摘要:

DECEMBER 1916. Vol. XLI. No. 489. QUANTITATIVE MICROSCOPY. BY T. E. WALLIS B.Sc. (LoND.) F.I.C. (Read at the Meeting November 1 1916.) INTRODUCTION THE use of the microscope for determining the proportioiis of substances present in mixtures is generally regarded as an unreliable method of procedure and the results obtained have failed to carry weight as evidence in courts of law. The difficulties experienced in such work arise partly from the methods of manipulation that must be followed for microscopical work and partly from the nature of the substances examined. A common method of working has been to mix the powder with a fluid medium in a mortar transfer a drop to a microscope ,slide apply a cover-glass examine with the microscope and take a count of the number of certain characteristic structures seen in a particular number of fields.This result is then compared with that obtained by making similar counts of pre-parations made in an exactly similar way from powders of known composition 358 WALLIS QUASTITATiVE MICROSCOPY Such a process is liable to error for various fairly obvious reasons as for instance, the variation in the size of the drop of liquid taken up by a glass rod and the de-pendence of the thickness of the film of liquid examined upon the weight of the cover-glass the amount of pressure used in mounting and the nature of the fluid. Moreover no guidance is given as to the selection of the fields to be counted aiid no indication is provided as to the range of error to which the resulting figures we subject .Purther difficulties arise from the smallness of the quantities actually exanlined during %he process. For most ordinary work I have found that a fluid containing 0.2 grm. of substance in 10 to 20 C.C. is suitable for examination with a one-sixth inch (4 mm.) objective which it is necessary to use when one desires to count with precision. The depth of fluid between the cover-glass and slide must not exceed about 0.1 mm. and with a cover-glass of 19 mm. ($ inch) diameter the total volume of fluid is about one thirty-fifth of a cubic centimetre. Since 10 to 20 C.C. conti-tiia 0.2 grm. of the powder the amount of material under the cover-glass is from two to four sevenths of a milligram. The diameter of the field given by the one-sisth inch objective that I use is 0.53 mm.and its area 0.22 sq. mm. and the area of a circular cover-glass of 19 mm. diameter being 284 sq. mm. there are 1,291 fields under the cover-glass and each field will represent approximately a quantity of material varying from about two to five ten-millionth parts of a gram. I n tweiitF fields one is concerned with about one 250th to one 100th part of a mgrm. of material. and i t is upon a correct analysis of this minute quantity of the substance that the final result depends. When one considers this fact in addition to the uncertainty and lack of precision arising from the methods commonly adopted one cannot wonder that figures based upon microscopical methods are regarded with a certain scepticism and it is easy to understand the failure of such methods in the absence of any exhaustive investigation of their worth to carry weight as evidence of extent of adulteration.It has also been recommended in the case of mixtures of starches that photo-graphs of preparations from mixtures containing known percentages of the mixed starches should be made and that the proportion present in an adulterated starch should be estimated by comparison of a photograph of a preparation from the sample with the photographs of the standard mixtures. This method must inevitably be unsatisfactory since the ratio of the two kinds of starch grains to one another varies considerably from field to field of the same preparation and a true proportiolz can only be obtained by counting a sufficiently large number of fields. The accom-panying figures representing counts of potato and maize starch granules in a 50 per cent.mixture of the two illustrate fhis point. The mixed starches were rublml down in a mortar with dilute glycerol and the counts of ten fields selected accorriillg to the plan suggested below were as follows: Potato starch . . . . 28 18 28 21 25 19 18 18 34 22 Maize starch . . 185 140 171 186 195 183 158 188 1’74 173 If the number of potato starch grains in each field is represented by 100 the numbers representing the maize starch are 661 778 611 886 780 863 878 1,044 512 an WALLIS QUANTITATIVE MICROSCOPY 359 786 respectively figures which show a difference of 100 per cent. between the extreme values. The types of substance to be examined may be classed as follows: 1. Material consisting of portions all of t'he same kind and all varying in size within certain definite limits.such as starches pollen grains and spores. 2. Material that is all of the same kind-e.g. wholly cellulose or wood-but composed of particles of sizes varying between arbitrary limits depending upon the brittleness or toughness of the substance and upon the method of sifting or grading. Fibres pine-wood sawdust powdered coco-nut shells and olive stones, are examples. 3. Material presenting a variety of structures among which there are some, such as starch grains crystals stone cells etc. which are of diagnostic value. The majority of food-stuffs and drugs fall under this head. The difficulty of dealing with these types increases in the order in which they have been enumerated and although one may be able with a small amount of preliminary research to obtain results of sufficient accuracy with the more simply constituted materials it will be only after extended investigation that one can hope to decide upon the line of approach that will lead to the successful application of a reliable method of counting in the case of a substance exhibiting structures of many different types.The work recorded in this communication relates t o experi-ments whose aim has been to devise a general method of procedure that will give precision 60 c n m t s made mder the microscope and so to emble one to obtain, by the use of this instrument quantitative results which will carry conviction in much the same way as do figures based upon ordinary chemical processes.ADMIXTURE OF A SL~BSTANCE AS A STANDARD FOR COMPARISON. The plan adopted by bacteriologists for the counting of bacteria in a vaccine by mixing it with blood a,nd determining the ratio of bacteria to red blood-corpuscles suggested the idea that if one could add to powders a substance consisting of uniform grains corresponding to the corpuscles it would be possible to use a similar device in the case of powders. This procedure eliminates the errors due to variations in the size of the drops falling from the glass rod used in making the mount and renders it unnecessary to bring the volume of liquid to any exact measure. The difficulty arising from variation in the thickness of the film of liquid between the cover-glass and the glass slide is also removed.A substance suitable for admixture in this way must exhibit certain important characteristics : 1. It must consist of grains of uniform size and having dimensions comparable with those of starch grains. 2. The grains should be fairly resistant to pressure and have strongly marked characters clearly differentiating them from all ordinary vegetable structures. 3. It should be unaffected by clearing reagents and stains used in microscopical work-that is i t must not be rendered invisible or be destroyed by such things as caustic soda chloral hydrate clove oil and strong hydrochloric acid. 4. It must be fairly easy to obtain the substance commerciall 360 WALLIS QUANTITATIVE MICROSCOPY It is soniewhat difficult to find a suitable material for admixture; but after a few trials I concluded that something which occurs naturally in uniform grains could be the only possibility.I finally decided to try lycopodium spores which are highly resistant to strong clearing reagents and have a diameter of from 2Op t o 28 p which is not larger than that of many stmarch grains. Their characteristically sculptured surface and tetrahedral shape makes them easy to identify and dis-tinguishes them clearly from all structures commonly found in vegeta,ble powders. A few experiments made it evident that t'hey fulfilled the requirements exactly. USE OF A SUSPENDING MEDIUM. T n my earlier experiments I tried working with the dry powders wit,hout any suspending fluid. The lycopodium and the powder under investigation were thoroughly mixed and then a small portion was taken with the point of a knife and placed upon a glass slide moistened with alcohol or in the case of a woody adulterant with a 1 per cent.solution of phloroglucinol in alcohol dilute glycerol or other iiiountant added the whole stirred with a glass rod and a cover-glass applied. The results were surprisingly exact; but every now and then a count which was obviously very far from correct would be obtained and this was due to the difficulty experienced in producing a perfect distribution of the constituents of the mixed powder. Such variations introduce an elenlent) of uncertainty and make it iixpoaaible 60 determinc the proportions c?f the materials in the mixtiire so satisfactorily that one would feel justified in reporting the figures found.To obtain a more complete mixing and to prevent the separation of heavier from lighter part'icles by tlhe liquid a number of suspending agents were tried. Such a substance should possess the following characters : 1. Its density should be less than that of lycopodium spores-i.e. less than 1.0S6-so that' all the material will tend to sink and not be separated into a flonting layer and a sediment consisting of entirely different materials. 2. The viscosity should be moderately high so that the suspended powders may sink slowly. 3. The medium should wet the powders readily and penetrate the substance of the walls of cellular structures so that air is excluded and the particles appear transparentl. 4. It must wet oily as well as dry and moist powders. 5 .It should prevent the deposition of the suspended matter or should allow the sediment to be easily shaken up to form an evenly distributed suspension. 6. It must mix readily with such reagents as alcohol and strong hydrochloric acid. There is no substance which satisfies all these conditions; But there are a few which show a near approach and by varying the details of working to meet special requirements one may hope to find a medium suited t o every case. Of the two common mucilages which immediately suggest themselves as sus-pending agents mucilage of acacia closely approaches the condition of a true solu-tion and for this reason behaves as a viscous fluid of considerable density. It i WALLIS QUANTITATIVE JIICROSCOPE' 361 not very suitable for microscopical work because i t completely separates a mixture containing lycopodium spores which after an interval of about twenty-four hours form a floating layer while starch and other matters collect as a sediment.The whole shakes up again fairly well but it is undesirable to use any medium which effects so complete a separation of the substances to be counted. Its stickiness and property of drying rapidly to form a hard brittle film when spread in a thin layer are also features which militate against the use of mucilage of acacia. Mucilage of tragacanth has an entirely different structure; it depends for its efficacy upon the presence of a fine network of cellulosic material distributed through an aqueous fluid. For this reason the mucilage tends to keep suspended particles in a more or less fixed position with respect to one another.That this is the case I have shown by making counts after suspensions have stood undisturbed during an interval of from three to five days when the proportions of lycopodium spores and of other particles have been found to remain constant. The suspending pro-perties of the mucilage are unaffected by alcohol and by strong hydrochloric acid. Mucilage of tragacanth is therefore a very efficient suspending agent and is most useful for quantitative work with the microscope. There are however certain drawbacks to the use of mucilage of tragacanth, such as the occurrence of a few granules resembling starch grains i t e lack of com-plete transparency and its unsuitability for use with oily powders. In the majority of cases the starch grains introduce no difficulty as they are only few in number and are readily distinguishable from aost othcr starches.The medium is rendered more transparent by using a mixture of 1 volume of glycerol and about 4 volumes of mucilage of tragacanth. If used for oily powders the fatty matter must be removed by a preliminary extraction with a suitable solvent. Oils such as olive oil and castor oil have proved extremely useful not only in the case of oily powders like mustard and pepper but also for general use with powdered vegetable substances. Their densities axe slightly less than that of water, and hence all the suspended matters are deposited on standing and settling takes place slowly owing to their considerable viscosity. In the case of olive oil the sediment is easily shaken up again to form a uniform mixture; but with castor oil this is not effected so readily and consequently owing to its very high viscosity, castor oil is not so useful as a suspending agent.The great penetrating power of the oils causes them to mix readily with dry powders to displace air from cavities, and to render all the particles transparent. Oils are useful for starches especially when one wishes to use the polariscope to aid in distinguishing one kind of grain from another. The possibility of using soft paraffin suggested itself as the result of experience gained while examining an ointment composed of mucilage of starch and vaselinc. A few experiments demonstrated its utilit,y as a suspending medium and an examplc of its apphation is given under the heading of niustard among the experiments cited below.Soft paraffin is less generally useful than olive oil because more time and trouble are needed to obtain a satiefactory mixture of the powders and medium than is the case with the oil. Also when polariaed light is used the crystalline sbrncture of the paraffin produces a confused network of bright lines which tends t 362 WALLIS QUAh'TITATIVE MICROSCOPY obscure the objects to be counted. It is quite possible however that the occasion may arise when the peculiar properties of soft paraffin will indicate its employment in preference to any other suspending agent. Glycerol can be used successfully but its high density results in a complete separation of the lycopodiuiii as a floating layer after the preparation has stood for some hours and its great viscosity increases the difficulty of redistributing the materials evenly when the suspension is shaken up again.A mixture of alcohol and glycerol in equal volumes has been recommended for suspending such materials as mixed starches (" Admixture of Oatmeal with Barley Meal," by E. L. Cleaver, ANALYST 1877 I. 189); but alcohol decreases the viscosity to such an extent that one finds considerable difficulty in producing a uniform mixture of the powders with the fluid and in breaking up small groups of spores or starch grains. Mixing the powders first with glycerol and thinning with alcohol afterwards is also un-satiefactory . GENERAL STATEMENT OF THE METHOD OF WORKING. Expressed in general terms one proceeds in the following way: 1.Make a mixture of the pure substance with an equal weight of the adulterant whose amount it is desired to determine. The two substances may either be dried at 100" C. or preferably used air-dry; estimate the moisture present and apply the necessary corrections in the calculations. Mix 0.2 grm. or other convenient weighed quantity of this standard mixture with 0.1 grm. or other suitable amount of lyco-podium and sufficient of the suspending fluid to produce a liquid of which 1 drop, when mounted and examined with a one-sixth inch objective shall show from 10 to 20 lycopodium spores in each fiald. I n most cases this result will be obtained when the total volume is about 20 C.C. 9 drop of the suspension is transferred t o a slide by means of a glass rod and it cover-glass applied.Count the number of particles of adulterant and of lycopodium spores in ten fields selected according to the scheme detailed below. Mount a second drop on another slide and again record ten counts. Find for each set of ten counts the ratio of the number of lycopodium spores to the number of characteristic elements of the adulterant and express the results as the number of characteristic elements counted for every 100 lycopodium spores. The numbers found for the two sets of counts should not differ by an amount greater than 10 per cent.; should they do so fresh counts must be made. 2. Mix 0.2 grm. or other suitable amount of the sample in which the percentage of adulterant is to be determined with 0.1 grni.or other convenient amount of lycopodium and about 20 C.C. of suspending fluid. Xount a drop on each of two slides and count ten fields on each. Calculate the ratio of the number of spores of lycopodium to the number of characteristic elements of the adulterant and express the result in the same form as for the standard mixture. 