摘要:

THE ANALYST. MARCH, 1891. A COMPARISON OF ENGLISH AND AMERICAN CIDER, WITH SUGGES- TIONS FOR ESTIMATING THE AMOUNT OF ADDED WATER. BY GEORGE EMBREY. (Read at Jfeeting, January, 189 1 .> I HAVE no doubt the members of this Society are as well acquainted with the nature of cider a8 myself. In Gloucestershire the farmers use special varieties of the apple, and collect the crop in Ootober. I t is stacked in the orchard for three or four weeks, then42 THE ANALYST. ~ crushed in an extremely rude mill, the pulp allowed to remain several days and placed between cloths made of horse-heir; the juice is then allowed to ferment for three or four weeks, and finally placed in casks, from which it is drawn for bottling in the following April. A common method of fining is by adding one quart of milk to each eighteen gallons of cider.Salicylic acid is frequently used for preserving, in the pro- portion of one ounce to ninety-six gallons of the cider. At the end of three or four months that portion which has become sour is mixed with sugar and water, bottled, and plold rn Herefordshire or Devonshire cider ; never as Gloucestershire, the latter term being reserved for pure cider. The fruit is bruised in a mill similar in structure to a root pulper, and is transferred to hair or manilla cloths, subjected first to hand pressure and afterwards removed to a hydraulic press, by which means the pips are crushed and the flavour of the product greatly improved. So completely is the juice removed that the remaining mass is air dried and used for fuel. The juice is then allowed to stand until fermentation has just commenced, a period of twenty-four to thirty-six hours, and filtered through a layer, a foot thick, of decom- posed granite, from which most of the clay has been removed by washing.The fer- mentation is then completed in the usual manner. Notwithstanding these precautions we are unable to produce a beverage equal to the Newtown Pippin cider brought over from America. The prejudice of Englishmen to American productions is now so great, especially in country districts, that, notwithstanding the superiority of the American products over our own, the statement is frequently made that Newtown Pippin cider is an artificiai product and even chemists of some eminence have been unable to pronounce it pure.Some months since I was asked by a client to make such experiments as would help to clear up the matter, and the somewhat generous offer oE 31,500 was made to me if 1 succeeded in proving the presence of anything besides fermented apple-juice. I am sorry to say that up to the present I have been unable to claim the prize, for in the interests of our local farmers I should be very glad to keep away the American supply, I am rather astonished at the small amount of literature available in connection with the subject. Mr. Allen, in his valuable book on organic analysis, quotes the following analysis by R. Kayser. In some cases the following more scientific method is adopted. Must. Cider. Total Solid Matter 16-25 per cent. 2.36 per cent. Aliohol ’’ Malic Acid .. .. Acetic Acid . . .. ,, yielbihg ash * -35 9 , ,, -31 $9 99 4-36 9 ) 9 , .. ‘33 ,P n 77 19 -08 ?, Y ? Sugar . . .. ,. . . 12*5 ,) ), -75 $ 9 99 - .. .. .. .3(j - There is evidently some mistake here, as the total solid matter of cider is given aa Then follows a table showing the mean of 2.36 per cent., probably 12.36 per cent. twenty analyses. Average of twenty Composition of Samples of Brittany good ordinary (Rousseau). (Rabot). cider cider one year old Alcohol (by volume) .. .. .. , , 2.06 per cent. 6 to 6 per cent. Total Solid Matter . . .. .. .. . . 1-93 ?, ,, 3 Y j 19 ,, ,, ), containing sugar . . .. 9 5 3, 9 2 8 ) 2, 9 , ,) mineml matter . . -15 $ 9 9 , -28 9s ?) -THE ANALYST. 43 ~- These evidently relate to much watered ciders, for reasons which I shall give later.Church gives the following as the composition of apples and pears, without stating the variety, tho information being therefore of little value :- Apples. Pears. Water . . * . . . 83-0 . , . . . . . . 84.0 Albumenoids, etc. . . . . -4 . . .. .. . . *3 Sugar . . . . . . 6.8 . . .. .. . . 7.0 Malic acid . . .. . . 1.0 . . . . . . . . *1 Pectose and gum . . . . 5.2 . . . . . . . . 4.6 Cellulose . . . . . , 3.2 . . . . . . . . 3-7 .. * 3 Mineral Matter . . .. *4 . . . . . . 1oo.o - 100.0 I am in a position to state that the difference in varieties of apples is so great as The following five t o account for the great difference in American and English ciders, atialyses will s‘ ow the varieties to which I refer :-- Specific gravity . . .. . . 1034% 1033.48 1032.35 1010.0 1021*48 Alcohol .. .. . . . . 2.91 3.49 2.45 3.64 3332 Grape sugar . . . . .. . . 7.91 8.8 6.9 3 -36 3.86 Volatile acid calculated as acetic acid, ,096 ,048 ,128 .222 a144 .Fixed acid calculated as malic acid . . -3 3 -671 0712 0244 ~244 Ash .. .. .. .. .. *3 -32 -24 .3 -34 Total extractive . . .. . . 9.2 9.6 8.96 4.5 6.7 Nos. 1, 2, and 3 are American. No. 4 is an old Engliah perry. No. 5 is LL new English cider. , On comparing the three American ciders with the two samples of English, it will . ke seen that the extractive matter is greater in the former, and this is mainly due to the much larger quantity of fixed acid and sugar. The following analysis shows the character of unfermented fruit juice from choice apples (table fruit) :- No. I.No. 2. No. 3. No. 4. No. 5. - - - - - Cane Sugar . . .. .. .. Specific gravity . . .. . . .. . . 1048.08 Alcohol . . . . 3 . .. . . . . a 2 1 per cent. Sugar . . . . .. . . .., . . 10.54 ,, 9 , Volatile acid calculated as acetic . . . . -024 ,, ,, Fixed ,, ’,, ,, malic . . . . -549 3 , 9 , Avh . . . . .. .. . . .. *3 9 9 9 9 Total extractive .. .. .. . . 12.06 9 9 7, I may mention that the malic acid and sugar increases with the quality of the fruit. i hope, on some future occasion, to submit to you a series of analyses showing thecom- psition of the chief varieties of English apples. NOW, as regards the addition of water ; is it possible to discover this? The following is an analysis of prime Herefordshire bottled cider, made, as I have already indicated, from cider, water and sugar :- No.6. Specific gravity . . .. . . . . . . 