摘要:

THE ANALYST. FEBRUARY, 1889. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS. THE Annual Meeting of the Society waa held on the 9th ult., at Burlington House, Piocadilly, Mr. A. H. Allen in the chair. The minutes of the previous meeting were read and confirmed, The auditor’s report on the accounts for the past year was read, and will be printed Mr. ALLEN then delivered his valedictory address as follows :- Following the custom which has prevailed in previous years, I now have to bring before you a ri%urn6 of the past work and present position of the Society. I n the first place, it is gratifying to find that the progress of the Society, so far as it is represented by the number of members, is mtisfactory. I n addition to the resigna- tion of two associates, three members have been removed from the list for non-payment of arrears of subscription, and six associates for the same reason.To counterbalance this, we have the election of ten new members and four new associates, so that the total number of subscribers is exactly the same as in the previous year ; but the number of ordinary members is increased by four, and that of the associates diminished by the same number, the honorary members still numbering ten. The Society has also suffered a loss in the death of Dr. William Wallace, of Glasgow. Dr. Wallace was for many years senior member of the firm of Wallace, Tatlock and Clark, and occupied the post of Public Analyst for Glasgow and several neighbouring counties and boroughs. He ranked as one of the ablest and best-known chemists in Scotland, and although the distance of his residence from London prevented him from regularly attending our meetings, he always took a great interest in the Society.Personally, I feel in the death of Dr. Wallace the loss of an intimate friend, who w4s always ready to give me the best advice and assistance in his power. and circulated as usual. THE PBESIDENT’S ADDRESS.22 THE ANALYST. Not only has the Society maintained its numbers, but the papers read have fully equalled in interest and importance those of previous years. They have numbered 34, as against 30 during the previous twelve months. The following is a list of the papers oontributed to the Society, in addition to which there are several paperti, such as that of mine on the presence of cocoa-nut oil in a sample of lard, which, though not actually read before the Society, would have been so had the matter arisen during the session :- PAPERS IN 1888.Date. Author. Jan. 11. “ Laboratory Notes ’) . . .. .. * . .. . . , , A. H. Allen Feb. 8. ‘ I A Sample of Navy-green Paint ” . . . . .. . , Bertram Blount ,: “ An Instrument for Calculating Milk Results ” . . . . . , H. D. Richmond I “ Composition of Milk and Milk Products ” . . . . , , Dr. Vieth “ An Apparatus for Nesslerising ” . . .. .. .. . . A. W. Stokes certain Fatty Acids . . . . . . .. .. , , Rowland Williams “ Some Analyses of Yeast ” .. * . .. .. . . Rowland Williams :, “ Pepper Adulteration and Pepper Analysis ” . . . . . . F. W. Rimmington M&ch 14.“ Iodine Absorptions, C$mbining Weights, and Melting-points of ,? 1 ‘‘ Some Analyses of Goose Fat ” .. . . . . * . .. W. C.Young 9 “ Wear and Tear of Platinum Dishes ” . . .. .. . . Dr. Vieth May 9. ‘ I Some Effects of Food Preservatives on the Action of Diastase ” :, ‘ I Notes on Liquorice and Spanish Juice ” .. .. . . B. Dyer ?, ‘‘ A New Form of Fat Extraction Apparatus ” . , . . Bertram Rlount , . Dr. A. Hill ,, “ Adulteration of Lard with Cotton-seed Oil ” , , .. . . A. H.Allen . . . . R. Williams June 20. “ Polluted Drinking Water and the Closure of Weils . . P? 9 9 ?? ?1 .. * . , . Otto Hehner 9J ? 9 9? 9 ) .. .. . . E. W. T. Jones :: “ Tempgature of Etcer in the Soxfdet Extraction ” . . . , Dr. Vieth ?, “ Notes on Senna ’’ . . .. . . . . .. . . , . C. Heisch ‘‘ Pepper Analysis ” . . . . .. .. .. ... . C. Heisch Julf: 27. ‘‘ On the Use of the Term ‘ Normal ’ in Volumetric Analysis ?’ . . A. H. Allen . . . . , . A. H. Allen 99 “ On the Examination and M&hod of Stating the Results of the Analysis of Boiler-waters . . . . 9f ‘‘ Note on the Examination of Lard ” .. .. .. . . Thos. S. Gladding ?? ‘( On Condensed Milk ” .. .. a . . . J. C. Shenstone ‘‘ Water Reports-a Dilemma ” . . , . .. . . M. A.Adams ‘‘ On the Preservation of Miik Samples ’‘ . . .. . . . . EL. D. Richmond “ On some Abnormal Samples of Butter ” ‘‘ The Werner-Schmidt Method of Determining Fat in Milk and No;: 14. “ Determination of the Melting-points of Soap-thickened Oils ” W. F. K. Stock Dd.’ 12. “ On the Determination of Citric Acid in Lemon-juice ” . . Rowland Williams ?, ?, A. H. Allen Cream ’’ ... . . . A. W. Stokes 97 “ On the Exarn’ination of Laid for Adulteration ” . . Thos. S. Gladding 11 ‘‘ On the Action of Iron Pipes on Water Conveyed therein ” . . Sidney Harvey Looking at the immediate objects of the Society, I think we may fairly claim that during the past two years the methods of examining food and drugs have made marked progress. We have been confronted with several novel forms of adulteration, which at first taxed all our resources to discover, but which we may now fairly claim to be in a position to detect with certainty. The use of pepperette, or ground olive-stones, for the adulteration of pepper is one of the cases in question. Although referred to as a possible and probable adulterant of pepper fully ten years ago, it does not seem t o have been extensively used until comparatively recently, when pepper adulterated with poivrette made its appearance in various parts of the kingdom, but notably in the neighbourhood of Liverpool, and it was Dr.Campbell Brown, Public Analyst for Liverpool and Lanca- shire, who first called prominent attention to the question, besides pointing out methods for its detection.THE ANALYST. 23 The adulteration of lard has also grown enormously during the past year or two, and, instead of meeting with the large proportions of water formerly so common, lard is now sophisticated in a novel and ingenious manner, namely, by adding a mixture of cotton- seed oil and beef or mutton stearin. &. E. W. T. Jones appears to have been the first analyst on whose certificate the prosecution for the presence of cotton-seed oil took place, and he was quickly followed by other analysts.For a time the sale of lard adulterated with cotton-seed oil seems to have received a serious check, but knowing how skilfully such sophistications are conducted, and with the express purpose of baffling the Public Analyst, we may expect that those interested are simply seeking a safe method of eluding our vigilance. For a long time it seemed as if the detection of beef-stearin in lard could only be effected inferentially, and until quite recently I was unable to satisfy myself of the presence of beef-fat in several samples of lard which I strongly suspected to contain it. I believe, however, that difficulty is now surmounted, and with the aid of some hints from Dr.Campbell Brown I have been able to detect positively the presence of beef-fat in lard. The use of cocoa-nut oil as an adulterant of lard does not seem yet to have become very extensive. I have condemned one sample myself on this ground, and have examined another submitted to me from a brother-analyst. But the detection of this adulterant presents no difficulty, and hence the use of cocoa-nut oil is not likely to be very extensively practised. With respect to butter, the determination of the volatile acids by the Reichert process has of late become fairly general, but I find comparatively few analyjts have adopted the precautions found necessary by Professor Wollny, of Kiel, a translation of whose report and paper, by Mr. 0. Hehner, was published in the ANALYST last winter.I cannot but feel the gravity of the figures I submitted t o the Society at its last meeting, showing that'the range of variation in the composition of genuine butter was greater than had been generally recognised; but the fact being absolutely beyond dispute it seemed to me that however much we might regret the immediate consequences of