3. The numbers obtained for the foreign substance in the two sections of work are directly proportional to the amounts present and a simple calculation gives the quantity sought. A correction must be appiied for moisture. Further manipu-lative details are given below in describing the experiments which were planned and carried out in order to illustrate and test this method of making quantitative determinations by means of the microscope WALLIS QUANTITATIVE MICROSCOPY 363 DISCUSSION OF DETAILS.The quantities of mixture and of lycopodium recommended for preparing the suspensions are such as have proved generally useful. In cases where the amount of inaterial to be counted is very small as in the determination of small percentages of powdered olive stones the proportion of mixture should be considerably increased ; and where the number of particles is very large as when one is dealing with a small-grained starch a greater propxtion of lycopodium must be used. Examples of these two cases will be found among the experiments. The powders used in preparing the 50 per cent. standard mixtures must be mixed very thoroughly by trituration in a mortar turning out on a tile or sheet of glass and mixing with a spatula returning to the mortar and repeating the process a few times until an intimate mixture is obtained.When dealing with powders in which woody structures are t o be counted the mixing should not be done on paper, since most paper contains woody tissue and a certain small amount of the fibres from the surface of the paper works up into the powder and causes errors in making counts of woody elements. A 50 per cent. mixture is recommended for use in most cases instead of the pure adulterant because difficulties that will arise in dealhg with the sample to be tested will also arise with the standard mixture and the operation of counting the sample will be facilitated and rendered more precise. There are occasidns when counts made with the pure substance are very useful as in the case of a mixture of two pawders b3th containing woody elements or other diagnostic structures of which a particular kind is to be estimated.Some confusion may tend to arise between those proper to the powder a.nd those belonging to the adulterant, and a useful check may be obtained by counting the pure adulterant against lyco-podium as well as counting a 50 per cent. standard mixture. Close agreement between these two results will greatly strengthen one’s reliance upon the accurMy of one’s judgment in distingaiahing the woody elements starch grains or other striictures similar in type but different in origin. Before adding the liquids to the weighed quantities of lycopodium and other substances these powders should be thoroughly mixed in a dry state by rubbing them together upon a sheet of glass with a spatula.This thorough trituration distributes the constituents much more evenly and breaks down any little collec-tions of adhering spores or starch grains. These mixinga may be carried out in a mortar provided that the trj turation is gentle ; otherwise the lycopodium spores will be largely broken. Mixing in a mortar presents no advantage and on the whole the use of a plate and spahula as described is to be preferred since it is almost impossible to break the spxes by this means and the mixing is quite satisfactory. CHOICE OF THE FIELDS TO BE COUNTED. In selecting the fields to be counted care must be taken to avoid the possibility of counting the same field twice and the positions of the fields chosen should be evenly distributed over the whole preparation.Their positions must also be fixed arbitrarily by soms previously axepted arrangement so as to avoid the errors that u!iiatsntionslly anise iii selscting fidds which one thinks suitable for counting 364 WALLIS QUANTITATIVE MICROSCOPY This selection can only be made by the use of a mechanical stage having graduaticns on the two movements at right angles to one another. For an jnstiuEcnt havir-g a plain stage one can use one of the very satisfactory forms of attachable mechanical stage. The position of the fields to be counted is best fixed by choosing positions at certain distances from the middle point; if the slide is then placed on the stage so that the lens is over the centre of the cover-glass one can note the reading for the position of the right-hand near corner of the Elide on the two scales of the mechanical stage and then move it precisely into the positions required for making the counts.For my own experiments I have counted ten fields on each slide and the positions selected are shown in the accompanying diagram all distanccs being D~a~eaiv SHOWING THE Posrrross OF TILE FIELDS C o c s m ~ . Tlie numbers indicate distances in millimetres from the centre of the cover-glass. given in millimetres from the centre of the cover-glass. To make the actual counts it is necessary to use an eye-piece micrometer ruled in squares and to count regularly along each line of squares in succession until the whole field has been covered. The number of fields to be counted will depend upon the intimacy of the mixing.If perfect mixing could be secured a very few counts-say three-would be suffi-cient; but since each field contains only about one four-millionth of a grm. of sub-stance and half that amount of lycopodium it is very difficult and in my experience, impossible to obtain by ordinary means so complete a mixing. One must therefore continue until so many fields have been counted that the counting of an additional one will not appreciably alter the ratio obtained. In actual practice I have found 20 fields give a reliable result ; and if these are counted in two sets of 10 upon different slides one set acts as a check upon the other and so adds to the precision of the operat ion WALLIS QUANTITATIVE MICROSCOPY 365 R,ECORD OF EXPERIMESTS.The following examples will serve to illustrate the method employed the kind of difficulties that arise in the course of such work. and the way in which modifica-tions may be introduced in order to meet special conditions. The mixtures chosen for experiment are such as have been reported as occurring in actual practice and consist of materials which cannot be determined quantitatively by other than microscopical methods. used as a suspending agent was prepared from the dry powder at the time of mixing; 0-2 grm. of the mixed flours 0.1 grm. of lycopodium and about 0.12 grm. of powdered gum tragacanth were carefully mixed together and put into a cylindrical weighing bottle of about 40 C.C. capacity. About 1.0 C.C. of alcohol was added and shaken with the powders; 20 C.C.of water were poured in rapidly the stopper replaced, and the whole shaken vigorously for two or three minutes. The counts made were MIXTURES OF WHEAT FLOUR AND CoRNFLOUR.-The mucilage Of tragacanth as follows : Mixture of Wheat ten fields: Maize starch L yc opodium . . Flour 50 per Cent. and Cornflour 50 per Cent.-B'irst set of 14 15 7 11 11 5 4 13 12 10 = 102 43 T4 53 33 61 39 25 38 57 59 = 482 Lycopodium spores - 100 Maize starch grains 473' Ratio - - _ _ - - - -Second set of ten fields : Lycopodiurn . . 11 11 11 7 12 7 4 9 9 12 = 92 Maize starch . . 51 45 57 52 63 28 23 37 47 36 = 439 Lycopodium spores - 100 Ratio - - -Maize starch grains 477' Lycopodium spores - 100 Maize st&rch grains - 475.Average ratio - -: Mixture of Wheat Flour 62.2 per Cent. and CornJlour 37.8 per Cent.-B%st set of ten fields : L y c opo dium . . 13 10 14 20 21 11 4 14 16 12 = 135 Maize starch . . 48 38 42 87 64 26 24 43 77 49 = 497 Lycopodiuni spores - 100 Ratio - -_ Maize starch grains 368' Second set of t,en fields: Lycopodium . . 11 6 5 8 12 5 8 8 14 6 = 8 3 Maize starch . . 30 23 34 46 26 17 18 11 44 40 = 294 Lycopodium spores - 100 Maize 'starch grains 354' Ratio Lycopodium spores - 100 Maize starch grains 361' Average ratio - - - - -Amount of cornflour found = 361 x-50 = 38.0 per cent. 47 366 WALLIS QUANTITATIVE MICROSCOPY Mixture of Wheat Flour 90 per Cent. and Cornjlour 10 per Cent.-Counts of ten fields on eaoh of two slides gave the ratios: 109 100 and -=--100 96.1 * Lycopodium spores - 188 - 100 Maize starch grains 187 99.5 101 92.7' -__ _- ~ - _ - _ With an average of Amount of cornflour found- 9 z L 3 0 = 10.1 per cent.470 N.B.-Where the counts of the individual fields are not given each ratio from a set of ten counts is expressed in two forms; the first fraction has for numerator and denominator the sum of the ten actual counts of lycopodium spores and starch grains or other characteristic elements respectively while the second fraction has in every case 100 for the numerator representing the lycopodium spores and for the denominator the corresponding number representing the starch grains or other structures. By dividing the numbers in the first fraction by 10 one has immediately the average number of grains or particles counted in each' field.treated in the same way as the mixtures of wheat flour and cornflour. fields on each of two slides gave the ratios: MIXTURES OF POTATO STARCH AND MAIZE STARcH.-These mixtures were Mixture of Potato Starch 50 per Cent. and Maize Starch 50 per Cent.-Counts of ten Lycopodium spores- - 58 - 100 R,nd -= 40 100 Maize starch grains 338 583 - - - - - 218 545. 100 With an average of ~- 564' Mixture of Potato Starch 90 per Cent. and Maize Starch 10 per Cent.-Counts of ten fields on each of two slides gave the ratios : Lycopodium spores- 108- 100 72 100 - and - = - Maize starch grains 117-108 84 117' 100 With an average of -. 113 113 x 50 564 Amount of maize starch found= - - -~ = 10.0 per cent. ilkfixture of Potato Starch 95 per Cent.and Maize Starch of ten fields on each of two slides gave the ratios: 144 - and - Lycopodium spores - 11 1 - 100 Maize starch grains 63 56-8 82 _-_-With an average of 56.9 x 50- Amount of maize starch found& ~ - 5-1 . 564 5.0 per Cent .-Counts 100 56.9 ' 56.9 * . 100 per cent. The method of making the mucilage of tragacanth at the moment of mixing has its advantages in aiding the even distribution of the constituent powders; bu WALLIS QUANTITATIVE MICROSCOPY 367 if the drops of suspension are mounted and examined immediately currents are produced owing to the continued swelling of the gum. If a few hours are allowed to elapse until the mucilage has properly formed this difficulty does not arise and the counts are easily made.It may be suggested that where a mixture of two starches is being dealt with, the addition of lycopodium is unnecessary because the ratio of the two kinds of granule to one another can be obtained. Although this is true it is preferable to add lycopodium because by doing so a greater precision is secured. It is impossible to mistake lycopodium spores for starch grains whereas if a few grains of one kind of starch are mistaken for those of a second sort a double error results since what is added to one side is subtracted from the other. So large an error cannot possibly occur when lycopodium is used; time also is saved because it is much easier to count the spores than to count starch grains. Up to this point no account was taken of the moisture present in tbe starches, and since the powders used in the various mixtures were identical with those used in the standard mixtures no error was introduced.In ordinary practice it would be necessary to make corrections for moisture; hence in the remaining experiments moisture was always estimated and the corrections applied. MIXTURES OF MUSTARD PLOUR AND CoRhTFLouR.-The mixtures were made with cornflour dried a t 100" C. For the standard mixture the mustard was also dried but for the 26 per cent. mixture the ordinary air-dry powder was used. In place of mucilage of tragacanth the 0.2 grm. of mustard and 0.1 grm. of lycopodium were mixed with olive oil by working them with a spatula upon a piece of glass until a thick paste was formed; this was further gradually diluted to the consistence of thin cream.The fluid was then transferred to a weighing bottle and more olive oil added until the volume was about 20 C.C. The whole was well shaken and a drop mounted for examination. Mixture of Dried Mustard 50 per Cent. and Dried Cornjlour 50 per Cent.-Counts of ten fields on each of two slides gave the ratios: Lycopodium spores- 194 - 100 and - 100 - - Maize starch grains 1289-664 645' 100 With an average of - 655' Mixture of Air-Dry Mustard 75 per Cent. and Dried Cornflour 25 per Cent.-The mixture was dried before weighing out and mixing with the lycopodium Counts of ten fields on each of two slides gave the ratios : Moisture= 6.67 per cent. and oil. Hence dry substance= 93.33 per cent. 87 100 and __ = ~ Lycopodium spores- 66 - 100 Maize starch grains 261 395 307 353' 100 With ail average of ~ 374' - - - ~ 374 x 50- Amount of cornflour found in the dry substance = - 28.5 per cent.655 Or in air-dry substance = 26.6 per cent 368 11' ALLIS QUANTITATIVE MICROBCOPY I n order to test the possibility of replacing olive oil by soft paraffin fresh counts were made for the mixture containing 25 per cent. of cornflour. The weighed quantities of the powders were thoroughly incorporated with about 6 grms. of soft paraffin by means of a spatula and glass plate. A small amount of this strong mixture was diluted wit#h more paraffin until examination under the microscope showed that a mixture containing a suitable proportion of the powder had been produced. Counts of ten fields on each of two slides gave the rafios: LYcoPodium 82 - loo and __ 96 - 100 Maize starch grains 303 370 371 390' 100 380' With an average of 380 x 30 Amount of cornflour found in the dry substance - - -- = 29.0 per cent.65a Or in air-dry substance = 27.1 per cent. The remaining experiments were made with air-dry powders; this was done because dry vegetable powders are very hygroscopic and may take up appreciable quantities of moisture during manipulation. The use of air-dry powders also results in a reducttion of the time required for the whole operation. MIXTURES OF WHEAT FLOUR AND POTATO STARcH.-It is generally easy to distinguish grains of wheat starch fliolil those of p t a t o starch; b u t there is 8 number of grains forming about 10 per cent. of the potato starch which it is difficult? to distinguish with certainty.With the polariscope wheat starch polarises feebly, whereas potato starch grains show a strongly marked cross. These differences are very clearly shown when the starches are mounted in oil and for this reason olive oil was used as the mountant for the mixtures and the counts were made with the polariscope using crossed Nicols. Although the majority of wheat starch grains polarise feebly one finds here and there one which shows a brilliant effect owing to the fact that the grain is on its edge. These grains are however distinguisha,bIe, because the potato starch grains always show a cross formed by the intersection of two lines whereas in the case of grains of wheat starch turned upon their edges the " cross " is composed of five lines of which four are arranged in pairs bifur-cating from the ends of the fifth line thus >-<.Some few potato starch grains show a circular outline and a cross formed by the intersection of two diameters, much as one finds in wheat starch. Such grains may be distinguished from brightly polarising grains of wheat starch by the fact that in potato starch the lines forming the cross are usually thicker towards the circumference and taper off to the pointJ of intersection which is clearly marked while the lines on wheat granules becoiiie wider as they approach the centre which is itself marked by a darker circular area. Keeping these points in mind it is possible to make an accurate count of potato starch mixed with wheat flour.I n each case 0.2 grm. of the substance was mixed with 0.1 grm. of lycopodium, and the powders worked up wit'h olive oil in the manner described above for the mustard mixtures WALLIS QUANTITATIVE MICROSCOPY 369 Jfizture of Wheat Flour 50 per Cent. and Potato Starch 50 p e r Cent.-;\iloisture Hence the mixture contains 39-62 per cent. of potato starch dry at 100" C. in t'he potato starch = 20.76 per cent. Counts of ten fields on each of two slides gave the ratios: 108 100 Lycopodium spores - 86 - 100 Potato st-arch grains 68 791 85 78.7 * 100 Wit'h an average of - - 78.9 ' and -= --,Mixture of Wheat Flour 80 per Cent. and Potato Starch 20 per Cent.-Counts of t e n fields on each of two slides gave the ratios : 154- 100 Potato starch grains 51 33;s 56 36.4 Lycopodium spores- - 151 - 100 and - ~~ 100 35.1 With an average of - --.39.62 x 35.1 = 17.6 or __-78.9 Hence percentage of dry potato starch in the mixture = 82.2 parts of air-dry starch. MIXTURES OF WHITE PEPPER AND GIXGER.-h this case the powders were mixed with castor oil using a spatula and a sheet of glass; the oil was added until a suitable dilution was obtained. I n each experiment 0.2 grin. of the mixture and 0.1 grm. of lycopodium were used. Mixture of White Pepper 50 per Cent. and Ginger 50 per Cent.