Ash in 100 Dry Mineral II Dry Mineral of each Substance Matter Nitrogen. Phosphoric Magnesia. Substance Matter Product. at 212" F.) (Ash). -Acid. st 212" F.) (Ash). I-First Grinding .-Wire 1 .. .. 84 *O 0 *78 1-91 45.3 6.95 84 -4 0 '78 1.59 0 *75 Wire 2 . .. 85 *2 45*0 6*25 83 -9 (1 -79 --1,47 0 *78 II -_I-___I --I Second Grinding :-I Wire 1 . . .. 85 .O 1.23 1 1-89 84 *8 1*60 1*22 Wire 2 . . .. 85 .O 1.17 1-76 85 -3 1*59 1.24 85 -4 Wire 3 . . .. -193 1-77 85 *4 1.54 2sol 1 I Bran .. .. 86 *5 5-76 2.08 87 -3 1.75 5 -70 53'0 13*57 ON THE COMP0SITION OF WHEAT-GRAIN &C. It should be mentioned& in reference to the working of the steel- hand-mill that on passing the grain through the apparatus four products were first obtained namely two fine flours thirds and bran; the last two products of the first grinding being mixed together were passed through the mill a second time and four products again separated.After this explanation the designation of the products in Tables XI and XI1 will be sufficiently intelligible. With the information derived from the previously recorded results a glance at tlie percentages of ash in the several products of the different grains as given in Table XII will show that the so-called ‘‘bran” here obtained retained more flour than from the ordinary flour-mill. In fact it was obviously pretty nearly equi- valent to the 9th 8th 7th 6th and part of the 5th products of the ordinary mill taken together. The five flours on the other hand but especially the three from the second grinding obviously contained rather more brariny particles than the ordinary bread- flours of the other series of the experiments. Such indeed was the obvious character from an inspection of the various products.Consistently with the character of the products thus defined the variations in their percentages of nitrogen are upon the whole much less than in the former series; but such as they are they are very curious. Thus in both instances though in a less marked degree in the manured than in the unmanured specimens the first product of the first grinding gives a higher percentage of nitrogen than the second; that of the latter being in both cases exceedingly low. In the products of the second grinding the tendencies are again parallel in the two series. Here again the first product gives a higher percentage of nitrogen than the second. The third is about equal to the second; and tlie fourth or bran is in both series the highest of the six products in this respect.Following up these curious results which show that the mechanical means employed had the tendency even within the limits of the farina1 part of the grain to separate products of different chemical characters-we may observe that the fluctuation in the percentages of ush are in detail strongly confirmatory of the direction of the variations in the amounts of nitrogen. Thus whether we look to the average percentages of nitrogen and of mineral matter respec- tively as influenced by season and as illustrated in the Summary Table No. 1-or to the parallel amounts in the scveral mill-pro- LATVES AND GILBERT ducts as shown in Table X we see that with a rise ill the percentage of nitrogen there is in comparable cases one in that of the mineral matter and vice versa".If with this point in view and carefully considcring the degree of these changes as shown in our more detailed Tables we compare together the columns of nitrogen and of ash we find that the fluctuation in the latter as seen in Table XII are perfectly consistent in direction with those in the former. This is more particularly observable in the products of the unmanured specimen. The middle Division of Table XII shows as before a rise in the percentage of the phosphoric acid in the ash as we proceed from the finer to the coarser products. The magnesia too follows the same order the ash of the "bran" containing about twice as much as that of the flours of the first grinding.In the last column of the Table XII for the sake of comparison with the individual results in the former ones we have the mean percentage of mineral matter for each product of five lots of grain which were similarly experimented upon in the steel-hand- mill. The next step in the prosecution of our inquiry would obviously have been-to separate the different proximate organic compounds of some series of these grains and their various mill-products- to determine the amount and composition of the mineral matters associated with each-and to submit the different grains and their mechanically separated parts to microscopic examiuation. Had this been accomplished the results would probably have been of high interest to the vegetable physiologist; and they wonld probably have tended to throw somc light on the functional actions or special offices of the differeiit mineral constituents known to be essential to the growth and elaboration of vegetable products.This labour however from pressure of other investi- gations we have hitherto beerr obliged to forego ;though sereral series of the mill-products themselves (necessarily to a certain degree artificially dried) and also of their respective ashes have been preserved with a view to the prosecution of the subject either by ourselves or others at some future time as far as such specimens mill allow. A great many scientific observers have investigated the clues-tions-of the practical gield of tired-flour from 100 of grain or meal-of the produce of bread from 100 of flour-of thc amounts ON THE COMPOSITION OF WHEAT-GRAIN &C.of dry substance of water and of nitrogenous compounds in bread-and of the changes which the flour undergoes in the bread- making process. The question as to what are the chemical qualities upon which depend the practical estimate of the miller and the baker of the comparative values of different flours for the purposes of bread-making has also frequently been discussed ; the conclusion generally arrived at being that it is the percentage amount of nitrogen or of gluten which rules this practical estimate. The opinion that the comparative value to the consumer too is measurable by the same standard as to chemical composition is also pretty universal.With regard to the latter points we may at once observe that the tendency of more recent investigations is at least to modify the currently adopted views. That this was desirable the whole course of our experimental inquiry and obser- vation during the last twelve years has led us to believe ; and we have occasionally treated of the subject in some of its aspects elsewhere. Without hoping to settle dogmatically questions involving too many factors to be dealt with in such a manner we propose now to adduce some few experiments and arguments of our own which may have a bearing upon some of those above enumerated; and we shall also provide as summary a view as possible in a tabular form of such published results of others on some of the points capable of illustration in that way.In the following Table XIII itre given :-1st. The results of some experiments of our own on the amount of bread yielded by 100 of the flour taken from the different parts of the dressing-machine; in some cases using the pro- ducts of each of the first 4 wires separately and in others (19 in number) taking the products 1 2 and 3 mixed together. 2ndly. The determinations (at 212' F.) of the dry substance and of water in Country and in London bakers' loaves. 3rdly. The recorded results of others on-the yield of flour from 100 of grain-the yield of bread from 100 of flour-and on the percentages of dry substance and of water in bread. LAWES AND GILBEBT TABLE XIJI. Bread made Experimentally.Particulars of the Grains. Flour Bread In 100 Bread. Number __ -from from of Bushels Pounds 'er cent 100 100 Sub-Water. Dry Experi-Harvest Per weight 2orn in Acre. Per Total gain. Flour. stance. ments. bushel. 'roducc. I-Product of Wire 1 . 6 64.1 35 9 Do. do. 2 . 6 251 63.3 38.1 62 -5 37.5 Do. do. 3 . 6 1847 61 9 38 .l Do. do. 4 . 4 1847 25t 61 .7 35.9 7-7 136.1 62.6 37'4 Total or Means. ... ... ..I ... ... 73 4 135.2 62 '8 37.2 Products 1 2 and 3 mixed ... _. 19 32 62.4 37 '3 70.8 137.8 61 -4 38'6 Baker's Bread. &leanof 4 Country Loaves 8 hours out of Oven .................. 62 *1 37 *9 64.2 Mean of 3 London Loaves 12 hours out of Oven .................. --35.8 Means ...... 63.0 37.0 Flour Bread In 100 Bread.~ rom 100 from100 Grain. Flour. Water. --4z:;r -I_ PEREIHA .. .. .. .. .. 128 .o .. .. .. .. 134 -0 >J DAUBENY .. .. +. .. 82 .O DUMAS .. .. .. .. .. 128.0 .* .. .. .. 130.0 62.5 37 '5 I. > .. .. .. .. .. 133 -0 >> URE -Practical Average . . .. .. .. 133.3 Paris {in 1835) Best Four .. .. 80 .O 127 .O HASSALL .. .. .. *. 77 -7 ALISONAND CHRISTISON(for Scotch Poor Law Board) .. .. .. 38 +o ON THE COMPOSITION OF WHEAT-GRAIN &C. Recorded Observations-continued. In 100 Bread. Flour Bread ;om 100 om100 bry Sub-Pater. Grain. Flour. gtance. JOHNSTON-English .. .. .. .. 75 *7 150 -0 56 '0 44 -0 English and French Ration .. .. .. .. 49 .o 51 *o BOUSSINGAULT-English .... .. .. 72 *O French .. .. .. .. 74 .o Paris .. .. .. .. 130 -0 64 *6 35 -4 a. Bechelbronn .. .. .. .. 140 *O 57 *1 42 -9 French Ration .. .. .. .. 139 *O Syrington .. .. .. '78 .O Lurzer .. .. .. .. 83 .o Dombasle .. .. .. .. 85 *5 PELIGOT .. .. .. .. 80 .O PAYEN-Paris Ordinary .. .. .. .. .. 64 *O 36 -0 .. .. .. .. .. 62 -0 33 *O Fr&ch Rkon .. .. .. 85 .O .. 61 -0 39 *o .. .. .. 80-0 .. 58 0 42 -0 Enilish C:bic Loaf .. .. *. .. 60 *O 40 *O .. .. .. .. 52 -0 48 -0 >Y >> Cdcd. Expt. MILLON-1. .. .. .. .. 136-0 135 -0 65.0 34 *98 2. .. .. .. .. 137 -0 137 -0 63 -4 36 *6 3. .. .. .. .. 131 -5 132.C 63.5 36 -5 4. .. .. .. .. 136 *O 134 *t 61.3 38 -7 5. .. .. .. .. 133 *O 133 *C 63 *3 36 *7 6... .. .. .. 134.5 133 *C 65 .5 34.5 7. .. .. .. .. 135 -0 134 *C 66 *O 34 *o 8. .. .. .. .. 137 .(1 13'7 *( 64 -9 38 -1 9. .. .. .. 133 .C 134.t 60 -5 39 5 Mean .. .. 134 ,E 134 -t 63 9' 36.3 -~---Military . .. .. .. .. 58 .O 42 *o 23 *. .. .. .. 57 -0 43 .o MACLAGAN-..IIKZ Bakers' First Quality 7'55 .. 134 *' 64 .2! 35 *75 .. Second , .. 7.99 .. .. 65 .O! 34.91 1 131 66 .l 33 .9 .I .. 133 58 -3 41 -7 .. 143 '1 60 -5 39 *5 .. .. 58 -5 41 -5 LAWES AND GILBERT Setting aside the incidental but much accounted measure of the quality of flour-colour it may be said that the standard of excellenceofthe baker is founded on the weight of the loaf which consistently with proper texture and lightness can be obtained from a given weight of flour.Leaving for the present the discussion of the question upon what point or points of chemical composition these properties individually or collectively depend we may observe that so far as our own experiments on the smdl scale go the quality of yielding the greatest weight of bread from a given amount of flour certainly did not seem to attach to the highest separated product of the dressing-machine ; which according to the results recorded in Table X would probably contain slightly the smallest proportion of nitrogen and consequently the largest amount of the starch series of compounds. On the other hand looking at the results more in detail than they are given in the Table it appears that the products of the grain of 1846 gave a notably greater weight of bread than the corresponding products of the more highly nitrogenous grain of 1847-the grain of the former year being admittedly a somewhat fuller and better sample than that of the latter.Judging then between the different pro- ducts of the same grain the experiments showed the weight of bread from a given weight of flour to be greater as we proceed from the less to the more nitrogenous products so long as the comparison is made between the first three or fine flours only. The fourth product however containing still more nitrogen but probably in a different condition gave a less proportional weight of bread notwithstanding that it also contained a considerable amount of branny particles which it has been stated have the property of retaining water by virtue of their structure indepen- dently of mere chemical composition.Comparing year with year on the other hand the separate products of the grain of highest weight per bushel of lower nitrogen and admittedly of the best development afforded the largest produce of bread. Passing from the experiments on the individual products to those on the mixture of the first three of them which would together constitute a $ne bread-flour we see that with this combi- nation there was on the average a higher yield of bread than from either of the separate products. This. was not the case taking the flours of 1846 alone; but it was remarkably so with those of 1847 the season of rather higher perceiitsge of nitrogen; arid it should he added that whilst on the average the mixed products of ON TEIE COMPOSITION OF WHEAT-GRAIN &C.1846 represented only 68.3 per cent. of the entire grain those of 1847 represented 71-5 per cent. Although however there is thus observed a tendency to increase in the weight of bread the higher the percentage of nitrogen within the range of the finer flours and especially so when mixed yet the grains and the flours of 1846 were pronounced by an experienced miller to be superior to those of 1847 and they would doubtless have given on the large scale a loaf of whiter lighter and better texture. In all these trials exactly the same treatment was adopted but as the result may be different in operating upon small and large bulks respectively the method followed should be described.32 ounces of flour were taken and giveu weighed quantities of compressed yeast and of salt were always employed. Water of a uniform temperature was also used and was worked in by a practised hand until the dough was decided to be of the proper consistency. The weight of water taken upr was then determined. The dough was always made quite late in the evening and after being allowed to ferment during the night it was put into a baker's oven early the following morning. Finally the loaves were weighed hot from the oven and again when quite cold towards evening. From the second weight the increase upon the original weight of flour was ascertained ; and the percentage of dry substance in the flours being previously known the percentages of dry matter and water in the bread were calculated making no allowance however for the probably 4 per cent.of dry substance lost by fermentation. The experiments of Millon given in the lower part of the Table XIII as well as the conclusion of other recent experimenters indeed seem fully to justify the assumption that the loss from that cause perhaps need not be estimated at more than the small amount above supposed. For the sake of comparison and as a check to our own bread- making experiments and calculations thereupon three loaves were bought at random at as many different bakers in the city of London and four from as many in our own locality in the country; and upon half of each of these first finely divided the dry substance was determined in a water-bath at 212'F.It will be seen that the mean of our own experiments with the separate products gives by calculation as above alluded to 62.8 per cent. dry substance and 37.1 water in the bread; and that with the products 1 2 and 3 mixed gave 61.4 dry matter and 38.6 water. LAWES AND GILBERT The four country bakers’ loaves (in July 1856-probably from wheat of 1855) gave 62.1 dry and 37.9 water ; and the three London ones 64.2 dry and 35.8 water. It is thus seen that our own results from the various flours of grain from two different harvests agree very closely with those of the country bakers’ bread from a third. They together indicate an average of 37 to 38 per cent.of water in the bread. The London bakers’ loaves which however had probably been four hours longer out of the oven than the country ones gave 64.2 of dry =35% of water. Upon tlie whole then these experiments from the flours of three different seasons indicate a probable average range of from 36 to 38 per cent. of water in bread; and taking an average of 15 per cent. water in flour and assuming the loss of dry matter by fermenta- tion and the gain by fixed saline matter added to about neutralize each other this would be equivalent to from 132.8 to 137.1 parts bread for 100 of flour. A reference to the recorded results of others as given in the Table (XIII) will show that this average of 36 to 38 per cent. of water in bread agrees very closely with the estimate of Dumas; with that of Payen for the ordinary bread of Paris; with that of Boussingault for Paris bread; with the mean of four kinds of‘ fermented bread experimented upon by Dr.Maclagan; with that of nine by Millon; and with the estimate of Alison and Christison. The estimate by Payen of 40 to 48 per cent. of water in the English cubic loaf is undoubtedly too high for English bakers’ bread as usually sold. The estimates by John- ston of 44 per cent. water in English bread and of 51 per cent. in English and French ration-bread are also no doubt too high. The results of Boussingault in France agree with our own in England in showing country bread to contain usually more water than that of the cities.Ration-bread seems according to most observers to be moister than that in ordinary use. To con- clude on this point although it is very desirable to have a proper estimate of the probable average proportion of dry substance con- tained in the most important article of the food of our population yet it is obvious that many circumstances must influence tlie amount in individual cases. The length of time that the bread has becn withdrawn from the oven must of course be taken into account; but in fixing general averages perhaps it is better to take it within the first twelve hours as this will hest represent the weights as ON THE COMPOSITION OF WHEAT-GRAIN &C. delivered by the baker and consequently those esthnated as consumed.* It must be remembered too that the character of the ripening season greatly affects the quality of the flour and in giving from the results of others as well as of ourselves a probable average of 36 to 38 per cent.water or 62 to 64 per cent. of dry substance in bread we would at the same time remark that all our own special data are derived from experiments on the pro-duce of three seasons of higher than average maturing character. That the season independently of either soil or manuring may very much influence the percentage of nitrogen in one and the same description of grain even in the same locality is amply illustrated by the results in Tables I and 111 given at the com-mencement of this paper. It cannot be mondered at therefore that different localities or countries should yield us grains showing a wide range of variation in their percentages of nitrogenous com- pounds.Rossigneau Boussingault Millon and Peligot have examined many of the characteristic wheats of commerce and we propose here to subjoin some additional facts relating to this branch of the subject. In the following Table (XIV) are given the mean results of a great many determinations by the mechanical method of the gluten in flour by Mr. W. Constable of Brighton. It is admitted that this method is an uncertain one and it is of course quite incom- petent to indicate the total nitrogenous substance of the flours. However we believe the experiments to have been made with great care and uniformity of manipulation and as they are also consistent dh results of another kind they are well deserving record.It may be premised that whilst the method in question is liable to a little depreciation in the amount of gluten by loss in the washing-especially when the substance itself is of an inferior character-yet on the other hand the drying is more likely to be in error in the other direction. These two sources of error there- fore so far as they operated in the experiments would tend to neutralize each other. It may be added that not the least inte- resting part of Mr. Constable’s results is that lie consistently with the observations of Peligo t and others establishes a very wide range in the character of the gluten obtained from different flours * It should be stated however that if the fresh weight of the ’ibaker’s loaves examined mere assumed to be 4 lbs.cach as it should have been then the dry matter which the loaves contained was on the average only equal to 60; per cent; the wafer on the same calculation being of course 394 per cent. ! -.