1023.08 Alcohol . . .. . . . . . . . . 2.22 per cent. Cane sugar . . . . . . . . .. -85 9 , ?? Grape sugar . . . . . . . . . . 5.52 1 , ?, Volatile acid calculated to ac6tic . . .. .log 29 ,, Fixed ,, ,, ,, malic . . . . -22 ?, 9 9 Ash . . .. .. Total Extractive . . .. .. .. 6.62 ?P ,, ,? 2, .. .. ..44 THE ANALYST, I t will be seen that ths amount of ash is only 016 per cent., and genuine cider not 1: am inclined to fix these figures as the lowest and Whenever the ash falls below -25 per cent., there is reason to believe A short time since T asked a farmer to give me a sample of genuine cider, and on less than -25 to -35 per oent. highest limits. that water has been added. analysis it gave the following result :- Specific gravity .. C . . . .. .. 1014.68 Alcohol .. 9 . * . . . .. . . 2 57 per cent. Sugar a . .. .. . . .. .. 2 7 9 ,, Volatile acid calculated as acetic . . .. -192 ,, Fixed acid calculated as malic . . . . 0 , -244 ,, Ash . . .. .. .. . . .. a 2 Total extractive. . .. .. . . .. 4.74 The ash here, *2 per cent., was lower than I expected, and asking him to try and recollect if any water had been added, he admitted that the mats had been washed with a few bucketsful which at once accounted for the reduction in amount of mineral matter. I can quite understand that it is possible for different amounts of ash to be yielded by products obtained from trees growing on a variety of soils, but I believe 9 5 is the lomest likely to be met with ; again, ciders which have been watered, always contain added cane eugar, and almost always salicylic acid.On reference t o analysis No. 6, it will be 8een that the extractive matter consists mainly of sugar. I feel convinced that if the members in cider-producing districts will apply themselves to this question we shall goon be in a position to report added water in the case of oider with quite as much accuracy as in that of milk, It is the low figure given for ash whioh leads me to believe that Mr. Allen’s figure refers to watered samples. DISCUSSION. The PRESIDENT said they were all very grateful t o Mr. Embrey for what he had He should done, which was very important, and a matter of great scientific interest. like t o see a few more figures of ash. Mr. EMBREY said these would be published.Dr. TWEED asked Mr. Embrey if he had calculated ’the original gravity of the ciders, using Hofmann’s tables for the original gravity of beer. I f a fallingoff was found both in original gravity and in ash, it would point to watering. If, on the other hand, the ash alone was deficient, and not the original gravity, it would point to watering and addition of saccharine material. Dr. VIETH said he was afraid that the determination of the ash would be hardly sufficient to discover, and certainly not to ascertain the extent of an adulteration. The amount of ash present was very small, being *3 per cent. only, and distilled water was not likely to be used for adulteration. Dr. MUTER asked if Mr. Embrey had tried taking the aIkalinit7 of the ash a t all? If something of that kind were done, the question of added water might be got over in that way.Mr. CASSAL said that the question of the definitions to be applied to articles of food had necessarily again been raised. He understood that Mr. Embrey would regard 0.25 per cent. of ash as characteristic of a genuine cider, and any departure from this figure as indicative of adulteration. This amounted to the creation of a definition. Mr. Embreg’s figure was, no doubt, based upon a large number of determinations, but If Mr. Embrey had not tried it, it would be interesting for him to do so.THE ANALYST, 45 it was hardly necessary to point out the great caution which ought to be exercised in accepting a limit of this kind for such a product as cider.As public analysts they would have t o come to a decision in this as in other matters, and, while admitting the great value of Mr. Embrey’s work, it would be very desirable to have something more to go upon. Determination of original gravity, as had beon suggested, and of the degree of alkalinity of the ash, might afford valuable supplementary information. There ought to be no difficulty in the way of prosecuting for admixture of salicylic acid with cider, even supposing that the salicylic acid used was absolutely pure, which they very well knew was not the case. He remembered seeing some cider presses on the continent several years ago partly coated with lead. Had Mr. Embrey come across anything of the kind, and had he examined cider for poisonous metals? Mr.COSTE inquired whether Mr. Embrey had examined both draught and bottled cider, since there was sometimes a very great difference in flavour between these, It was popularly supposed that hops were often added to the latter, the taste of which in some cases resembled that of ale rather than draught cider. Mr. EMBREY, in reply, said his experience was confined entirely to Gloucestershiro. There was certainly a vast difference between bottled and draught cider, and so much importance was attached to some bottled cider that it fetched as much as 48s. a dozen, He had never seen lead used, but iron was common enough for bolts and so on, and he had never found any other poisonous metals in cider. He had never calculated the original gravity in the way indicated, but would try and do so, although he had his doubts as to whether it could be done. As regards the ash, he always searched for mineral acids. On ignition, if the soluble ash was alkaline, they might be Bure there was no sulphuric acid. Gloucestershire well waters contained from 60 to 60 per 100,000 of mineral water. Ths reason he brought the paper before thsm was that the inspectors in his district proposed buying samples of cider, and he thought it would be desirable to have the views of the Society.