-Noisture in the ginger= 13-91 per cent. Hence the mixture contains 43-05 per cent. of ginger dry a t 100" C. Counts of ten fields on each of two slides gave the ratios : Lycopodium spores- 81 - 100 68 100 Ginger st'arch grains 247 305 206 303' and- =--100 With an average of - 304 ' Mixture bof White Pepper 90 per Cent.and Ginger 10 per Cent.-Counts of ten fields on each of two slides gave the rat>ios: 135- 100 Lycopodium spores- - 343- 100 and -Ginger starch grains 234- 62- 87 64.4' 100 66.3 a With an average of 66.3 x 4 3 ~ 0 5 ~ 9.4 or 10.9 per 304 Hence percentage of dry ginger in t,he inixt>ure = -cent. of air-dry ginger. siiisll grains and judging from the relative size of maize starch grains it seemed probable that for a preparation containing starch and lycopodium in the propor-fion of 0.2 of the former to 0.1 of the latter the number of grains to be counted in each field would approach 2,000 which is too large a number for comfortable working. The proportions were accordingly altered and for this set of experiments MIXTURES OF WHITE PEPPER AND RICE STARCH.-RiCe starch Consists Of Ver 370 WALLIS QUANTITATIVE MlCROSCOPY 0.2 grm.of I~-copodium was niixecl with 0.05 grm. of starch or pepper. Olive oil was used as the fluid medium and the volunie was made up to about 20 C.C. as before. I n addition to counting a standard mixture of pepper and rice starch pure rice starch mixed with lycopodiuin was also counted. This was done to accustom the eye to the size and appearance of the rice starch and also to give a ratio that would act as a check upon the remainder of the work. To count ri2e starch in the presence of pepper is not so difficult as might be anticipated and that for two reasons. In the first place by far the greater part of the pepper starch occurs in angular masses so that the number of loose grains is small; and secondly pepper starch grains vary in size from 0 4 p to 5 0 p while rice starch grains vary from 5p to 8p in diameter so that if one omits all starch grains having a diameter less than half that of the larger rice starch grains the count obtained will represent the rice starch.Pure Rice Starch-Moisture in the rice starch = 15-96 per cent. Counts of ten fields on each of two slides gave the ratios: 181 - 100 and ---. Lycopodiuni spores- 218 - 100 Rice starch grains 5853 2686 5135 2836 .- - -. -100 With an average of -~ 2761' Mixture of White Pepper 50 per Cent. and Rice Starch 50 per C'ent.-This mixture Counts of ten fields on each of two slides gave the ratios: contained 42.02 per cent.of rice starch dry a t 100" C. Lycopodium spores- 211 - 100 141 100 ~- - and -=-Rice starch gramins 2670 1266 1703 1208' 100 With an average of ~ 1237 * Mixture of White Pepper 80 per C'ent. and Rice Starch 20 per Cent.-Counts of ten fields on each of two slides gave the ratios: 265 100 and - = - Lycopodium spores - 200 - ~ 100 Rice starch grains 921 460.3 1232 465' 100 463 With an average of Hence percentage of dry rice starch in the mixture = 463 42*02 = 15.72 or 1237 18-71 per cent. of air-dry rice st,arch. The figure 1237 for the rice starch in the 50 per cent. mixture is about 10 per cent. smaller than the figure 1380 obtainable by calculation from the pure starch. This is due to one's anxiety to avoid the inclusion of pepper starch in the counts, and the consequent omission of some of the smaller rice starch grains.This fact also emphasises the desirability of using a mixture for the standard rather than to base the calculations upon a figure obtained from counts of tlhe pure adulterant WALTAIS QUANTITATIVE MICROSCOPY 371 NIIXTURES OF GENTIAN ROOT AND COCONUT SHELL.-The powdered gentian root was an ordinary commercial sample and the coconut shell was a No. 80 powder prepared in the laboratory. In t,he case of the pure coconut shell the 50 per cent. and the 5 per cent. mixtures the mixed powder and lycopodium were rubbed together on a glass plate with about 1-0 C.C. of a 1 per cent. solution of phloroglucinol in alcohol until nearly dry; 1.0 C.C. of strong hydrochloric acid was next added and the mixing continued; 3 C.C.of glycerol were then incorporated and the volume adjusted by gradually adding mucilage of tragacanth. The whole was transferred to a weighing bottle and well shaken. For the 29.3 per cent. and the 8.5 per cent'. mixtures about 0.12 grm. of powdered gum tragacanth was added and all the powders were thoroughly mixed in the dry state. They were then treated with phloroglucinol hydrochloric acid and glycerol as described above. The thin paste thus produced was transferred to a weighing bottle water was added and the whole shaken vigorously until a uniform mixture resulted; the suspension so formed was very satisfactory. No attempt was made to count the individual stone cells present; any portion or group of stone cells was counted as one unit.The bright rose-pink colour assumed by the woody elements of gentian helped in distinguishing them from the coconut shell which nearly always takes a yellowish-red colour. Pure Powdered Coconut Shell.-Moisture in the coconut shell = 12.42 per cent. The quantities used were Coconut she!! 0.2 gr". and ljxopdiurn 0.1 grm. Counts of ten fields on each of two slides gave the ratios: 230 100 and __ =- Stone cells 197 = 83.8 191 83.0' 100 With an average of -83.4' Lycopodiuni spores - 235 100 -~ ~~ ~ Mixture of Gentian Root 50 per Cent. and Coconut Shell 50 per Cent .-This mixtme The quantities used were Mixture 0.2 grm. and lycopodium 0.1 grm. Counts of ten fields on each of two slides gave the ratios : contained 43.79 per cent.of coconut shell dry at 100" C. Lycopodium spores - 164- 100 and 160 __ 100 100 With an average of -41.05' - __- - Stone cells 71 43.3 65- 38.8 ' Mixture of Gentian Root 70.7 per Cent. and Coconut Shell 29.3 per Cent.-The quantities used were Mixture 0.4 grm. and lycopodium 0.05 grm. Counts of ten fields on each of two slides gave the ratios : Lycopodlum spores-65- . - 100 and 76 - ~ 100 Stone cells 55 84.6 67 88.2 100 86.4 - With an average o 372 WALLIS QUANTITATIVE MICROSCOPY If the quantities used had been the same as for t>he 50 per cent. mixture the value 86.4 would become 86.4 +- 4 = 21.6. Hence percentage of dry coconut shell in the mixture= 21D6 ~ 43*79- - - 23.04 or 41.05 26.3 per cent. of air-dry coconut shell. quantities used were Mixture 0.4 grm.and lycopodium 0-05 grm. Mixture of Gentian Root 91.5 per Cent. and Coconut Shell 8.5 per Cent.-The Counts of ten fields on each of two slides gave the ratios: Lycopodium spores - 109 - 100 and 135 =- LOO Stone cells 33 -303 41 30.4' 100 With an average of __ 30.35' -___ -- . __ . . -If the quantities used had been the same as for the 50 per cent. mixture the value 30.35 would become 30.35 +- 4 = 7.6. 7.6 >c 43.79 - Hence percentage of dry coconut shell in the mixture= -<- - 8.1 or 9.25 41.05 per cent. of air-dry coconut shell. tities used were Mixture 0.8 grm. and lycopodium 0.05 grm. Mixture of Gentian Root 95 per Cent. and Coconut Shell 5 per Cent.-The quan-Counts of ten fields on each of two slides gave the ratios : Lycopodiuni __________- spores- - 118- 100 and 136- 100 100 31.2 ' Stone cells 38- - 32.2 41 - 30.15' With an average of If the quantities used had been the same as for the 50 per cent.mixture the value 31.2 would become 31.2 -+ 8 = 3.9. Hence percentage of dry coconut shell in the mixture= 3*9 43*79= 4.2 or 4.8 41.05 per cent. of air-dry coconut shell. When examining mixtures such as this of coconut shell and gentian root it would ordinarily be necessary to determine by measurement and by comparison with standard powders the degree of disintegration to which the powdered substance to be counted had been reduced and to make the standard mixtures with a similar powder. Also where the amount to be determined is very small the dried crude fibre could be worked upon instead of using the original substance WALLIS QUANTITATIVE MICROSCOPY 373 CONCLUSION.For the purpose of reviewing as a whole the results obtained by the method described I have arranged them in tabular form : z 2 3 4 5 6 7 8 9 10 11 12 -Substance. Wheat flour 7 9 ? 9 Potato starch , 9 , Mustard WGat flour White pepper Gentian root 2 9 9 , Y ? Aditiix ture. Name. Cornflour 7 ,, Y , PotLio starch Ginger Rice starch Coconut shell Amount Present per Cent. 37.8 10.0 10.0 5.0 25.0 25.0 20.0 10.0 20.0 29.3 8.5 5.0 -~ A moan t Found per Cent. 38.0 10.1 10.0 5.1 26-6 27.1 22.2 10.9 18.7 26.3 9.3 4.8 Suspending Agent. Powdered gum traga-canth Glycerol Powdered gum traga-canth Powdered gum traga-canth Olive oil Soft paraffin Olive oil Castor oil Olive oil Powdcrcd gum traga-canth and glycerol Powdered gum traga-canth and glycerol Mucilage of tragacanth and glycerol A study of the figures in the table shows that a high degree of accuracy is attain-able.The errors may be taken to represent such as one may expect to find in every-day practice. It is difficult to draw any general conclusion as to the magnitude of error because the.conditions of working vary so largely in the different experi-ments and a degree of precision attainable with one type of mixture is not always possible with another. The table shows however that one may generally anticipate that the error of working will not exceed 10 per cent.on the amount present while in many cases it should be much smaller. Even when the larger errors occur one could reduce them by increasing the nvmber of counts made or by repeating the work. In each instance one can gain a very good estimate of the probable error in the working by preparing a mixture containing the materials in the proportions found and then determining its composition microscopically ; this additional work is a wise precaution to take in many cases as for instance where the problem includes a determination of the degree of disintegration of a powdered substance. The time required to make one set of ten counts varies from about fifteen minutes to as much as an hour and a half in exceptional cases; the average time s about half an hour 374 WALLIS QUANTITATIVE MICROSCOPY This method of working conqtitutea a process of general applicability and makes it possible to obtain precise quantitative results by means of the microscope.The use of lycopodium enables the observer t o attack successfully many problems that it has been hitherto impossible to solve with any approach t o certainty and in the case of such mixtures as that of two starches where the counting method has already been applied with only an approximate accuracy the error of working is reduced to such an extent as to give the results a real value subject to only a small error. DIscussroN. The CHAIRMAN (Mr. J. H. B. Jenkins) in inviting discussion remarked that the lycopodium presumably simply served as a unit for calculation and one did not know to what extent the weighing of a definite quantity of it was essential.So long as it simply functioned as unity it did not seem to him to make much difference what quantity of it was present. Professor H. G. GREENISH said that a good deal of work had been done in this direction but he had never seen the problem attacked by the method which Mr. Wallis had used. All who had tried to determine the proportion of a substance like coconut shell or almond shell when mixed with gentian root liquorice root etc. must have felt that the results of their examination were very uncertain amounting rea,lly to little more than an approximate guess. In cases like the first four in Mr. Wallis’s table one could probably attain a fair degree of precision without the use of lycopodium ; but with mixtures of mustard and wheaten flour pepper and rice or gentian root and coconut shell the problem was very much more difficult.In the casc of say gentian root and coconut shell it became a question of making the standard mixture with coconut shell reduced to about the same degree of fineness as the powder under examination by measuri’ng the particles of coconut shell and endeavouring by some suitable method of grinding to produce particles of the same size for use in making the standard inixture. To succeed as Mr. Wallis had in determining the proportion of coconut shell in such a mixture within 10 per cent. either way was more than he should have thought possible. Mr. W. PARTRIDGE said that in counting the bacteria in a vaccine the bacterial emulsion was mixed with normal human blood in a known proportion the slide was dried and stained and the bacteria and blood corpixscles counted against one another.This method by which the different elements were fixed in situ and stained where it could be adopted seemed preferable to counting the particles in a liquid medium. With a liquid medium the Thorna-Zeiss counting chamber designed for counting the red and white cells in blood might be used with advantage. The cells were counted in a standard volume of liquid the height being that mentioned by Mr. Wallis namely one-tenth of a millimetre. The fields counted were moreover squares which made the counting easier than with circles as there was no difficulty with regard to particles occurring on the edges; those touching the top and right edges could be included and those on the bottom and left ignored or riceuersa.B4r. C. REVIS said that in counting milk cells diluted with red blood corpuscles he had experienced very great difficulty with circular fields but this was obviated by the use of a square diaphragm. He had had no experience with larger particles but when red blood corpuscles were used as a “diluent ” of larger cells of the size of whit WALLIS QUANTITATIVE MICROSCOPY 375 corpuscles he had found i t very difficult to get a properly proportioned mixture of the two. With larger particles i t would probably be less difficult to get a satisfactory mixture. Mr. A. CHASTON CHAPMAN remarked that sodium nucleate might be useful in some cases as a suspending medium.Solutions containing about 1 to 2 per cent. of sodium nucleate were quite limpid whilst solutions containing about 5 per cent. (of the gelatinising variety) were almost solid so that varying degrees of viscosity could be obtained. One objection was that the solution was very apt to froth and the sodium nucleate would of course be decomposed by some of the reagents used in making the microscopical preparations. Mr. C. C. ROBERTS suggested that it might be worth while to photograph the fields counted in order to preserve a record of them for use as evidence. Mr. E. T. BREWIS asked whether Mr. Wallis had considered what was generally meant by say a No. 80 powder. It meant a powder which had passed through a sieve having meshes of the size indicated but such a powder might consist of particles of any degree of fineness from No.80 to still finer and the question was what effect any such variations in fineness might have upon the counting. In the case of the first four items of Mr. Wallis’s table all the particles would be of approximately the same size; but in the case of the white pepper or the gentian root the ultimate particles of pepper or of gentian root would be different in size and also possiblyin shape and would have a ten-dency to sift apart. Again before the actual examination was begun the question would arise as to whether. the sample worked upon was a fair average portion of the few ounces constituting the sample submitted which again would perhaps be taken from a bulk weighing some hundredweights or tons.Mr. WALLIS in reply said that although the mixtures referred to in the table were actual binary mixtures it did not matter how many substances were present. The counting in each case had reference to one constituent only so that all mixtures were binary mixtures from that point of view. He had found that weighing was necessary in order to get accurate results. At first he thought that weighing might be dispensed with and had made a number of experiments in which everything was measured with, in some cases-mixtures of ground olive stones with pepper for instance-very good results; but that method was bad in principle. The only cases to which it could be satisfactorily applied would be cases in which the different constituents were of almost the same density. The question of the counting of particles a t the edge of a field. was a little difficult. He used a squared micrometer and the particles a t the edges were averaged as fairly as possible. The particles could not very well be fixed as in bacterio-logical work. He was not quite sure whether sodinm nucleate would be a satisfactory suspending medium because of the possible action of reagents upon it. Alcohol for instance might create some diffixdty ; but i t would be well worth trying. The No. 80 powder was prepared by sifting through a No. 80 sieve and of course contained particles of varying sizes. He had not made any attempt to investigate the difficulties that might be caused by such variations but he thought that with patience it would be pos-sible to obtain correct results. As to how far the 0.2 grm. worked upon was represen-tative of the bulk this would probably depend upon the care taken in mixing before weighing out. If the samples he had worked upon had not been representative none of his experiments would have succeeded