--- LAWES AND GILBERT as to colour tenacity elasticity and so on. AUr.Cons table's results with which he has kindly furnished us are recorded by him seriatim in the order in which they were obtained and without any special reference to the point for the illustration of which we here adduce them. It will be seen that in our Table we have classified the results according to their reputed locality of growth or shipment and arranged the means so obtained somewhat in the order of latitude ranging from north to south adopting the same general arrangement for the European and American samples respectively.TABLE XIV. Percentage of Gluten in different Flours. MEANRESULTS. Number Mean Reputed Localities of Growth or Shipment. of Gluten Experiments. Per Cent. America-Canada .. .. .. 6 9.8 Genessee (New York) .. 7 9.8 Other New York . . .. 7 10 -1 Ohio .. .. .. 18 11 .a Maryland .. ,. .. 3 11'3 Richmond (Virginia) .. .. 8 11-8 George Town (South Carolina) ,. 18 13 .7 New3rIeans . .. .. 1 13 -4 Miscellaneous .. .. 11 9 -35 Mean .. .. .. 79 11.4 North Europe- Dantzig .. .. .. 4 8 -9 .I 1. Hamburg .. .. Stettin .. .. .. .. 1 10.3 8 Pomerania .. .. .. .. South and East Europe- Tuscany .... .. .. Spain .. .. .. .. -8 10 *3 Portugal .. .. .. .. Black Sea Soft .. .. .. 2 12 -5 Black Sea Hard .. .. .. 9 14 '9 Mean.. .. .. 31 11-6 England-White .. .. .. 45 10 .8 Red .. .. .. .. 13 10 -4 Not Specified .. .. .. 45 10 *5 Mean . . .. .. .. 103 i 10 -7 ON THE COMPOSETION OF WHEAT-GRAIN &C. It cannot fail to be observed that there is a general tendency in the specimens from both the European and American continents to increase in the percentage of gluten proceeding frop the north to the south. It may therefore be concluded that among other circumstances a relatively high temperature at the ripening period is favourable to a high per-centage of gluten. The mutual adap- tations of heat and moisture throughout the various stages of the progress of the plant are however so almost infinitely varying even from season to season in one and the same locality that it is not surprising there should be many exceptions to any such sweep- ing generalization as the one here indicated in regard to widely differing localities.A study of the variations in the chafacter of the crop and in the composition of the grain grown from year to year in our experimental field side by side with the varying cir-cumstances of root and leaf supply of moisture and of tempera- ture is sufficient to show how numerous and how indeed ever changing in their mutual relations are the factors which lead to one or another order of development in the growing plant. We have at various times determined the nitrogen in individual specimens of foreign wheat which have come in our way and recently through the kindness of Mr.W. J. Harris of Fenchurch Street London we have been provided with a series of characteristic samples the result of the examination of which we had hoped to embody in this paper. Unfortunately the laboratory work is not sufficiently completed to allow of this any further than by a few general remarks on the tendency of the results already obtained. This tendency from the examination of a series of contrasted samples is fully to confirm the indications of LMr. Constable's results as to general influence of latitude or locality on the nitrogenous per- centage of the grains. There are how ever as above inferred some interesting and instructive exceptions brought to light.It is obvious too that both soil and variety must have much to do with the character of the grain; and that to elicit without exception the influence due to climate alone the same description of wheat should be grown in as far as possible similar soils in different localities for a series of years consecutively. In defect of specimens of this kind we must to a certain extent rely on the assumption that those descriptions will be generally cultivated in a particular locality which experience has shown to be most adapted to its climate and other characters and that hence the qualities of the E LAWES AND GILBERT grains will be at least some indication of the general tendencies of the climatic circumstances which have yielded them.It may be remarked that among the American specimens examined by Mr. Constable the Genessee is seen to contain the lowest average percentage of gluten yet it is one of the most highly esteemed of the American flours imported into this country. Again among the foreign European samples enumerated the Dantzic yielded the smallest percentage of gluten whilst it has above all the highest range of value in the English market. The soft Spanish is perhaps the next in order of value among the imported European wheats and we may observe that it is also one of the lowest in percentage of Nitrogen which we have yet examined On the other hand the flours from many of the highly nitrogenous foreign wheats have the undoubted character of imparting great ‘‘ strength” to the dough and for this purpose they are much valued to mix with weaker flour; especially with that from grain which has been imperfectly developed and matured.Some of the most important of these highly nitrogenous wheats are however both inferior in the colour of their flour and very hard and horny; and owing to the inappropriateness of the English method of milling to the defective whiteness of the flour and of the bread and to the somewhat close texture of the latter other flours of lower percentages of nitrogenous compounds have notwithstanding this great ‘‘strength,’’ a higher character when used alone for bread-making purposes. These highly nitrogenous wheats are chiefly imported from Russia and independently of a high ripening temperature they are for the most part grown on very rich soil and sown in the Spring.On this point it is worthy of notice that home-grown Spring wheat has sometimes the character of imparting strength to the flour of an inferior Winter wheat and in the only instance of this kind which we have examined the reputed stronger (Spring) wheat had the higher percentage of nitrogen. It may be stated generally that the highly nitrogenous foreign wheats have the admitted character of imparting strength to infe- rior flour; and they are thus highly valued for the purpose of admixture with home-grown grain imperfectly developed and matured. These highly nitrogenous imported wheats have as the rule been matured under a much higher temperature than our own; their nitrogenous constituents would appear to be in larger proportion in the form of gluten; and it is in wheats so ripened ON THE COMPOSITION OF WHEAT-GRAIN &C.that the higher percentage of fatty matter is also found the proper blending of which according to the experiments of Peligot consi- derably affects the physical characters of the gluten. The opinion of Peligot-indeed of other recent investigators and in this we fully concur-is that the measure of value of different flours for the pur- poses of bread-making is certainly much more dependent on the con-dition of their constituents than on their mere percentage amount of nitrogenous compounds. This high condition of the nitrogenous and also the other compounds would seem to be alike possible in wheatsof high andof somewhat low percentage of nitrogen-provided other things being equal they have been well developed and ripened at a high temperature; whilst when this is so an undoubted prefer- ence is given to the less nitrogenous grains.This is partly due to the latter being generally softer and more amenable to current milling methods ; and partly to the widely-differing structural character of the farina1 matter by virtue of which the flour not only makes a better and more workable dough but the bread produced is of superior texture and lightness-conditions which all analogy mould lead us to conclude must materially aid its digestion and assimilation and consequently so far increase its value as food.A high percentage of nitrogenous compounds provided the grain be well-developed and matured and not so hard as to offer mechanical obstacles to fine division and easy separation of the bran in the mill will tend to a great weight of bread and a good quality as to texture. It would appear however that a smaller percentage if with equally high elaboration will tend to a similar result as to weight and to even higher qualities as to texture and whiteness. Witliin the limits of our own island however on the average of seasons the better-elaborated grain mill probably be the less nitrogenous,% though the nitrogenous matter it does contain will be in a high condition as to elaboration and to its mutual relations structural and chemical with the other consti- tuents of the flour.Hence it comes to pass that as our home- grown flours go those which are the best in the view of the baker will frequently be those having a low percentage of nitrogenous compounds-a higher coizditioia more than compensating for the * This is however not always the case ;and had we extended our review beyond the ten years to which Tables I and 111 refer we should have found in the season of 1855 both high development and maturation of grain and high percentage of nitro- genous compounds. Of the cases included in our survey the season of 1847 afforded in tho highest degree the combination of characters here referred to. E2 LAWES AND GILBERT higher percentage of nitrogen generally associated as it is in our climate with an inferior degree of development and maturation.We conclude then that condition of makuration or perhaps rather elaboration as well as mere percentage composition should be theoretically as it is practically admitted as an essential element in estimating the relative qualities of different wheats or flours for bread-making purposes. The opinions of some of the most recent and perhaps the most competent observers certainly point in the same direction as the one here indicated. Still the current opinion derived from several of our standard works would seem to be that a high percentage of nitrogenous compounds should be taken as an almost unconditional measure of value. But besides the frequently reiterated statement that the baker’s estimate is founded on the amount of the gluten it is also pretty generally maintained that it is the amount of this or of the nitrogenous constituents collectively which determines the com-parative values of different flours or breads to the cowrner.With regard to those foreign wheats which have their nitrogenous sub- stance in a highly-elaborated condition and favourably related to the other matters and in which the whole is structural13 fitted for easy milling and to yield a light and easily-digestible bread we would not say that with such a comparatively high percentage also of the nitrogen might not be an additional point of value But even with the foreign wheats it is but a small proportion that combine these several qualities; whilst those which have the most of the others have generally less of the amount of nitro- genous substance.With home-grown wheats too as already said information at present at command tends to show that high per-. centage of nitrogen is frequently at least associated with low condition of elaboration of the constituents of the grain yielding an inferior bread-flour-and thus though from opposite causes to those which depreciate the richer nitrogenous grains of the higher- ripening temperatures a less valuable food. Let it be conceded then that condition or elaboration must affect the digestibility and assimilability of our food. But we think it may be inferred yet on other grounds that us flours go the richer in the more directly respirable and fat-forming compounds will generally be more valued as food.* The following Table (for * Thcre is experimental evidence to show that the nitrogenous constituents of food may serve one or both of these offices ;but when in excess probably at a greater cost to the system.ON THE COMPOSITION OF WHEAT-GRAIN &C. some of the data of which we are indebted to Dr. Playfair) showing the estimated average percentage of nitrogen and of carbon in a number of standard articles of food arid also the rela- tion in them of the one constituent to the other will aid us in illustrating our meaning :-TABLE XV. Estimated Average Composition of Standard Articles of Food. 1 Nitrogen Foods. to 100 Dry Subs t'ance. Carbon. Nitrogen.Carbon. Meat (fresh) .. .. .. 45.0 30 -0 2.0 6.6 Bacon (green). . .. .. 80.0 57 .o 1.13 2.0 , (dried). . .. .. 85.0 61 -0 1 a 4 2 *3 Suet or Butter .. .. 85.0 68 *O 0 *o I, Milk .. .. 10.0 5 -4 0 *5 9.3 Cheese .. .. .. 60.0 36 -0 4.5 12*5 Flou~(wheaten)Bread .. Maize *. .. .. .. .. .. .. 85 .O 64 -0a$-0 38 *o 28 *5 40 .O 1*72 1 *29 1.75 4 -5 4.5 4 -4 Oatmeal .. .. .. a5 -0 40*O 2 -0" 5 .o Rice .. .. .. 87 *O 39 -0 1 -0 2 -56 Potatoes .. .. .. 25 -0 11 -0 0 *35 3 *2 Vegetables (succulent average) Peas .. .. Sugar .. .. .. .. .. 15 *O 95 *O a5 eo 6.0 39 -0 40 *o 0.2 3.3 3 -65 9 -4 0 *o Cocoa and Chocolate .. .. 92 *O 56 *2 2.0 3.6 Beer or Porter .. .. 9.5 4*5 0 *01 0 -2 By this Table it is seen that wheaten flour and bread contain as high a proportion of nitrogen to carbon as most of the current a.rticles of food of our working population excepting the important items of fresh meat milk and cheese.Were we to ask to what staple articles the working man next resorts when his means allow him to add other foods to his main diet of bread?-the answer would be cheese bacon and perhaps hutter; and me think it would further be that his preference mould generally be for the bacon. The Table shows that so far as he took cheese he would considerably increase the proportion of the nitrogen to the carbon he so consumed. The amount of it he would eat would however be less than that of bacon and in the latter he would only con- sume half as much nitrogen in proportion to the carbon as he would in bread alone.In fat or butter he would have no nitrogen * Scotch oatmeal would range higher than this. LAWES AND GILBERT at all so that the addition of either of these to his flour or bread would still further reduce the proportion of nitrogen to carbon in his food. But all these substances besides their respirable carbon have a large proportion of respirable hydrogen due to their fatty substance. Even cheese which contains the least amount of this has nevertheless a very considerable percentage of it ; bacon much more; whilst fat and butter excluding their water are of course wholly composed of it. If therefore we take into calcula- tion the respirable hydrogen it will be seen thzt the respiratory capacity (so to speak) of the cheese would be much higher rela- tively to theflesh forming than the relation to the carbon alone as in the Table would indicate.In the bacon on the other hand the relation even of the carbon alone to the nitrogel? is much greater than in bread; and if we further take ir,to account its respirable hydrogen its respiratory relatively to its flesh-forming capacity will appear still greater in comparison with the bread. Lastly even taking the case of fresh meat so large is its amount of fat and therefore of respirable hydrogen that its respiratory and fat-forming relatively to its flesh-forming capacity mould be much higher as compared with bread than the figures in the Table relating to carbon alone would shorn. From these considerations we think it may fairly be concluded that the first more urgent call of the system of our under-fed or only bread-fed working man is for an increased supply of respira- tory or fat-forming rather than of flesh-forming constituents of food.Indeed it is tofat itseq in some form that he first resorts. If then the first demand of the system be generally for more of the more directly respirable or fat-forming material than bread alone supplies :-if the foreign wheats of more than average percent- age of nitrogen have frequently structural characters which render them with greater difficulty made into an easily-digestible bread :-if the more highly-nitrogenous wheats of our colder summers have their constituents frequently in a less highly-elaborated condition :-and if finally the introduction of' more of the nitrogenous constituents of oiir grain into the bread-flour generally introduces at the same time branny particles which cause the food to pass in too large a proportion undigested from the body-it would appear that the standard of value of food-stuffs as they go according to their nitrogenous percentage is at least only conditionally correct and that the current views on the point require to be somewhat modified.Prom all the data at our command we have adopted 1.29 as the probable average percentage of uitrogeu in wheaten bread. That ON THE CO3fPOSITION OF WHEAT-GRAIN &C. taken by Dr. Maclagan is from 1-1to 1.2; and that by Playfair and Pay e n about 1-1. These amounts represent respectively about 8 74 and 7 of nitrogenous compounds.* It will not be sup- posed that because from the facts adduced we are led to believe that in addition to siich a bread as is here assumed the first call of the system of the working man would be for more of respiratory and fat-forming material we would therefore deny the advantage of an increased supply of nitrogenous constituents also.We would however submit as worthy of reflection that whilst the relation of nitrogen to 100 of carbon in wheaten flour and bread is 4.5 that in the average of the food consumed taking eighty-six cases divided into fifteen classes and including both sexes and all ages was only 5.34. These dietaries included many which were exceed- ingly liberal so fmas the nitrogen supplied was concerned; yet a careful consideration of their details showed that taking into calculation their respirable hydrogen the relation of purely respi- ratory or fat-forming to flesh-forming material in most of these numerous dietaries would be nearly as great in bread.Indeed it would appear that that which is admitted to be a superior class of diet is distinguished much more by including a certain amount of the important non-nitrogenous constituents in the condition and state of concentration as in fatty matter and of the nitro- genous ones in the high condition as in animal food than by the higher proportion of its flesh-forming to its more exclusively respiratory and fat -forming constituents.