the discovery, it was our plain duty to accept the position, and strive so to modify and improve our methods of analysis as to render it possible to distinguish a butter adulterated with a small percentage of margarine from one which was simply abnormal in composition, and I believe it will be found possible t o effect this. A committee has been appointed to investigate the matter. For various reasons, it is not desirable to increase the number of the committee to any great extent, but it is t o be earnestly hoped that other Public Analysts, and the members of the Society generally, will co-operate with the committee, who have undertaken work of a very laborious and responsible character.With their help and sympathy much may be done, and it is, in my opinion, a great misfortune that the Public Analysts of this country, who have done so much good work in the past, should have to work under such disadvantageous conditions, and without that encourage- ment from other chemists which they have a right to expect. That the Government of the country should persistently ignore the Public Analysts as a body, as has been done in his official position by the Chancellor of the Exchequer, among others, is a lamentable fact.The Public Analysts, as a body, are now a set of competent and highly trained men, doing their disagreeable duties without fear or favour, while liable at any time to have their reputaticns injured by reference to a Court of Appeal, unsatisfactory in its composition, and having a narrow and one-sided idea of its duties. I n a few months the position of some of the Public Analysts will be materially changed, as many will hold their appointments under the newly created County Councils. It is only t o be expected that these bodies will, like other new brooms, sweep clean, especially as the only argument for supporting some of the candidates seems to be that they are prepared t o reduce salaries all round. Under these circumstances it behovea Public Analysts to stand together and make a determined and united effort to24 THE ANALYST.- resist the attempt, which will donbtless be made in some quarters, to reduce still further the already insufficient remuneration of many of those holding appointments under the Sale of Food and Drugs Act. As to the future, I think we may, at some time, see an amended Act passed. We are sadly in need of a rovised system of reference in the case of disputed analyses. Again, it is very desirable that some means should be devised for tracing milk and butter to their sourceg, so that if peculiarity of composition be really due to natural causes the vendor may have the fact demonstrated, while, on the other hand, it will become more difficult than at present to plead natural poverty of the milk as an excuse.The Margarine Act has worked fairly well during its twelve months’ enforcement, but experience has shown that it is not free from defects which might be very easily removed by an amending Act. The difficulty of dealing with drugs is, a t present, greatly increased from the absence of any authoritative and legal standard, although it is a curious fact that the Pharmacopceia was not made the formal standard in the Sale of Food and Drugs Act Amendment Act, of 1579, simply because Dr. James Bell held that it was already practically accepted as the standard. Unsatisfactory as the existing Pharmacopceia is, and discreditable to certain of those entrusted with its compilation, its formal adoption as the legal standard for drugs mentioned therein would be a distinct advantage, and would have the additional good effoct of hastening the publication of a new edition, which might be free from the defects which characterise t h a t of 1885.There are other directions in which the Adulteration Act might be extended and improved. It certainly should apply to such arbicles as disinfecting powder, which at present escapes through its meshes ; and I think it is not too much to hope that in the future me may see its scope extended so as to make it an offence to sell as ‘‘ all wool ” an article which is in great part cotton or other fibre, and even to prevent the false description of articles of jewellery. And now it simply remains for me to express my regret that I have on many occasions failed t o fill this chair in a satisfactory manner.I am fully aware of my own shortcomings in this respect, but have tho satisfaction of knowing that in the immediate future the position lately occupied by me will be filled by one in whose care tho dignity and interests of the Society of Public Analysts of Great Britain may be left with the fullest confidence. Mr. ALLEN proposed, and it was unanimously resolved, that a vote of thanks be accorded to the Chemical Society for the use of their rooms dnring the past year. The election of Officers and Council for the ensuing year was then proceeded with, and on the ballot-papers being opened it was announced that the following gentlemen were elected :- President.-M. A. Adams, F.R.C.S., F.I.C. Vice-presidents (who have filled the office of President).-A.H. Allen ; A Dupre, Ph.D., P.R.S.; C. Heisch; Alfred Hill, M.D.; J. Muter, Ph.D., M.A., F.R.S.E. (Who have not filled the office of President).-Sir Chas. Cameron, M.D. ; S. Harvey ; T. Stevenson, M.D., F.R.C.P. Treasurer. - C. W. Heaton. Hon. 8ecretaries.--Bernard Dyer, B.Sc. ; Otto Hehner. Other Members of CounciZ.-C. E. Cassal ; R. H, Davies ; W. Fox j R. H. Harland ; W. Sedgwick Saunders, M.D. ; P. Vieth, P1i.D.; C. R. Alder Wright, D.Sc., F.R.S. The names of those members of Council whose term of ogce has not yet expired, and who consequently do not retire this year, are J. Baynes; J. A. R. New- lands; E. Seaton, M.D., F.R,C,P. ; W. J. Sykes, M.D.; J, A. Voelcker, Ph.D.THE ANALYST. 25 The following gentlemen were also elected :- As Members : T.S. Gladding, New York ; Professor V. Stein, Copenhagen. As Associate : Sydney Steel, assistant to Mr. Bernard Dyer. Mr. ALLEN then vacated the chair, which was thereupon taken by the newly elected President- Mr. ADAMS, who thanked the members for the honour which had been conferred upon him, acd said he was fully conscious of the great gap which their retiring President would leave behind him, but he rejoiced to know that Mr. Allea’s large and varied experience mould not be lost to the Society-they would have him with them in the future, as they had had, so much to their advantage, in the past. He (Mr. Adams) was, hovever, afraid that it could not be denied that Mr. Allen had left them in some- what of a mess-a greasy mess, He had certainly upset the fat in the fire, and they would not want for lack of work in the forthcoming season in clearing up after him.Of course they would have him to assist them, and the wonderful instinct that had put them in the right direction, although he had made this mess just at the end of his term, showed that Mr. Allen was just the one to clear it up for them. In conclusion, Mr. Adams said that he could assure them he should have the greatest pleasure in devoting himself to the interests of the Society, and nothing should be wanting on his part to show how fully he appreciated the honourable position to which they had elected him. The following papers were read :- “Remarks on a Recent Case of Alleged Injurious Pollution of the River The discussion on this paper was adjourned until the February meeting, in the ‘‘ On the Analysis of Pepper, and the Occarrence of Piperidine therein.’’ By ‘( On the Westphal Balance.” Medway by the Sewage of Maidstone.” By Dr. DuprC?, F.R.S. hope that Dr. Tidy and Mr. Wynter Blyth might then be able to attend. Dr. W. Johnstone. By Mr. W. F. K. Stock. The Annual Dinner was afterwards held a t the St. James’s Hall Restaurant, where a very enjoyable evening was spent by the members and their friends. The next meeting of the Society will be held at Burlington House, on Wednesday, the 13th inst., when the adjourned discussion on Dr. Duprk’s paper will be resumed. (The papers 69 Br. Dupr6, Dr. Johnstone, and Mr. Xtock, will bepublisl~ecl in our next issue.)