ISSN:0003-2654    

DOI:10.1039/AN916410357b

出版商:RSC    

年代:1916

数据来源: RSC

摘要:

376 ROBERTS EUTYRO-REFRACTOMETER ZEISS BUTYRO-REFRACTOMETER: THE CONVERSION OF SCALE- READINGS TO REFRACTIVE INDICES. BY C. C. ROBERTS, M.A., A.I.C. (Read at the Meeting, November 1, 1916.) IN the book of directions sent out with the Zeiss butyro-refractometer there is a table showing the refractive index for sodium light corresponding to every tenth degree of the scale of the instrument. For 0" of the scale the refractive index is 1.4220, and for 100" it is 1-4895. In a paper by Leach and Lythgoe (ANALYST, 1905, 30,176) i t is pointed out that the change in the refractive index corresponding to a rise of 10" in the scale- reading is less between 90" and 100" than between 0" and 10".If, however, the increase of the refractive index per 1" of scale-reading decreases at a uniform rate, it will be possible to express the relation between the refractive index and scale-rertding by the formula 1000[n],,= 1422 +ax - bx2, where [?&ID is the refractive index for sodium light and xis the scale-reading; a and b are constants.Using the values of [nIn for 0", 50", and 100" on the scale, I find that 1000[n],= 1422 + 0.817~- 0-00142~~. Using these values for a and b, I find that the results calculated by the formula agree perfectly with those in the table supplied with the instrument a t 10, 30, 40, 60, 80, and 90, and that a t 20 and 70 there is a difference of one unit in the fourth place of decimals; from this I think that the formula may be safely w t d for con- verting intermediate scale-readings into the corresponding refractive indices. The following will perhaps be found more convenient for calculation : [%ID= 1.4220 +0*00142~ DISCUSSIOX.Mr. E. R. BOLTON said that by the use of this formula a chart could be construc- ted from which the figures could be read off without calculation. I t could be constructed to read to the fourth decimal place, which probably would not be given very accurately by the slide-rule, while the butyro-refractometer almost gave the fift,h place.While referring to this subject he should like to put in a plea for uniformity of temperature in the recording of refractive indices. He had made it a practice not to record a refractive index at any other temperature than 40' C. ; but one found figures obtained at 15", 20°, 25') 40°, or 45'. Mr. ROBERTS said that his object in working out the formula in the first instance had been to provide a ready means of converting readings when a chart had been mis- laid-as had happened in his own case.

ISSN:0003-2654    

DOI:10.1039/AN9164100376

出版商:RSC    

年代:1916

数据来源: RSC

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FOOD AND DRTTGS ANALYSIS 377 ABSTRACTS Progressive OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Oxidation of Cold-Storage Butter. D. C. Dyer. ( J . Agric. Research, 1916, 6, 927-951.)-Since approximately 10 per cent. of the volume of butter is air, it was considered that an examination of the air in packages of butter and of butter-fat might furnish data as to whether the undesirable chemical changes (development of unpleasant flavour) occurring in stored butter are caused by a progressive oxidation of the fat itself or in some one or other of the non-fatty in- gredients.The air contained in various cold-storage butters was, therefore, sepa- rated and analysed. The composition of the air confined within a package of pas- teurised sweet-cream butter known to contain bacteria and made from cream having an acidity of 0.11 per cent. (calculated as lactic acid) showed little or no variation from its original composition after storing for six months at 0" F.; when stored under like conditions, the butter-milk from the same cream did not affect the composition of the air in the vessel containing the milk. When the butter was kept at 32" F., the composition of the enclosed air underwent a decided change, and this change wars increased when the butter remzincd f ~ r z, short time at ordinary teiiiperatiire, the oxygen content decreasing and the carbon dioxide content increasing. The butter itself possessed no unpleasant flavour after six months' storage a t 0" F.The composition of the air enclosed in a butter made from sweet cream and churned immediately after the addition of 15 per cent.of a commercial starter showed but little change after storage for six months at 0" F., and the butter kept well; the air from butter made from cream to which lactic acid had been added underwent con- siderable change during storage, the oxygen and carbon dioxide decreasing in quan- tity. The flavour of this butter became unpleasant after three months.A small quantity of butter-milk from butter prepared with the addition of lactic acid was exposed to the action of a very large and confined surface of air at 0" F.; after one month the whole of the oxygen had disappeared. The carbon dioxide content, originally 2.37 psr cent., had increased to 34 per cent.; it then decreased.Further experiments with pure butter-fat and the same mixed with varying quantities of protein, lactose, etc., showed that after storage a t 0' F. the quantity of carbon dioxide in the enclosed air was directly proportional to the amount of non-fatty ingredient present, and that the oxygen content showed a relative decrease. The pure butter-fat was not oxidised t o any appreciable extent, but when the fat was spread on pumice and exposed to the action of a large volume of air at 32" F., a slight oxidation was noticed.The results of the investigation may be summed up as follows : The unpleasant flavours which develop in butter during cold storage are not produced by the oxidation of the fat itself, but by' some chemical change which takes place in one or more of the non-fatty ingredients.The exteqt of this chemical change is proportional to the quantity of acid present in the cream from378 ABSTRACTS OF CHEMICAL PAPERS which the butter was prepared. The quantity of carbon dioxide present in cold- storage butter probably depends on the amount of butter-milk in the butter, and may increase to a maximum, followed by a progressive decrease.w. P. s. Estimation of Citric Acid in Milk. R. Kunz. ( A r c h . Chem. Microsk., 1915, 8, 120-133; through Int. Rev. Sci. and Prac. of Agriculture, 1916, 7, 739.)- Stahre's method for the estimation of citric acid in wine (ANALYST, 1915, 40, 464) may be used for the estimation of this acid in milk. Fifty C.C. of the milk are treated with 20 C.C. of 50 per cent.sulphuric acid, 2 C.C. of 40 per cent. potassium bromide solution, and 20 C.C. of phosphotungstic acid solution; the mixture is diluted with water to 200 c.c., shaken and filtered. To 150 C.C. of the filtrate are added 25 C.C. of freshly prepared saturated hydrobromic acid solution; the mixture is heated at 50" C. for five minutes, and then treated with 10 C.C. of 50 per cent. potassium permanganate solution, the latter solution being added gradually while the mixture is stirred.The remaining part of the process is then carried out as described in the case of wine. Fresh milk contains aboht 0.19 grm. of citric acid per 100 c.c.; the quantity is slightly larger in the first milk drawn than in that obtained at the end of the milking. In ordinary milk the citric acid content diminishes progres- sively as the milk sours; curdled milk is free from citric acid, but " Yoghurt " contains about 0.16 grm.per 100 c.c., and this quantity does not decrease when the preparation is kept. w. P. s. Estimation of the Fat Content of Dried WholeMilk. K.Mohs. (Zeitsch. ges. Getreidew., 1916, 8,37-41; through J. Xoc. Chem. Ind., 1916,35, 1127.)-Samples of dried whole milk which have been kept for some time show an apparent reduction of fat content as determined by extraction with ether.This appears to be due to adsorption of the fat by the coagulated protein of the milk. The adsorbed fat is not removed by simple extraction with ether. The following procedure, based on a method described by Neumann (Zeitsch. ges. Getreidew. , 1912, 4, 8) is recommended for the determination of the fat: 1.5 grms.of the finely divided milk powder are heated with 50 C.C. of water and 6 C.C. of hydrochloric acid of sp. gr. 1.125 for one and a half hours in a boiling water bath. After cooling, the solution is made neutral to methyl orange by addition of concentrated sodium hydroxide solution, then acidified with dilute hydrochloric acid, and filtered.The filter with its contents is dried for two hours at 105" C., and then extracted with ether for six hours in a Soxhlet apparatus. Valuation of Nitrogenous Compounds in Feeding-Stuff s. N. Passerini. (Annali Chim. Applic., 1916, 6,162-164.)-The method is based on the fact that the proteins of ordinary feeding-stuffs are rapidly hydrolysed by 25 per cent.sulphuric acid into soluble dialysable substances (peptones, etc.). After three hours' boiling the amount of ammoniacal nitrogen in the hydrolysed liquid, derived largely from the amines and amino-acids, remains constant. For example, 5 grms. of the sample hydrolysed with the acid yielded the following amounts of ammoniacal nitrogen : After one hour, 0.347 grm.; after three hours, 0.397 grm.; and after four hours,FOOD AND DRUGS ANALYSIS 379 0 397 grm.For the analysis 1 grm. of the finely divided material is taken for the esti- mation of the total nitrogen (a). The amines are then separated in 2 grms. of the sample by Kellner’s method of precipitating the proteins with copper oxide, and the protein nitrogen ( b ) is estimated in the copper precipitate.Kellner’s method is repeated on 5 grms. of the sample, and the copper precipitate is boiled for four hours on a sand-bath beneath a reflux condenser with 100 C.C. of 25 per cent. sul- phuric acid. The liquid is treated with hydrogen sulphide to eliminate the copper, made up to 500 C.C. and filtered. The excess of hydrogen sulphide is expelled by boiling from an aliquot part (200 c.c.) of the filtrate, and the ammoniacal nitrogen ( c ) is distilled.In the residue left on the filter the non-hydrolysable nitrogen (d) is estimated, and is to be regarded as nucleiizic nitrogen. The amounts thus obtained may be assigned as follows: (1) Nitrogen of free amines (asparagin, etc.) = a - b ; (2) nitrogen of amino-acids =b - (c+ d ) . The following results obtained with a vetch flour illustrate the method.Total nitrogen, 3.66; nucleinic nitrogen, 0.14; nitrogen of amino-acids, 1.79 ; ammoniacal nitrogen in hydrolysed liquid, 0.42 ; and preformed amino-nitrogen, 1.30 per cent. C. A. M. Presence of Copper in Tomatoes and Tomato Preserves. G. Liberi, A. Cusmano, T. Marsiglia, and C. Zay. (Ann. Stax. chim.-agrur. sperim. Roma, 1916, 8, 163-303; through Int.Rev. Sci. and Prac. of Agriculture, 1916, 7, 662-664.) -Numerous samples of tomatoes grown at the experimental farm belonging to the Stajtion of Agricultural Chemistry, Rome, and other samples obtained from various districts in Italy, were all found to contain copper in quantities varying from 0.14 mgrm. to 2.1 mgrms. per kilo of juice and pulp, or from 388 mp;rms.to 19-45 mgrms. per kilo of dry substance. All the soils on which the tomatoes had been grown contained copper, the maximum quantity found being 110.74 mgrms. per kilo of dry soil. The amount of copper in the fruits was not affected when the plants had been sprayed with Bordeaux mixture. Preserved tomatoes contained corresponding quantities of copper. w. 9. s. Analysis of Rhamnus Barks.0. Tunmann. (A/noth.-Zeit., 1915, 30, 642; through J . Chem. Soc., 1916,110, ii., 504.)-The red-coloured foam which is obtained when drugs containing anthraquinones are shaken with sodium hydroxide solution is probably due to the presence of chrysophanol; the latter is present, therefore, in Rhamnus carniolicus as well as in R. catharticus, and the reaction simply’ serves to distinguish these from the American rhamnus bark, R.purshiana. Tschirch’s colorimetric method indicates that the quantities of anthraquinone derivatives in R. frartgulus and in R. purshiana have a ratio of 4 : 1, ’whilst according to the author’s gravimetric method the ratio between the two respective quantities is 3 or 2.5 : 1. Use of the Iodic Acid-Starch Reaction in the Examination of Wine and Vinegar.J. Jaenpretre. (Chem. Zeit., 1916, 40, 833.)-A mixture of sblphurous acid, iodic acid, and starch develops a blue colour after some length of time-a reaction which was first pointed out by Landolt (Be?., 1886,19,1317). Investigation380 ABSTRACTS O F CHEMICAL PAPERS of this reaction showed that the development of the blue coloration deyeiids on the kind and concentration of the acid, the temperature, etc.The reagent used consists of a mixture of 10 C.C. of 0.2 per cent. scdium iodate solution, 10 C.C. of 0.2 per cent. sodium sulphite solution, 5 C.C. of 0.5 per cent. starch solution, and 75 C.C. of water. When 10 C.C. of this reagent are mixed with 10 C.C. of $; acid solutions, the time which elapses before the coloration appears is as follows: Acetic acid, 438 sees.; succinic acid, 320 sees.; malic acid, 52 sees.; citric acid, 45 sees.; tartaric acid, 26 sees.; oxalic acid and mineral acids, immediately.As the time required for the development of the coloration is considerably diminished by the presence of a trace of free mineral acid, the reaction may be used for the detection of mineral acids in wine and vinegar.If, when mixed with the reagent, 10 C.C. of the sample give a blue coloration in less time than do 10 C.C. of citric acid of equal strength, an abnormal amount of free mineral acid is present. As a rule, a non-sulphured, non- plastered wine reacts as slowly as does a succinic acid solution. w. P. s. Detection of Artificial Colours in Wines. H. Kreis. (Chew,. Zeit., 1916, 40, 832.)-Certain dark red wines, even when diluted, contain colouring matter which fixes on wool and cannot be removed by washiiig the wool with boiling water; con- sequently, this test may indicate the presence of aniline dye although this may be absent. If the wine dyes wool, the latter should be heated on a water-bath with a small quantity of 1 per cent. ammonia solution which destroys the natural colouring matter derived from the wine, whilst aniline dyes, for the most part. go into solution. The ammoniacal solution is then acidified with sulphuric acid and heated with a fresh thread of wool. The latter remains white if aniline dyes are absent. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9164100377