ISSN:1743-6893    

DOI:10.1039/QJ8581000001

出版商:RSC    

年代:1858

数据来源: RSC

摘要:

ON THE CO3fPOSITION OF WHEAT-GRAIN &C. K-On a new Series of Organo-Thionic Acids. BY JOHNTHOMAS HOBSON DALTON SCHOLAR IH THE LABORATORY OF OWEN’S COLLEGE MANCHESTER. THEresearches of Dr. Franklxndt have shown that thereexists a class of bodies containing metals in combination with the alcohol radicals and to which he has given the name of “organo metallic bodies.” One of the peculiar features possessed by these com-pounds is that they bear a very strong molecular analogy to the inorganic compounds of the metal they contain which inorganic compounds may therefore be regarded as the types of their organic derivatives. Thus antimony which with hydrogen forms anti-moniuretted hydrogen SbH, and with oxygen teroxide of antimony SbO, gives with ethyl stibethyl Sb(C1,H5)3; and arsenic which * These estimates have reference to the bread from rather fine flour ;that from the coarser flours contains rather more of nitrogenous matters.f-Chem. SOC.Qu. J. vi. 57 andPhil. Trans. 1852,p. 417. 56 HOBSON dth the inorganic elements sulphur and hydrogen gives arseiiiu.. Petted hydrogen ASH, and bisulphide of arsenic ASS, forms with methyl cacodyl As (C2H3),; and with ethyl ethylic cacodyl As(C,H,),. Cacodyl also unites with oxygen forming oxide of ca- codyl As {(‘bH3)2} resembling arsenious acid AsO ; and caco- ilylic acid agreeing with arsenic acid. From the recentresearches of Wohler Hofmann and Cahours it appears that this singularity of behaviour is not exclusively confined to the combinations of metals with the alcohol radicals but that the metalloids selenium and phosphorus form with these radicals compounds molecularly similar to their inorganic types and possessing for the most part the property of uniting directly with oxygen.Thus selenethyl forms with oxygen oxide of selenethyl Se {‘hH5} which is mole- cularly homogeneous with selenious acid SeO, whilst phosphorus with ethyl gives phosphethyl P(C,H,) corresponding with phosphorus acid PO,. Considering the strong analogy existing between sulphur and selenium I was induced to try whether thc sulphide of ethyl would not like selen-ethyl unite with oxyb wen to form compounds of the thionic acid type. In preparing sulphide of ethyl for this purpose I tried several of the methods usually recommended but found most of them to yield only a very poor product.By passing chloride of ethyl into an alcoholic solution of protosulphide of potassium I obtained only traces of the compound ; and the distillation of dry protosulphide of potassium with sulphovinate of potash yielded scarcely a better result. The following method however gave a satisfactory pro-duct :-An alcoholic solution of protosulphide of potassium was made by saturating a weighed quantity of caustic potash dissolved in alcohol with sulphuretted hydrogen and adding to this the same weight of alkali as that previously used. This alcoholic solution of protosulphide of potassium on distillation with sul- phovinate of potash yielded a large quantity of sulphide of ethyl.The sulphide of ethyl thus prepared was treated with dilute nitric acid. On the application of a gcntle heat dense nitrous fumes were given off the sulphide of ethyl entirely disappearing When all action had ceased the liquid which contained an excess of nitric acid was evaporated for some time in a water bath to expel as much as possible of this acid ; it was tlicii saturated with carbonate of baryta arid tlic evaporation contitiucd to dryness. The dried mass being afterwards treated with alcohol aitd filtered ON ORGANO-TIIIONIC ACIDS. from the nitrate of bxryta the filtrate on long exposure to the heat of a water-bath yielded a small quantity of a thick syrupy liquid which contained sulphixr ethyl and baryta but showed no disposition to crystallize and could not be obtained in a satisfactory state for analysis.This experiment showed however that an acid had been formed which most probably contained sulphur ethyl and oxygen; but finding that this acid was obtained in such small quantities from sulphide of ethyl I abandoned this process of forming it. The recent researches of Dr. Frankland on the substitution of oxygen by an alcohol-radiciil in the case of binoxide of nitrogen,* led me to hope that a corresponding reaction with an oxygen compound of sulphur and one of the organo-zinc compounds would produce the desired substitution. For obvious reasons I selected for this reaction sulphurous acid and zinc-ethyl ; and a preliminary experiment showed that these bodies act upon each other very energetically forming a whitc crystalline mass which mas evidently the zinc-salt of a thioriic acid.On a large scale the process was conducted as follows :-A quantity of zinc-ethyl prepared according to the plan recommended by Dr. Frankland,? was placed in a flask and sulphurous acid evolved from sulphuric acid and copper turnings and dried by passing through a Woulfe’s bottle containing concentrated sulphuric acid was allowed to come in contact with it. The gas was very rapidly absorbed by the zinc-ethyl and so much heat was produced that it was found necessary carefully to cool the flask during the whole process of absorption. In a short time a white crystalline body was formed in the zinc-ethyl and gradually the whole contents of the flask were converted into a mass of minute crystals which pro- tected some of the zinc-ethyl from contact with the sulphurous acid; so that unless the action of the gas was very prolonged and the crystalline mass broken up the latter effervesced with water owing to the presence of undecomposed zinc-ethyl.After purifi- cation and crystallization first from alcohol and then from water it yielded on analysis the following numbers :-I. 6.02 grs. burnt with oxide of copper a tube of peroxide of lead being interposed between the chloride of calcium tube and potash apparatus gave 3-20grs. of carbonic acid and 1.91 grs. of water. * Proceedings of the Royal dociety viii. 198. + Phil. Trans. 1855 p. 259. 58 HOBSON 11. 6-28grs. similarly treated gave 3.35 grs.of carbonic acid and 2.16 grs. of water. 111. 6.155 grs. gave 3.25 grs. of carbonic acid and 2.065 grs. of water. IV. 12.30 grs. dissolved in water and precipitated boiling by a solution of carbonate of soda the precipitated basic carbonate of zinc washed dried and ignited gave 2.995 grs. of' oxide of zinc. IT. 5.96 grs. cautiously ignited then treated with nitric acid and afterwards strongly heated and exposed to a current of air gave 1.46 grs. of oxide of zinc. VI. 3-80 grs. ignited with a mixture of clilorate of potash and carbonate of magnesia thc product clissolvcd in hydrochloric acid and precipitated with chloride of barium gave 7.82 grs. of sul-phate of baryta. VIT. 3-14 grs. similarly treated gave 6-67 grs.of sulphate of barg ta. These results as is seen from tlie following comparison agree with tlie formula :-Calculated. Analyses. Mean. 1 234567 C. . 24 14.41. 14.49 14.54 14.40 -* -14.48 HG . . 6 3-80 3'52 3-02 3.72 --3-69 --19.53 19.62 -19-57 Zn . . 32.5 19.52 S . . 48 28.82 ---28.23 29.15 28.69 0; . . 56 33'65 -_---33.57 -___ 166.5 1G0-00 100*00 This compound is thereforc the ziuc-salt of a new acid formed by the substitution of one equivalent of oxygen in three equiva- lents of sulphiirous acid by ethyl. This acid I propose to call Ethylotrithionic Acid. Ethylotrithionate of zinc presents the appearance of minute acicular crystals which are colourless and lime a peculiar odour ; they are almost insoluble in cold but moderately soluble in boiling alcohol.It dissolves sparingly both in hot and cold water and also in ether; on evaporating its aqueous solution the salt crystal- lizes out as a pellicle which floats on the surface. Ethylotrithio-nate of zinc possesses a peculiar and somewhat bitter taste. It contains one atom of water of crystallization which it retains at loo0 cr. ON ORGANO-THIONIC ACIDS. The crude salt produced by the action of zinc-ethyl on sulphu- rous acid had not however such a simple constitution as the zinc-salt mentioned above since owing to the presence of an excess of oxide of zinc derived from the action of water on the undecomposed zinc-ethyl a basic salt had been formed. This salt submitted to analysis yielded the following results :-I.5.42 grs. burnt with oxide of copper yielded 2.47 grs. of carbonic acid and 1-76grs. of water. 11. 10.50 grs. dissolved in boiling water and precipitated with a solution of carbonate of soda the precipitated basic carbonate of zinc mashed dried and ignited gave 3.305 grs. of oxide of zinc. 111. 4.63 grs. ignited with a mixture of chlorate of potash and carbonate of magnesia the product dissolved in hydrochloric acid and precipitated with chloride of barium yielded 8.37 grs. of sulphate of baryta. The following calculation shows that these numbers agree with thc formula :-Calculated. Analyses. 1 2 3 A /-\ -C . . 48 12-55 12-43 --Isl3. . 13 3.39 3.61 -Zn . . 97-5 25.49 -25-25 -s6 96 25-09 -24-80 I O, .. 128 33-48 --382.5 100.00 Ethylotrithionate of Baryta BaO,S C4H5 I-+ 1x0. -This 05 salt is prepared by adding to a boiling solution of the zinc salt caustic baryta in excess and then passing carbonic acid through it till the excess of base is precipitated. It crystallizes on cooling fi*omits concentrated solution in water in the form of a pellicle mhich floats on the surface. It isa colourless salt which does not decompose when heated to 170° C; it contains one atom of water of crystallization which is driven off at 100' C. Ethylotrithionate of baryta exposed for some time over sulplzuric acid in vacuo yielded the following analytical results. I. 7*52grs. burnt with a mixture of chromate of lead and oxide of copper gave 3.34grs. of carbonic acid and 2-05 grs.of water. 60 HOBSON 11. 4.235 grs. dissolved in water and the baryta precipitated with dilute sulphixric acid gave 2-40grs. of sulphate of baryta. 111. 6.35 grs. ignited with carbonate of magnesia and chlorate of potash the product dissolved in hydrochloric acid and precipi- tated with chloride of barium gave 10.835 grs of sulphate of baryta. These results correspond closely with the above formula. Calculated. Analyses. 1 2 3 -c * . 24 11*84 12-11 --TI . . 6 2.96 3.03 -Ra . . 68.6 33.86 -33.33 - 48 23-68 -23.41 S . -0 . . 56 27.66 -202.6 100.00 Bthylotrithionic Acid.-HO,S { 'hr5 } -To prepare this acid in its free state a quantity of its zinc-salt was distilled with dilute sirlphuric acid. The thermometer during the distillation stood fixedly at 140' C and a liquid passed into the receiver which reddened litmus strongly but contained the acid in a very dilute form.In the hope of obtaining it in a more concentrated state the zinc-salt was distilled with strong sulphiiric acid; but this iiiethod did not succeed as the thionic acid was entirely decom- posed thc mass in the retort being charred and large quantities of sulphurous acid evolved whilst an oily liquid with an alliaceous odour distilled over. Finding howcv-er that neither of these methods was adapted for obtaining large quantities of the free acid I exactly precipitated the baryta from ethylotrithionate of baryta by dilute sulphuric acid separated the sulphate of baryta by filtration and thus obtained a moderately concentrated solution in water.A quantity of this aqueous solution was subjected to prolonged evaporation in a water bath but the acid could not be obtained by this method in its monohydrated state ; since after very lengthened evaporation it still retained five equivalents of water. To determine however whether the acid retained its original constitution a baryta-salt was formed by dissolving in it a quantity of carbonate of baryta. The salt thus obtained on being recrystallized from water and dricd at 100' C gave 011 analysis the following numbers which ON OIXGANO-TECTONIC ACIDS. agree with the formula of the anhydrous baryta-salt of ethylo-trithionic acid 1. 8.54 grs. burnt with chromate of lead gave 3.79 grs.of carbonic acid and 1.825 grs. of water. 11. 447 grs. burnt with oxide of copper gave 1,975 grs. of carbonic acid and 1-00grs. of water. 111. 9.30 grs. dissolved in water and precipitated with dilute sulphuric acid gave 5.44 grs. of sulphate of baryta. IV. 4-43 grs. ignited with chlorate of potash and magncsia the product dissolved in hydrochloric acid and precipitated with chlo- ride of barium gave 7-82 grs. of sulphate of baryta. -Calculated. Analyses Mean. 1 2 3 4 C,. 24 12.39 12-10 12-05 - - 12-08 Ba H . 68.6 . 5 35-43 258 -2.37 -2.48 3 B.41 - - 2.43 34.41 S,. . 48 24-79 - - - 24-22 2 4.22 0 . 48 2481 - - - - 26.86 193-6 100*00 100*00 Ethylotrithionate of Silver.-AgO,S {'by5}-This salt was obtained by dissolving carbonate of silver in the free acid prepared as above.It is very stable neither evaporation in a water-bath nor exposure to light decomposing it in the slightest degree. The ethylotrithionate of silver is a white crystalline body very soluble in water; on exposure to the air it rapidly attracts moisture becoming liquid. It will bear heating to 100"C but if the tem- perature be raised much above this it is entirely decomposed. This salt after being dried over sulphuric acid in vacuo yielded the following analytical results :-I. 9-42 grs. burnt with oxide of copper gave 3.52 grs. of car-bonic acid and 1.882 grs. of water. 11. 8-30 grs. similarly treated gave 3-15 grs. of carbonic acid and 1.66 grs. of water. 111. 10.75 grs. gave 4.005 grs.of carbonic acid and 2.17 grs. of water. IV. 3-60 grs. cautiously ignited and exposed to a stream of air gave 1.665 grs. of metallic silver. V. 5.92 grs. similarly treated gave 2.73 grs. of silver. VI. 11.40 grs. dissolved in water and precipitated with hydro- chloric acid gave 6.995 grs. of chloride of silver. 62 ROBSON T'II. 5.27 grs. ignitcd with a mixture of chlorate of potash and carbonate of magnesia the product dissolved iii hydrochloric acid and precipitated with chloride of barium gave 7-87 grs. of sul- pirate of baryta. The following comparison shows that thesc nurnbei s agrce with the above formula :-Calculated. Analyses. Mean 1 2 3 4567 P C . 24 10.30 10.20 10.35 10.16 --10.24 H5 . 5 2.15 2-22 2.22 2-24 --2-23 Ag .108 46.35 --46.25 46.11 46-18 -46.18 S . 48 20'60 ----20-49 20.49 0 . 48 20.60 ---20.86 233 100.00 100-00 Ethylotrithionate of Copper. -'6;.{CuO,S,-}-This salt can be prepared either by the double decomposition of the baryta-salt or by dissolving carbonate of copper in the free acid. It crystal-lizes both from its aqueous and alcoholic solution in the form of greenish blue needles which are deliquescent. When dried at 100' C it gnve on analysis the following results :-I. 6.55 grs. burnt with oxide of copper gave 3.64 grs. of car-bonic acid and 1.96 grs. d' water. 11. 5.85 grs. similarly treated gave 3-26grs. of carbonic acid and 1.725 grs. of water. 111. 4.27 grs. cautiously ignited and exposed to a stream of air gave 1.08 grs.of oxide of copper. IV. 3-21 grs. ignited with a mixture of chlorate of potash and carbonate of ningneais the prodrict dissolved in hydrochloric acid and precipitated with c!doride of barium yielded '7.065 grs. of sul-yhte of barpta. These numbers agree with tlie formula above given as will be seen from the follomirig cnlculation :--Calculated. 1 Analyses. 2 3 4 Mean. C,. . 24 15-33 15-15 15.20 - - 15.18 13 . 5 3.19 3.32 3.27 - - 3$29 Cu s 0 -31% 48 48 20.18 30.65 30.65 -_ - -- 20.18 - -30.20 - 20.18 30.20 31.15 156.6 100.00 100~00 ON ORGANO-THTONIC ACIDS. Ethylotrithionic Ether.-C,H,O S {'6:5} -This ether was obtained by distilling a mixture of crystallized etliylotrithionate of baryta with sulphovinate of potash. On applying the heat of an oil bath the crude ether came over which after being washed dried by standing over chloride of calcium arid redistilled yre- sented the appearance of' an oily yellow liquid slightly heavier than water and possessing a disagreeable smell.It is insoluble in water but miscible with alcohol in all proportions. Unfortunately I did not obtain a sufiicient quantity of the ether to admit of the determination of its specific gravity and boiling point. Ethylotrithionic ether after being thoroughly dried by chloride of calcium yielded the following analytical results :-I. 3.72 grs. burnt with oxide of copper gave 4.22 grs. of car-bonic acid and 2-21grs. of water. 11. 2.43 grs. burnt with magnesia and chlorate of potash the product dissolved in hydrochloric acid and precipitated with chlo- ride of barium gave 5.50 grs.of sulphate of baryta. The followiiig calculatioii agrees with the above formula :-Calculated. Analyses. 1 2 -C . 48 31.17 30.93 -HI(). 10 6.49 6-60 S . 48 31.17 -31.05 0 . 48 31.17 -154 100*00 Ethylotriti~ionateof Soda.-NaO,S c4H5I-+ 130. -This (05 salt was also prepared by dissolving carbonate of soda in the free acid evaporating to dryness and treating with alcohol which dissolves the ethylotrithionate of soda whilst the excess of carbonate remains insoluble. The alcoholic solution on evaporation in vacuo over sulphuric acid yielded colourless crystals in the form of needles which were however very small and not well defined. Deter-minations of the sulphur and sodium contained in this salt after being thoroughly dried in vacuo gave the following results :-I.8-40 grs. evaporated to dryness with sulpl-ruric acid and ignited gave 3-94grs. of sulpliate of soda. 11. 4-52 grs. burnt with a mixture of chlorate of potash and magnesia the prorluct clissolvd in hydrochloric acid and precipi- 64 HOBSON ON ORGANO-TIIIONIC ACIDS. tated with chloride of barium gave 9.90 grs. of sulphate of baryta. These numbers agree sufficiently with the above formula. C'alculated. Analyses. 1 2 1 Na . 23 14-65 15.21 -S . 48 30.57 -30.05 Sulphurous acid is also rapidly absorbed by zinc-methyl a white crystalline body being produced as in the case of zinc-ethyl. I reserve however for a future communication the complete history of this body which contains most probably the zinc-salt of the first acid of this series-viz.the Methylotrithionic Acid. It is also highly probable that a complete series of org;mo-thionic acids will be produced by acting upon sulphurous acid with the various zinc-compounds of the alcohol-radicals. The following is a list of the names and formulz of the bodies which have been described in this memoir :-Ethylotrithionic Acid. -HO,S3 { '6:5} Ethylotrithionate of Zinc. -ZnO,S { 0 } C4N5 + II0. Basic ethylotritliionate of Zinc.-2(ZnO,S,{'b;s) + HO) t Zn0,Ilo. Ethylotrithionate of Baryta.-BaO,S { C4H5 0 } + Ho* Ethylotrithionate of Baryta dried at 100' C.-BaO,S Ethylotrithionate of Silver.-AgO,S Et,hylotrithionate of Copper.-CuO,S '(f5} { Ethylotrithionate of oxide of Ethyl.-C,H,O,S {C$5) Ethylot rithionat c of Soda.-NaO S