ISSN:0003-2654    

DOI:10.1039/AN889140021b

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

THE ANALYST. 25 ON THE DETERMINATION OF CITRIC ACID IN LEMON-JUICE. BY ROWLAND WILLIAMS, F.T.C., F.C.S. (Read at the Meeting, December, 1888.) THE general chemistry of citric acid has already been so ably dealt with in the excellent and exhaustive papers by R. Warington (Journal o f the Chemical Society, vol. xxviii., p. 925), and by B. J. Grosjean (Journal ofthe Chemical Society, vol. xliii., p. 331), that it is not necessary for me to dwell at any length on that part of the subject. I may say at once that my special object in bringing this matter before the Society of Public Analysts is to promote a discussion among the members, with the view to attain, if possible, a standard process for estimating the citric acid in lemon-juice, as, in the face of recent improvements in analytical chemistry, this question certainly deserves further26 THE ANALYST.consideration-former methods being more or less unreliable, owing to the unsatis- factory nature of the indicators employed. Litmus, logwood, and cochineal solutions, all of which have, I believe, been used in the past, are unsuitable indicators, while litmus-paper is, for a reason which will presently appear, not very much better. Samples of lemon-juice are sometimes sent to my laboratory for examination by calico-printers and others, and my results nearly always come out lower than those of Mr. G. H. Ogston, upon whose certificate, lemon- juice is, I understand, generally sold in this country. These discrepancies having occurred rather frequently, I communicated with Mr. Ogston, in order, if possible, to come to an understanding as to the method to be adopted in the analysis of future samples, so as to avoid any further differences between our results.I n the course of his reply Mr. Ogston said, “The process agreed upon for the commercial analysis of lemon-juice is titration by carbonate of soda solution, using litmus-paper as indicator.” Mr. Ogston then points out certain precautions necessary to be observed, and admits that the exact point at which to cease adding the carbonate of soda is difficult to see, and can be determined only after a good deal of experience. I was rather surprised to hear of an analyst employing carbonate of soda in esti- mations of citric acid. I myself use pure caustic soda solution, which I find to be preferable in every respect.Litmus-paper is also, in my opinion, a very unsatisfactory indicator, as it is affected to a considerable extent by normal citrate of soda-the real end reaction being thus diEcult to tell with accuracy. It is a well-known fact that citrate of soda solution, according to its degree of dilution, turns pink litmus-paper more or less blue, and it becomes, therefore, to a certain extent a matter of chance as to what excess of soda must be added when litmus- paper is used as an indicator. In order to overcome this difficulty it is, I believe, customary to ascertain the exact strength of the alkali by means of pure citric acid and pale litmus-paper, taking as nearly as possible the same shade of blue for the end reaction, both in standardising and in performing the actual analysis; but even using every precaution, I find this plan to be unsatisfactory, in addition to being very tedious.In estimating citric acid I have long since discarded litmus as an indicator in favour of phenolphthalein, as recommended by R. T. Thomson (JourmaE of the Xuciety of Chemical Industry, vol. Vi., p. 195) and other chemists. This latter indicator I have proved to be quite unaffected by citrate of soda, whereas this salt is distinctly alkaline to litmus, as already mentioned. The end of the reaction is also seen with the greatest precision when phenolphthalein is used, one drop of normal caustic soda solu- tion in excess being sufficient to produce an unmistakable change of colour. No reliance can, of course, be placed on results obtained by titrating with either hydrate or car- bonate of sodium in the presence of mineral acids, but in their absence neutralisation with alkali gives a fairly accurate idea of the amount of citric acid present, especially in concentrated lemon-juice.THE ANALYST.27 ~- In the presence of other acids which might interfere with the ordinary soda test it is necessary to employ the calcium chloride process described in Mr. Warington’s paper. The plan which I adopt in the analysis of concentrated lemon-juice is as follows : The specific gravity is first taken at 60“ Fah. For this purpose some analysts employ a special hydrometer, termed a ‘Lcitrometer,” on the scale of which every -004 above unity is equivalent to one degree. As is the case with so many commercial products, the density indication is of little or no value, unless the lemon-juice is free from adulteration.Nevertheless, it is cus- tomary to state the ‘‘ citrometer ” indication on commercial certi6cates. Indeed, many calico-printers in my district actually buy according to the citrometer ” degrees, without paying much attentinn to the proportion of citric acid present, and thus become ready victims to the wiles of unscrupulous drysalters. In order to determine the total acidity of the juice, I dilute 1,000 grains measure of the sample to 10,000 grains with water in a stopped measuring-flask, and take one-tenth of the whole (equivalent to 100 grains of the original juice) for titration with alkali. This aliquot portion is placed in a large porcelain basin, and diluted with water until the liquid is of a pale yellow shade, and after the addition of a few drops of alcoholic phenolphthalein solution, normal caustic soda solution is run in from a burette until a rose colour appears.I n order to avoid any possible chance of error, I always perform the entire process in duplicate. Two determinations of the total acidity should agree within two grains of normal soda solution. The results are calculated into ounces of citric acid per gallon. As a confirmatory test, another carefully measured portion of the sample may be taken, and without any previous dilution, neutralised with the requisite amount of caustic soda. Rather more than the calculated quantity of a 20 per cent. solution of calcium chloride is next added, and the whole heated in a salt bath for some time.The calcium citrate is filtered off, washed slightly with boiling water, the filtrate concentrated to a small bulk, taking care to keep the solution neutral, and again filtered. If necessary, the filtrate is again concentrated, and any precipitate which comes down filtered off through a very small filter. The precipitates are gently ignited in a platinum crucible, in order to convert the calcium citrate into calcium carbonate, which is then decomposed by excess of normal hydrochloric acid, filtered and titrated back with normal caustic soda. When testing genuine samples of lemon-juice I have generally found this process to give figures agreeing fairly well with those obtained by direct titration with soda, the results being in most cases rather lower, owing to part of the total acidity being due to organic acids, other than citric, which do not form an insoluble lime salt.I have tried the carbonate of soda method used by Mr. Ogston, in comparison with my ordinary process, on several samples of lemon-juice, some of which were taken from pipes imported from abroad, while the others were prepared from lemons pressed and concentrated in my own laboratory. The figures obtained will be found in the accompanying table ;-28 THE ANALYST. NaHO. Ounces of Citric Acid per Gallon. Na,COs. Foreign, Xamples. No. 1 . . .. .. .. No. 2 . . .. .. .. No. 3 . . .. .. .. No. 4 , . .. .. .. No. 5 . . .. .. .. No. 6 .. .. .. .. Sample No. 1 . . .. .. .. .. ,, No. 3 . . . . .. .... ,, No. 3 . . .. .. .. .. ,, No. 4 . . .. .. .. .. ,, No. 5 . . .. .. .. .. ,, No. 6 . . I . .. .. .. 5, No. 7 . . .. .. .. .. Laboratory Sanph. No. 1 * . * . .. .. No. 2 . . .. .. .. No. 3 . . .. .. .. 7.03 6.96 6.94 6.99 7-09 7-14 7-02 .. .. .. .. .. .. .. .. .. NaHO Method. 68.24 63-48 61.80 62-88 60.86 66-74 94.32 63-36 75.48 Na, CO, Method. 69.42 64.56 63-55 63.96 67.88 6i.84 94.56 64-32 76-20 CaCI, Method. 64.1 2 58.98 58-24 60.14. 57.98 64.92 96.08 62.52 75.60 I I - 7.32 7.37 7.1 2 7.13 7-26 7.24 7.21 On averaging these figures, it will be seen that 100 grains normal caustic soda equal 7.02 grains citric acid, while 100 grains normal carbonate of soda equal 7-23 grains citric acid. For all practical purposes, the 7.02 grains may be regarded as 7 grains, tho slight difference being, no doubt, due to the presence of traces of impurities in some of the samples of citric acid.This result would then agree exactly with the figure demanded by theory. The accuracy of titrations made with caustic soda, using phenolphthalein as in-THE ANALYST. 29 dicator, having thus been proved beyond doubt in the case of citric acid, it seems undesirable to employ carbonate of soda in the analysis of lemon-juice, as the estimation then occupies so much longer time, besides not giving such reliable results. I would suggest, therefore, that tho citric acid in lemon-juice should in future be determined by titration with caustic soda and phenolphthalein in the absence of interfering bodies, the result to be confirmed, if necessary, by the application of the calcium chloride test previously described.In conclusion, I should like to add that the calcium chloride method indicated 99.4 per cent. of citric acid, when tried on a portion taken from the mixture of the seven samples of citric acid already referred to. DISCUSSION. The PRESIDENT said that he was glad to find that Mr. Rowland Williams appre- ciated the use of phenolphthalein as an indicator. He thought that the tendency was to use phenolphthalein more and more in all cases in which it was suited for the pur- pose-that is, where a weak acid was to be determined and the absence of carbonic acid could be ensured. He had no doubt that the process of titrating citric acid and lemon- juice by caustic alkali and phenolphthalein was novel so far as Mr.Williams was con- cerned; but it had been in constant use for some years, to his (tho President’s) knowledge, in several laboratories where such essays were required, and the process was fully described in his ‘‘ Commercial Organic Analysis,” vol. i. Phenolphthalein alwap gave very satisfactory results where the colour could be seen ; but in the case of very dark juices it sometimes became necessary to have an outside indicator, in which case very delicate litmus-paper, made by brushing a neutral solution of litmus on to white writing-paper, not absorbent paper, was the best substitute for it. Congo-red paper would probably also be valuable. It was disheartening to learn that chemists of repute were still content to titrate lemon-juice with an alkaline carbonate and litmus. €19 was not surprised that Mr. Williams’s results did not agree with those who employed so antiquated and unsatisfactory a process, and there could be no doubt on which side the truth lay. I n titrating with phenolphthalein there was one direction in which he thought an improvement might be made, and that was to use a standard solution of baryta instead of caustic soda. Baryta had the advantage that it was certain to be free from carbonic acid, which, of course, was not the case with caustic soda. However, he would have occasion to refer at greater length to this point later in the evening. Mr. DYER said he happened to know that Mr. Ogston used litmus-paper that was not bibulous, but painted on one side, and that he laid great stress on that. Mr. WILLIAMS, in reply, said he had not tried congo-red paper, but congo-red solution did not answer the purpose a t all.