出版商:RSC    

年代:1916

数据来源: RSC

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380 ABSTRACTS O F CHEMICAL PAPERS BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Deteetion and Estimation of Hydroeyanie Aeid in Beans. L. Guignard. (Ann. Falsific., 1.916, 9, 301-305.)-Burmah beans may be imported into France provided that the consignment, on analysis, does not show a higher hydrocyanic acid content than 0.02 per cent. The beans, which belong to the PhaseoZus Zunatus species, are of two kinds, red and white, and the white beans are frequently used for food. The author has found 0.025 per cent.of hydrocyanic acid in certain samples of the dried beans. The method employed for detecting the presence of hydrocyanic acid consisted in mixing the powdered bean with five times its weight of water in a flask and suspending in the upper part of the flask a strip of paper which had been dipped in solution containing picric acid and an excess of sodium carbonate An orange-red colour developed on the paper within twelve hours if the bean contained a hydrocyanic glucoside.The quantity of hydrocyanic acid was estimated by macerating 20 grms. of the powdered bean with water for twelve hours, then submitting the mixture to steam distillation, and collecting the dis- tillate (125 c .~ . ) in a receiver containing dilute ammonia. The distillate was then titrated with & silver nitrate solution, using potassium iodide solution as the indi- cator. w. P. s.BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 381 Salicylic Acid Reaction of Soya Beans. H. C. Brill. (Yhilipp. J . Sci., 1916, 11, 81-89.)-All the samples of Japanese soya beans tested gave the ferric chloride colour test for salicylic acid.American, C'hinese, and native beans gave either negative or faintly positive tests with the same reagent. All samples of soya beans gave a negative result for salicylic acid with the Millon reagent and with the Jorisseii reagent (see AFAL: ST, 1910, 35, 252 and 253). The reacting conipouncl in the beans has all the ordinary test properties of salicylic acid, but is undoubtedly similar to the inaltol of Brand (Ber., 1894, 27, 806).Jorissen's reagent should therefore be employed in testing beans for salicylic acid. H. F. E. H. Resistance of Non-Sporing Bacteria in Milk to the Action of Heat. C. Gorini. (Rend. R. Institut. Lombard0 Sci. Lettere, 1915, 48, 056-961 ; through Int. Rev. Sci.and Prac. of Agriculture, 1916, 7, 74O.)-Experiii1~nts showed that the presence of non-sporing bacteria in milk which had been pasteurised was due to the formation of a protective covering of casein round the bacteria, this covering prob- ably being caused by the action of the bacteria themselves, before or during the sterilising process. Thus the explanation of the apparent resistance of non-sporing bacteria to the action of heat is rendered more comprehensible.In none of the experiments was any case found of resistance to heat above 85" C., and no bacterium, even when artificially covered with casein, ever survived a temperature of 90" C., whilst under normal conditions the bacteria resisted sterilisation a t 100" C. As the survi-s~ing bacteria-, howeverj were localised in small clots of casein and had acid- coagulating properties, the difference is attributed by the author to the unavoidable difference between natural and artificial conditions, which do not affect the theory that the thermo-resistance is due to the protective layer of casein.w. P. s. Yeast Preparation for Use in the Estimation of Crystallisable Sugar by Inversion.H. Pellet. (Yroce's- Verbaux de Z'Ass. d. Chim. de Xucr. et d. Dist., 1915, 33, Bull. 1-3, 12-13; through Int. Rev. Sci. and I'rac. of Agriculture, 1916, 4, 592.)- A preparation of yeast which is very active and retains its inverting capacity for a prolonged period may be made by the addition of sodium salicylate at the rate of 0.2 grin. of salicylate per 3 grms. of yeast, which is thereby liquefied almost instan- taneously. Yeast may be thus treated in, quantit)y and when required for use diluted in the proportion of 30 grms. in 100 c.c.; 10 C.C. equivalent to 3 grms. of yeast being used per 50 C.C. of sugar solution (neutral and free from lead). Inver- sion is complete in half an hour a t 55" C., the ordinary Clerget forniula being em- ployed to calculate the cane-sugar, using the constant 141.8 - & t in place of the 144 (Clerget) or 142.7 (German formula and method). H. F. E. H.