ISSN:1743-6893    

DOI:10.1039/QJ8581000055

出版商:RSC    

年代:1858

数据来源: RSC

摘要:

BROWN ON A NEW VOLUMETRIC METHOD &C. 111.-On a new VolumetricMethod for the Determination of Copper. BY E. 0. BROWN ASSISTANT IN THE CHEMICAL ESTABLISHMENT OF THE WAR DEPABTMENT. A SERIES of experiments conducted by Mr. Abel in connection with the manufacture of bronze guns involved the analysis of a large number of samples of gun metal with which I was entrusted by him; and the much greater rapidity with which copper can be estimated by volumetric methods than by precipitation as oxide led in the first instance to the selection of the method of Pelouzc for adoption in these experiments as the one of that class most likely to furnish trustworthy results. The process in question as originally described by P elouze is as follows :-1 gramme of copper is dissolved in 5 or 6 grammes of com- mercial nitric acid with the addition of a little water if necessary ; this solution is then mixed with 40 or 50 cubic centimetres of concentrated ammonia raised to the boiling point and a standard solution of sulphide of sodium added until the blue colour disappears.During the whole of the operation the liquid is kept in a state of gentle ebullition fresh quantities of ammonia being added from time to time to make up for the loss by evaporation. The useof the large quantity of ammonia keeps the boiling point of the liquid below the temperature of 80' C. beyond which it is not to be allowed to rise. The precipitate produced is expressed by the formula CuO 5CuS; but it is stated to have a different composition if the liquid at the time of precipitation is at a higher temperature than that above stated.Following these directions as closely as possible an attempt mas made to standardize a solution of sulphide of sodiutn by means of electrotyped copper. The results are given in the following table :-Quantity of Copper Measures of Sulphide of Calculated for 10 grains taken. Sodium taken. of Copper. 9.10 82-5 90.6 9.10 82.8 90.9 9.10 82.2 90.3 9-10 82.5 90.6 14!*443 136.0 93.9 13.29 121.5 91.4 13-21 1z.a 92.2 F BROWN ON A NEW VOLUMETRIC METHOD It will be observed that there is little discrepancy between some of these numbers and it is necessary therefore to notice that when this is the case the same quantities of copper were emplayed and especial care was taken that the operatiQn should be conducted in a precisely similar manner.In those instances in which there was any material difference in the amount of copper taken and the quantity of sulphide of sodium necessary to obtain corresponding results was consequently unknown the numbers obtained exhibit bnt little similarity. It should also be remarked that whenever the contents of the flask were not shaken but only agitated by boiling a smaller amount of sulphide of sodium was required. Considerable difficulty was experienced in deciding on the exact point at which the blue colour disappeared; since it was found on agitating the liquid a short time after decoloration that the colour was restored and this continued to be the case for a considerable period after its first disappearance.Finding that little dependence could be placed on the disappearance of the blue colour and observing that on reaching this point the sulphide of sodium still gave a copious black precipitate the addition of the sulphide of sodium was continued until the copper was completely precipitated and the following results were obtained :-Quantityof Copper Meaaures of Sulphide CaIcuIated for 10 grains taken. of Sodium taken. of Copper. 9.10 88.3 97.0 9.10 89.4 98*2 9.10 88.6 97.8 9*10 88-4 97.1 12.42 123.0 99.0 13.06 12700 97.2 The same remarks apply to these determinations as to the former series. The wide difference which exists between these numbers and the quantity of sulphide of sodium required after the disappearance of the blue colour to precipitate the whole of the copper naturally led to the inference that some chemical change not hitherto noticed had taken place.The following experiments were consequently made :-1st. A small quantity of a solution of sulphate of copper was diluted with 2 oz. of water containing a considerable excess of' FOR THE DETERMINATION OF COPPER. ammonia and the solution which was of a light blue colow was then boiled; on adding a drop of sulphide of sodium a precipitate mas produced which was almost immediately redissolved the solution changing to a greenish-brown. A second drop of sulphide of sodium produced a similar effect. On allowing the solution to stand five minutes it became perfectly clear its original blue cdour being restored.2nd. To a solution of copper iu all respects similar to the last 3 drops of sulphide of sodium were added with the same effect as before. On the addition of the fourth drop the precipitate ceased to redissolve and subsided in a few seconds leaving the solution still of a brown colour but of a lighter shade. The three next drops of sulphide of sodium each produced the same effect after which it was found that the whole of the copper had been entirely precipitated. 3rd. A solution of copper was taken similar to the last but of double the strength. Two drops of sulphide oi sodium produced no permanent precipitate the solution retaining its original blue colour. The third drop changed the blue colour to a brown.No permanent precipitate was however produced till after the seventh drop but only a darkening of the brown colour. On the addition of the seventh drop a precipitate appeared which after much agitation of the liquid gradually subsided leaving the solution nearly colourless. The eighth drop again darkened the colour of the liquid this effect also disappearing on violent agitation. The ninth drop produced no effect the whole of the copper having been precipitated. 4th. To a similar solution of copper but of four times the original strength four drops of sulphide of sodium were added without changing the blue colour of the solution the precipitate redissolving as soon as formed. The fifth drop produced a greenish-brown tint; but on allowing the solution to stand about half a minute the original blue colour was restored.After the lapse of two or three minutes a sixth drop was added; the precipitate redissolved leaving the solution still brown. On the addition of the seventh drop the greenish-brown tint again made its appearance gradually becoming darker with each successive drop until the fourteenth when a permanent precipitate was first produced. 5th. To a solution of copper prepared as before but eight times the original strength eight drops of sulphide of sodium were F2 BROWN ON A NEW VOLUMETRIC METHOD added before the blue colour changed to a brown and a permanent precipitate was first obtained after adding fourteen drops.In order to ascertain whether the amount of ammonia present influenced the solubility of the oxysulphide of copper these experiments were repeated with a much larger as well as with a smaller quantity of ammonia than usual but with the same results. From these results it is evident that the first quantities of oxysulphide of copper formed are redissolved in the arnmo-niacal sulphate of copper and that the amount so dissolved depends on the quantity of copper in solution. The following experiment mas then made in order to ascertain whether the oxysulphide of copper dissolved without undergoing any change :-To an amrnoniacal solution of coppcr sulphide of sodium mas added so long as the precipitate produced was redissolved; the solution was then boiled and a drop of chloride of mercury added which produced a white precipitate showing that no sulphide existed in the solution.It is evident therefore that oxidation of the sulphur must have taken place which was proved to be the case by the following experiment :-Sulphide of godium was added to an ammoniacal solution of copper until the blue colour was destroyed; the liquid was then agitated by boiling and the clear liquid decanted off it was then acidified with sulphuric acid ; and on boiling a brown precipitate of sulphide of copper made its appearance rendering it highly probable that the sulphur had passed into the state of hypo-sulphurous acid or some of the lower oxides of sulphur. It would appear that the oxysulphide of copper was oxidised at the expense of the protoxide of copper in solution the suboxide being produced; whilst the repeated restoration of the blue colour on agitation of the liquid as already described clearly shows that suboxide of copper exists in solution.This is also further proved by the fact that on filtering an ammoniacal solution of copper to which sulphide of sodium has been added till the blue colour is destroyed the blue tint immediately reappears in the filtrate from oxidation of the suboxide having taken place in its passage through the pores of the filter. In order to show still more clearly that the changes above mentioned take place the following experiment was made :- FOR THE UE’IERMINATION OF COPPER. Sulphide of sodium was added to an ammoniacal solution of copper until the blue colour disappeared.After allowing the precipitate to subside the colourless liquid was decanted off and divided into two portions one of which was acidulated with sulphuric acid and boiled when the brown precipitate before mentioned made its appearance. The other portion was passed through a filter when it was observed that the blue colour immediately reappeared and on acidifying no precipitate was produced; showing that in the latter case by passing through the pores of the filter (which may be considered equivalent to a lengthened agitation) the sulphur had passed horn the lower into the higher oxides and the suboxide of copper into the protoxide. Throughout these experiments the ammoniacal solution of COP-per was boiled previous to adding the sulphide of sodium.The standard solution of sulphide of sodium used was made by dissolving 2 02. of caustic soda in 1 quart of water. This solution was then divided into two equal parts one of which was saturated with sulphuretted hydrogen ; after mixing this saturated portion with the remainder of the solution of caustic soda the whole was placed in a vessel capable of holding one gallon which was then filled with distilled water. It appears therefore that in determining copper by this method the following changes take place :-1st. That a portion of the oxysulphide of copper is oxidised at the expense of the salt of copper in solution the latter being reduced to the state of suboxide and consequently that a considerable quantity of copper must exist in the solution after the disappearance of the blue colour.From the great affinity of an ammoniacal solution of suboxide of copper for oxygen it necessarily follows that agitation of the liquid must give rise to a constant reproduction of protoxide of copper. 2nd. That the sulphur of the sulphide of sodium also passes into solution in the form of hyposulphurous acid or some other low oxide of sulphur thereby lessening the effect which the sulphide of sodium would otherwise produce. It should also be remarked that in adding sulphide of sodium to a solution of suboxide of copper a smaller quantity of sulphur is required for a given amount of copper than in precipitating the prot oxide.These changes in addition to the different composition of the osysulphide of copper produced according to the temperature of BROWN ON A NEW VOLUMETRIC METHOD the liquid at the time of precipitation as stated by Pelouze sufficiently explain the difficulty experienced in obtaining accurate results by the use of this method. The conclusion to be drawn from the above results appears to be that the method of determining copper by means of sulphide of sodium cannot be considered as chemically correct inasmuch as an equivalent of sulphur does not precipitate a constant amount of copper; although it is evident from the great number of determinations detailed by Pelouze that by long practice and skilful manipulation considerable accuracy may be attained as by adhering closely to the same mode of operating in all cases the errors in each must necessarily be nearly alike.A trial was next made of the method proposed by Parkes which is thus described in Mitchell’s Manual of Assaying. “Take a given quantity of pure copper (say 10 grains) place it in a flask and dissolve it in nitric acid add ammonia in excess and then make it into a bulk of 2500 grs. by measure (about 1-thirdof a pint) by the addition of water although this is not absolutely necessary. Dissolve 1ounce (avoirdupois) of pure cyanide of potas-sium free from ferrocyanide or sulphide of potassium in 6 oz. by measure of water; filter if necessary and place the solution in a well-stoppered bottle till required for use. I then ascertain the quantity of this solution of cyanide of potassium required to decolorize the solution of copper by taking a given quantity in any graduated vessel-as a burette-and pour it by degrees into the solution of copper adding the last quantity drop by drop until it is decolorized.This is very easily perceived as there is no precipitate to interfere and the operation is conducted at the ordinary atmospheric temperature.” In the course of the experiments made by this method it was observed that the bleaching effect of the cyanide of potassium was gradual in its operation; and it was found that on allowing an ammoniacal solution of copper to which cyanide of potassium had been added (but not sufficient to destroy the blue colour) to stand for a short time it became completely bleached; the quantity of cyanide of potassium necessary to produce complete decoloratiori being in proportion to the length of time taken in the opera- tion.Under these circumstances the point at which the addition of the cyanide of potassium should cease became a matter of great iincertainty and as this method did not promise more accurate FOR THE DETERMINATION OF COPPER. results than those obtained by sulphide of sodium it was not pursued further. In the course of a number of experiments made with the view of obtaining some other method of determining copper with greater cel‘tainty than either of the preceding the reaction of iodide of potassium upon a salt of copper which results in the production of subiodide of copper and free iodine appeared likely to be available for this purpose.Knowing with what accuracy iodine may be determined by means of sulphurous acid according to the method proposed by Bunsen it seemed reasonable to expect that by determining the amount of iodine liberated by the action of iodide of potassium upon a salt of copper an equal degree of accuracy could be attained in the estimation of copper. Bunsen’s method for the determination of iodine is to add an excess of a very dilute solution of sulphurous acid of known strength and to estimate the amount of sulphurous acid unacted upon by a standard solution of iodine. On calculating the amount of S 0 in this state of dilution required for the determination of 10 grs.of copper I found the quantity would be inconvelliently large and that the use of a stronger solution was not practicable. Whilst endeavouring to obviate this difficulty it occurred to me that the reaction of hyposulphurous acid on iodine which results in the formation of hydriodic and tetrathionic acids might be substituted for that of sulphurous acid; and a number of experi- ments were instituted to ascertain whether this was the case the results of which proved that iodine may be determined by means of hyposulphurous acid with as great a degree of accuracy rn by Bunsen’s method and moreover with the advantage of requiring only one standard solution instead of two and that of a more stable character than a solution of sulphurous acid. The method finally adopted for determining copper is as follows :-Ten grains of copper are dissolved in dilute nitric acid and the solution boiled until free from nitrous acid; it is then diluted with about an ounce of water and carbonate of eoda added until a portion of the copper is precipitated.Pure acetic acid is then added in excess and the solution poured into a flask capable of holding about 12 oz. Allout 60 grains of iodide of potassium are then thrown into the flask and sufficient time having been allowed for the crystals to dissolve a standard solution of hypo- BROWN ON A NEW VOLUMETRIC METHOD sulphite of soda is added until the greater part of the iodine has disappeared which is indicated by the liquid changing from a brown to a yellow colour.A little clear- solution of starch is then added and the addition of the hpposulphite of soda cautiously continued until no further effect is produced. The bleaching effected by the last portions of hyposulphite of soda may be best seen by allowing the drops to fall into the centre of the flask whilst the liquid is in motion when streaks of a lighter colour will beproduced so long as any iodine remains. When the quantity of iodide of potassium employed was less than six times the weight of the copper to be determined satis- factory results were not obtained. Care must be taken that the iodide of potassium employed is free from iodate of potash and that the acetic acid contains no sulphurous acid. Thesolution of starch should be made by boiling with a large quantity of water any undissolved portions allowed to subside and the clear liquid only used.A solution of hyposulphite of soda obtained by dissolving about 4000 grains of the salt in two gallons of water was standardized by means of electrotyped copper. The burette employed was capable of holding 1500 grains of solution each drop corresponding to about 0.006 of a grain of copper. The numbers obtained were as follows :-Qrs. of Copper Measures of Standard CalcuIated to 10 grs. taken. used. of Copper. 8.02 124.6 155.3 7*44 115.7 155.4 7.67 119.2 155.4 8.32 129.4 155-5 Another quantity of standard solution gave the following:-8.38 131.4 156% 8.78 137.5 156.7 Several experiments were made in order to ascertain to what extent the results obtained by this process were liable to error from irregular manipulation or changcs of temperature the same amount of copper (9-10grains) being used in each experiment.In the first the directions above given were strictly observed ; the quantity of standard solution required was 134.4measures. FOR TIIE DETEI~MINX~ION OF COPPER. In the second time mas not allowed for the crystals of iodide of potassium to dissolve before beginning to add the hyposulphite of soda ; the number of measures required was 134-3. In the third the solution of copper was diluted with as much water as could be conveniently contained in the flask ; the number of measures required was 13L.5. In the fourth the solution of copper was as concentrated as possible; the number of measures required was 134.4.In the fifth after adding the crystals of iodide of potassium the solution was shaken up and allowed to stand for a quarter of' an hour before proceeding with the hyposulpliite of soda; the number of measures required was 134.3. In the sixth the operation was conducted at 150' F. ; the number of measures required mas 131.2. The flask in this experiment was observed to be filled with the vapour of iodine. In the seventh the operation was conducted at the temperature of 90' F.; the number of measuresrequired was 134.0. From these experiments it is evident that slight differences in the mode of manipulating do not in any way affect the results so long as the solution is not heated.The presence of tin lead iron or zinc in small quantities is also immaterial. When the alloy in which the copper is to be determined contains a large proportion of lead or iron these metals should be separated previous to the determination of the copper since the yellow precipitate of iodide of lead and the red colour of the acetate of iron render it difficult to distinguish the effect produced by the last quantities of hyposulphite of scda. The following determinations of copper in a number of speci-mens of gun-metal taken from castings at the Royal Gun Factory at Woolwich mill serve to show the accuracy which may be obtained by this method :-Grs. of Metal Measures of Standard Per centage of Copper taken.used. in alloy. 10.13 139.7 90.79 9-99 137.7 90.66 10.54 145.0 90.59 10.46 144.1 90.68 10.09 139.3 90.90 10.52 145.5 91-09 74 GUTHiLIE Grs. of Metal Measures of Standard Per centage of Coppcr taken. used. in alloy. 10.23 141.9 91.32 10.15 140% 91.23 10.52 146.7 91-79 10.40 144.9 91.75 993 1364 (30.48 10.14 139.3 90.42 10.19 141.1 91.21 10.26 142.3 91.36 9.79 136% 89*17 9-82 137.0 89-19 9-96 142.7 90.78 10-05 144.2 90.72 10.00 144.6 91060 10.10 146.2 91.52 It may therefore be safely stated t,hat copper can be estimated with ease and certainty by this method to within or & per cent. and that the method possesses the advantage over those hitherto used of being likely to give similar results in the hands of different rn anipulators.