ISSN:0003-2654    

DOI:10.1039/AN8891400025

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

THE ANALYST. 29 THE WERNER-SCHMID METHOD OF DETERMINING FAT IN MILK AND CREAM. BY A. W. STOKES, F.I.C., F.C.S. (Bead at Meeting December, 1888.) OF the various methods of determining fat that I have practically tried, including thoso of Wanklyn, the Lactobutyrometer, Adams’s paper-coil, and the Lactocrite, not one is perfectly satisfactory. The two former are not accurate, the paper-coil takes too long, and the lactocrite is too expensive and unsuitable for a laboratory. All who have many samples of milk to analyse will, I think, welcome a method that combines almost the simplicity of the Wanklyn process with the accuracy of the30 THE ANALYST. Adams’s paper-coil method, and in addition gives a quickness that neither can pretend to. All this, I believe, the Werner-Schmid method does.About two months ago, in vol. xxvii., part 4, of the Zeitschrift fur Analytsche Chemie, appeared a notice which was translated into the Chemical News of October 19th, 1888, and has since appeared in the December number of the Journal of the Chemical Society. 16 is so short that I quote the whole of it :- ‘I Dr. Werner-Schmid takes a test-tube of about 50 C.C. capacity, graduated in tenths of a c.c., introduces 5 C.C. of cream or 10 C.C. of milk, accurately measured, adds 10 C.C. of strong hydro- chloric acid, boils, with shaking, until the liquid turns dark brown, cools by placing the tube in cold water, adds 30 C.C. of ether, shakes round, lets stand, measures the volume of the ethereal solution, draws off 10 C.C. with n pipette, evaporates down in a weighed porcelain capsule on the water-bath, and finally in an air-bath at looo.He then weighs and calculates for the original quantity of the ethereal solution. If the process has been rightly conducted, the ether separates from the aqueous solution clear, without the slightest turbidity. The ethereal solution, as it flows out of the pipette, should not show any watery drops. The results are perfectly accurate, and differ from each other and from the ordinary gravimetric methods by less than one-tenth per cent. The operation requires at most fifteen minutes.” Nowhere eould I find any further information or any experimental proofs of the accuracy of the method ; I therefore now supply my experience. At first I tried to simplify the process by using a 50 C.C.flask, in which it was easier to boil the mixed acid and milk than in a tube. From this, after filling up with ether, I took 10 C.C. for evaporation, assuming that there was present 30 C.C. of ethereal solution of fat. This gave, however, too high results, because some of the ether was taken up by the acid mixture. I now, therefore, use calibrated test-tubes, but do not actually boil the mixture of milk and acid, but plunge the corked tubes into the boiling water of the water-bath for 5 to 10 minutes, then cool them down by immersion in cold water. On adding ether up to the 50 C.C. mark, and vigorously shaking for half a minute, a contraction of the ether takes place; it usually stands at 49.5, while the acid and milk mixture takes up some ether, so as usually to occupy 26 c.c., leaving 23.5 C.C.of ethereal fat solution. After standing for 3 to 5 minutes, this ethereal solution separates com- pletely; 10 C.C. or any aliquot part may be pipetted off and evaporated. I find t h a t flat-bottomed glass dishes, of 29 in. diameter, are very suitable for rapid evaporation of the portion of ether taken. The whole operation takes from 15 to 20 minutes, but of course a number can be going on at the same time. Ordinary milks gave the following comparative results by the various methods of- Wankly n. Adams. No. 1 2.64 2-91 No. 2 2.53 2.71 No. 3 2-48 No. 5 2.71 .. No. 6 .. .. No. 7 .. .. No. 4 2:04 .. Schmid. Calculation, 2.90 3.14 2.70 3.11 2-37 2.95 2.53 2-70 3.08 .. 2.88 3-22 3.48 3.61 These are a few examples of milks received in the ordinary course from various parishes.Most of them are watered samples, taken from the top of the churn, hence the agreement between the Adams or Schmid with the calculated fat is not so near as usual. It is, however, evident that the Wanklyn process doos not extract the whole of the fat, even when, as in some of the cases, the milk after weighing was curdled with acetic acid, and its solids boiled with benzoline for two days. The Adams’s process and the Schmid agree, I think, within the limits of experimental error, Skimmed milks gave the following comparative results ; -THE ANALYST. 31 Wankl y n . Adams. Schmid. Calculation. No. 8 0.20 0.30 0.24 .. No. 9 .. 0.5 1 0.50 .. No. 10 .. 0.65 0.64 No. 11 .. .. 1.14 l;i4 No. 12 .. .. 1 -02 1-12 Condensed milks, I find, are best treated by weighing out 10 grms., and diluting A sample gave by Adams’s method 12.4, by Schmid’s 12.1 per cent.fat. #tale milks are readily treated by this process. this to 100 C.C. with water, then taking 10 C.C. of this for the Schmid process. When shaking such a milk to obtain a fair sample an enormous mass of gas-bubbles is formed, such as prevent an accurate volume of the milk being taken. If, however, after shaking vigorously, the milk be poured into a 100 C.C. flask, in which 75 C.C. of water are present, with frequent agitation while pouring, all the bubbles will break, and the flask may readily be filled to the 100 C.C. mark. Prom this four-times-diluted mixture of the stale milk 10 C.C. may be taken for the Schmid process, and be treated as described :- No.13 gave 3.69 when fresh,and 3.63 after an interval of 39 days. No. 14 ,, 0.69 99 0.66 9 , 39 9 3 No. 15 ,, 2.87 9 9 2.82 3 9 40 ,¶ No. 16 ,, 3.12 9 , 3.24 9 ) 17 9 , No. 17 ,, 2.73 9 , 2.76 9, 15 99 Creams.-I find it best to weigh out 10 grms. of the sample, and to make this up to 100 C.C. with water, then to take 10 C.C. of the mixture for the Schmid method. Otherwise, if the cream is treated direct, or only slightly diluted, the pipette cannot deliver its proper amount. Besides this, the resulting ethereal solution is so dense as to make it necessary to wait a long time for the other parts of the mixture to settle after shaking. Samples thus treated gave the following results :- Wanklyn. Adams. Schmid. No. 18 42.8 .. 42.4 No.19 .. 52.8 52 *5 The mtion of the process is that the acid destroys the casein almost entirely, and acts upon the milk-sugar to produce the brown colour, while the fat is set free and rises to the surface. The ether dissolves this fat, but I think not entirely. There is always a minute amount of fat present in the hydrochloric acid solution. I am trying to find whether this is a constant proportion, so that it might be allowed for. It is necessary to use ether that has been washed with water, otherwise the alcohol usually present in commercial samples will interfere with the results. No contraction or alteration of volume occurs in the mixture of acid and milk after boiling and cooling, but when the tube is filled to the mark with ether and well shaken a contraction of the total quantity takes place.I determine the amount of this (usually 0.5 to 1 c.c.) for each tube, and make a mark above the usual 50 C.C. contents-mark, and fill with ether to this before shakbg. The ethereal solution of fat when pipetted off is always acid. I have, however, carefully tested a large number of such combined extracts for milk-sugar, but have never found a trace. Should the tube, by accident, be filled above its proper mark with ether, it is easy to evaporate off the excess. Should the first portion of ethereal solution be lost, another portion may be readily pipetted off. Doubting whether it was sufficient to shake the mixed fluids for half a minute, and to let stand for 5 minutes only, I have shaken duplicates for longer periods, and have let them stand for 2 i days. The results have been the same, Frequent repetitions of the same milk agree,32 THE ANALYST. It is necessary to see that pipette, burette, and tube are properly graduated and ti3 So far the method seems to me to possess the advantages of accuracy, speed, Calibrated tubes, made weigh accurately. simplicity, cheapness of apparatus, and little loss of reagents. for the purpose, may be obtained of Messrs. Cetti, Holborn.