ISSN:0003-2654    

DOI:10.1039/AN891160041c

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

THE ANALYST, 45 REMARKS ON THE ANALYSIS AND COMPOSITION OF BUL'TER-FAT- A CRITICISM. B.y OTTO HEIINER. (Read at Neeting, February, I8 9 I .> IN the February number of the ANALYST (Vol. XVL) and in the CYILsrnical ,Yews of January 31st (Vol. LXIII.) are contained two papers by Mr. W. Johnstone on the Com- position of Butter-fat, containing statements and views, so starbling that they will probably have received some attention from public analyats. As the paper in the ANALYST is the more explicit, and embraces most of the stats- ments contained in the article in the Chemical News, I propose to lay before you a criticism mainly of the former paper. It will be seen that the paper is divided into two sections, one dovoted to analyticd results, the other to theories based upon these.The principle of working, as adopted by Mr. Johnstone, is simple and old. Me ascertains, as a number of chemists have propcsed before him, the total amount of alkali necessary to saponify a weighed quantity of butter. He then separates, washes, dries, and weighs the insoluble fatty acids, and finally dissolves these and titrates the acidity, the difference between the two titrations being calculated into butyric acid,46 THE ANALYST. The method is therefore a combination of Koettstorfer’s principle and that introduced by myself, and sound when properly carried out. The means of saponification adopted will appear clumsy to those accustomed to batter analysis, and objection will probably be raised to the use of aqueous normal alkali, as almost certain to cause introduction of carbonates, which are well known to be fatal to accurate work when phenolphthalein is used as an indicator.No special pre- cautions as t o this head are mentioned in the paper, and it would be fair to the author to assume that such precautions were not neglected, did not the tabulated results raise doubts in the mind of the critic, as will be seen in the following : Tho Koettstorfer process has been used upon thousands of samples of butter and of other fats since it was first published, and it will be held to be established beyond pos- sibility of doubt that, whilst butter-fat uses from 22-15 to 23.27 per cent. of KHO for saponification (Allen, ANALYST Vol. XI., p 145), corrosponding to a saponification equiv:dent from 241 to 253, animal fats of the beef-fat class use only from 19.2 to 19.8 per cent.of KHO, corresponding to an equivalent of 283 to 292. Mr. Johnstone’s statements as to the potash neutralising power of butter-fat and of beef-fat are utterly at variance with the above. He finds two butters, 2.5 gram. of which use 11-50 and 11.92 C.C. of normal alkali for saponification, equal t o 25.8 and 26-76 per cent, of KHO, or an equivalent of 21’7.11 and 209.7 respectively, whilst his sample of beef-fat uses 23.69 per cent. of alkali, equivalent 236.8. Now, whatever the composition of butter may be, it is proved beyond dispute chat beef-fat consists almost wholly of stearine, palmitin, and oleine, with saponification equivalents of 296.7, 268.7, and 294.7. Simple as is the Koettstorfer process, i t does not involve, when worked by a skilled operator, any sources of error wbich should lead to differences such as I have pointed out.It is then attempted to be shown in the paper that when the titration of the excess of alkali is carried out at a temperature of between 80’ to 95°F. lower results are obtained than at 60*F., a t the latter temperature the proportion of KHO consumgd rising from 25.6 to 27.78 and from 26-75 to 27.71 per cent. respectively. I recall the mode of procedure adopted by Mr. Johnstone :-To 2.5 grams. fat, 2 oz. of 95 per cent. alcohol, 1 oz. ether, and 25 C.C. aqueous normal soda solution are added, and after saponification, another 3 oz. of proof spirit. We have thus a solution containing about 64 per cent, of alcohol and ether and about 36 per cent.of water as solvents. Should the aqueous normal soda have contained sodium carbonate, this would in the cold partially separate from this solution, reducing its alkalinity, the precipitated sodium carbonate being counted as alkali used for saponification. On reheat-ing this sodium carbonate would dissolve and consume a further quantity of normal acid, as stated by the author. The saponification equivalents of the insoluble fatty acids which may readily be calculated from the weights given on page 28, and the volumes of normal soda con- sumed, are equally extraordinary. Thus the fatty acids from butter I. had an equiva- lent of 260.9, of 11. 251.0, and from beef-fat of 223.8. Now it is well known that the equivalent of insoluble butter acids is somewhat smaller than that of fatty acids fromTHE ANALYST.47 ~ beef, instead of far larger, as given by our author. The fatty acids from beef have an equivalent lying between that of palmitic (26G) and stearic and oleic (382 and 284), wbilst Mr. Johnstone finds only 223.8 ! It is impossible to avoid coming to the conclusion that the results published by Mr. Johnstone in the ANALYST are not deserving of confidence, as far as the saponification experiments are concerned. From these extraordinary results the percentage o€ butyric acid is calculated by the author under review. The results, as might be expected, are again incompatible with wcertained facts. 11.7 per cent. of butyric acid are thus deduced to be present, or almost 50 per cent. more than the most careful experiments have shown to be con- t'ained in butter-fat.Curiously enough, this figure is corroborated by a direct distil- lation experiment, recorded on page 32. Here again I refrain from attempting any explanation, but let analysts draw their own conclusions. Upon this substructure of analyses Mr. Johnstone proceeds to build up his theories. The first and simpler kind (which I will call A), consists of one homogenous molecule, in which iso-oleic, palmitic, and capric acid are held together by a glycerine molecule; whilst in the second kind another molecule (B), consisting of the fatty acid C, 9 , and heptylic acid, held together by glycerine, is mixed in various proportions with the iso-oleic molecule. Concerning the molecule No. A, on saponification it should yield, besides glycerine, palmitic, capric acid, and iso-oleic acid, which latter splits up by treatment with sodium hydrate into tridecylic acid (C, 0,), butyric acid, methyl-alcohol, and hydrogen.Concerning the latter, the formula requires that 2.5 grams. of butter-fat furnish no less than 74.5 C.C. of hydrogen, an interesting and certainly very novel discovery if it would but fib in with the facts. It is well known that if alkali free from carbonic acid be used for saponification no trace of gas is evolved during or after saponification, let alone 74.5 cubic centimetres of hydrogen. The author certainly speaks of the evolution oE a continuous stream of small bubbles during one period of his operations, and he probably bases upon that circuni- stance the assumption that hydrogen is evolved ; but unfortunately his continuous scream of bubbles evolves, not during the saponification, as the formula requires, but after tho saponification is completed and after the free alkali has been neutralised with normal acid, the bubbles undoubtedly being carbonic acid, from the standard alkali solution.Molecule A weighs 748, and requires four equivalents of KHO for resolution, or exactly 30 per cent., instead of 22 to 