ISSN:1743-6893    

DOI:10.1039/QJ8581000065

出版商:RSC    

年代:1858

数据来源: RSC

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74 GUTHiLIE IIV.-On the Action of Light upon Chloride of Silver.. BY FREDERICK GUTHRIE,B.A. Ph.D. ASSISTANT IN THE LABORATORY OS' OWEN'S COLLEGE HANCHEBTER. THEblackening produced by light iipon chloride of silver in the moist state was ascribed by Sclieele to the liberation of chlorine and the deposition of metallic silver. He proved that the black- ened mass was only partially soluble in ammonia and that the portion which remained undissolved by this re-agent was soluble in nitric acid. Dan i ell and others considered the blackening to be due to the formation of oxide of silver imagining the clecom- position of the mater present by the chlorine to be accompanied by a corresponding oxidation of the reduced silver. 0them again have supposed the formation of' a subchlorids.ON THE ACTION OF LIGEfT UPON CHLORIDE OF SILVER. 75 The few experiments which I subjoin tend unmistakeably to support the view originally advanced by Scheele. (1.) Two or three grammes of dry chloride of silver were sealed in a glass tube and exposed to direct and diffused sunlight. There was increased tension in the tube. Chlorine was shown by the iodine test to be present in the free state. (2.)A portion of chloride of silver dried at loo' was intro- duced into a perfectly dry tube. The tube being then half-filled with pure and dry benzole and heated until the boiling of the benzole had expelled all the air was hermetically sealed and exposed with agitation to the light. The rapid blackening which the chloride here underwent proved the presence of oxygen to be unnecessary.(3.) Four or five grammes of moist chloride of silver were sealed in a tube. The tube was half filled with water and hermeti- cally sealed. After exposure to the light for ten or twelve days with frequent agitation it was opened the contents thrown upon a filter and mashed with cold water. On adding nitrate of silver to the filtrate a precipitate of chloride of silver was formed. The grey mass on the filter was treated with strong ammonia until the latter ceased to dissolve any more of the unaltered chloride. There remained on the filter a slaty grey body which in the dry state took the metallic lustre under the pestle. This body was solublc in nitric acid not reprecipitable by ammonia but precipitated by dilute hydrochloric acid.The non-precipitatiou of the nitric acid solution by the most gradual addition of ammonia seemed already to point to the absence of chlorine. (4.) About ten grammes of the moist chloride were introduced into a tube of 1+ft in length and 9 in. internal diameter. After adding water and sealing the tube was exposed as before. The supernatant liquid was poured off and the mass washed by decan- tation. The hydrochloric acid was thrown down by nitrate of silver. The chloride of silver was estimated on a weighed filter (dried at 100°C.) Ag C1 = 0.2125 grm. The washed material from the tube was digested with strong ammonia. The slaty-grey residue which subsided leaving the liquid above quite clear was collected upon a weighed filter and washed first with ammonia then with water (dried at 100°C.) Grey substance = 0.1756 grm.76 GUTHR1E This substance assumed the mctallic lustre under the burnislier. It dissolved in warm nitric acid dccomposing the latter. The substance together with the filter was thrown into strong nitric acid after digestion and due dilution it was filtered. The silver was thrown down by dilute hydrochloric acid collected on a weighed filtcr and estimated. (dried at 100OC.) Ag C1 = 0-2254grm. Supposing now the grey substance obtained to have bcen metallic silver it should have given 0.2333 grm. of chloride. The amount actually obtained though too small is yet sufficiently near to the calculated quantity to show that the original chloride of silver subjected to the light had really undergoue decom- position into chlorine and metallic silver.That the chloride of silver obtained from the hydrochloric acid found in the tube on breaking it open was somewhat smaller than that from the silver was probably due to an escape of a portion of the free acid by evaporation during manipulation. (5.) About twelve grammes of the chloride of silver mere intro- duced into a tube; the tube was then half filled with fuming nitric acid sealed and exposed as before. On opening the tube it was found to contain hydrochloric acid. The chloride was found to have undergone a blackening quite as deep as that which had taken place in chloride of silver surrounded by water which was exposed to the same light for the same time.On treating the contents as in experiment (at) there was found Grey substance . . = 0.1643 which gave . Ag C1 = 0.2040 The quantity supposing the substance to have been silver should have been Ag C1 = 0.2183 This is sufficiently near to show that the substance in question was nothing else than metallic silver. (6,) Confirmatory of experiment 5. (7.) The circumstances were as in experiment 5 excepting that the nitric acid employed was more dilute. On treating the contents as in experiment 4 I found Grey substance = 0.2207grm. and this gave Ag C1 = 0.2870 ON THE ACTTON OF LIGHT &C. instead of the calculated quantity Ag C1 = 0.2932 In experiments 4 5 6 the grey substance when dry assumed the metallic lustre under the burnisher.The fact that the chloride of silver was reduced to the metallic state even in the presence of nitric acid was quite unexpected. I found that neither by removing the affected mass from the light and agitating it nor even by warming it was the original white- ness restored. Indeed the silver was only very gradually attacked by boiling nitric acid unless the undccomposed chloride had becn previously removed by the action of ammonia. It seems as if the light in reducing the silver in spite of the nitric acid had thercby thrown it into a more passive state and that only after contact with the alkaline ammonia mas its original basic condition restored. The chloride of silver used in these experiments mas in every instance washed by decantation in order to avoid the presence of organic matter.

ISSN:1743-6893    

DOI:10.1039/QJ8581000074

出版商:RSC    

年代:1858

数据来源: RSC

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ON THE ACTTON OF LIGHT &C. V.-On some Thermo-electrical Properties of the Metals Bismztth and Antimony when used as single elements. BY RICHARD ADIE,LIVERPOOL. I WISH to shew that when bars of bismuth are- cast so as to break with a smooth cleavage surface or with a granular surface they possess different thermo-electrical properties. Also that bars of antimony under similar treatment partake in a lesser degree of the same character. Square bars of bismuth 7 inches long by -15of an inch square were cast in a brass mould which opened along two of the oppo- site diagonal edges of the bar to admit the removal of the casting. Bismuth cast in this mould previously heated to the melting temperature of the metal and slowly cooled broke with a fracture which presented a large shining surface; and when cast in the mould cold the fracture of the bars presented a surface similar to some of the common varieties of cast iron.It was with these two classes of bars that I obtained the differelit results noted in the exper in1 ent s. ATITE ON TIIRRSfO EIAECTItTCALPROPERTIES &C. Antimony bars were prepared in like manner but the frac- ture of those cast at the highest temperatures was never free from the effect produccd by the chilling of the sides of the mould. The results are arranged in the following table. The signs + -are put opposite the bars when they were negative or positive according to the direction in which the heat was made to cross the joint. First Bar. Sign. Second Bar.Sign. Description. Bismuth cast + Bismuth cast + This was a bar broken in of large grain -of large grain -two the surfaces for contact being slightly rounded with a file Heat and electricity crossed the joint in the same direction. Bismuth cast + Bismuth ‘cast + This was a broken bar; the of small grain -of small grain -broken surfaces for contact being rounded. Heat and electricity crossed the joint in opposite directions. Bismuth cast + Bismuth cast + Heat and electricity crossed of large grain -of small grain -the joint in the same direc- tion. Antimony + Antimony + This was a broken bar; the large grain -large grain -broken surfaces rounded. Heat and electricity crossed the joint in the same di-rection. Antimony,fine -Antimony,fine + These were two separate steel-like stecl-like castings.The direction of fracture fracture the flow of heat across the joint did not govern that of the electrical current gene- rated. Antimony + Antimony,fine + Separate castings. Heat large grain -steel-like -and electricity crossed the fracture joint in the same direction. When a thin leaf of bismuth was nipped bctween the two antimony surfaces heat and electricity immediately crossed the joint in opposite directions. I G EhEDB H GaEbEDR vIII.AWzdqe uf .Pu,?z?xs x. M5.P G?&& H 6-a P~ED H G EbBD XVI .7& L@2xmm& G FbEDB H G FbEDB XX. Bz2w-m of Atash. XXll. L5z&duw Zz4?722& . P bE DB bE D A G F-bED G F BEDB H G PbED