ISSN:0003-2654    

DOI:10.1039/AN8891400029

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

32 THE ANALYST. EXAMINATION OF LARD FOR ADULTERATION. BY THOMAS S. GLADDING, NEW YOBK. (Read at Meeting, December, 1888.) IN the examination of lard the following tests have been found most reliable :- (3) Milliau’s modification ol Bechi’s test. (5) Belden’s microscopic test for beef fat, as described by Professor Sharples in a lato number of the ANALYST. No lard should ever be condemned by a single test. A certificate should never be given except one based upon a full examination. The term is a very convenient abbreviation, and the value of the test itself will appear from the results of the work done. The following table gives the tests of eight samples of whose purity no doubt is entertained. Samples 4, 5, 7 were tried in our laboratory. Samples 2, 2, 6, 8 were received from reliable houses, and their purity guaranteed.Most of the work was done in careful duplicate. Hubl’s method was strictly followed, the hyposulphate solution being standardised by chemically pure iodine prepared by ourselves, and also by chemically pure iron ammonia sulphate. (1) Specific gravity at looo C. (2) Hubl’s Iodine test. (4) Dalican’s “Titre ’’ test. The “ titre” is Dalimn’s crystallising points of the fatty acids. Specific Gravity at lOOQ C. ‘‘ Titre.” Iodine Test. 1. Lard cil ... ... ... - 31 *40° C. 74.60 per cent. 3. Lard ... ... ... ... 0.86 14 36.40 67-60 4. Leaf lard, 1 (soft) ... ... 0.8610 38.20 65.80 5. Leaf lard, 2 (bard) , . . ... - 41.40 57.00 6. Lard stearine ... - 43.50 4 9-50 7. Beef fat (soft yellow)’’’ ... - 41.60 43.80 8. Cotton-seed oil (summer white) 0.8690 33.30 108*00 2.Lard (very €oft) ... ... 0.86 10 36.40 68.40 The striking point in the above table is the wide range of the iodine test on samples of lard of undoubted purity. The higbest tests hitherto published have been about 61 to 62 per cent. The above “titre” tests at once explain this great range of the iodine tests. From Dalican’s table we find that a tallow having a titre of 41.40° C. contains approximately 59 per cent. of olein, and one of 43.50 contains 53 per cent. of olein. The iodine absorbed will vary approximately with these varying proportions of olein. I n any examination, therefore, of lard the titre of the sample should be known, in order t o interpret the meaning of the iodine test. The wide difference between the titre 31.40 of lard oil and 43.50 of lard stearin and the corresponding iodine tests of 74-60 and 49.40 is a further and more extreme illustration of the same truth. The beef fat in the table was a soft yellow fat of lower titre than usual. The common titre of prime solid beef fat is about 44, and would show an iodine test of about 40, the number usually given for beef.Com- paring the iodine test 43.80 of beef fat above with the iodine test of 56-20 of lard of about the same titre, it becomes apparent that there is some difference in the chemical nature of the two fats which is demonstrated by the iodine test, but not revealed by the With soft lards the figures 67.60 and 68.40 were obtained.THE ANALYST. 33 titre. I have been informed by good authority that the cotton-seed oil (summer white) in the above table is the form commonly used for adulteration of lard, and not the cotton- seed stearin as has been stated.The low titre of 33.30 is therefore interesting, and its influence will appear in some analyses to be given later. I have made thorough trial of Belden’s microscopic test, and have been greatly pleased with it. It is very valuable for the detection of beef fat in lard, and in most cases is the ONLY reliable test for that adulterant, but requires much practice with samples of known purity and samples of known percentage of adulteration. The following analyses of samples sent in for examination will prove interesting. Four samples were sent in to determine the chemist’s ability to detect adulteration.One sample was to be pure lard, another adulterated, and the other two were to be the pro- ducts of rival houses that were suspected of adulterating their goods. The samples were numbered 1 to 4, with no other mark. 1 2 3 4 Specific gravity at 100’ C. 0.8610 0-8606 0-8636 0’9631 Titre . . .. .. 36-40 39*60 36#15 36-60 Iodine test .. .. 68.40 58.33 76-60 75.40 Belden test . . . . Lard. Beef lard. Beef lard. Beef lard. Bechi- Milliau test . . Negative. Negative. { d:Ez&. dfgA&, Nos. 3 and 4 are at once seen to contain cotton-seed oil from sp. gr., from iodine test, and from Eechi-Milliau test. Sample 2 would be called pure lard, but the crystals of beef fat were formed so readily and abundantly as to show at least 20 per cent. of that adulterant. The impossibility of detecting beef fat without Belden’s test is at once evident.These samples contain at least 25 per cent. of beef fat. The expla- nation is found in the presence of cotton-seed oil, similar to that in the table, having a low titre of about 33, by which the titre of the mixture is correspondingly lowered. The approximate percentages of cotton-seed oil can only be deduced from specific gravity. Taking that of normal average lard as 0.861, and that of cotton-seed oil as 0.869, we con- clude there must be about 32-5 per cent. and 26 per cent. of cotton-seed oil respectively in these two samples. The very low titres of 3 and 4 need explanation. The titre should, therefore, be at least 38. Two other suspected samples have just given the following results :- 1 2 Specific gravity at looo C... .. 0.8600 0.8606 Titre .. .. .. .. 38.00 38.80 Iodine test . . .. .. .. 65-40 60.27 Bechi-Milliau test . . .. , . Blackening. Negative. Belden test . . .. .. , . Much beef fat, Much beef fat. Judged by special gravity and by iodine test, both samples would be pronounced pure. The Bechi-Milliau test in sample No. 1 finds marked confirmation in the fact that though a t least 20 per cent. beef fat is present, yet the iodine test, instead of drop- ping to at least 60, as we should expect from the reducing action of the beef, remains as high as is ever found in a pure lard showing a titre of 380 C. The presence of 5 to 10 per cent. cotton-seed oil can be positively affirmedin view of the whole analysis. Ten per cent. of cotton-seed oil might not have any visible effect on specific gravity, but would raise the iodine test from 65.4 to 70, which in turn is reduced in the above sample to 65.40 by the presence of, say, 20 per cent.of beef fat. The fatty acids are prepared by saponifying in such a way as to secure as colourless fat aoids as possible. They are washed in a separating bulb with several additions of34 THE ANALYST, very hot water, and finally filtered through a dry filter paper into a test tube of 12 to 2 centimetres diameter. The '' titre " is taken with a delicate thermometer graduated to tenths of a degree. 5 C.C. are then tested for cotton-seed oil by Bechi-Milliau test, and the remainder may be used to ascertain the combining number. A portion also can be used to obtain the iodine number. The iodine absorbed by the fat acids, multiplied by 95.5 (in the case of fats consisting of stearin, palmitin, and olein), will give the iodine absorbed by the original oil. The great advantage of Dalican's method over any other method of finding the melting-points of oils is the accuracy of the results obtained. The results are correct, as proved by scores of duplicate tests to within -1, or a t most *2 degrees Centigrade. While the above work seems to destroy the value of Hiibl's iodine test for examining lard (by itself), yet it by no means cripples the analyst in his ability to reach a correct conclusion when the examination is made a complete one, and all the data attainable have been ascertained.