23 actually used by butter-fat, or instead of 25.S and 26.7 found by Mr. Johnstone himself on the very butters which he declares to consist of this interesting compound. The three insoluble fatty acids from molecde A have a total calculated equivalent of 642, hence an average equivalent of 214, against 360.9 and 281.0 observed by Mr.Johns tone. As to iso-oleic acid, C,,H,,O,, or C,,H,,O According to him there are two kinds OF butter-fat. H, CH, C * W48 THE ANALYST. Chemists might have a right to expect some evidence of its existence, were it ever so slight. No fatty acid, primary or secondary, is a t present known, which by heating with alcoholic or aqueous potash solution repolves itself into two acids of lower atomic weight and marsh gas, or methylic alcohol and hydrogen. Against the allegation that certain butters a t least consist of a homogenous mole- cular compound, we have the indisputable fact, first pointed out by Dr. J. Bell, and lately again by Cochran (ANALYST, Vol. XIII., p G5), that by treatment with alcohol every sample hitherto examined furnishe3 oily matter with a larger proportion of volatile acids and a less proportion of insoluble acids than was present in the entire sample; also that by pressure, or by fusion and partial crystallisation, a similar sepa- ration is observed, a circumstance utterly incompatible with the theory that butter-fat is a uniform compound.On the other hand, if it were possible to dissolve molecule A in aicohol, there would exist certain butters, which must be entirely soluble in alcohol; others from which from 50 to 60 per cent., containing the Whole of the volatile acid, could be extracted, leaving a residue free from bntyric acid. This, I need not point out, is not borne out by experience. Turning our attention to molecule B we meet with the statement that this furnishes on saponification, two molecules of C,,H,,O, (an acid hitherto unknown), and heptylic acid.The average equivalent of these is 242, that is to say, also lower than the total equivalent found by Mr. Johnstone of insoluble butter acids, I would here point out that heptglic acid is not quite insoluble in water as assumed by the author in construct- ing his formula. Here again we fail to find a particle of evidence in support of the formula, Yet we are told that if the analyst be fortunah enough to detect stearic acid in a sample of butter, he need have 110 hesitation in declaring i t adulterated. But it does not seem to strike the writer in question that a most delicate analysis would be required to dis- tinguish the CIS acid from stearic, the former using 18.83 per cent of KHO for saponi- cation, the latter 19 75 per cent.The samples of butter previously commented upon were of an abnormal nature, the percentage of insoluble fatty acids furnished by them being extraordinarily low. The author, therefore, furnishes us also with the analysis of three samples, A, W, and Y, in which the fatty acids are equally extraordinarily high. Indeed normal samples do not seem to have been examined by the author in question, Oaicuiating from their stated composition the percentages of KHO required for esponification, we find for A 27.00 per cent., for W %6*36, and Y 27.22 per cent., figures which are utterly a t variance with every-day experience. The whole of the fatty acids stated by Mr. Johnstone to exist in butter.fat are saturated fatty acids. As, however, butter-fat and the fatty acid from butter has a considerable iodine absorption, about 31 per cent.(corresponding to about 36 per cent. of oleic acid), whilst saturated fatty acids are incapable of absorbing iodine, the theory further clashes with ths facts. And further, we h o w , from the circumstances that butter-fat has an acetylation figure of some magnitude, that it must contain a large proportion of hydroxy-acids. For theso also the diwoverer has no room in the fwmula given by him.THE ANALYST. 49 The observation that the solid fatty acid which collects in the condenser consists mainly of capric acid had been made long before Mr. Johnstone took up the subject. It might well be held that such a paper needed no criticism and refutation.And indeed it is melancholy work to criticise it. It would, however, tend to discredit English chemistry were it believed that such a research as that published by Mr. Johnstom passed un- challenged or met with the approval of anyone conversant with the subject. Much remains to be done before the actual constitution of butter-fat is explained j the pages of many volumes of our journal, and of chemical literature generally, prove it; but theories without proof, juggling with formuh without regard for facts, will never bring us nearer to the solution of this problem. IliIeanwhile, this problem should not be confounded, as it is by the author whom I have been criticising, with the question of butter analysis, I n the Chemical News of January 30th, Mr. Johnstone places ‘‘ butter analysis on a satisfactory basis.” I n the ANALYST of February lst, butter analysis is declared by him to be ‘‘ in a most unsatisfactory state at present.” Very unsatisfactory indeed is the proof of some of the assertions referred to, but the subject of butter analysis is left untouched by the author.Since working at the above paper I am informed that Mi-. W. Johnstone has notified his withdrawal of the whole of the theoretical part of his paper in THE ANALYST. As his assertions have gone out to the world I see no reason to keep back my criticisms on either his alleged statements or his theories. But I may be allowed to quote from his letter of withdrawal the following reasons: “I ventured to suggest such a theory on two determinations, namely, on that of the soluble fatty acids calculated as butyric acid, and on the amount of glycerine, calculated from the amount of oxalic acid formed on boiling with alkaline permanganate. ” “ My reason for withdrawing that theory is that since the, writing of that paper I find that but-jric acid is easily converted into oxalic acid by boiling with alkaline per- manganate, thus : C4R,02==2C,Hp0, + H,.The following quantities of butyric acid were taken and boiled with alkaline permanganate and the oxalic acid resulting from mme estimated and calculated into butyric acid, Butyric acid taken , , L . @ , -3916 01858 ,, ), found . . . I . , a3684 .1740 1 have also tried the bichromate process, and have found no difficulty in readily oxidising the butyric acid into carbonic acid.So much, therefore, for trusting to pro- cessees advanced by Messrs. Allen and Hehner without verifying their accuracy.” I n the first place, it will be seen that if butyric acid were really osidised into oxalic acid in the manner described, the experimenter should have obtained a figure far higher than the theoretical one, whilst precisely the contrary is the case. H e calculates glyceryl 6-82 and 6.03 (by the way, here glyceryl means C,H,, not the usually accepted radical C,H,), andjnds 5 01 and 5.04. In the second place, butyric acid does not yield a trace even of oxalic acid with alkaline permanganate, as I have proved to my satisfac- tion, much less does it yidd a quantitative amount. Here one cannot even conjec- ture how Mr. Johnstone obtains his results, It certainly seems somewhat peculiar to see quantitative results given as to the oxalio acid produced, when it is a well-known50 THE ANALYST.