ISSN:0003-2654    

DOI:10.1039/AN9164100380

出版商:RSC    

年代:1916

数据来源: RSC

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BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 381 ORGANIC ANALYSIS. Detection of Arachidic Acid. R. H. Kerr. ( J . Ind. and Eng. Chmn., 1916, 8,904.)-The following method is simpler than Renard’s official method, and obviates the use of ether: Twenty grms. of the oil are heated with 200 C.C. of 95 per cent.382 ABSTRACTS OF CHEMICAL PAPERS alcohol in a 300 C.C. Erlenmeyer flask, and 10 C.C. of 10 per cent.potassium hydroxide are added to the boiling liquid. After saponification of the oil the excess of alkali is neutralised with a solution of 50 C.C. of glacial acetic acid in 150 C.C. of 95 per cent. alcohol, and 5 C.C. of a 5 per cent. solution of magnesium acetate in a mixture of equal volumes of water and 95 per cent. alcohol are added. The flask is cooled, with_foccasional shaking, and then left in a refrigerator a t 10" to 12" C.until the next day. The precipitate is filtered off, washed twice with 50 per cent. alcohol and three times with water, and returned to the flask. It is then treated with 100 C.C. of hot water and sufficient dilute sulphuric acid (50 : 150 c.c.) to deconipose the magnesium salts, and heated until the fatty acids form a clear layer.After solidification, these are washed with hot water, again left to solidify, drained from water, and dissolved in 100 C.C. of 90 per cent. (by volume) alcohol. The arachidic acid which crystallises is separated by the method of the Ass. Off. Agric. Chemists (Bull. 170, Revised, Bureau of Chemistry, p. 146). The method gives results as good as those obtained by Renard's method, and is capable of detecting 5 per cent.of arachis oil in olive oil, cottonseed oil, soya-bean oil and niaize oil. C. A. M. Estimation of Carbohydrates-V.: The Supposed Precipitation of Reducing Sugars by Basic Lead Acetate. W. A. Davis. (J. Agric. Xci., 1916, 8, 7.)- Since Gill (J. Chem. Xoc., 1871, 24, 91) observed that the addition of an excess of basic lead acetate to a solution of invert sugar reduced the negative rotation of the !m-u!ose owing t o the fmiliaticjii of a soluble co~npou~ici, rriany workers 'nave assumed that this sugar is precipitated by the defecating agent to a greater or less degree.The author shows that, a t least in dilute solutions, lzvulose is never precipitated by basic lead acetate even in presence of salts such as chlorides, sulphides, or carbonates.No loss of lzvulose occurs unless the excess of lead is allowed to act for some length of time upon the sugar before the lead is precipitated. Thus, if basic lead acetate is left with a solution of pure lzvulose for periods of time such as fifteen minutes, one hour, or twenty-four hours, and the lead is then precipitated by sodium em- bonate or sulphate, amounts of laevulose are found to have disappeared, depending solely on the time of action, the solution becoming more and more yellow, but no visible separation of lzvulose occurs. It is probable under these conditions that a substance resembling or identical with the so-called glutose of Lobry de Bruyn and van Ekenstein (Rec.Trav. Chim., 1897, 16, 262) is formed, having little or no optical activity and a reducing power about one-half that of dextrose.It is shown that, provided basic lead acetate solution is added in small quantities a t a time until precipitation is just complete, and that the excess is not allowed to reach more than about 5 C.C. in 300 to 500 of sugar solution, there is no loss whatever of reducing sugar. The excess of lead should be removed with sodium carbonate or sulphate as boon as possible after filtering off the precipitate.Dextrose and maltose remain practically unchanged in presence of a considerable excess of basic lead acetate, although eventually even with these sugars soluble lead compounds having a different optical activity may be formed (4. Watts and Tempany, ANALYST, 1908, X3, 130; Eynon, ibid., 1909, 34, 349).H. F. E. H.ORGANIC ANALYSIS 383 Analysis of Crude Calcium Cyanamide. E. Truninger. (Schzueiz. ver. anal. Chem., May 26 and 27, 1916.)-A slight alteration is to be made in the method previously dekcribed : the cyanamide should be precipitated with neutral silver nitrate and the ammonia added afterwards. For the present, the dicyandi- amide may be determined indirectly by the simultaneous precipitation of cyanamide and dicyandiamide with silver nitrate and 2 per cent, potassium hydroxide solution, and subsequent determination of the nitrogen in the precipitate by Kjeldahl's method.The determination of urea has not been deeply studied because it is not yet certain whether that substance is present. Caro's method (ANALYST, 1916, 36, 76) could not give accurat'e results, because the prolonged heating with alkali to drive off the ammonia would cause losses not only of dicyandiamide, but also of urea if present.Determinations of the insoluble nitrogen in the residue from the extraction of the crude material with water, and dilute nitric acid showed an average of 1 per cent.: in a few cases 2 per cent.was found. Agricultural experi- ments with calcium cyanamide on oats confirmed its favourable effects; with the exception of a single sample rich in dicyandiamide, an increased yield was recorded. The injurious influence of considerable quantities of this substance was shown a t an early stage, but could be largely inhibited by the simultaneous application of a readily assimilable nit'rogen compound.I n considering the unfavourable influence of the dicyandiamide, its great stability in the soil must be taken into account; nitrification had not taken place after a period of two months. Secondary ill-effects were observed in the case of oats even in the ~eccjfid year; or, the ot'her hand, calcium cyanamide which had lain for a long time on the moist ground had lost much of its valuable properties.Vegetation experiments with urea and urea nitrate showed excellent results with oats. With winter wheat a top dressing of calcium cyanamide and urea showed the great value of urea used in this form. Casein and its Technical Applications. D. Marotta. (Annali China. AppZic., 1916, 6, 165-176.)-Pure casein has a sp. gr. of 1.259. When dried in the air a t 70" to 80" C.for five hours it loses 5 to 8 per cent. in weight, while when dried in vacuo it retains 2 per cent. of moisture. It is readily soluble in 1 per cent. Eolutions of sodium fluoride, ammonium oxalate, and potassium oxalate, and in 5 per cent. solutions of ammonium chloride or sulphate. It ought to be free from Eoluble salts, lactose, or peptones, and should yield less than 1 per cent.of ash on ignition. Technical casein is yellowish, and yields up to 6 per cent'. of ash. It contains 12 t o 13 per cent. of water, 12 t o 13 per cent. of nitrogen, and about 0.5 per cent. of fat. When prepared by the action of acids, it is soluble in solutions of alkalis and sodium salts of the following strengths : Sodium hydroxide, 2.0; carbonate, 2.5; bicarbonate, 3; silicate, 10; arsenate, 20; sulphite, 9; tungstate, 12.5; borate, L:-5: and ammonia 2.5 per cent.The casein obtained by the action of rennet is in~oluble in solutions of sodium carbonate and bicarbonate, partially soluble in borax and ammonia solutions, and soluble in sodium phosphate Eolution. Of the pharnia- ceutical preparations of casein, perriodo-cas&n contains 17.89 ; iodo-casein, 1 5 7 ; and caseo-iodine, 8.7 per cent.of iodine. A casein still richer in iodine (21.6 per cent.) is prepared by adding iodine to milk and precipitating the compound with acetic354 A BS'l'RACTd OF CHEMICAL PAPERS acid. The Zacfo-iodine-periodine of commerce contains 5.7 per cent. of iodine. Pre- parations of bromo-casein contain from 4.5 to 11 per cent.of bromine. There is also a chlorine preparation wit'h 2.8 per cent. of chlorine, and a Fuoro-ca.sein con- taining 1.6 to 1.8 per cent. af fluorine. Xilver caseinate contains 80'16 to 9.66 per cent. of silver, and there are also preparations containing 4, 10, and 15 per cent. The compound " argonine," which is prepared by treating sodium caseinate with silver nitrate and precipitating the compound with alcohol, contains 4.2 per cent.of silver. Another commercial product, " argonine L," contains 10 per cent. of silver. Coiiipouiids of casein with alkaloids are prepared by suspending the casein in alcohol and editing an alcoholic solution of the alkaloid. Iron caseinate contains 3-6 per cent. of iron. C. A. M. Comparison of Barbituric Acid, Thiobarbituric Acid, and Malonylguani- dine as Quantitative Precipitants for Furfural.A. W. Dox and G. B. Plai- sanee. ( J . Amer. Chem. Xoc., 1916, 38, 2156-2166.)--Unger and Jiiger (Ber., 1902, 35, 4440, aiid 1903, 36, 1222) applied the reaction between barbituric acid and furfural to the quantitative estiination of the latter, but a large excess of the acid appears to be necessary for conipjete precipitation although the reagent has the advantage of not precipitating hydroxymethyl furfural.The authors found that for various reasons thiobarbituric acid-CH?(CO),(~~),CS-is much the better reagent t o use, and this was prepared according to the method of Fisher and Dil- threy (AWN., 1904, 335, 350), in which twice thg themetical a:~,=unt ~f sediurn dis- solved in a little alcohol is mixed with 16 grms.of iualonic ester and '7.6 grms. dry thiourea previously dissolved in absolute alcohol. The mixture is heated for fifteen hours in a closed tube a t 105" C., and the product, after acidifying with hydrochloric acid, separates as a slightly yellowish crystalline powder cont aiiiiiig 19.6 per cent. of nitrogen. The yield is 45 per cent. of theory.The precipitation of the furfural is carried out in 12 per cent. hydrochloric acid solution at room teiiiperature in a total volume of 400 c.c., using slight excess of the thiobarbituric acid exactly as in the case of phloroglucinol, and after being allowed to stand overnight the precipitate is filtered off and dried till constant a t 100" C. I n the case of malonylguanidine, the condensation of furfural is not quantitative, the best results being 50 per cent.in error, while with barbituric acid only 95 per cent. of the furfural taken is re- covered when using about 60 ingrins. of furfural, while with small amounts of fur- furel (12 to 35 mgrms.), only from 25 to 80 per cent. is recovered. With thiobar- bituric acid, however, the theoretical weight of precipitate is obtained working on quantities of furfural varying froin 11 to 60 mgrms.Variations in the amount of precipitant were of little influence. The subst aiice formed-furfuralinalonyl- thiourea (C, H,O,N,S) is a bright yellow precipitate, very flocciilent and voluminous, practically insoluble in cold dilute acids, alcohol, ether, petroleuin ether, methyl alcohol, acetic acid, benzene, carbon disulphide, and turpentine.In ammonia, pyridine, and caustic alkalis it dissolves readily, giring a greenish-blue solution which gradually loses its colour. It is essential that the thiobarbituric acid em- ployed should be strictly pure and free from dicyandiacetylthiourea, or error will be introduced, and it is recommended that the malonic ester used for its prepara-ORGANIC ANALY81S 385 tions shoitlcl be subjected to a repetition of the siniultaneous saponification and esterification before condensation with thiourea, and that the thiobarbitnric acid itself be purified by one or two crystallisations of its sodium salt.The authors do not find that any reliance can be placed upon the separation recommended by Ishida and Tollens ( J .Landzc., 1911, 60) for the separation of the phloroglucides of furfural and methyl furfural based on the solubility of the latter in alcohol. Since methyl furfural is also precipitated by thiobarbituric acid, evidence can only ke obtained of its presence bj- analysis of the condensation product, which in the care of the methyl salt contains nitrogen 11.86 per cent.and sulphur 13-56 per cent., as against the 12.6 and 14-41 in the furfural compound. The author considers that such an analysis would show the presence of methyl furfural if present to the extent of 1 in 3 of furfural; but where the ratio is less, the lowering of the nitrogen would be within the limits of analytical error. H. F. E. H. Benzoyldihydromethylketol Hydrazine.New Reagent for Galactose. J. von Braun. (Ber., 1916, 49, 1266-1268; through J . Xoc. Chem. Ind., 1916.)- Benzoyldihyclromet hylketol hydrazine, is a specific reagent for galactose, with solutions of which it gives a colourless cry- stalline precipitate in froin half to two hours according to the concentration. With dextrose, laevulose, mannose, arabinose, and xyloee no precipitate is produced.The base is prepared froiii beiizoyldihydromethylketol, which is nitrated and reduced t o m-amino-K-benzoplclihydromethylketol. This is diazot'ised and reduced with stannous chloride, a i d the hydrazine isolated in the usual way. It crystallises from alcohol in colourless needles (m.-pt. 150-151" C.), and is apparent,ly quite stable when dry. The h5-drochloride melts at 195" C'., and the semicarbazide derivative at 213" C.Highly Unsaturated Hydrocarbon in Shark Liver Oil. M. Tsujimoto. (J. Ind. and Eng. Chem., 1916, 8, 889-896.)-Ai-zami oil, extracted from the liver of the Japanese squaloid shark, Xqualus mitsukurii, gave the following analytical values: Sp. gr. at 13"/4' C., 0*8644; solidification point, below - 20" C. ; acid value, 0; saponification value, 22.98 ; iodine value (Wijs), 344.63 ; f n ] ~ 200 c , 4930. qatty acids (10.62 per cent.) : Pu'eutralisation value, 168.52; iodine value, 119.25.Glycerol, 0.52 per cent. ; and unsapoiiifiable matter, 9O*l'i per cent. Heratsuno-xamh oil from the liver of another sqaaloid shark, Deania eglantina, gave the following values: Sp. gr. a t 15"/4" C., 0*8'721; acid value, 0.49; saponification value, 52.46; iodine value (Wijs), 261.72; [ n ] ~ 20 c., 1.4850.Fatty acids (26.59 per cent.) : Neutralisation value, 168.39; iodine value, 7335. Glycerol, 0.39 per cent. ; and unsaponifiable matter, 72-88 per cent. In each case the unsaponifiable matter, after deducting the cholesterol (0.65 and 1.24 per cent. respectively), consisted mainly of a hydrocarbon or hydro- carbons, which could be separated by shaking the saponified oils with petroleum spirit. It was a colourless oily liquid and had the composition Cf0H,,, and showed386 ABSTRACTS OF CHEMICAL PAPERS the following charasters : Boiling-point, 262' to 264" C. (10 iiini. pressure) ; solidifica- tion point, - 55" C. ; sp. gr. a t 15"/4" C., 0.8587; iodine value, 388.12 (Wijs) ; [ n ] ~ Z O C O . , 1-4965. It dried rapidly, yielding a colourless film superior to that formed by vegetable drying oils. It formed an addition compound with bromine, C,oH,oBr,, . The hydrogenated product, C,,HBZ, resembled the so-called liquid paraffins, but was more stable in the cold. It could be used for lubricating machinery. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9164100381