ISSN:0003-2654    

DOI:10.1039/AN8891400032

出版商:RSC    

年代:1889

数据来源: RSC

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34 THE ANALYST, ON THE ACTION OF IRON PIPES (RUSTED) UPON WATER CONVEYED THEREIN. BY S. HARVEY, F.C.S., F.I.C. Read at Meeting, December, 1888. That iron-oxide effects some changes upon certain constituents of drinking water, specially as regards the nitrates present, has long been known, and I lay claim to no originality in bringing the following observations before the Society of Public Analysts. Nine months ago (March) the Public Water-supply of the Borough of Ramsgate was extended to the village of Minster, the latter place having previously derived its water for drinking purposes from private wells, most of which were polluted. No sooner however had the Ramsgate supply reached Minster than complaints were made as to its character and appearance. It was very turbid, depositing ferruginous sediment, and when submitted to analysis was found to yield in addition to a considerable amount of combined chlorine ‘‘ high figures ” for “ AWW&O~~LI,’~ ‘‘ Oxygen absorbed,” and ‘‘ Nitrites,” and this state of things has now continued for several months.Samples taken from the new supply a t Minster were submitted to me, and I bad some difficulty in convincing the senders that the appearance of the water was not due to sewage or organic impurity. As my acquaintance with the Ramsgate water has extended over several years, and as the supply is very pure and uniform, ranking among first-class waters, I felt that a good opportunity presented itself for testing the action of iron pipes (presumably rusted) upon water of a known constant composition. Accordingly I had a number of samples taken all at one date, July 23rd last, and with as little interval between each as the distance would allow.Every care was used both in the collection of the samples and the analysis, which followed immediately. In the case of the twrbid samples the clear supernatant water only was analysed. None of these samples contained sufficient iron in solution to affect ‘‘ ammonium sulphide solution.” Samples 1, 2, and 3 were takenfrom the old Ramsgate mains, Samples 4, 5, andTHE ANALYST. 35 clear 5.60 0.72 trace 0*0017 -024 35.70 wry slight none 6 were taken at Minster after a run of from five to six miles through the new mains to the latter place, the pipes being four, five, and six inches in diameter. PUBLIC WATER SUPPLY, RANSGATE. clear 6-60 0.74 trace 0.0017 *024 35.63 very slighl none Appearance Combined Chlorine Nitrogen as Nitrates Ammonia Albuminoid NH, Oxygen in 4 hours Total Solids Deposit Nitrites and Nitrites { clear 5-53 0.1 9 0.0182 0°0016 -090 29.89 slight n quantity Total Nitrogen in NH, Nitrates and Nitrites Nitrogen Missing very turbid turbid 5*ss 5-60 0.49 0.58 0*0168 0.0025 0.0014 0.0022 -118 *068 34-79 34.72 Iron-oxide Iron-oxide in quantity in quantity Taken a t Ramsgate (old mains).0.205 0.522 0.504 0.582 0.223 0.145 + 0.720 1 0'740 I - - No. 3 clear 6-2.b 0.72 trace 0*0018 -028 36.19 slight none 0.720 - Taken at Minster (new mains). I 1 N,B.-The figure for combined chlorine in the Ramsgate water fluctuates a little, and differs but little from what it was five years ago. Omitting details common to both sets of samples, it will be observed that the nitrates have diminished considerably in the last set (4, 5, and 6), The ammonia has risen from traces in the first set to considerable amount in the latter, while nitrites appear in quantity in the latter, their amount being measured practically (minus a small deduction) by the oxygen absorbed.What has become of the missing nitrogen in the three last sampIes, and how may the small but distinct variations of combined chlorine be accounted for ? There is also a mom1 consequent upon the above, which was the chief reason for my bringing this matter before the Society. How far is an analyst justified in pronouncing an opinion upon the purity of a drinking water in the absence of all information as regards the origin, and mode of storage and conveyance of the same, or when such particulars are purposely witheld? It would be interesting to know how the Minster supply would fare in the hands of an analyst who had been kept in ignorance of its antecedents.I n connection with this subject, viz., the effects of iron oxide upon water, perhaps the following analyses may be interesting, and they confirm some remarks by Dr. E. Frankland (vide Water Analysis p. 19). The water from these wells has been a cause of unpleasantness between analysts in my own experience, very pure as it is. Two questions present themselves,36 THE ANALYST. WATER FROM LOWER TERTIARIES,” (THANET BEDS) BELON “ LONDON CLAY.” Taken from wells six miles N.N. W. of Canterbury. Appearance , . .. .. Combined Chlorine . . .. Phosphates . . . . .. Nitrogen as Nitrates . . .. Ammonia .. I. .. Albuminoid Ammonia . . .. Oxygen absorbed in 4 hours . . Total Solids . . .. .. Deposit . . .. .. .. Sulphates .. .. .. Nitrites. . .. ... .. .. * . .. .. .. .. .. .. .. .. . , No. 1 very turbid 7.1 4 very distinct traces 0.02 0*1190” 0-0014 ,023 52.78 chiefly Ferruginous present absent No. 2 rather turbid 7.14 distinct traces 0 *02 0*0878* 0.001 9 0.02 6 52-22 chiefly Ferruginous present absent Canterbury, December 10, 188s. (Conclusion of the Xociety’s Proceeding$.)

ISSN:0003-2654    

DOI:10.1039/AN8891400034

出版商:RSC    

年代:1889

数据来源: RSC

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36 THE ANALYST. NATURAL APERIENT BITTER WATERS. BY OTTO HEIINER. SOME time ago the attention of the medical profession was drawn to the important subject of accuracy in dispensing of medicines, by the publication of a joint report by Dr. Edward Seaton and myself. That report having been productive of some good, I venture now to refer to an allied subject, in the hope that a remedy may be found for an evil which concerns medical men and the public alike. For a number of years past the sale of natural aperient magnesian waters has been considerably increasing, and there is now a large variety of such waters at the disposal of the practitioner. These waters are generally sold in bottles, upon the labels of which, in most cases, analytical figures are printed, which allege to represent the composition of the contents, and are doubtless intended as a guide in fixing the dose of the water to be used.There are also, generally, directions on the bottles to the effect that a wineglassful is the average dose. It should be generally known that the waters in question, being obtained in the majority of cases from very shallow wells, are liable to very wide fluctuations in com- position and consequently in therapeutical activity, and that it is impossible to represent, once for all, the composition of the waters by a single analysis. True mineral waters, coming from great depths, may and do remain unchanged in composition for a long number of years, but magnesian bitter waters, as at present collected, fluctuate in strength almost from day to day; stronger waters collect at the bottom of the wells than in the upper strata, and it is possible, therefore, t o obtain at will strongly or relatively slightly saline solutions from the same well.The following analyses, obtained from samples which I have lately purchased in the London market, represent six different waters, all coming from the Ofen district in Hungary, and frequently taken to be equivalent of each other. 10,000 parts contained :- Sulphuric acid. .187*53 197.08 232.20 242.34 247.48 279.37 310.60 Chlorine . . 13-80 15.95 8.87 10.60 10.30 13.85 14.00 Carbonic acid . , 2.29 2.51 3.87 4.36 3.08 5.81 5.06 Magnesia ., 54-00 53.19 56.85 71.95 65.66 97.24 101.60 Lime . . 6.52 6.12 6.36 6.42 6.24 7.22 7-27 Soda . . 67.75 79036 91-74 87.88 96.40 91.05 92-17 Specificgravity , ,1031*1 1032.7 1037.0 1039.5 1039.7 1048.7 104906 A B C D E F GTHE ANALYST.37 Samples D and G represent the same brand of water at different times. To render these analyses more readily comparable with each other, I will assume that the whole of the magnesia and soda is present in the form of sulphates, which may the more readily be done as the proportions of carbonate of magnesia and chloride of sodium are small, and but little diEerent in the seven samples :- Magnesium sulphate . ,162.00 159.57 170.55 215.85 196.98 291.72 304.80 Sodium siilphate . .155.16 181.76 210.11 201.27 220.79 208.53 211.09 317.16 341.33 380.66 417.12 417.77 500.25 515 89 -----__I- Taking the proportion of magnesium sulphate as the standard of strength, it is seen that of sample E 1.91 parts are necessary to produce the same effect as one part of sample G.As the laxative powers of magnesium sulphate and sodium sulphate are nearly equal, we may more fairly compare the totals of the two salts as the measure of the activity of the waters. I n that case, 1.63 parts of sample A are equal in effect to one part of G . According to this A stands to G as 1 to 1.59, the quantities to be taken being of course inversely proportional. It appears to me that the medical profession should be distinctly aware of the wide differences in the composition of these waters, and should either insist upon some measure of uniformity, which by care in bottling the waters could easily be obtained, or upon an exact statement of strength upon each bottle, be it by analytical figures, or by specific gravity only.Imagine a patient who has been accustomed to a particular dose of, say, water A, taking an equal dose of sample G. The purgative action would be increased by almost two-thirds. Even if serious consequences might not be the result, the uncertztinty of the remedy is apparent. There could not be any practical difficulty whatever to obtain uniformity in com- position, by excluding from the wells all surface water, or such coming from strata poor in saline ingredients. Even then fluctuations, but within narrower limits, would occur. An exact statement of the specific gravity of the contents of each bottle should there- fore be made, so that any medical man would be in a position exactly to determine the necessary dose." The analyses at present given updn the labels are of no value what- ever for this purpose, as they do not represent the composition of the contents, but of samples specially selected to show high saline proportions, and often made many years ago. The readiest measure of the strength is the specific gravity. * The figures of the specific gravity above 1,000 very nearly representing the sum of the magnesium and sodium sulphates per 1,000 parts of the water. Thus in sample A a specific gravity of 1031.1 corresponds to 81.7 parts 9f the snlphates per 1,000 of the water.