~~ fact that alkaline permanganate oxidises butyric acid into carbonic acid. (See Beilstein, Org. Chem., Vol. I., p 402). I n the third place, as to the bichromate process, I have stated in my papers on the subject that I had tried the action of bichromate on butyric acid under the conditions of the process published by me, and found that it was not attacked. On the other hand, I was and am well aware that butyric acid treated with concentrated sulphuric acid and chromic acid is oxidised into CO, and acetic acid. I have now repeated the trial. To about 1OOc. of distilled water about 26 c. of strong sulphuric acid were added, and some pure butyric acid.To the hot mixture a small drop of bichromate solution was added, not the faintest reduction being observed, even after some hours’ heating. I fear, therefore, Mr. Johnston’s retraction wants u further withdrawal. DISCUSSION. Dr. DUPRE (who had taken the chair as senior Vice-president) said-Gentlemen, allow me in the first place to express my great pleasure a t seeing Mr. Hehner in the chair of our society. I am quite sure that no one has worked harder and better for the success of the society, and there is no doubt we have attained success-a success in great measure due to the admirable work of Mr. Hehner. I take this first opportunity of stating this because, unfortunately, I was unable to be present when he was elected, or 1 would have given my vote for him with more pleasure than I have ever given a vote before.As regards this paper, there are a number of atnalysts here who have con- siderable experience on the subject, and you will probably like to hear them. Mr. ALLEN said that his name having been mentioned in the letter of withdrawal from Dr. Johnstone, read by Mr. Hehner, he desired to say a few words on the subject in question. Dr. Johnstone alleged that he (Mr. Allen) had stated that no oxalic acid was formed by the oxidation of butyric acid by permanganate in alkaline solution, which is in opposition to Dr. Johnstone’s experience, described in his letter withdrawing his theory of the constitution of butter. But he (Mr. Allen) was unaware that he hadever made the statement ascribed to him by Dr.Johnstone, and dismissed somewhat con- temptuously by him. Dr. Johnstone must be aware of his (Mr. Allen’s) exact position in the matter, for only a few days previously he (Mr. Allen) had furnished him, by request, with the references to the Journal of the Society o f ChemicaZIrzdustry and Com- mercial Oryanic Analysis, in which particulars of the process of estimating glycerine by conversion into oxalic acid with permanganate in alkaline solution were given. On page 292 of Vol. 11. of the latter work the following passage occurred :-“ The writer (Mr. Allen) has proved by experiments on known quantities of oxalic acid that that body: is not acted on by permanganate in strongly alkaline solution, and Beizedikt and Zsigmond9 have f o m d that the soluble fatty acids of oils, such as acetic, butyric, caproic, etc.: do ?lot.b y treatment with the same reagent, yield any acids the calcium salts of which are precipitcitet.? from acetic solutions. The higher fatty acids of the stearic series are insolubJe in water, and hence would not in any case interfere. On the other hand, certain acids of the acrylic or oleic series, and possibly oleic acid itself, yield oxalic acid by oxidation with permanganate. The higher acids of the oleic saies are, however, insoluble in water, and the lower are not known to occur in fixed oils under normal conditions. Under certain circumstances, however, the method is wholly invalidated.” With this passage presumably before him it was strange that Dr. Johnstone should assert that he (Mr.Allen) had found butyric acid to yield no oxalic acid by oxidation with alkaline perman- ganate. Not, however, that he thought much weight should be attached to Dr. John- stone’s statement that o d i c acid was formed. It was just possible that Dr. Johnstone had not worked on normal butyric acid at all, and it was barely possible that if he usedTHE ANALYST. 51 isobutyric acid he might get oxalic acid by its oxidation, though even this was opposed to the experience of other observers, who found that iso-hydroxy butyric acid was formed, the calcium salt of which was very soluble, and could not be mistaken for calcium oxalate. Dr. Johnstone’s observation, therefore, required confirmation before it could be accepted as accurate. With regard to formation of carbonic acid from butyric acid by oxidation with chromic acid in acid solution, it was quite possible that such a result might be obtained if Dr. Johnstone employed a very hot and concentrated oxidisiiig mixture.But with the ordinary chromic acid mixture his experience was completely opposed to that of other observers, and to what was to be expected from analogy. Thus E. T. Chapman, with whom the process originated, found acetic, propionic, and valeric acids to suffer no change by treatment. with chromic acid mixture of moderate strength. Further, the modification of amylic alcohol having the constitution of a methyl-propyl- carbinol yielded the theoretical quantity of butyric acid with chromic acid mixture, and this underwent no further change.At a later date Chapman and Thorpo actually em- ployed butyrate of ethyl a s a body simply yielding acetic and butyric acids on oxidation, and obtained results which conclusively showed that the butyric acid was perfectly stable under the conditions of the experiment. Under these circumstances there was probably some fallacy underlying Dr. Johnstone’s experiences, and this was the more likely as he had made public in the communications just criticised by the President a number of figures which on the face of them were absolutely inconsistent with probability, if not with possibility. He thought Mr. Hehner had done right in calling the attention of chemists to the nature of the experimental evidence on which Dr. Johnstone had founded his remarkable theories. It was extremely difficult to understand how Dr. Johnstone could have obtailned such astonishing results, and still more surprising that he had not perceived the true interpretation of them. Mu.. CASSAL said that, had it not been for the necessity of repudiating this produc- tion on behalf of the Society of Public Analysts, it might be thought that it had been dealt with sufficiently. It was exceedingly unfortunate that the necessity had arisen, but the fact that the paper ” had appeared in the pages of THE ANALYST left them no alternative. I n examining this curious paper, the main difficulty-after having unravelled the knotted language in which it was couched-was to make out what the author meant to convey. It would appear that he intended to give t o the world some fragments of a transcen- dental chemistry known to himself alone, and the existence of which had not previously been even suspected. (rhe letter of withdrawal from Dr. Johnstone, referred to in Mr. Hehner’s paper and in the discussion that follows it, was addressed to the Editor of the ANALYST, who deemed it right, in consequence of certain of its contents, to communicate i t to Mr. Hehner, since he (Mr. Hehner) had already given notice of his criticism of Dr. John- stone’s already published paper. Since the meeting at which Mr. Hehner’s communi- cation was read and discussed, Dr. Johnstone has written to the Editor requesting; that his letter of withdrawbtl should not bs published, and accordingly it does not appear, though its purport is conveyed in the extracts given above.) (Conclusion of the Society’s Proceedings.)