ISSN:1743-6893    

DOI:10.1039/QJ8581000077

出版商:RSC    

年代:1858

数据来源: RSC

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THE PRISM IN QUALITATIVE ANALYSIS. VI.-On the use of the Prism in qualitative analysis. BY DR. J H. GLADSTONE, F.R.S. THE ordinary methods of qualitative analysis depend on a system of exclusion. We first determine that the substance analysed does not contain any member of certain large groups but consists of one or more members of certain other groups and these we sub-divide excluding one division after another till we arrive at the individual member or members and these me at length distinctly recognized by special characteristics or perhaps special tests. In this process the indications of colour have hitherto played but a very subordinate part. They have indeed been esteemed most valuable when we come to special charac- teristics or tests but in any previous stage of the process they are not relied on.Thus to take an instance :-if in mineral analysis we meet with a metal not precipitable by hydrochloric or hydro-sulphuric acids but thrown down by sulphide of ammonium as well as by ammonia or potash as a gelatinous oxide soluble in the fixed alkalis the green colour of the oxide at once confirms the conclusion that the metal is chromium; but if we see an unknown salt or mixture of salts of a similar green colour we do not conclude that it contains cliromium nor if we fail to recognize that colour do we necessarily infer that chromium is absent. We know indeed on the one hand tliat there are many other green salts and on the other hand we speak of some of the salts of chromium as not green but red or blue.Now this arises in a great measure from merely observing the colour as it appears to the untutored and unaided eye. It should be remembered that the colour of an object is the resultant of the various rays of the spectrum which it reflects or transmits or perhaps more philosophically of the various rays which it does not absorb. Yet that colour may be produccd by the union of totally different rays ; thus-one substance may appear indigo because it reflects the indigo ray another because it reflects the blue with a little red. This can evidently be determined only by the prism; and in examining the coloured solutions of various salts by that instru- ment I have been led to the conviction that chromatic phenomena may be relied on in analysis to an extent which I think has been GLADSTONE ON THE USE OF rarely if ever suspected.There is this advantage too in such a mode of determining the character of a body that not a particle of it need be used up in the analysis nor altered or destroyed by the addition of reagents-a matter of no slight importance when we have to deal with organic compounds or valuable mineral substances. Mr Pesr sall and perhaps others have used the prism with success in particular cases ; Professor Stokes has claimed for it a place in the laboratory;* and it is to draw the attention of chemists still more decidedly to this mode of analysis and to lay down some gerieralized observations that I have written the present paper. The use of the prism is not difficult.Many different methods may be pursued. Professor Stokes examines the chromatic effect of some metallic oxides by fusing them with a bead of micro- cosmic salt and ‘‘viewing through a prism the inverted image of the flame of a candle formed by the bead the latter being so held as to be seen projected on a dark object.”Jy In examining a powder or small crystal I have found the following plan answer :-A plate of glass is held in the sun-light in such a position that few if any rays are reflected by its surface to the eye while through it is seen a piece of black cloth or paper in the shade. On the glass is then placed a thin line of the powder or a small crystal or two which mill of course appear brightly illuminated against a dark ground.By viewing this through a prism the line of powder will be expanded into a ribbon or the crystal into a broad image which by its varied colours will show what rays are reflected. Another way of examining a solid substance is by looking at it with a prism through n slit in a black card. But these are inelegant and inexact methods of observation as com- pared with what is practicable when liquids are examined We have then to deal especially with transmitted light. The common method is to view by a prism a slit in the window shutter seen through a glass vessel containing the liquid; but this method generally fails to give intelligible results unless attention be paid to the strength of the solution and the thiclmess of the stratum * Since the above was written my attention has been called to the fact that Mr.Talbot (Ed. Journ. Sci. v 77 and Phil Mag. iv 114 and ix 3) and Mr. Crookea have recommended the prism as a means of distinguishing the different flames given by metallic salts; but this plan of procedure though doubtless very accurate in certain cases is of limited and. difficnlt application. -i. Phil. Trans. 1852 p. 522. THE PRISM IN QUALITATIVE ANALYSIS. through which the ray passes ;for in most cases the different rays of light are not absorbed immediately on their entering a liquid but when they have penetrated it to a greater or less distance and they disappear not suddenly but by becoming gradually fainter and fainter. Hence for holding the solution I am in the habit of employing not a vessel with parallel sides but a hollow wedge of glass held in such a position that the slit in the window-shutter is seen traversing various thicknesses of the liquid from the thinnest possible film to a stratum of perhaps three-quarters of an inch in thickness.This line of coloured light does not then appear uniform as will be at once foreseen it varies in intensity from almost pure white to a deep shade ;and it frequently displays variations of a much more unexpected character being of a totally different coloiir in one part to what it is in the other ;for instance blue at one end of the line and red at the other every shade of purple intervening. When this colourcd line of light is analysed by a prism very remarkable appearances often present themselves the whitish portion of‘ the line where the light traverses very little liquid will be expanded into a ribbon differing but little from the spectrum given by unaltered light; but as the line is viewed through deeper and deeper portions of liquid some rays are seen to diminish in intensity others gradually to die out while others again almost immediately disappear giving place to perfect darkness.If the prism be a tolerably good one the slit narrow and the day not too dull the most visible of “Fraunhofer‘s lines” will be readily seen running like black threads along this coloured ribbon and serving to mark with perfect accuracy what rays are transmitted and what absorbed. The appearances thus presented to the eye can be easily transferred to paper thus giving at one glance the optical character of the rays which penetrate every different thickness of the solution.From the numerous observations I have made in this manner it may be laid down as a general rule that aZl the compounds of a partieular base or acid have the Same efect on the rays of light. Occasionally but very rarely a glaring exception occurs ;and much more frequently there are certain variations in degree-the same rays being absorbed but to a slightly different extent as compared with one another. This truth has been partially recognized for a long time thus every chemist knows that the salts of nickel are green and those of zinc colourless ;but there are other cases in which it is not so a GLADSTONE ON THE USE OE evident-in fact where apparent exccptions occur.Some of these anomalies are here discussed. Chromium XaZts,-It has been already stated that some salts of chromium are called not green as the generality are but red or blue. This remark applies to both solid and dissolved salts. Yet when these various-coloured solutions are examined in the way described above they all give the same or very nearly the same spectrum and that a very characteristic one. See Fig. 1. The thinnest stratum of liquid suffices to cut off all the yellow rays and nearly all the indigo and violet as the thickness increases the transmitted light appears more and more con-centrated about two points the one at the least refrangible end of the spectrum the other between the lines F and b.It is there of a bluish green tint and is at first supported on either side (if such an expression may be allowed) by blue and by yellowish green which however soon disappear leaving it also gradually to be absorbed while the red which was at first accompanied by orange passes through the deep liquid alone and with almost undiminished brilliancy. The result of this great penetrating power of the red ray as compared with the green and blue is that the chloride nitrate sulphate sulphocyanide and other salts of chromium which appear green in tolerably dilute solution appear red when we look through a strong or a very deep solution. This circumstance has been noticed by Schretter and others and has been explained by Sir John Herschel,* who gives the name of dichromatism to the phenomenon.Now the acetate though it absorbs the same rays as the above-mentioned salts does not transmit the green so readily; hence it appears usually red and it is only in very thin or weak solution that it assumes the green appearance while the I‘ red potassio-oxalate ” absorbs the green so speedily that that colour never preponderates and the thinnest stratum never approaches it nearer than a bluish red. Yet these present a pris- matic appearance scarcely distinguishable from that of the salts previously described. Again there are two apparently isomeric modifications of some chromium salts which differ in colour as well as in chemical properties.Thus it is the blue and not the green sul- phate,? that combines with sulphate of potash to form potash * Ed. Phil. Trans. Vol. ix. Berzelius and Bchretter have both proved this. THE PRISN IN QUALITATIVE ANALYSIS. chrome alum but this double salt though it appears so unlike one of the green compounds to the unaided eye gives the same peculiar prismatic appearance. The blue potassio-oxalate,” also though the thinnest stratum of its solution is a faint bluish purple exhibits the same two maxima of transmission the only perceptible difference being that the blue space near F if; very brightly illu- minated. An easy method of observing these two modifications is to take an ordinary green solution of nitrate of chromium divide it into two parts and boil one of them for a few minutes with an excess of nitric acid.When cool again the contrast between the two by daylight will be very great the one a deep green the other a bluish purple; but if examined in the way described above they will present very nearly the same prismatic appearance the only difference being that the acid solution transmits more light at least more of the red and blue rays. Thus the various chromium salts though optically very different to the unaided eye present almost exactly the same appearance and that a very characteristic one when examined in the manner suggested. Cobalt Salts.-We are accustomed to speak of blue and red salts of cobalt; but this difference depends really on the state of hydration and the prism reveals an analogy otherwise unsuspected between the two colours.The chloride and other salts when anhydrous are blue. Alco-holic solutions of the chloride and acetate are also blue. The chloride and other salts when hydrated whether in the crys- tallized condition or actually dissolved in water are red. The only exception to this with which I am acquainted is the sulphocya- nide which crystallizes of a magnificent blue and gives a saturated aqueous solution also of a blue colour. The addition of more water however gradually changes this to the same red as any other solution of a cobalt salt ; while the subsequent addition of alcohol restores the blue colour to a greater or less degree. A blue salt of cobalt such as smalt blue glass or an alcoholic solution of the chloride is dichromatic and if the light reaching the eye has traversed a sufficiently large quantity it appears red.The alcoholic solution examined in the manner described above exhibits a very remarkable appearance. It is represented in Fig. 10. The extreme red ray pefietrates with the greatest facility indeed it is much more visible where the stratum is thick than where it is thin because in the latter case the neighbouring orange G2 GLADSTONE ON THE USE OF by its great luminosity renders it almost imperceptible. Imme-diately succeeding this narrow red ray is a thin space of perfect absorption followed by auother red ray which penetrates a short distance and by the orange which penetrates a little farther.Then coincident with the line D but considerably broader is a space of absolute blackness while the rays between it and E advance far into the liquid yellow and bright green. The suc- ceeding rays till near F are greatly reduced in brilliancy on their first entering the liquid yet they succeed in penetrating it to a considerable distance as a faint bluish green. The blue rays are admitted very readily the indigo still more so and the violet advances further yet into the liquid the lines F d and G being very discernible. A red solution of a cobalt salt gives the appearance represented in Fig. 11. The red and orange rays are transmitted with the greatest ease the line D is strongly marked the yellow penetrates not quite so far while the rays between E and F are very faint though they are not soon wholly absorbed ;the blue passes readily and the indigo and violet show a constantly increasing power of penetration.The lines d and G are very distinct. On comparing the prismatic appearances of these two classes of cobalt salts it will be at once perceived that both the anhydrous and the hydrated salts transmit the extreme rays of each end of the spectrum most freely. They are analogous also in the faint greenish blue which penetrates for some distance though with but feeble luminosity between E and F. Through a strong and deep solution of either the red ray alone passes. There are how- ever some equally well marked points of contrast the orange ray is almost immediately absorbed by the blue salt but is transmitted with the greatest facility by the red; and the maximum of absorp- tion is in the one case about B and in the other about F.Copper Salts.-Anhydrous copper salts present a variety of colours hydrated crystals or solutions are generally blue but sometimes green; yet the green salts themselves become blue when dissolved in a sufficient amount of water. Alcoholic solutions not merely of the green chloride but of the blue acetate are green. When examined by the prism they give the appearance delineated in Fig. 5. A thin stratum even of a very dilute solution cuts off at once the least refrangible red rays and the whole of the more refrangible half of the spectrum. The rays from a little before D to a little before F are transmitted THE PRISM IN QUALITATIVE ANALYSIS.and penetrate indeed with almost undiminished luminosity through a very great thickness of solution appearing to the eye of an almost uniform bright green colour. At first they are accompanied on either side by a little red and blue but these are soon absorbed. This description applies equally to a saturated aqueous solution of the chloride. The blue salts of copper and all aqueous solutions if sufficiently diluted give an appearance not differing widely from the normal spectrum. The rays about the blue portion are admitted very freely while those at each end are partially but not wholly absorbed. They differ considerably in the extent to which these other rays are suppressed; the consequence of which is that solu- tions of some salts for instance the acetate appear of a much deeper blue than solutions of other copper salts though of cor- responding strength.Fig. 13 is taken from the acetate. Most if not all double salts of copper (as for instance the double sulphate of copper and potash or ammonia,) are nearly identical with the simple salt both in the eharacter and intensity of thecolour. The true ammoniacal salts of copper which appear so intensely blue must be distinguished from these as they appear to contain the copper in some state of combination with the elements of ammonia and they give a very different prismatic appearance. The maximum of absorption is about .D,the red and the green rays are transmitted a short distance while the indigo violet and still more refrangible invisible rays are suffered to pass most freely.Ferric Xalts.-Au examination of the various ferric salts is very instructive in respect to the limits within which there may be diversity in the action of different compounds of the same base on the rays of light. It is well known that they are for the most part red yet there is an immense difference in the degree of redness exhibited by different salts when dissolved. Thus the nitrate is almost colourless unless in strong solution; the acetate is vastly redder; while the meconate and sulphocyanide are most intense in their colour. Yet the ferric chloride is orange-yellow and a solution of the citrate sometimes appears green. In all these cases however there is an absorption more or less complete of all the more refrangible rays leaving the least refrangible to penetrate almost any thickness withoiit much diminution.This great transmissibility of the red ray causes GLADSTONE ON THE USE OF those salts which appear of another colour in dilute solution to be dichromatic. On closer inspection several groups of ferric salts may be dis- tinguished ; all of which however agree in this permanence of the extreme red. 1. Those ferric salts which are red at any thickness for instance the sulphocyanide. An extremely thin film of a strong aqueous or alcoholic solution of this compound permits all the rays of the spectrum to pass; but suddenly all are cut off except those less refrangible than the line D and after awhile the extreme red alone penetrates.See Fig. 14. If a weaker solution of ferric sulpho-cyanide be examined there will be observed a tendency of the blue ray to manifest itself ;for this salt as is well known is altered by the addition of water. See Fig. 15. 2. Solutions of the ferric chloride and citrate give the same prismatic spectrum at least as far as configuration is concerned though they appear very different to the unaided eye. The chloride is of an orange-yellow and whether the solution be strong or weak deep or shallow it appears of very nearly the same tint and depth of shade. The citrate on the contrary if little be presented to the eye at once is green; if more it is warm brown; if still more red. In each case the prism shows that all the rays from the least refrangible to E are freely transmitted ;at b the blue begins to fringe the green but it is soon absorbed; while every ray beyond that is cut off absolutely the violet by even a thin stratum of a very dilute solution.See Fig. 6. There is a difference as will be anticipated between the intensity of the rays transmitted by these two salts the chloride admits the orange and yellow to almost any distance with apparently undi- minished luminosity ; while the citrate transmits the green rays subduing the intensity of the others to such a degree that the yellow space at least appears green also. 3. The compounds of ferric oxide with meconic acid and its derivatives form a very distinct group. The meconate itself is dichromatic appearing red en masse but of a peach-blossom colour when in a very thin stratum.The prismatic appearance is given in Fig. 16. The red and orange rays are transmitted freely the yellow and green are rather soon absorbed; about F no ray mhat-ever enters the solution but the more refrangible are admitted gradually fade mid disappear all at about thc same distance and THE PRISM IN QUALITATIVE ANALYSIS. a7 rather abruptly. The comenute of iron gives a prismatic appear- ance which is almost identical see Fig. 17; but the more refrangible half of the spectrum is not so luminous I think; and the indigo ray penetrates farther than its neighbours. The maximum of absorption is about half may between b and F. The ferric pyromeconate appeared indistinguishable by the prism from the comenate.There are two compounds of comenamic acid and ferric oxide the one affording an intense red the other a still more intense purple solution. Yet different as these are to the unaided eye they give the same configuration of spectrum when examined with a prism and this configuration differs from that of the comenate only in the same manner as the latter differs from that of the meconate. It is represented in Fig. 18. The acid comelaamate which is red transmits the red orange green and blue as its congeners do but allows the violet to penetrate farther even than the indigo. The basic cornenamate,which is blue-purple in thin and red-purple in thick stratum transmits the same rays as the acid salt; but the luminosity of the more refrangible half of the prismatic appearance is much greater and it penetrates farther.The ferric gallate ferrocyanide and ferridcyanide are perfectly different to other salts of the same base in their action on the rays of light. Chrornates,-It is well known that chromic acid and its com-pounds are all highly coloured but that the colour is not the same in dl cases; yet the prism while it indicates a perfect differ-ence between the compounds of chromic oxide and those of chromic acid exhibits a close analogy between the various chromates. Thus bichromate of potash is red while the neutral chromate is yellow; but a glance at Figs. 19 20 will show that their prismatic appearances bear a certain analogy.The red salt in thin stratum permits the least refrangible half of the spectrum to pass but cuts off at once every ray more refrangible than F; as the stratum of liquid increases it absorbs the slight amount of blue and thc red also until nothing is visible except a bright band of orange and yellowish green extending equal distances on each side of D but not quite including either Bor E. The yellow salt admits a somewhat wider spectrum as seen through the hollow wedge it presents an uniform band of light extending the whole length and consisting of the ordinary spectrum as corn- GLADSTONE ON THE USE OF prized between A and F; only when it is very thin a little more bhie and red appear. Both chromic acid and bichromate of silver though red in the solid state give orange-yellow solutions and prismatic appearances alnnost identical with that presented by yellow chromate of potash.Litmus.-As an instance from the organic world litmus may be selected. Every tyro in chemistry is familiar with the fact that this substance is blue when neutral more blue when alkaline red when acid and of a peculiar wine-red colour when affected by either carbonic or boracic acid. Now the prismatic appearances presented by these differently coloured kinds of litmus are only modifications of a common type. If a neutral solution of litmus be placed in the hollow wedge its dichromatic character becomes at once evident the thin por-tion appears bhne the thick portion red while every shade of purple intervenes.If a line Qf light passing through these various thick- nesses be examined by a prism it shows that the red penetrates any distance almost unchanged that the orange is more readily absorbed that the rays a little less refrangible than D are absolutely stopped that the green is transmitted to a considerable distance and is very luminous that the blue is transmitted not quite so far and the indigo and violet are still more quickly absorbed. See Fig. 21. If to this solution of litmus an alkali whether fixed or volatile be added the passage of the red yellow green and violet rays is little if at all affected but the liquid becomes more opaque to the orange ray and far more transparent to the blue and indigo. See Fig. 22. The extent to which this alteration takes place depends on the amount of alkali present.If to the solution of neutral litmus boracic acid be added it manifests its presence by causing the indigo and violet to be more freely transmitted than even the blue but besides this it produces little change. See Fig. 23. If however an ordinary acid be mixed with the litmus a more exten- sive alteration is effected the maximum of absorption takes place not in the yellow but in the bluish green space about midway between 6 and F the red and orange rays are transmitted with the greatest readiness the yellow less rendily the green is speedily absorbed while the blue indigo and violet though faint penetrate some distance into the liquid. See Fig. 24. The transparency of this solution to the more refrangible part of the spectrum depends THE PRISM IN QUALITATIVE ANALYSIS.on its degree of acidity; indeed if very slightly acid a thin stratum of litmus appears of a light bluish purple. Salts each constituent of which is co1oured.-When two bodies combine each of which exerts an influence and a different influence on the rays of the spectrum it might be expected at the first thought that the resulting colour would be the colour of the first constituent plus the colour of the second constituent ;but a moment’s reflection will show that this cannot be the one con- stituent mill absorb certain rays and the other certain other rays and the salt itself will transmit only those rays which are not absorbed by either or in other words those rays which are trans- mitted by both.Thus the resulting colour may sometimes to the unaided eye bear no kind of relation to the original colours. As an instance acid chromate of chromium may be taken. This salt compounded of two substances which give respectively yellow and green solutions is not a bright green but a brownish red yet this is just what theory requires as will be evident on noticing the rays not absorbed by either Fig. 1 or 19. And even where the combination of the two substances does give the reputed resultant of the two original colours as in the chromate of copper (Fig. 9) which is yellowish green the resulting colour really does not con- tain the whole of either of the original prominent tints but is due to the rays that lie between them and are common to both.Compare Figs. 13 and 19. This persistence of the chromatic effect of substances with whatever they are combined renders it sometimes impossible to decide whether two coloured constituents have combined or not; thus on mixing permanganate of potash with ferric chloride we still see the very remarkable series of bands that characterizes the first of these solutions (Fig. 12) and the complete absorption of the blue caused by the second (Fig. 6) but there is nothing in this circum- stance either to prove or disprove the formation of permanganate of iron. Nor does the fact that the mixture of the blue perman- ganate with the yellow ferric salt has produced a red solution afford any indication of a chemical change; that colour might be and indeed mas anticipated from a consideration of what rays were absorbed by each.Indeed if blue sulphindigotate of potash be mixed with yellow chromate of potash the resulting colour is likewise red and not green although certainly no combination has taken place between them. How easily might a chemist be GLADSTONE ON THE USE OF misled and suppose that the unexpected colour indicated the production of a new substance ! This examination of apparent exceptions to the general rule that “all the compounds of a particular base or acid have the same effect on the rays of light,” shows that even in these cases the rule still holds good or at least that the differences are only modi- fications of a common type.The following conclusions of practical value in analysis may be drawn 1. When the light transmitted by a coloured solution of unknown composition is examined by a prism little can be inferred from the fact that a particular ray is absorbed unless indeed we happen to recognize some of those very peculiar black bands which characterize certain bodies as the permanganates ; but from the fact of a particular ray being transmitted we may con-clude as almost certain that none of those bodies which in ordinary combination absorb that ray are there present in any kind of combination. 2. Beside this negative inference we may frequently arrive at a positive conclusion. It is a rare circumstance that the mere colour of a solution will inform even the most experienced eye of what it is that imparts the colour; but directly it is examined by the hollow wedge and prism some familiar spectral appearance may be recognized which cannot be mistaken and is at once dis- tinctive.Thus suppose we have an inorganic salt which gives a green solution it may be a compound of nickel or of protoxide of iron or of uranium of sesquioxide of chromium or possibly of copper of ferric oxide or of the protoxide of molybdenum or it may be a ferridcyanide or a compound salt such as chromate of copper. True these greens are not all alike to the unaided eye but the differences of their character are not easily described or remem-bered ;but let the prism be applied to them and they are at once distinguished and that without losing a drop of the solution.The different appearances are represented side by side in the plate viz. Figs. 1to 9. Fig. 1. A salt of sesquioxide of chromium in weak solution. Already described. Fig. 2. A salt of nickeI. A spectrum in which the extreme ends the red and violet are soon cut off while the whole middle porticn is transmitted without change. THE PRISM IN QUALITATIVE ANALYSIS. Fig. 3. A protosalt of iron after being exposed for a short time to the atmosphere. The pale bluish green solution of a pure ferrous salt admits all the rays freely but the most refrangible are reduced in intensity. Fig. 4. A protosalt of uranium. These remarkable absorption bands were pointed out first by Stokes. Fig. 5.Green chloride of copper. Already described. Fig. 6. Citrate of the sesquioxide of iron in dilute solution. Already described. It differs from the copper salt principally in the constant presence of the red ray. Fig. 7. Green chloride of molybdenum. Similar to the chloride of copper but transmitting red for some distance and a larger amount of blue. Fig. 8. A ferridcyanide. The potassium-salt (the only one examined) appears green except in very deep solution when it is red the prismatic appearance of thin strata resembles that of citrate of iron but afterwards absorption takes place of the rays just beyond D,and those more refrangible are gradually absorbed afterwards till at last the rays between E and b alone penetrate; then these disappear and the spectrum between A and D passes onwards alone.Fig. 9. Chromate of copper. The yellow and green are con- stantly transmitted ; the red and orange are gradually absorbed; the more refrangible half of the spectrum is cut off at once. These observations Till be sufficient to prove that the varying chromatic phenomena exhibited by different substances may be taken advantage of in qualitative analysis to an extent which has been hitherto unappreciated. My remarks have been almost confined to transmitted light ; but the phenomena of reflected light offer a similar and as yet almost unoccupied field of inves- tigation. What 1 have here marked down must be considered rather as a tentative inquiry than as a really valuable contribution to our knowledge of the effect oi different chemical substances on the rays of light; but should any one be induced to take up the matter systematically he might easily make such a series of obser-vations as would furnish data for regular tables of comparison and the prism would then take its place as the blow-pipe does now among the recognized and almost indispensable instruments of the analytical laboratory.