ISSN:0003-2654    

DOI:10.1039/AN8891400036

出版商:RSC    

年代:1889

数据来源: RSC

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THE ANALYST. 37 A NEW PEPPER ADULTERANT. BY F. WALLISTODDART, PUBLIC ANALYST FOR BRISTOL. A NEW material in extensive use for the addterntion of pepper having recantly come under my notice, I wish to call the attention of public analysts to it, that a united effort in all quarters may stamp out what bids fair to become a very successful fraud. The material in question consists of rice atarch, barytes, calcic carbonate, and lead chromate, all, of course, finely ground and intimately mixed. The lead chromate amounts to about 10 per cent. of the whole compound. By the addition of about 5 per cent. of this mixture, the colour of pepper is so immensely improved as to raise38 THE ANALYST. its market value very considerably, but I have met with pepper containing fully 10 per cent.Such confidence do the manufacturers of this delectable mixture feel in it, that they guarantee their peppers coloured with it to be genuine, and I saw one invoice endorsed, ‘‘ warranted genuine as per Somerset House analysis.” Nevertheless the detection of this adulteration is not difficult. The increased ash and presence of rice mould arrest attention, whilst the peculiar and unnatural tinge communicated by the chromate is readily noticeable. The method of examination, however, which has proved most successful in my hands is agitation with chloroform, by which means the mineral ingredients of the adulterant are obtained in their natural combinations. The well-washed residue is gently warmed until the chloroform has evaporated, treated with a very little sodic carbonate solution and allowed to cool. A few drops of ether, which has been agitated with aqueous hydrogen peroxide, are then added, and the mixture carefully acidified with hydrochloric acid, when the delicate blue colouration is readily obtained, and the barium and lead remain to be estimated in the usual way.

ISSN:0003-2654    

DOI:10.1039/AN8891400037

出版商:RSC    

年代:1889

数据来源: RSC

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38 THE ANALYST. MONTHLY RECORD OF GENERAL RESEARCHES INTO ANALYTICAL CHEMISTRY. H. SCHREIB. Zeitschr f. angew Chmie, No. 24, 1888.-The author recommends to estimate the proteids by combustion, and also to take the moisture and the ash. The starch is thus found by difference, bilt an allowance is made for other carbo-hydrates and fatty matter. Although it seems at first sight absurd to make three determinations instead of one, in practice this way will be found more convenient than a direct estimation of the starch. The best direct pro- cess as yet known, viz., Lintner’s, takes more than 6 hours, in which time it is much easier to finish the combustion and do the water and ash. Even if Lintner’s process left nothing to be desired from a point of accuracy, it will still give unreliable results to the starch manufacturer, because no notice is taken of the starch, which will be retained by the albumenous matter.The author finds that every pound of gluten will cause the loss of one pound of starch. Soluble proteids will, of course, cause no loss. The value of a commercial Starch is best got a t by direct experiment. Four parts of starch boiled with fifty parts of water must give a proper set paste. Before boiling ESTIMATION OF STARCH FOR TIEHNICAL PURPOSES, the starch must be powdered and thoroughly mixed with the water. L. DE K. IMPURE REAGENTS. L. L. DE KONINCK. 2eitschr.f. angew. Chemie, No. 1, 1889.- Lead peroxide often contains manganic peroxide. Being sometimes used for the detec- tion of traces of manganese, it is important to know whether it is perfectly free from that body.The best way is to first heat a portion of the powder with strong sulphuric acid to dryness, which will yield plumbic and manganous sulphates. A fresh quantity of the lead is now added and the whole boiled with nitric acid, when the test will be successful. Ether often deserves the name of su&huric ether, as it sometimes actually contains free sul- phur. This impurity will be easily detected by shaking the sample with mercury, which will more or less blacken. Chloroform often contains alcohol. The usual test is agitation with alkaline permanganate, which should not turn green. The author found this test not to be reliable, as the greening may be caused by impurities in the potash, He therefore uses a solution of potassic permanganate in baryta-water.Mere boiling with nitric acid will not be always successful. L. DE K*THE ANALYST. 39 MONTHLY RECORD OF ANALYTICAL RESEARCHES INTO DRUGS. IMPERIALIN,” A NEW ALKALOID, K. FBABNER. Berichte, Dec. 12, 1888,-The author examined the bulbs of the poisonous crown imperial, frittikmia or coronaria imperialis, of the family ZiZiacece, and prepared a new alkaloid, ‘‘ imperialin,” by two processes, of which the following is the best : The crushed bulbs are rubbed up with lime, and the mixture completely dried on the water-bath, and repeatedly extracted with hot chloroform, which is afterwards shaken up with water containing tartaric acid. The concentrated acid solution is precipitated with Na@O,, and the precipitate freed from mot her-liquor by means of the suction-pump.By repeated re-crystallisation from alcohol, the substance is obtained perfectly white. The yield is about 0.08 to 0-12 per cent. The formula Fragner calculates from his combustions (the carbon determinations vary considerably) is C,,H,,,NO,. The alkaloid gets yellow at 240°, brown at 24S0, and melts completely at 2 5 4 O . It crystallizes in short, colourless needles, is very slightly soluble in water, soluble in alcohol--especially so on warming-less soluble in ether, ben- zene, petroleum-ether and amyl-alcohol, dissolving very readily in chloroform. Its solutions have a bitter taste. Imperialin turns the plane of polarised light to the left. Fragner gives the specific rotation [ ( c ] ~ = - 35*40°. Tannin precipitates the soh- tions of imperialin salts yellow, flocculent ; pottassium iodide, dark yellow, amor- phous ; potassio-mercuric iodide, reddish-yellow, flocculent ; potassium bismuth iodide, orange-red ; potassium cadmium iodide, white flocculent ; potassium bichromate, yellow, crystalline ; picric acid, yellow, flocculent.The following reactions of the dry substance are given. With concentrated HeSO,, a yellow colouration ; mixed with sugar and then treated with H,S04, the colouration is first yellowish-green, then pale-brown, flesh- coloured, cherry-red, and finally dirty-violet. Frohde’s reagent becomes greenish-yellow with it, Mandelin’s, olive-green, reddish-brown, and finally dark brown. After tritura- tion with cold HzSO,, KNO, and KCIO, give orange-yellow colourations, which become dark reddish-yellow if the acid solution has previously been warmed. Warm HNO, colours the alkaloid yellow. With HCl a strong fluorescence is produced ; on warming, a brownish-green colouration is obtained, which gradually turns brownish-red. No pressure is observed on opening tubes in which imperialin and HCl have been heated to high temperatures ; therefore, no easily-removable methyl-groups are in the compound. Preliminary experiments seem to show that imperialin acts on the heart. A. L. G.