ISSN:0003-2654    

DOI:10.1039/AN8911600045

出版商:RSC    

年代:1891

数据来源: RSC

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TRE ANALYST. 51 - VOLUNETRLC ESTIMATION OF GASEOUS OXYGEN BY MEANS OF' T'JITRIC OXIDE." BY Prof. Dr. L. L. DE KONXNCK (and Mr. ENNOT, Pharmacist). WHEN a few months ago I made expsriments on the volumetric estimation OF free oxygen by means of metallic solutions, chiefly with an alkaline solution of ferrous ~ _ _ _ _ _ _ _ * Zeitsch. F'. Amgem, Chemie, Feb. 1891.52 THE ANALYST. tartrate, I also made some experiments concerning the original process of Priestly, which has been classed by W. Winkler among the abandoned methods. The results were, just as might have been expected from previous experiments conducted by Berthelot and Lunge, very irregular and uneatisfactory. My work con- firmed the results of Winkler, who previously had made experiments on the estimation of nitric oxide by means of air or oxygen, and who remarks :-“ The contraction multi- plied by two-thirds ought to have corresponded with the original nitric oxide, but masin effect a varying quantity.” A short time ago my attention was again called to this question by two articles from Messrs.Wanklyn and Cooper. In their first notice they not only called the nitric oxide process an accurate one, but even the best method ever known. I n their second notice they communicated a very few test analyses t o show the accuracy of the process :- 1 A. 1. 2. Pure oxygen taken 30 C.C. 40 C.C. Error . , , .. 2 per cent. 1% per cent. abstain from any comments. B. 1. 2. 3. Air taken .. 80 C.C. 50 C.C. 70 C.C. Oxygen found . a 16-47 C.C. 10-27 C.C. 14.47 C.C. Experimental error .. .33 per cent. -38 per cent. .25 per cent. ), ,, found 30.6 C.C. 39.27 C.C. Assuming air to contain 20.92 per cent. of oxygen, the errors in these experi- ments are comparatively small. I n consequence of these publications, I thought it best to repeat some of my experiments before replying to these authors, particularly a8 I had not kept any record OF the figures of my previous work. The modus operandi which I have followed is practically identical with that of Messrs. Wanklyn and Cooper-at least as far as I can judge from their extremely brief notices, If there should be any diflerence, i t will be perhaps the preparation of the nitric oxide. An old-fashioned Hempel’s hydrogen pipette, containing a spiral of sheet copper, ie filled with dilute nitric acid of 1-1 spec. gravity.I n the same way as hydrogen is pre- pared by means of zinc and sulphuric acid, nitric oxide is formed when required, although very slowly, and the apparatus always contains a certain quantity of the gas. But even with this dilute acid the gas is not perfectly colourless, but a faint yellowiah tinge betrays the presence of traces of nitric peroxide. To prevent any analytical errors, the gas was in every experiment treated with water before measuring. I n carrying out an analysis the oxygen (or air) and the nitric oxide must be, of course, measured separately, and afterwards mixed over water. On account of its simplicity and easy execution, I have preferred the following plan :-The gas (air) is introduced into a Winkler-Hempel burette; the nitric oxide is introduced into a similar apparatus, and, as already mentioned, well shaken with the water to remove any peroxide, and also t o saturate the water with the oxide. After a few minutes’ rest the volume of the two The experiments were conducted in the following manner :--THE ANALYST.53 gases are recorded, and after connecting the two burettes with a capillary tube filled with water, the oxygen is forced into the nitric oxide, and the two burettes are now disconnected. After thoroughly shaking the burette to assist the absorption, the volume of the gas is read off with the usual precautions. I t is as well to wait for about twelve or fifteen minutes, so as to get the temperature, and consequently the volume constant. As the residue contains nitric oxide, the experiment must be conducted as described, viz., the oxygen must be mixed with the nitric oxide. If the nitric oxide were forced into the oxygen, it would amount to measure a mixture of the two gases in the same burette, and as both are slightly soluble in water, errors would be introduced.The calculated figures in the table have been got by assuming air t o contain 20.92 per cent. of oxygen, and the process to proceed according to the equation : 2 NO,+O, = 2 NO,. 2 NO, + H20 = HNO, + HNO,. The contraction, according to these formuh is equal to three times the amount of oxygen. A. ATMOSPHERIC AIR. __. NO. 1 2 3 4 6 6 7 8 9 10 11 1 2 13 16 17 i .r. .H n ‘3 @ 50 49-6 49.3 50.0 50.0 50.0 50.0 50.0 50.0 50.0 504 50.0 50.0 B. 49.2 51.1 50.0 16.5 W Q O Z $2 6$ 45.1 40.7 40.6 37.0 36.6 36.6 34.8 29.5 28.5 24.4 21.0 21.0 20-9 95.1 90.3 90.4 87.0 86.6 86.6 84-8 79.5 7s 8 74-54 71-0 71-0 70.3 1- J )I M 3 z 62.4 52.2 54.0 52 a8 52.6 52.6 51 I 45 s 45.7 44.0 45.6 45-6 45.6 d 2 3 32.7 3 3-1 36.4 34.2 34.0 34.0 33-6 33.7 33.1 30-4 25.4 25.4 24.3 .,-i Y +J ‘3 -~ a + a + g 0 ; 21.80 .25.60 24 37 2.2-80 22.67 22.67 22.40 22.47 22.07 29-27 16-93 16.93 16.20 - +I 8 & 3 8 L? 2 G w --- + -88 + 4.68 + 3.45 + 1.88 + 1.75 + 1.75 + 1-48 + 1.55 + 1-15 -- -65 -3.99 -3.99 -4.72 MIXTURE OF OXYGEN AND NITROGEN CONTAINING 17.6 N. 41.4 I 90.6 I 55.0 51.1 93.2 64-0 50.0 1 80.2 I 55.1 32.6 29-2 25.1 22-09 I +4-49 & a a n s a d C e w o g 1-3.13 ‘S o$$% Q, ‘5: C. q$ 1-3.67 1-3.27 1-3-25 1-39 1 1-3-22 1-2.91 1-3-49 1-3-25 1-3-16 1-2.43 1-2.43 1-2.32 1-3 76 1-3.25 1-2.85 C. PURE OXYGEN.8064 I 96.9 1 48.6 1 48.3 1 97.58. I -2-42 I 1-2.55 D. U S E OF NITRIC OXIDE MIXED WITH NITROUEN. Experiment No. 18. To the residual gas of No. 7 62.4 c~c., which, as may be easily calculated consisted of 39.4 C.C. nitrogen and 22.86 of nitric oxide, 20 C.C. of air was added, and then 15.82 C.C. of nitrogen and 4.18 of oxygen-total, therefore, 82.4 C.C. After the reaction was over, the residue measured 68.2 c.c., which equals a contraction of 14.2 c.c , and the relation between this and the oxygen as 3.40 : 1.54 THE ANALYST. From an analytical point of view, these figures need no comment ; a process which gives results varying from 77.5-1 22.5 instead of 100 is absolutely useless. From a general point of viow, the comparison of the different experiments gives rise to some observations which are not without, interest.The relation between the volume of the oxygen and the contraction after the action of the nitric oxide, may theoretically vary betwen 1 : 2.33 and 1 : 5, as the following equations will make clear :- 4N0 + 0, = 2H,O + 4HN0, relation 1 : 5 4 VOl. 1 1-01. 2NO+0,=H20+HN02+HN03 ,, 1 : 3 2 VOl. 1 Vol. 4 VOl. 3 VOl. 4N0 + 3 0 , = 2 H,O + 4N0, ,, 1 : 2.33 The experiments Nos. 2-13 show that when the amount of nitric oxide increases this causes a larger proportion of nitrous acid to form, if the mixing of the gases is done under the same conditions. I n experiment No. 2, three-fourths of the nitric oxide had bean converted into nitrous acid, as is proved by the corresponding formule ; 2.67NO + 0, + 1*33H,O =,HNO% + *67HNO,. In experiment No. 13, we see, on the other hand, the complete conversion of the nitric oxide into nitric acid, although, from the amount of nitric oxide used, we might have expected it to yield equal parts of nitrous and nitric acids. The compaiison of experiments 1 and 2, also of Nos. 14 and 15, shows the influence on the result of the celerity with which the gases have been mixed and shaken with the water (Nos. 1 and 15 were very rapidly mixed). Finally, No. 18 shows that the dilution of the oxygen and nitric oxide mixture with an inert gas, which of course retards the reaction, favours the formation of nitrous acid.