出版商:RSC    

年代:1916

数据来源: RSC

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386 ABSTRACTS OF CHEMICAL PAPERS INORGANIC ANALYSIS. Aeration Method for Ammonia. B. S. Davisson, E. R. Allen, and B. M. Stuttlefield. ( J . I n d . and Eng. Chem., 1916, 8, 896-899.)-The authors have in- vestigated the conditions under which ammonia can be quantitatively distilled in a current of cold air, with minimum risk of decomposing nitrogenous organic matter and with complete absorption of the ammonia in standard acid.Magnesia is prefer- able t o stronger alkalis for liberating the ammonia, as it has less effect on organic matter and is less liable to be carried forward mechanically into the standard acid by strong air currents. Magnesia, of which 0.6 grm. is usually sufficient, works admirably, but rapid air cur- rents are requisite when using it, if the determination is to be complete in two and a half hours.For these rapid air currents (about 1,000 iitres an hour), Folin tubes are useless, and the apparatus illustrated is used by the authors. The main part of the absorption tube is 14 inches in diameter and 15 inches long. The side arm has a bore of 8 rnm. C and E are glass rods, about 1+ inches long, held in place by baffles made from rubber gasket.The purpose of the baffle at E is to stop any acid which spatters from the lower part of the tower. The aeration bulb D is well perforated, so tha.t complete stirring of the solution will be obtained, and should extend well to the bottom of the flask. The tubes connecting the flask t o the absorption apparatus an one side as shown, and to the next unit in the series, which may conveniently be as many as ten sets, are of 5 mm.bore. The entering air should be scrubbed successively with sodium hydroxide and 25 per cent. sulphuric acid. If the scrubbing with sodium hydroxide be omitted, the part set in the series may yield low results, owing to the small quantity of magnesia, used becoming largely carbonated, and it is desirable not to use large (10 grin.) quantities, as is sometimes done.NOTE BY EDIToR.-The use of magnesia is undesirable in ammonia distillations in presence of phosphates, as some ammonia may be retained as ammonium magnesium phosphate. G. C. J. Volumetric Estimation of Cobalt. W. D. Engle and R. G. Gustavson. (J. Ind. and Eng. Chem., 1916, 8, 901-902.)-The method depends on the fact that sodium perborate, in presence of alkali hydroxide, oxidises cobalt to cobaltic hydroxide, butIXORGANIC AKALYBIS 587 does not oxidise nickel.The excess of the reagent is readily decomposed by boiling and the cobalt can then be estimated iodometrically. The ore or other material is dis- solved by means of acids, and the metals of the copper and iron groups, and also manganese, are removed by standard methods.The solution so obtained may contain cobalt, nickel, and zinc, but must be free from substances capable of liberating iodins from an acid solution of potassium iodide. The solution (100 c.c.) is acidi- fied with dilute sulphuric acid, of which an excess of about 5 c . ~ . is added. Sodium perborate (1 to 2 grms.) is added, and, after it has dissolved, sodium hydroxide is added to strong alkaline reaction and the mixture boiled for ten miqutes t o decom- pose the excess of perborate.When cool, 1 grm. potassium iodide is added, the solution acidified with dilute sulphuric acid, and, after solution of the precipitate, the liberated iodine is titrated against standard thiosulphate. The latter may be standardised against pure, anhydrous cobalt snlphate, treated as described, or more conveniently against potassium bichromate, K2Cr,0, = 6 Co.The extreme error of the method, even in presence of ten times as much nickel as cobalt, appears to be no more than corresponds to 0.1 C.C. of the standard thiosnlphate used. G. C. J. Use of Solutions of Borax and Boric Acid in the Colorimetric Estimation of the Concentration of Hydrogen Ions in Sea-Water.S. Palitzsch. (Compt. Rend. Trav. Lab. Carlsberg, 1916,11, 199-211 .)-In Soerensen and Palitzsch's method fgr the estimation of the concentration of hydrogen ions in sea-water by colori- metric comparison with standard solutions with the addition of suitable indicators (phenolphthalein, naphtholphthalein, methyl red), the standard solutions of sodium borate and hydrochloric acid indicated (see AXALYST, 1910,35,216 ; 1913,38,394) give satisfactory results.In the case of a Polar expedition, however, practical difficulties arose which made it desirable to prepare the standards beforehand in the form of accurately weighed quantities of solid ingredients which could be dissolved in dis- tilled water when required for use.The author has therefore worked out a com- bination of borax and boric acid, the utility of which is not confined to the special purpose for which it was designed, and which shows many adva'ntages over the older standards for general use. Borax specially purified for analysis and suitable for the purpose is readily obtain- able; its purity should be checked by titration of the base with & hydrochloric acid in presence of methyl red, which gives a much sharper end-point than methyl orange.The moisture is determined by heating carefully but fairly strongly to redness in a platinum crucible. The boric acid is titrated in presence of glycerol and a moderately large quantity of phenolphthalein, using for comparison a blank solution of glycerol; results sufficiently accurate are obtained with 75 C.C.of gly- cerol for 0*5grm. of borax, although 150 C.C. are required for very high degrees of accuracy. If carbonates are present the carbonic acid must' first be expelled by boiling with sulphuric acid under a reflux condenser for five minutes. The con- centrations of the solutions most suitable for estimations in sea-water are: ,& of borax, equivalent to To sodium hydroxide-Le., 19*108 grms.per litre-and :' of boric acid-Le., 12.404 grins. per litre-to which are added 2.925 grms. of sodium388 ABSTRACTS OF CHEMICAL PAPERS chloride to compensate the '-salt error," the error due to the iiiodification of the eolour of the indicator by the salts apart from their influence on the ionic conceii- trittion. The author has staiidardised mixtures of borax and boric acid solutions by the electrical method, obtaining values set forth in the table below: CONCENTRATIONS OF HYDROGEN IONS IN MIXTURES OF BORAX AKD BORIC ACID.Borax TT. C.C. 10.0 9.0 8.0 7.0 6.0 5.5 5.0 4.5 4* 0 3.5 3.0 2.5 2.3 2.0 1.5 1.0 0.6 0.3 Boric Acid y. P&. 9.24 9.11 8.98 8.84 8.69 8-60 8.51 8.41 8.31 8.20 8.08 7.94 7.88 7.78 7.60 7.36 7.09 6-77 CA x109.0.58 0.78 1.05 1.45 2.04 2-51 3.09 -3.89 4.90 6.31 8.32 11.5 13.2 16.6 25.1 43.7 64.6 170 The errors due to the salts in sea-water have not been re-determined in the case of the borate solutions now proposed, but the corrections to be applied are the same as were prescribed for the older standards (ANALYST, Zoc. c i t . ) . J. F. B. Loss of Phosphoric Acid during Fusion with Ammonium Fluoride.W. A. Davis and J. A. Prescott. ( J . Agric. Sci., 1916, 8, 136-138.)-1n the analysis of salts or minerals containing phosphoric acid, treatment with hydrofluoric acid or ammonium fluoride was found to result in a considerable loss of phosphoric acid, which appears to be volatilised as phosphorus fluoride. The loss is least with phos- phates of the alkali metals, while the loss from phosphates of the alkaline earths is considerably greater and may rise to over 50 per cent.in the case of minerals such as apatite. The loss from disodium hydrogen phosphat,e is less than that from potassium dih-ydrogen phosphate. Experiments showed that the loss which occurs during ignition with sulphuric acid only takes place when there has been previous treatment with ammonium fluoride.H. F. E. H.INORGANIC ANALYSIS 389 Estimation of Moisture in Resinous Woods. E. Azzarello, (Annali Chirn. Applic., 1916, 6, 154-15$.)-From 1 to 3 grins. of fine shavings of t,he wood are weighed in the tared flaskd provided with a stopper I. The stopper is then replaced by the tube B-B, which has previously been charged with fragments of calciuin oxide placed in alternate layers with tufts of glass wool and then weighed.To the end of the small tube P is attached the tube C, filled with calcium chloride, to prevent the lime in B absorb- ing moisture from the air. The stopper E is turned so as to put B in communica- tion with A , the tap H is opened, and the apparatus is placed in an oven main- tained at 125' to 130" C.After thirty minutes it is allowed to cool with the tap H closed, and then replaced in the oven with the tap - open, this process being repeated until water is no longer condensed on the walls of the connection between A and B. The flask A may then be detached and weighed from time to time until the weight diminishes less than 2 to 3 mgrms. The loss gives the amount of volatile oil and water.The tube B-B is then heated wiOh the tap open in an oven at 200" C. until the weight becomes constant within 2 to 3 mgrms. This gives the moisture absorbed by the lime. Experiments with mixtures of water, volatile oil, and dry mineral matter show that the results are invariably too high, but are accurate within 0.5 per cent. C. A. M. Detection of Small Quantities of Selenium and its Distinction from Arsenic.J. Meunier. (Comptes rend., 1916, 165, 332-334.)-Selenious acid and selenites, when reduced with zinc and sulphuric acid, yield hydrogen selenide, a gas which is readily decomposed by heat with the deposition of selenium. The deposit of selenium obtained in a Marsh tube, however, has a red colour, particularly a t its densest part, and is quite unlike the deposit yielded by arsenic under similar con- ditions. When oxidised, the deposit is converted into white selenious acid. Larger quantities of selenious acid may be distinguished from arsenic by t'reating their hot solution with hydrogen sulphide; a turbidity due to precipitated sulphur is obtained, and, by heating the mixture for some time on a water-bath, this sulphur settles and390 ABSTRACTS OF CHEMICAL PAPERS entrains the selenium and arsenic sulphides which are formed. If seleiziurn sul- phide is present, the precipitated sulphur has a brown appearance, whilst the yellow colour of the sulphur is not altered by the presence of arsenic sulphide. If the pre- cipitate is collected, dried, and cautiously heated in a tube, t'he free sulphur vola- filises and a black residue of selenium sulphide remains. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9164100386

出版商:RSC    

年代:1916

数据来源: RSC

摘要:

390 ABSTRACTS OF CHEMICAL PAPERS APPARATUS, ETC. Washing Precipitates by Mechanical Means. E. Sinkinson. (Chew. News, 1916, 114, 170-172.) - The paper describes and illustrates an elaborate device which is intended to supersede the ordinary wash-bottle in washing precipitates, once they have been transferred to the filter. The funnel containing the filter is supported in a ring at the end of one arm of a balance, the other arm carrying a movable counterpoise and also an electrical commutator.Over the beam is fixed a table carrying two electric motors, one to control through a specially constructed mercury valve the flow of water to a jet, which is rotated by the other motor. The two motors are connected to the current supply through the commutator in such a way that, when the funnel end of the beam is up, the water supplied by gravity from a flask or tin-lined copper tank, passes freely to the jet, which sprays the water round the edge of the paper containing the precipitate.The counterpoise a t the other end of t'he beam is moved into such a posit,ion that, whez suscient water has flowed into the fume!, the increased weight causes the beam to drop, thus shutting off the water supply to the jet, so that no current is wasted during the period it is not required.As the water drops from the funnel, the arm supporting it becomes lighter; the beam rises and water again enters the filter from the rotating jet. G . C. J. Respiration Calorimeter, partly Automatic, for the Study of Metabolic Activity of Small Magnitude.Langworthy and Milner. (J. Agric. Res., 1916, 6, 703-720.)-The apparatus is similar in principle to, but modified in various ways from and much smaller than, that described by the same authors for the purpose of human experiments (ANALYST, 1916, 49), and can be used for investigations on the ripening of fruits and the wintering of bees. Chambers of varying sizes can be employed; that generally used has a capacity of 185 litres, being 45 cm.square and 91 cm. deep. The respiration chamber is part of a closed air circuit through which a stream of air is constantly moving; the air which leaves the chamber is passed through purifying devices and returned again to the chamber. The amount of heat resulting from the activity of the material employed is ascertained from determinations of (1) the quantity of latent heat in the 11-ater-vapour of the out- going water, (2) the quantity of sensible heat absorbed and carried away by water flowing in a coil of pipe in the chamber, and (3) the quantity of heat involved in changes in the temperature of the active material aiid of other objects in the chamber and also of the walls of t'he chamber.KO gain or loss of heat occurs through the walls of the chamber.Photographs and very full details of the apparat'us are given in the original paper. H. F. E. H.APPARATUS, ETC. 391 New Form of Viseosimeter. H. C. Hayes and G. W. Lewis. (Chem. Eng., 1916, 24, 103-104.)-The apparatus is based on the principle that a solid body having a surface of revolution, when suspended in a rotating liquid, is subjected to a torque which is proportional to the viscosity of the liquid.In the illustration of the instrument (see figure), the sample X is contained in a cylindrical chamber which is rotated uniformly by a motor, M , through a worm-drive, R. A cylin- der, C, is suspended in the liquid by a thin steel wire, W , so that the axis of the cylinder coincides with the axis of the rotating liquid.The rotating container is provided with a cap, B, so shaped that the excess of liquid can overflow when the cap is seated and thus give constant con- ditions within the chamber. The specimen chamber is surrounded by an oil jacket, J , with a thermometer, T. and the outside of the rotating chamber carries sinall mixing wings which cause a circulation of the jacket-oil; the jacket may be heated to any’ desired temperature by ineans of a coil or other device.The cover of the jacket chamber, D, is graduated in the form of a scale marked in degrees or calibrated in terms of a standard liquid, and the torque imparted to the suspended cylinder is indicated by the pointer P. The suspended cylinder and rotary container are made of copper to ensure rapid uniformity of temperature.If the temperature of the jacket be slowly raised, it is possible to secure direct readings for the temperature-viscosity curve in a con- tinuous experiment. The accuracy of this instrument has been verified by com- parisoii with observations made on gas-engine oils by a standard capillary tube instrument; on the other hand, determinations made with the same oils in a short capillary tube instrument and an orifice instrument showed far lower results. With the new rotary viscosimeter the sensitiveness can be varied by varying the speed of rotation or using suspension wires of various diameters. The density or change in density of the liquid is not a factor in the results, so that the indications are correct at all temperatures. The error of measuring short time intervals is excluded and the presence of suspended particles in the oil is without effect. J. IF’. B.