ISSN:0003-2654    

DOI:10.1039/AN8891400038

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

THE ANALYST. 39 LAW NOTES. ADULTERATED CHEESE.-& Glasgow Sheriff Court, on the 28th December, Sheriff Guthrie pre- siding, Alexander Moffat, 36, Orr Street, was charged, at the instance of Mr. Peter Fyfe, sanitary inspector, with having on Thursday, 27th September, sold 1 lb. of cheese which was not of the nature, substance, or quality demanded by the purchaser, in respect that it contained 14*12 per cent. of fat which was not butter fat. He pleaded not guilty, and was defended by Mr. T. C. Young and Mr. John A. Spens. Mr. R. G. Ross appeared for the prosecutor. Mr. Spens objected to the relevancy of the complaint, on the ground that there was no averment The Sheriff repelled the objection on the merits, but said that the points might be raised as the case went on. Dr.Tatlock, who analysed the cheese, reported that it contained 3T46 per cent. of casein, 12.56 of butter fat, 14.12 of foreign fat, 3.94 of mineral matter, and 31.92 of water. Cross-examined by Mr. Spens: The proportion of butter fat in a skim-milk cheese ranges from 1 per cent. to 10 per cent. So far as he could judge, there was a greater proportion of butter fat in the cheese analysed than in the ordinary skim-milk cheese. A cheese made purely from sweet milk would contain about 33 per cent. of fat. That fat would be all butter fat. He detected the presence of foreign fat by the absence of butyric acid. That was the best method of testing. Butyric acid is always present in butter. There was, of course, some butyric acid in the cheese in question, but there was certainly not so much as there ought to be.He believed the foreign fat in the cheese was quite wholesome, and he believed the cheese was quite wholesome and nutritious. Personally, he would as 60011 eat thesecheeses as skim-milk cheese. There was more fat in them than in skim-milk cheese, but less of the other nourishing ingredients. The foreign fat could not be got in without taking out some of the other nourishing ingredients, such rn casein. The percentage of casein in skim-milk hat a little added fat took away from the character of the cheese.40 THE ANALYST. cheese ranges from 35 to 45 per cent. I n this particular case he found 37.46 per cent. of casein. The percentage of water should be 25 to 35 per cent., and of mineral matter from 3 to 6 per cent.Nourish- ment is got from the fat, but he wonld not call it the principal source of nourishment, for there is also casein. There was cheese made in America mixed with fat. It was sent here in large quantities, and sold as cheese, but he did not allow that it was cheese. By Mr. Ross : He believed the latter class of cheese was called margarine cheese in America. Skim-milk cheeses made in this country are very dry. The addition of foreign fat gave the cheese an appearance of being richer-more like a sweet-milk cheese. This closed the case for the prosecution. Preceptor Alexander Osborne was the first witness called for the defence. He stated tbat he is a partner of the firm of Alexander Osborne and Sons, cheese merchants, Candleriggs, and a shareholder in the Creamery Company, Dunragit, who made the cheese in question.What was formerly known as skim-milk cheese is almost an unsaleable article now. It is of very poor quality, and to make a sale- able article they found it necessary to improve it by adding a little fat, which made it rather dearer tban skim-milk cheese. This is about the cheapest quality of cheese sold in the market. The retail price of the lowest quality of sweet-milk cheesa at present ranges from 6d. to 10d. Sweet-milk cheeses are commonly understood to be made from milk that is not skimmed, but cheeses that are made from milk as it comes from the cow are properly called whole-milk cheeses. No one could expect to get whole-milk cheeses at 4d. per lb. The price indicated that they were something different from what were sold as sweet-milk cheese.The cheeses in question were superior to skim.milk cheeses, because fat was added that made them soft and more digestible. The added fat compensated for the cream that was taken away, and made the cheese very nearly, if not quite, as good as the clearer article sold as sweet-milk cheese, and much better than some of them. Originally all Scotch cheeses were skim- milk cheeses, but when the system was changed in the parish of Dunlop the cheeses made there from whole milk were called Dunlop cheeses, to distinguish them from what were called Scotch cheeses. By Mr. Ross : No person tasting the cheeses in question would distinguish them from ordinary cheeses, except that they might be rather better. Dunragit cheeses have been in the market €or two or three years, and the company would prefer that shopkeepers should sell them by that name, Cheeses mixed with foreign fat have been made elsewhere for a long time, but not in Scotland, so far as he was aware.Mr. Andrew Clement gave similar evidence. The fat introduced into the cheese is cow fat, pure and wholesome. The Sheriff remarked that if there had been an attempt to sell the cheese a t 6d. the case would have been different, but it was sold at 4d., which was not a price above its value. Mr. Ross contended that when a purchaser asked for cheese he was entitled to get cheese that was made entirely from milk. The Sheriff said he was satisfied that the case fell under the proviso in the 6th section of the Food and Drugs Act, ‘(Where any matter or ingredient not injurious to health has been added to a food or drug because the same is required for the production or preparation thereof as an article of commerce in a state fit for carriage or consumption.” That must be read as meaning that it was intended to prepare the article for consumption with reference to the price that was to be paid for it and the purpose for which it was intended.It was quite clear that there was not in this case anything done “fraudulently to increase the bulk, weight, or measure of the food or drug, or conceal the inferior quality thereof.” What the result of another prosecution for a similar case might be it would be wrong for him to prognosticate, but from the evidence it was clear that this case did not fall within the section.The case was accordingly dismissed. In his report, which was included in the minutes of the Health Committee, Mr. Peter Fyfe, sani- tary inspector, in referring to the above case, says that, in giving decision in favour of the accused, his lordship said that the sixth section of the Adulteration of Food and Drugs Acts must be read as meaning ‘6 that it was intended to prepare the article for consumption with reference to the price that was to be paid for it and the purpose for which it was intended.” It was quite clear that there was not in this case any thing done “ fraudulently to increase the bulk, weight, or measure of the food or drug, or conceal the inferior quality thereof.” The principle here laid down that 6‘ foreign ” fat may be introduced legally into cheese, so long as the fat used is not injurious, and the cheese is sold a t a moderate price, is (says Mr. Fyfe) a new one, which places cheese in the list of mmzflactwed articles, and displaces it as a purely milk product. This lays the market open to large importations of 6‘ imita- tion cheese ” from America. Mr. Crawford said he did not desire to say very much about the case. The Committee were not satisfied with the decision, and they had the matter fully under view, and would in course of timetake such measures as seemed to them necessary in the circumstances.

ISSN:0003-2654    

DOI:10.1039/AN8891400039

出版商:RSC    

年代:1889

数据来源: RSC

摘要:

40 THE ANALYST. APPOINTMENTS. Dr. H. Leffmann has been appointed Pathological Chemist to the Jefferson Medical College Hos- pital, Philadelphia. Mr, Beam has been appointed Demonstrator of Chemistry at the Pennsylvania College of Surgery,

ISSN:0003-2654    

DOI:10.1039/AN8891400040

出版商:RSC    

年代:1889

数据来源: RSC