ISSN:0003-2654    

DOI:10.1039/AN8911600051

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

54 THE ANALYST. METHODS I N USE AT THE LABORATORY OF THE BOURSE DE COMMERCE, PARIS. BY M. FERDINAND JEAN, DIRECTOR OF THE LABORATORY. (1.) ESTIMATION OF STEARIC ACID. INTRODUCE into a flask 3 or 4 grams. of the sample for analysis, and bring it to the boiling point with 60 C.C. of alcohol of 9 6 O ; shake whilst cooling, and then titrate the alcohoiic solution with half normal soda, employing phenol phthalein as an indicator. Wax being only slightly soluble in cold alcohol, there is no need to take notice of its acidity, and the amount of the mixture can be calculated as stearic anid from the number of C.C. normal soda used in the titration, knowing that 7.8 c c. of half normal soda = 1 gram. of commercial stearic acid. (2.) ESTIMATION OF PARAFFIN AND OF MYRISTIC ACID. TO the flask containing the neutralised alcoholic solution, add 3 to 4 C.C.of solution of soda of 60 per cent. ; attach tho flask to an upright condenser and heat for an hour to saponify. The saponification being complete, distil off the excess of alcohol, put the residue into a capsule, mix with dry sand and short asbestos, dry a t looo, pulverise and 1.-EXAMINATION OF WAX FOR ADULTERATIONS.THE ANALYBT. 55 extract it with warm chloroform (or petroleum ether), which dissolves the whole of the paraffin and the myristic acid, representing a part of the wax. To sepmate the paraffin, Horn has recommended acetilisation and solution of the produced ether by means of acetic acid, in which paraffin is insoluble. According to Horn, sapoaified wax should, under these conditions, yield 50 per cent.of matters soluble in glacial acetic acid. Following Horn’s process, we have neither been able to properly separate the parzffin nor to obtain a constant factor for the part of the wax soluble in chloroform. We effect this separation in the following manner :- The chloroform holding in solution a part of the wax and all tho paraffin is distilled off in a weighed flask, and the residue, having been dried a t 100, is weighed. Then weigh, in a small flask, a part of the residue left by the evaporation of the chloro- form, and treat it under an upright condenser for an hour with 4 to 5 C.C. of anhydrous acetic acid. The acetilisation being complete, pour the resulting fluid into a glass tube graduated in 10 C.C. and divided into tenths ; rinse the flask with boiling crystallisable acetic acid, and turn the whole into the graduated tube.The volume of the liquid should be about 9 C.C. Place the tube in a water-bath a t 9O0, then close it up with a cork and shake it forcibly so as to well emulsify the liquids, and replace in the water-bath, When the acetic acid has become clear, the volume of insoluble matter which floats on the acid is read OK Renew the shaking and place in the water-bath until a constant volume of parafin insoluble in acetic acid is obtained, of which calculate tho weight, remembering that 1 gram. of paraffin =from 1-35 to 1.4 C.C. On deducting the weight of the paraffin from the weight of the residue furnished by the chloroform, we obtain by difference the weight of the portion of the saponified wax soluble in chloroform.(3.) ESTIMATION OF STEARIN. The saponified part insoluble in chloroform is formed by the soap of stearic acid and of stearin and by saponified cerotic acid. To estimate the stearin, dissolve in boiling water, filter to separate the sand and asbestos, and decompose the filtered liquor by a slight excess of nitric acid diluted so as to set free the fatty acids, filter and esti- mate the glycerine in the filtered liquid (after neutralisation and precipitation by plumbic acetate), by the potassium bichromate process. From the weight of the glycerine, calculate the stearin or suet, keeping in mind that 5 of anhydrous glycerine =95 of stearin. I n cases where the proportion of stearin is small, it would be preferable to saponify 10 or 25 grams.of the substance and t o estimate the glycerine by the bichromato process. We therefore estimate by this method :- 1. Stearic acid by alkalimetry. 2. Paraffin by measuring the part insoluble in acetic acid. 3. A part of the wax (myristic acid) by deducting the paraffin residue from the weight of the residue soluble in chloroform. 4. Stearin by the estimation of glycerine. 5. The second part of the wax (cerotic acid) by difference,56 THE ANALYST. II.-A N A L Y S I S 0 F WINE. (1) ESTIMATION OF GLYCERINE. Evaporate 250 C.C. of the wine to the volume of 100 c.c., then agitate this con- centrated liquid with freshly precipitated plumbic oxide, and rander it slightly alkaline with bargta water. Filter, wash, and neutralise the filtrate with dilute sulphuric acid.Concentrate in a flat porcelain capsule, and when the volume of the liquid has been rednced to 60 C.C. incorporate therain 5 grams. of plumbic oxide, 10 grams, of sand, and 20 grams. of barium sulphate, evaporate and dry at looo C. During this drying the basin should be covered with a plate of glass t o avoid spurting. The dried mass, having been powdered, is extracted with a mixture of equal parts of alcohol and ether, the extraction being continued until 60 C.C. of liquid has been obtained. Thirty cubic centimbters of this liquid is placed in a tared glass capsule, and 20 grams. of dried and powdered litharge having been added, the whole is evaporated in the water-bath, and then dried to a constant weight between 105 and 1 0 6 O C. The other 30 C.C.is evaporated in a tared glass capsule 6 centimdtres in diameter, and the residue is placed in the air bath between 160 and 170° C. until a oonstant weight is obtained. The weight of residue No. 1, after deducting that of the litharge and capsule employed, rninue the weight of residue No. 2, being first multiplied by 1.243, and then by 8, gives the weight of glycerine present in a litre of the wine. (2) ESTIMATION OF ASTRINGENT ACIDS, (a) Estimation of Oenontannin. Concentrate 200 C.C. of wine down to 100 c.c., shake with an excess of freshly pre- cipitated arsenious sulphide, filter and wash. Concentrate the filtrate to 50 c.c., add 10 grams. of silica, and 20 grams. of barium sulphate, and dry at 100' C. Powder the residue and extract it with warm ether ; evaporate the ether and dissolve the residue in a little alcohol.Take 1 gram. of powdered hide which has been washed with alcohol, and dry at 100" C. Moisten it with a few drops of distilled water, and having added the alcoholic extract, allow the whole t o macerate for half an hour. Filter through a square of cambric, previously dried and weighed, wash with alcohol, press out excesg of liquid, and dry at 100" C. The increase in weight of the hide, multiplied by four, gives the oenontannin in one litre of the wine. (b) Estimation of Oenogullic acid. Dilute the alcoholic filtrate from the hide with distilled water to i00 cc., and in 20 C.C. of this estimate the acid by means of a solution of iodine that has been previously standardised with gallic acid as follows :- Prepare solution of iodine in potassium iodide containing 2 decigrams.of iodine per litre, and also a solution containing 0.125 gram. of gallic acid in 250 C.C. of distilled water. Mark a beaker a t 50 c.c., place into it 10 C.C. of the gallic acid solution, and 3 C.C. of cold saturated solution of sodium bicarbonate. To this add the iodine drop by drop from a burette until a drop of the mixture, tested on thick filter papos dressed with powdered starch, leaves a stain surrounded by blue. Now add distilled water to the 50 C.C. mark and continue the addition of the iodine until a similar stain is again obtained. The amount of iodine thus used must be further corrected by making a blankTHE ANALYST. 57 experiment on 50 C.C. of distilled water with 3 C.C.bicarbonate solution, and deducting the amount of iodine required to produce the stain. Having thus standardised the iodine, it is used in a similar manner on the 20 C.C. of the alcoholio liquid from the wine which has been previously neutralised with sodium bicarbonate. (3) ESTIMATION OF COLOURING MATTER. 250 C.C. of the wine concentrated by evaporation (but without boiling) t o 100 C.C. is rendered freely alkaline by ammonia, and then well shaken up precipitated arsenious sulphide. The whole is then filtered and washed with distilled water, and the filtrate having been rendered acid by acetic acid, t o precipitate any sulphide of arsenic dissolved by the ammonia, is again 61tere3 and washed. The two filters containing the sulphide of arsenic are digested on the water-bath in alcahol acidulated with acetic acid, and the whole having been again filtered, the residue is washed with hot alcohol until all the colouring matter is extracted. Finally, the alcoholic solution is evaporated in a tared capsule, desiccated at 105O C , and the residual colouring matter is weighed. 1IT.-PREPARATION OF BUTTER FOR THE REFRACTOMETER. The butter is melted in a porcelain capsule, and then beaten up with two or three pinches of fused and pulverised calcium chloride, which takes up the water and the casein. The whole is then kept warm until it settles, and the clear butter-fat is de- canted off and filtered through a plug of cotton wool; the clear butter-fat is heated t o 60° C. and placed in the prism of the instrument, and the reading is taken a t the moment when the inner thermometer marks 4 5 O C.