ISSN:0003-2654    

DOI:10.1039/AN9164100390

出版商:RSC    

年代:1916

数据来源: RSC

摘要:

APPARATUS, ETC. 391

ISSN:0003-2654    

DOI:10.1039/AN9164100391

出版商:RSC    

年代:1916

数据来源: RSC

摘要:

392 RE VIEWS REVIEWS. A METHOI) FOR THE IDEXTIFICATION O F PURE (IRGAXIC: COMPOUXDS. VOl. 11. By SAMUEL PARSONS MULLIKEN, PH.D. Chapman arid Hall, Ltd., London. John Wiley arid Sons, New York; By the author’s system of classification, described in Vol. I., organic compounds are divided into order, genus, division, section, and species, which, when it is not logical, is at least biological. Having dealt with Order I., Dr.Mulliken now brings under review Order II., comprising the substances which contain the elements (a) carbon and nitrogen, ( 6 ) carbon, nitrogen, and hydrogen, (c) carbon, nitrogen, and oxygen, (d) carbon, nitrogen, hydrogen, and oxygen, an imposing array of close upon 4,000. Preceding the tables in which t,hese materials, with their physical and chemical properties, are arranged according to the above system, there are described the tests necessary to supplement tlhose already given in Vol.I., and among them are included scales of bitterness, sweetness, and pungency, based upor, quinine sulphate, cane-sugar, and ammonium hydroxide, respectively. Then follow the tables :- Suborder I., Genus I. (Acidic), Division A (Solid), Division B (Liquid).Suborder I., Genus 11. (Basic), Division A (Solid), Division B (Liquid). Suborder.I., Genus 111. (Neutral), Division A (Solid), Division B (Liquid). All these are colourless, or have colours “ less saturated than Tint 3 of the color standard accompanying Vol. I.,” and it is stated in a footnote to page 3 that “ this color standard, consisting of the two cards A and B and a perforated screen, will be mailed to any person owning this work upon receipt of a postal money order for one dollar.” Suborder 11.comprises the solid “ species ” of this order, which are more saturated in colour than Tint 3 of the standard, but, for a reason which is obscure, acids, bases, and neutrals in this suborder are not distinguished. The compounds in each division are tabulated in ascending order of melting- point or boiling-point, as the case may be.The work is thus directed towards paving a royal road to identification, and a t first sight would seem to be a godsend to the harassed examinee; it looks almost as simple as furnishing at Drage’s. Nobody has yet invented a thornless rose, however, and one disadvantage of the book from the standpoint of the sanguine student lies in the enormous number of materials involved, and of which hardly more than 3 per cent.are likely t o be presented by any humane examiner. Consequently, to be useful, melting-points must be taken with meticulous accuracy, since a popular temperature, slightly confused by an unfaithful thermometer, may confront the victim with twenty or thirty alternatives.Moreover, there is always Tint 3 lurking in the background, tempting the ingenious examiner to crystallise his picric acid from petroleum. Dr. Mulliken and his associates deserve the greatest possible credit for the monumental industry which they have exercised, but it remains questionable whether the tortoise method of identification is not, after all, the best education for the chemical sleuth.M. 0. FORSTER. Price 21s. net.REVIEWS 393 CHAKGES IN THE FOOD-SUPPLY AND THEIR RELATIOX TO NUTRITIOK. By LAFAYETTE In this suggestive essay, written for the meetings of the second Pan-Anierican Scientific Congress at Washington, December, 1915, the author touches, somewhat lightJly, on many interesfing aspects of the question of national food-supply, more especially as affecting America, the object being rather to indicate the importance of inany of the factors concerned than t o make any definite suggestions.Short sections deal in turn with food production, preservation, and transportation, custom in diet, and changing social and hygienic conditions, and many interesting and curious facts are brought forward.The author lays stress on the circumstance that the most diverse diets in various parts of the world are known to produce adequate nutrition, so that, no one food material can be regarded as essential. He further points out, basing his observation 011 the recent work on nutrition carried out both in America and at home, that a profound.modification of the food problem may be effected by the addition to un- satisfactory food-stuffs, such as maize, of a small proportion of some other material rich in the constituents which are missing from the former.The importance of " accessory food factors " is also duly and rightly insisted on, and the danger accruing from the unrelieved employment of " a.rtificja1 products " is indicated. It is comforting to find that as regards the future food-supply of the world the author takes an optimistic view, considering that the progress of knowledge will for a very long period be more than able to cope with the increase of popu1at)ion and all its attendant difficulties.A. HARDEX. B. MEXDEL. Oxford University Press, 1916. Price 2s. 6d. net. &hCROSCOPY OF VEGETABLE FOODS. By A. L. WINTON, PH.D. Second Edifion.New York, J. Wiley and Sons, Ltd.; London, Chapman and Hall, Ltd., 1916. Price 27s. 6d. net. The first edition (1906) of this excellent work-which, however, is but a slightly improved issue, in English, of the second edition (1905) of Moeller's " Mikroskopie der Nahrungs-'und Genussinittel "-was reviewed in the ANALYST (1907,32, 138). This second editlion (1915) is little more than a reprint of the first edition, and those who possess Moeller's work or Winton's first edition will hardly need to provide themselves with this.There are exactly the same number of pages in t,he two editions-viz., 701. The Table of Contents, Glossary, and Index are exact reprints of those in tlhe First Edition, and the General Bibliography so closely follows the earlier one that no additions to it have been made, though there is mention of some in the text of the work, and all that has been done is to substitute the date of a later for an earlier edition.That there are only five references in the General Bibliography to any work issued since 1906 would seem to indicate that finality had been reached in this subject. As one puts the bwo editions side by side, page after page is ruled off without coining to any alteration, and when such does occur, by substitution of one diagram for another, or by the interpolation of new matter, there is seen the anxiety to catch up and get t'he old similarity of page-numbering and page-material restored.394 REVIEWS The failure to have observed, or unwillingness to recognise, any work done subsequently to 1906, and to bring the present edition up to date, is shown by the occurrence in identical terms in the two editions of the footnote on p.62 : ‘‘ Recently Brahms and Buckwald have found that the name aleurone cells is . . . erroneous.’’ What was recent in 1906 would hardly be so in 1916. Beyond the possible call for a re-issue of the work, and which one can well understand and appreciate-for the book is a really good and valuable one-the main idea of the second edition has been to give prominence to the work of the author’s collaborateuse, Kate Barber Winton, and of Miss Kate G.Barber, whom, from the similarity of the diagrams in the two editions, one takes to be the lady who assisted in the preparation of the first edition.Thus, there are now 635 illustrations as against 589 in 1906, 68 new ones- all but one being by one or other of the above-named ladies-being introduced. while 22 (mostly Moeller’s) have been dropped, and sometimes not to advantage. The new matter is stated in the preface to consist of “addit’ions to the sections on wheat and flour; a complete revision of such parts of the chapter on oil seeds as treat on mustards, rapes, cruciferous weed seeds, and linseed; a description of the histology of alfalfa, with distinctions from red and Alsike clover; a revision of the sections on ponies and drupes, with practical hints on the examination of almond pastes, jams, preserves, and other products ; and rewritten descriptions of the cucurbitaceous fruits used as food and adulterants.” An examination of these new features will lead to the conclusion that the revisions are not important, nor extensive, nor are the additions material.I n short, little or notthing has been done to supplement the information given in the first edition or t o remedy defects in it. When it is noticed that the subjects of mustards, rapes, etc., and of alfalfa, as well as of fruits generally, are those with which the additional illustrations supplied by K.B. Winton are associated, and that K. G. Barber has made all the illustrations of cucurbitaceous fruits, it will be seen that the new matter of this edition is con- cerned practically with t’he work of these ladies. Under Wheat and Flour come-on p. 50 an expansion of the description of the Pekar colour test, and on p.55 a similar one of Banichl’s test; two new cuts on p. 66, a slight alteration of the descriptive text on p. 67, the replacing of one of Moeller’s illustrations by a K. B. W., and the dropping out of another illustration (p. 68 in first edition) by Moeller, which, to the reviewer’s mind, gives to the analyst accustomed to deal practically with these matters a better idea than all the other illustrations, of what he is likely to come across in the actual examination of samples he has to identify.These are all the changes in this secttion. Under Oil Seeds there are-a slight change in the analytical key to cruciferous seeds; three additions to the Bibliography (none of them noted in the Index); 10 illustrations by K. B. Winton of white, black, and brown mustard, and rape, in place of 6 of Moeller’s, all of which have been dropped.Moeller suffers siniilar replacement in the case of false flax, but there are 4 new illustrations by K. B. W i n t o n f shepherd’s purse and pepper grass. Under Linseed there are 5 new To take the new features in detail.REVIEWS 395 K. B. FIT. illustrations. Moeller’s 2 being now omitted, and an addition of 10 lines is made to the histological description of the plant. Under Legumes, alfalfa now has 3 pages devoted to it in place of 20 lines, the extra space being occupied niainly by 8 new illustrations, all by K.B. Winton. Coming next to Fruits, there are 12 new illustrations by K. B. Winton, and the additions to the text do not occupy over a dozen lines.In the section devoted to Vegetables, Miss Kate G. Barber has her turn, coming out strongly with 14 new illustrations of pumpkin, squash, cucumber, and melon, 2 of Moeller’s having to make room for them. After the description of water-melon -which ends a t p. 410 in each edition-the pages to the very end (p. 670) are exact duplicates throughout. It is a pity that the opportunity was not taken to amplify in some cases the information given concerning the occurrence and use of the materials described, and to revise the somewhat loose statements met with here and there.If morc is dealt with than the actual description and the microscopical characteristics, such additional information should be fairly complete and also correct. This is not always the case here-e.y., i t is merely said of linseed cake that it is “ often contaminated with cruciferous and other seeds ” (p.206), and that it is “ the muci- laginous substance found in linseed that gives the seed its value in medicine ” (p. 204); alfalfa (p. 266) is spoken of as being grown especially in the arid and semi- arid regions of the United States, but there is no mention of the Argentine or other parts where it is extensively cultivated; to Carob bean (p.277) the alternative and better-known name “ locust bean ” is not given, nor to pea-nut (p. 269) those of “ earth-nut ” and ‘‘ ground-nut ”; to Soya bean (pp. 248-9), because of its now largely increased use, more space might have well been given, and there is no mention of its being made into a feeding:cake or of its other uses in the manufactures. Here and there, and especially in the section relating to condimental foods, paragraphs bearing on “ chemical examination ” have been inserted, but these are of such a general nature as to be practically useless.Either this should be set out adequately or it should be omitted altogether, and reference be made to special books where it can be found.It is to be regretted that the author, while giving such prominence to vegetables such as cucumber, melon, etc., has not seen his way to deal more fully with the distinctions that occur between seeds, etc., that may occur together and be readily mistaken one for the other--e.g., cotton seed and kapok (silk-cotton) seed. The work would be made much more useful to the practitioner if it contained more information of this kind.It’ is comparatively seldom that the analyst has single materials only to recognise, but he has more frequently to identify different ones in the presence one of another, and a setting-out of the main characteristics as they present them- selves in actual practice would be a great help to him. Thus, while it may be com- paratively easy, by the aid of such illustrations as this book supplies, to recognise single substances, the occurrence of several together requires special experience to enable one to identify them, and it is to be feared that this work, valuable though it is, will give only- modified help.Materials as they occur in actual practice, as, for example, in the case of an adulterated linseed cake, a compound feeding cake, or a food containing castor bean or other poisonous seed, do not present the clear396 REVIEWS appearances set out in the illustratioiis given, and the anaryst looks in vain for a setting-out of those characteristic features presented by each material or seed on which his experience tells him he must mainly rely.There is still a field open for a work which will supply this practical guidance.J. A. VOELCKER. TECHNICAL CHEMIST'S HANDBOOK: TABLES AND METHODS OF ANALYSIS FOR MANU- FACTURERS OF INORGANIC CHEMICAL PRODUCTS. By GEORGE LUKGE, PH.D. hcond edition, revised. London : Gurney and Jackson, 191G. Price 10s. 6d. net. The authors intention in writing this text-book has been to assist as far as possible in securing uniformity not only amongst practical chemists and analysts, but also amongst buyers and sellers, in regard to numerical data and analytical inethods employed in checking processes and testing the resulting product,s.As in the previous edition, one good analytical method only is given in each case, one process for the preparation of standard solutions, and also one for the examina- tion of each of the materials used in the particular industry concerned.This, as Dr. Lunge points out, tends to avoid discrepancies such as might arise should two or more methods be described. In the present edition numerous small changes occur in the numerical data given, due to the recalculation of the latter on the basis of the atomic weights pub- lished by the International Committee for 1916.The first few tables include per- centage compositions of the majority of chemical compounds in general use, factors for calculatling gravimetric analyses, densities of gases and vapours, solubilities of salts and gases in water, specific gravities of solids and liquids, melting and boiling points. These are followed by gas analysis tables, properties of liquefied gases of commercial importance, mathematical tables, and also factors for the conversion of weights, measures, and coinage of different countries.A very useful chapter devoted to fuel and furnaces gives also concise inethods for testing the gases evolved, and tables to facilitate the work of the analyst. The manufacture of sulphuric acid, the examination of the materials employed and by-product's obtained, are briefly described, the necessary calculation tables being appended. Bleaching powder, chlorate of potash, soda ash, and nitric acid, their ninnu- facture and commercial examination, are all dealt with in turn, and the descriptions, though brief, are clearly given, and should suffice for the trained chemist, for whom the book is primarily intended.I n t,he final sections the cement industry and the,production of coal-gas are discussed in a similar way, and some useful notes provided on the preparation of rtandard solutions and on methods of sampling. The little book is compiled with skill and discretion, and in addition possesses the advantage of being handy in form, going conveniently into the pocketl. Great care has evidently been taken in revising the proofs, a matter that in a work of this nature, filled as it is with numerical data, is all-important. There is' little doubt that the need for tables of ,tlhis kind is experienced by every analyst and technical chemist, whatever branch of work he may be engaged in, and hence Dr. Lunge's Handbook should find a welcome place in every laboratory. Some fifty pages in all are allotted to this important industry. P. A. ELLIS RICHARDS.

ISSN:0003-2654    

DOI:10.1039/AN9164100392

出版商:RSC    

年代:1916

数据来源: RSC