ISSN:1743-6893    

DOI:10.1039/QJ8581000079

出版商:RSC    

年代:1858

数据来源: RSC

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PROCEEDINGS AT THE MEETINGS OF THE CHEMICAL SOCIETY. January 19 1857. Dr. MILLER, President in the Chair. The following donations were announced :-‘‘ The Pharmaceutical Journal :” from the Editor. ‘‘ The Journal of the Society of Arts :” from the Society. ‘‘Memoirs of the Academy of Sciences of Madrid :” fiom the Academy. A paper wasread :-“On the Composition of Wheat Grain and its products in the Mill with some observations on Bread:’’ by J. B. Lawes Esq. and Dr. Gilbert. February 2 1857. DR. MILLER,President in the Chair. The following donations were announced :-I( The Journal of the Society of Arts :” from the Society. ICThe Journal of the Photographic Society :” from the Society. “The Pharmaceutical Journal :” fiom the Editor.The following gentlemen were elected Fellows of the Society :-Cornelius H anbury Esq. Plough Court Lombard Street. John Jones Esq. Duffryn Chemical Works Riscn. Thornton John Herapath Esq. Bristol. Francis Thirkill Conington Esq. C.C.C. Oxford. PROCEEDINGS OF THE CHEMICAL SOCIETY. Papers were read :-“ On Alum in Bread and its Detection:” by E. H. Hadow Esq. On the use of the Prism in qualitative Analysis:” by Dr. J. H. Gladstone. February 16 1857. Col. PH I L I P YOR KE Vice-president in the Chair. The following gentlemen were elected Fellows of the Society :-Rev. John Barlow M.A. F.R.S. 5 Berkeley Street. Thomas William Burr F.R.A.S. Gresham Villa Highbury. Henry Hancock Jun. Esq. 59 Harley Street. Papers were read :-(( On the valuation of Nitre,” by Messrs.Abel and Bloxam. (( On the Thermo-electric properties of various Metals in refer- ence to the direction in which Heat and Electricity cross their Joints :” by R. Adie Esq. (‘Note OIL Crystallized Binoxide of Tin:” by F A. Abel Esq. “On the temperature of Charcoal while traversed by an Electric Current :” by R. Adie Esq. The Chairman declared the names of the Officers and Members of Council who retire from office at the approaching Anniversary Meeting in accordance with the bye-laws; and of the Officers and Members of Council recommended by the Council for election. March 2 1857. Dr. MILLER,President in the Chair. The following donations were announced :-‘‘The Pharmaceutical Journal :” from the Editor. ‘(The Journal of the Photographic Society:” from the Soci&y.The Proceedings of the Royal Society :” from the Society. PROCEEDINGS OF THE CHEMICAL SOCIETY. “The London University Calendar :” from the University. “The Journal of the Franklin Institute :” from the Institute. ‘I The American Journal of Science and Art:’’ from the Editors. Dr. B. Winstone 7 Ely Place; and Dr. George Harley University College were elected Fellows of tbe Society; and Dr. Frederick Dupr6 53 Burton Crescent was elected an Associate of the Society. A Discourse was delivered entitled “A Report on recent Patents connected with the Reduction and Purification of Iron and its Conversion into Steel:’’ by F. A. Abel Esq. Director of the Chemical Establishment of the War Department.March 16 1857. Dr. MIL LE R President in the Chair. The following donations were announced :-Dr. Miller’s “Elements of Chemistry Part 3 (Organic Che- mistry) :” from the author. ‘‘The Journal of the Franklin Institute :” from the Institute. ‘‘The Journal of the Society of Arts :” from the Society. William J. Dent Esq. was elected a Fellow of the Society; and Jo.hn Spiller Esq. and Edwin 0. Brown Esq. were elected Associates of the Society. A paper was read:- “On circumstances tending to disguise the presence of various Acids and Bases in Chemical Analysis:” by John Spiller Esq.