ISSN:0003-2654    

DOI:10.1039/AN8911600054

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

THE ANALYST. 57 REPORT OF RECENT RESEARCHES AND IMPROVEHENTS IN ANALYTICAL PROCESS. A DELICATE REACTION FOR CYTISINE. DR. J. VAN DE MOER. (Ned. Tydschr v. Pharmacie, etc. February, 1891.)-This alkaloid, obtained from the seeds of Cytisus Laburnum, has been supposed to be insoluble, or nearly so, in chloroform, but the author discovered this t o be the solvent par excellence. This fact enabled him to extract the alkaloid in a far superior state of purity than before, and, as the result of a great many elementary analyses, he proposes the formula C,,H,6N,0 instead of C,,H,,N,O. The author also has proved the identity of this alkaloid with ulexine, the active principle contained in the seeds of Ulex Europoeus. In case of poisoning with this alkaloid, the expert should test particularly the vomit and the urine; but in case of sub-cutane administration of small doses, the urine is the only material worth testing.Physio- logical experiments have proved the rapid elimination of the poison through the kidneys, The toxicological analysis is performed according to Dragendorff’s method, and advant - age is taken of the solvont action of petroleum ether, etc., on the accompanying impurities. After these have been removed, the old plan was to shake the alkaline ~olution with amylic alcohol, but this not being a good solvent, the author has replaced it by chloroform. Although analysts could without difficulty isolate the alkaloid, all their trouble went for nothing, as there was no proper and reliable test for traces of this body.56 THE ANALYST. The author has, however, been fortunate enough to discover a most delicate test, which plainly detects *00005 gram.of the poison. The alkaloid is moistened with a drop of a weak solution of ferric-ammonium alum, which will give a reddish colour. On addition of a little hydrogen peroxide the coIour dis- appears, but, particularly on warming, soon changes to a very persistent, splendid blue. If now moistened with ammonia (not potash or soda) the colour changes to a reddish violet, and the blue is restored by acids. The quantitative analysis is best done by titration with Mayer’s solution. No other alkaloid gave the reaction. L. DE K. ANALYSIS OF CRUDE GLYCERINES. F. FILSINGER. (Chenz. Z e d , No. 102, 1890.)- A few years ago an estimation of the specik gravity, coupled with an ash determina- tion, was all what was required ; but these simple tests are, of course, of little use in determining the value of soap-leys.Apart from any mixtures, there are three different kinds of glycerine in the trade. 1. Saponification glycerine obtained from the few works where they still saponify fats with lime. This glycerine is characterised by ft straw-yellow or brownish colour, of an agreeably sweet taste and absence of smell when rubbed on the hands. The reaction is generally neutral unless a little free lime should be present. This. glycerine, which has an average specific gravity of 1.24, ought not to contain more than -5 per cent. of ash, and must remain fairly clear on addition of sub-acetate of lead or hydrochloric acid.Tested in Gerlach’s apparatus it should show a boiling point of about 138OC. 2. Distillation glycerines, the product of the saponification of fats with sulphuric acid, with or without presaure. They are met in the trade in various states of purity. They have a burning, astringent: taste which often hides the sweet one completely, smell nasty and leave often up to 3.5 per cent. of ash, consisting chiefly of salt and lime sulphate. On adding sub-acetate of lead there forms a voluminous precipitate, sometimes enough to gelatinise the whole. Hydrochloric acid often gives a copious, fusible precipitate, chiefly consisting of fatty matter. Even the best brands of these glycerines are about 10 per cent. lower in price than the worst saponification glycerines. 3. Soap-leys glycerine.This is the most impure of all, and has to be put through many processes before it can be distilled. When sold for that purpose it should have a brownish colour and contain no more than 10 per cent. of ash and 8 or 10 per cent. of water. Now as far as analysis goes, a chemical one is not wanted for the pure glycerines. All what is needed is the estimation of the specific gravity with a gravity bottle or a Westphal balance, or the taking of the boiling point in Garlach’s apparatus. For the chemical analysis of impure samples, the only process which has stood the test for years is the permanganate method originally described by Benedik t and Zsigmondi. The Acetin process devised by Benedikt and Cantor gives good results with very concentrated glycerines.The author further communicates a process which has been in use for some years in a Hamburg laboratory. For the estimation of water, 20 grams. of the sample are put into a flask provided with a ground stopper and exposed for ten hours to a tempera- ture of 100OC. The loss is taken as water. To estimate the fixed impurities, 5 grams. The boiling point is generally lower than 125OC. Acrylic compounds do not interfere.THE ANALYST. 59 ~ of the sample are heated in a flat platinum dish up to 180°C, at which temperature the glycerine completely volatiliaes without perceptible charring. After cooling and weighing it is as well to once more heat to see if there be any further loss, To complete the analyak the ash may be taken. This simple process gives results quite accurate enough ON THE ANALYSIS OF WHITE WAX.G. BUCHNER (‘%em. Zeit., No. lO1,1890).-8ome two years ago the author called attention to the fact that a genuine sampleof white wax may &ill show a too high saponification or acidity equivalent, if it has been bleached by chemical means. Although this does not frequently happen, analysts should, however, be careful in giving an unfavourable report without further testimony. The author’s statement has been doubted by D. H. Riittger, who supposed he was not supplied with genuine samples ; but experiments recently conducted by Messrs. Buisine prove the author to be in the right. In fact, the acidity equivalent of an undoubtedly genuine sample may come as high as 24, and its saponification number as high as 100.for technical purposes. L. DE I(, L. DE K. ESTIMATION OF CARBON IN IRON AND STEEL. L. RUEUP (Chern. Zed., No. 102, 1890).-After some practice, an analyst may easily execute five analyses daily, by adopting the author’s process. A few grams. of iron filings are put into Thorner’s carbon apparatus, containing 40 C.C. of a hot solution of sulphate of copper. After the lapse of ten minutes, 50 C.C. of a saturated solution of chromic acid and 120 C.C. of &&rated sulphuric acid (saturated with chromic acid) are added, and the whole heated to 80° C. for about three quarters of an hour. To make sure of complete oxidation of the carbon, another 50 C.C. of this sulphuric acid are added, and the liquid heated to nearly boiling. After cooling somewhat, air is forced through the apparatus by means of an aspirator.The apparatus consists of Thorner’s boiling apparatus, connected with the u s d chloride of calcium and soda-lime tubes. The air is passed at the rate of two or three bubbles per second through a, wash bottle,containing sulphuric acid. L. DE I(. _-____ EBTIMATION OF SULPHUR IN PIG LEAD. PROF. W. HAMPE (Chem. Zeit., No. 105, 1890).-50 grams. of the finely divided sample are by degrees put into a crucible con- taining 100 grams. of fusing nitre. A spirit lamp should be used. The mass is constantly stirred with a bent glass rod until the oxidation is complete, which generally t&es about one hour. The crucible is emptied whilst hot, and the mass extracted with boiling water. The solution is treated with carbonic &d until all the lead is precipi- tated and then filtered. After removing nitric compounds by evaporating with excess of hydrochloric acid, the sulphuric acid is precipitated with barium chloride.The author has proved the accuracy of the procem by experimenting on mixtures of pure lead and pure galena. Another process communicated by the authorg but which is rather too complicated for chemists employed in metallurgical works, consists in heating the metal in a current of chlorine, as in the analysis of grey copper ore. The metal is, however, never quite chlorinised, so, after removing the coating of chloride of lead, the operation must be60 THE ANALYST. repeated. As mme lead chloride gets into the absorption tube, the author recommends to first convert it into carbonate by boiling with excess of pure carbonate of foda. The filtrate containing the sulphuric acid is then acidified and precipitated with barium chloride.L. DE ‘R. NOTE ON GLASER’S PROCESS FOR THE ESTIMATION OF IRON AND ALUMINA IN MANURES. D. TH. MEYER. (Chem. Zed., No. 102, 1890.)-A joint committee of German manure- makers and agricultural analysts, assembled last year in Bremen, has reported in favour of Glaser’s spirit method instead of the ammonia and acetic acid process. That process cannot very well be defended. I f too much acetic acid is added, the resulta are too low, and if the manure contains a fluoride, they will be too high. These Bources of error do not occur in Glaser’s process. The separation of the iron and alumina from the lime is very successful, and allows the latter to be very accurately determined. The gypsum takes, however, some time for complete separation.The drawback to Glaser’s process is his complete ignoring of the magnesia. True, its sulphate is practically insoluble in absolute alcohol, but far fiom insoluble in a mixture of alcohol, water, and sulphuric acid. A fluid prepared by shaking 35 C.C. of absolute alcohol, 20 C.C. of water, and 5 C.C. of sul- phuric acid with powdered Epsom salts, contained 3.2 per cent. of magnesia-per 250 C.C. Suppose the sample to consist of pure magnesia, every trace of it would remain in the alcoholic fluid. Another experiment convinced the author of the co-precipitation of the magnesia with the iron and alumina. He twice analysed a solution of lime, iron, and aluminic phosphates, but in one case added sulphate of magnesia. The separated sd- phate of lime proved to be pure, but in the second experiment the precipitated iron and alumina phosphates weighed three times heavier than in the first one.And a qualita- tive analysis proved this to be due to the presence of magnesia. It is, therefore, not a matter of astonishment, that Glaser’s method gives, as a rule, higher results than the conventional method, even if the manure should contain fluorides. To see in how far the process can be trusted for commercial purposes, the author tried several Belgian phosphates. The magnesia was each time estimated by re-dissolving the precipitate in hydrochloric acid, boiling with some ferric chloride, and precipitating the excess of this, togethor with the phosphoric acid, with ammonia, The magnesia was then precipitated as usual with phosphate of soda. Sample No. 1 : Obtained -63 per cent. of mixed iron and alumina; but, after esti- mating the magnesia, this became reduced fo *48 per cent, Sample No. 2 : Obtained 4.23 per cent. After allowing for magnesia, only 4.15 per cent. Sample No. 3 : Obtained 3.52 per cent. After allowing for magnesia, 3-12 per cent, Of course, if the amount of magnesia in the manure is very trifling, no harm will be done; but if large, it must seriously interfere with the accuracy of the p r m , Glaser’s method is, therefore, not yet fit to become the-recognised trade process, and is, in fact, a t the moment, not much better than the old conventional one, unless one hkea the trouble to estimate the co-precipitated magnesia. L. DE I(. AppOINTMENT.-Dr. James Baynes, of Hull, has been elected t o the post of Public Analyst for the City and Borough of Peterborough.

ISSN:0003-2654    

DOI:10.1039/AN8911600057

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

60 THE ANALYST. EaaaTnM.-?!k. Cassal’s paper on “Dyed Sugar” was unfortunately omitted from the list of papers read during 1890, contained in the retiring President’s address in our last isaue.

ISSN:0003-2654    

DOI:10.1039/AN8911600060

出版商:RSC    

年代:1891

数据来源: RSC