ISSN:1743-6893    

DOI:10.1039/QJ8581000093

出版商:RSC    

年代:1858

数据来源: RSC

摘要:

INDEX A Abel F. A. note on crystallised bin-oxide of tin 119. Abel F. A. Report on recent patents connected with the reduction of iron and the manufacture of steel 125. Abel F. A, and C. L.Bloxam on the valuation of nitre 107. Acetate of Allyl 322. Acid anchoic 169. -anisic on the action of sulphuric acid on by L. Zervas 211. -anisic preparation of 212. -butyric a product of the oxida-tion of Chinese wax by nitric acid 178. -caprglic a product of the oxida-tion of Chinese wax by nitric acid 178, -carbonic estimation of by abeorp-tion with potash 258. -quantity of produced by res-piration of animals 252. -table showing the distribution of in dwelling rooms &c. 269. --table showing the results of deterniinationa of in various loca-lities 268.--volumetric estimation of atmos-pheric by MatxPettenkofer 289. -chlorohydrated sulphuric 99. -_ citric action of in modifj-ing the reactions of various acids and bases 112. -disulphanisolic 217. -disulphophenic 218. -__ ethylotrithionic 38 60. -hydriodic formation of the crys-talline compound of with phosphu-retted hydrogen by A.W. Hofmann 210. -margaric in human excrements 166. -methylodithionic 245. -nitric action of on aporetin 305. --action of on Chinese wax 167. -pimelic a product of the oxidation of Chinese wax by nitric acid li5. -racemic retardation of the preci- pitation of sulphate of baryta by 117. -stearic in human excrements 163. -suberic a product of the action of nitric acid on Chinese wax 174.Acid sulphallylic 321. -sulphanisic 214. -snlpho-salicylic 218. -sulphuric on a compound obtained by the action of fuming on chloride of phenyl by L. Hutchings 102. -on compounds obtained by the action of anhydrous on the chlorides of hydrogen and ethyl by R. W i 11 i a me son 97. -on the action of on anisio acid by L. Zervas 211. -tartaric prevention of precipitation of various substances by 117. Acids and Bases on some remarkable circumstances tending to disguise the presence of various in chemical analy- sis by John Spiller 110. -_ organo-thionic on a new series of, by J. T. Hobson 55 243. -volatile present in the distillate from Chinese wax and nitric acid 177. Ad i e R.on some thermo-electric pro-perties of the metals bismuth and anti- rnonywhen used as single elements 77. Agriculture on the application of sewage to by D. Campbell 272. Air volumetric estimation of carbonic acid in the by M. Pettenkofer 292. Alcohols on a new class of by A. C a-hours and A. W. Hofmann 163. Algodonite on by F. Field 289. Allotropic chloride of silver 242. Allyl acetate of 322. -benzoate of 322. -butpte of 322. -cyanate of 323. -iodide of 317. -oxalate of 321. -sulphide of 320. -valerate of 322. Allylamine 325. Allylammonias 324. Allylic alcohol 328. Allylic mercaptan 320. Allyloxamethan 3 21. Allyl-potassium-alcohol 319. Allyl-urea 323. Alum in bread and its detection byE A. H a d o w 103.Amido-phenol 207. Ammonium anchoate of 170. 390 INDEX. Analysis on some remarkable circum-stances tending to disguise the presence of various acids and bases in by J oh n S piller 110. -on the use of the prism in qualita- tive by J. H. Gladstone 79. Anchoate of barium 170. -of potassium acid 171. --neutral 173. -of silver 169. Anchoates of ammonium sodium zinc copper lead mercury and ethyl 173. Antimony modification of the reactions of by citric acid 126. ‘ -,thermo-electric properties of 77. Aporet.in action of nitric acid on 305. Appendix to Lawes’ and Gilbert’s paper (p. 1.) “ On some points iu the composition of mheat-grain,” &c. 269 Arsenic modification of the reactions of by citric acid 116.Ash of wheat-grain analysis of 17 Atmosphere of dwelling houses some chemical facts respecting the by H. E. Roscoe 251. Balance-sheet of the Chemical Society 1856-7 190. Barium anchoate of 173. -sulphanisate of 214. IkL-ryta ethylotrithionate of 59. I_ methylodithionate of 246. -prevention of the precipitation of by citric acid 112. Beef on the juice of by C. L. Bloxam 153. Bessemer’s process for the manufac- ture of iron 142 151. Binoxide of tin note on crystallised by P. A. Abel 119. Bismuth modification of the reactions of by citric acid 116. -thermo-electric properties of 77. Bistearate of soda in human excrements 164. Bloxam C. L. on the juice of beef 153. Bloxam C. L.,and F. A. Abel on the valuation of nitre 107.Bread on alum in and its detection by E. A Hadow 103. -on some points in the composition of wheat-grain its products in the mill and by J. B. Lawes and J. H. Gilbert I 269. -table showing the composition of and the quantity obtained from dif- ferent samples of flour 42. -table showing the composition of wheaten 271. Bromide of silver 241. Bromine Reparation of from iodine and chlorine 234. B r o w n E. O. on a new volumetric method for the determination of coy-per 65. Buckton G. B. on some of the pro-ducts of the oxidation of Chinese wax 166. Burlington House negociations respect- ing the occupation of by the Royal LinnEau and Chemical Societies 180. Butyrate of allyl 322. Benzoate of allyl 322.C. Cadmium modification of the reactions of by citric acid 116. Cahours A. and A W. Hofmann on a new class of alcohols 316. C a m p b e 11 D. on the application of sewage to agriculture 2i2. Chinese wax action of nitric acid on 167. -on some of the products of oxida-tion of by 0. B. Buckton 166. -volatile acids present in the dis- tillate from and nitric acid 177. Chloride of phenyl on a compound ob-tained by the action of fuming sulphu- ric acidon byL. Hutchings 102. __ of silver crystallised or allotropic 242. -I -on the action of light on the by F. Guthrie 74. Chlorides of hydrogen and ethyl on compounds obtained by the action of anhydrous sulphuric acid on the by R. Wiliamson 97. Chlorine separation of from bromine and iodine 234.Chlorobromide of silver 239 240. Chlorohrdrated sulphriric acid 99. Chlorosulphate of ethyl 100. Chromates chromatic phenomena of 87. Chromium modification of the reactions of by citric acid 113. Chromium-salts chromatic phenomena of 82. Chrysophane preparation of 300. -properties of 302. Cobnlt-salts chromatic phenomena of 83. Cobalt modification of the reactions of by citric acid 114. Copper arichoate of 173. -cthylotrithionate of 63. -rnetliglodithionntc of 250. modification of the reactions of by citric acid 116. INDEX. 391 Copper on a new volumetric method for the estimation of by E. 0. B row n 65. -remarks on the action of heat on gold and on its alloy with by J.Napier 289. Copper-salts chromatic phenomena of 84. Crystallised chloride of silver 242. -iodide of silver 243. Cyanate of allyl 323. D. De la Rue Warren and H. Miiller, on some constituents of rhubarb 297. Dial1 ylamine 326. Diallyl-urea 324. Didymium on an optical test for by J. H. Gladstone 219. Diffusion of gases through brick and mortar walls 256. Dwelling-houses some chemical facts re- specting the atmosphere of by H. E. Roacoe 251. Dwelling-rooms distribution of carbonic acid in 269. Em Emodin 304. Ether; ethylotrithionic 63. Ether methylodithionic 249. Ethers allylic 3 19. Ethyl anchoate of 173. Ethyl and hydrogeu on compounds ob- tained by the action of sulphuric acid on thechlorides of by R.William-son 97. Ethyl chlorosnlphate of 101. -methylodithionate of 249. Ethyl-allyl-urea 323. Ethylotrithionate of baryta 59. -of copper 62. -of ethyl 63. -of silver 61. -of soda 63. -of zinc 58. Ekhylotrithionic acid 59. -ether 63. Excrements on the fatty matters of human in disease by W. Marcet, 163. F. F8rrio salts chromatic phenomena of 85. F i e 1 d F. on algodonite a new mineral containing arsenic and copper 289. -on the separation of iodine bromine and chlorine and the comparative de- gree of aEnity of these elements for silver with Borne analyses of their com-binations with that metal occurring in Chili 234. Flesh on a new base from the juice of by A. Strecker 121. Flour percentage of gluten in 48.Food composition of standard article8 of 53. G. Garlic esBence of 320. Gaseous diffusion through brick and mor-tar walls 256. Gerhardt Charles obituary notice of 187. Gilbert J. H. and J. B. Lawes on some points in the composition of wheat-grain its products in the mill and bread 1 269. Gladstone J. H. on an opticaltest for didymium 219. -on the use of the prism in quali- tative analysis 79. Gluten percentage of in different fiour0 48. Gold modification of the reactions of by citric acid 117. -mmarks on the action of heat on and its alloy with copper by J. Na-pier 229. Grape-sugar prevention of precipitation of sulphide of manganese by 117. Gu rlt ’s process for the manufacture of iron 132 151.Guthrie F. on the action of light on the chloride of silver 74. Had o w E. A. notes on alum in bread, and its detection 102. H obso n J.T. on a new series of organo- thionic acids 55. Hof m ann A. W. contributions towards the history of thialdine 193. -Miscellaneous observations 1. On nitrophenol 203. 11. On a new mode of forming tri- ethylamine 208. 111. Formation of the crystalline com- pound of hydriodic acid and phosphuretted hydrogen 210. Hofmann A. W. and A. Cahours on a new class of alcohols 316. Hutchings L. on a compound ob-tained by action of fuming sulphuric acid on the chloride of phenyl 102. Hydrogen and ethyl on compounds ob-tained by the action of anhydrous sul- phuric acid on the chlorides of by R Williamson 97.392 INDEX. I Iodide of allyl 317. -of silver 241. -of tetrallyl-arsonium 327. Iodine separation of from bromine and chlorine 234 Iron modification of the reactions of by citric acid 113. -report on recent patents connected with the reduction of and the manu- facture of steel by F. A. Ab e 1 125. Irrigation by sewage-water 287. L. Lawee a. B. and J. H. Gilbert on some points in the eompositioln of wheat-grain its products in the mill and bread 1,269. imd,anehoateof 173. -modification of the reactions of by citric acid 114. -sulphanisate of 212. Letter from the Secretary of the Trea-sury to the President of the Royal Society respecting the occupation of Burlington House 181.Leucine alleged formation of from thi-aldine 199-202. Light on the action of on chloride of isilver by F. (3iith r ie 74. Lime? methylodithionate of 248. -prevention of the precipitation of. by citric acid 112. Litmus chromatic phenomena of 88. Me Macvicar J. GI. notice of a new maxi-mum and minimum mercurial ther-mometer 221. Magnesia methy idithionate of 247. -modification of the reactions of,by citric acid 113. Manganese modification of the reactions of by Citric acid 114. -prevention of precipitation of aul-phide of by grape-sugar 117. Manures analysis of prepared from sewage 212. Manurial value of fowngewage n8. Marce t W. on the fatty mattera of human excrements in disease $63. Mercnptan allylic 320.Nercuricum anchoate of 173. 3€ercurosum anchoate of 173. Mercury modification of the mtions of by citric acid 116. Methylodithionate of baryta 246. -copper 250. -ethyl 349. -lime 243. -magnesia 247. -nickel 250. -silver 249. I_ zinc 245. Methylodithiouic acid 245. I_ ether 249. Methyl-thialdine 194. Mill-products of wheat grain percentage of nitrogen in 30. Mullei; H. and Warren De la Rue on some constituents of rhubarb 297. Murray Robert obituary notice of 191. Nm N a p i e r J. remarka on the action of heat on gold and on ite alloy with copper 229. Nickel methylodithionate of 251. -modification of the reactions of by citric acid 114. Nitre on the valuation of by F. A. Abel and C. L. Bloxam 107.Nitrogen percentage of in mill-products of wheat grain 30. -in the dry matter of wheat-grain grown at Rothamstead 10. -in the products of wheat-grain from the colonial steel hand-mill 37. Nitrophenol alkaline salta of 206. I_ on by A.W. Hofmann 203. Om Obituary notice of Charlea Gerhardt 187. 7- Robert Murray 191. Optical test for didymium by J. If. Gladstone 219. Organo-thionic acids on a new aeries of by J. T. Hobson 55 243. Oxalate of allyl 321 Pm Pettenkofer Max on a volumetric method of estimating atmospheric car- bonic acid 292. Phenyl on a compound obtained by the action of fuming sulphuric acid on chloride of by L. Hutchinga 102. INDEX. 393 Phosphuretted hydrogen formation of the crystalline conipound of hydriodic acid and by A.W. Hofmann 210. Platinum. modification of the reactions of by ditric acid 117. Potassium anchoates of 171 173. Prism on the use of in qualitative analysis by J. H. Gladstone 79. Proceedings at the meetings of the Che- mical Society 93 180. Qualitative analysis on the use of the priem in 79. R. Report of the President and Council of the Zhemical Society 180. -on recent patents connected with the reduction of iron and the manu- facture of steel,I!’. A. Abel 125. -on the application of sewage to agriculture by D. Campbell 272. Respiration of animals quantity of car-bonic acid produced by 252. -quantity of air required for 254. Rhubarb on some constituents of by Warren De la Rue and Hugo Muller 297.R o a c o e H. E. on some chemical facts respecting the atmosphere of dwelling houses 251. Royal Society extract of minutes of the Council of December 18,1856 respect-ing the occupation of Burlington House 182. s. Salts each constituent of which is co- loured chromatic phenomena of 89. Sarcine 121. Sewage analysis of Edinburgh 286. -analysis of manures prepared from 282. -on the application of to agriculture, by D. Campbell 272. Sewage-water irrigation by 287. Sewage Works at Croydon 284. Siver anchoate of 169. -bromide of 241. -chloro-bromide of 239-240. c- crystallised chloride of 242. --_ iodide of 243. -ethylotrithionate of 61. -iodide of 241. -methylodithionate of 249.-modification of the reactions of by citrio acid 114. 3ilver. on the action of light on the chlo- ride of by F. Guthri; 74. -on the separation of iodine bromine and chlorine and the comparative de- gree of theae elements for with some analyses of their combination8 with that metal occurring in Chili 234. Sinapoline 324 Soda biatearate of in human excre-ments 164. -ethylotrithionate of 63. Sodinm anchoate of 173. Spiller. John on some remarkable circumstances tending to disguise the presence of various acids and bases in chemical analysis 110. Steel report on recent patents connected with the reduction of iron and the manufacture of by F. A. Abel 125. Strecker A. on a new base from the juice of flesh 121. Stroutia prevention of the precipitation of by citric acid 112.Sulphanisate of barium 214. -_ of lead 212. Sulphide of allyl 320. T. T a y 1or J. remarks on Bessemer’a pro-cess for the manufacture of iron 151. Teti-ally lammonium hydrated oxide of 326. Tetrallylarsonium iodide of 327. Thermo-electric properties of bismuth and antimony when used as single elements by R. Ad i e 77. Thermometer notice of a new maximum and minimum mercurial by J. G. Macvicar 221. Thialdine alleged transformation of into leucine 199 202. LI contributions towards the history of by A. W. Hofmann 193. Thornson J. analysis of the Tun- bridge Wells water 223. Tin modification of the reactions of by citric acid 116. -note ou crystallised binoxide of by F.A. Abel 119. Tincture of rhubarb investigation of a deposit found in byWarren De la Rile and Hugo Sluller 297. Town-sewage manurial value of 278. Triallylamine 326. Triethylamine new mode of forming by A. W. Hofrnann. 208. u. Uraninm modification of the reoctiona of by citric acid 114. 394 INDEX. v. Valcrate of allyl 322. Ventilation chemical and physical me -thods of determining the amount of 260. Volumetric estimation of atmospheric car- bonicacid,byMax Pettenkofer 292. Volumetric method for the deterinination of copper by E. 0.Brown 65. w. Water analysis of the Tunbridge Wells by J. Thornson 223. Wax on some of the products of oxida-tion of Chiuese by G. B. Buckton 166. Wtieat-grain ash analysis of 17.-composition of the products of from the Colouial steel hand-mill 38. -on some points in the composition of its products in the mill and bread by J. B. Lawes and J. H. Gilbert 1 269. END OF Wheat-grain percentage of nitrogen in mill prodncts of 30. _-percentage of nitrogen in the dry matter of grown at Rothamstead 10. _-perceutnge of nitrogen in the pro- ducts of from the Colonial steel haud- mill 37. Williamson Robert on some com-pounds obtained by the action of an-h.ydrous sulphuric acid on the chlv- rides of hydrogen and ethyl 97. W o r sley P. J. remarks on Dr. Gurlt's process for the manufacture of iron 151. Z. Zinc anchoate of 173. _-ethglotrithionate of 58. -modification of the reactions of by citric acid 114. Zervas L. on the action of sulpharic acid on auisic acid 211. Zinc methylodithionate of 245. VOL. X. PRINTED BY HARRISON AND SONS ST. MARTIN'S LANE W.C.

ISSN:1743-6893    

DOI:10.1039/QJ8581000389

出版商:RSC    

年代:1858

数据来源: RSC