摘要:

ahl# IKCLUDXNG awlgat, THE PROCEEDINGS OF Opening Notice . . . . . . 3 Meeting of the Society of Public Analysts . 3 Examination of Spirits for Methylated Spirits and Fousel Oil, by A. Dupr6, Ph.D., F.R.S. . . . . . 4 The Analysis of Butter, by Dr. Muter. . 7 THE “ SOCIETY OF PUBLIC ANALYSTS.” The detection of Alum in Flour and Bread. By J. Alfred Wanklpn, M.R.C.S. . . 14 Retailing Milk in the Streets .. . 15 The preparation of Ferrous Phosphate . 15 Death of Dr. Letheby . . . . 15 A novel reading of the Sale of Food and Or to S~tbscribcvs 3s. 6d. [No. 1.3 31st MARCH, 18’76. [PRICE 6d. 9ederannnrn. PveebyPosf.1 Discussion on ditto . . . . . 13 Drugs Act . . . . . 1 6ahl# IKCLUDXNG awlgat, THE PROCEEDINGS OF Opening Notice . . . . . . 3 Meeting of the Society of Public Analysts .3 Examination of Spirits for Methylated Spirits and Fousel Oil, by A. Dupr6, Ph.D., F.R.S. . . . . . 4 The Analysis of Butter, by Dr. Muter. . 7 THE “ SOCIETY OF PUBLIC ANALYSTS.” The detection of Alum in Flour and Bread. By J. Alfred Wanklpn, M.R.C.S. . . 14 Retailing Milk in the Streets . . . 15 The preparation of Ferrous Phosphate . 15 Death of Dr. Letheby . . . . 15 A novel reading of the Sale of Food and Or to S~tbscribcvs 3s. 6d. [No. 1.3 31st MARCH, 18’76. [PRICE 6d. 9ederannnrn. PveebyPosf.1 Discussion on ditto . . . . . 13 Drugs Act . . . . . 1 6

ISSN:0003-2654    

DOI:10.1039/AN8760100001

出版商:RSC    

年代:1876

数据来源: RSC

摘要:

SOCIETY OF PUBLIC ANALYSTS. On the 15th Inst. an Ordinary Meeting of the above Society was held a t Cannon Mr. Wanklyn, Vice-president, occupied the Chair. There was a numerous attendance of members, and the interest of the Meeting was enhanced by the presence of an unusally large number of visitors. After the ordinary routine business had been transacted the following resolution was put from the Chair :- ‘( That the name of Professor A, G.Anderson be removed from the roll of members (I of this Society, and that the Secretaries be directed to inform him of such removal, ‘‘ and announce the fact in the Society’s journal.” Street Hotel. A ballot was taken and the Resolution was carried unanimously. The Scrutineers appointed to examine the voting papers, announced that the following gentlemen had been elected.Member-Hr. J. W. Thomas. Associates-Messrs. S. T. Clothier, Francis Heron, I;. de Koningh, E. Lapper, A Paper on the Determination of Quinine was read by Mr. Ailen, and another on Each Paper led to a lengthened discussion, and the Neeting did not terminate till a The announcement by Mr. Wigner of the early appearance of the first number of H. G. D’Arcy Power. the Analysis of Butter was read by Dr. Muter. late hour, three other Papers being held over. THE ANALTST was received with applause.

ISSN:0003-2654    

DOI:10.1039/AN876010003b

出版商:RSC    

年代:1876

数据来源: RSC

摘要:

4 THE ANALYST. NOTE ON THE EXAMINATION OF WHISKY AND OTHER SPIRITS, FOR METHTLATED SPIRIT AND FOUSEL OIL. BY A. D U P R ~ PH. D., F.R.S. Read at an Ordinary llleeting of (( The Society of Public Analysts ” held on FeB. 16th, 1876. EXAMINATION FOR METHYLATED SPIRIT. Now and then we hear of a whisky supposed to be adulterated with methylated spirit. I myself have had several such suspected whiskies t o examine, but failed to detect such an adulterant.My belief is that such adulteration is extremely rarely if ever practised, and that most, if not all, of the cases reported, are based on an error in analysis. Under these circumstances, I have thought it might be of interest to other analysts to describe the method I have adopted for some time past, for testing spirits suspected of being adulterated with methylated spirit.Five fluid ounces of the suspected spirit are distilled twice, having been rendered alkaline the first time, and acid the second time, about two-thirds being distilled over each time. The distillate is now shaken up with dry potassium carbonate, and, after standing over night: the upper layer is taken off by a syphon or pipette, and again twice distilled, about half an ounce being driven over this time.This last half-ounce will be found to contain any methylic alcohol present in the original five ounces. All the distillations should be conducted in an apparatus having the receiver con- nected air-tight with the condenser, and furnished with a mercury valve, allowing of expansion and contraction of the air, but presenting loss by evaporation during the distillation.About one-third of this distillate is now diluted to a strength of from 10 to 15 per cent. by the addition of distilled water, or 70 fluid grains are made up to about 500. lst, by specific gravity; 2nd, by means of Geissler’s vaporimeter ; and 3rd, by oxidation into acetic acid, and volumetric estimation of the latter.With pure alcohol, all three methods give results which should agree t o within at least one-tenth of a per cent. If, however, any appreciable amount of methylated spirit is present, the results will differ more or less widely. The specific gravity will give the total amount of both alcohols present, the specific gravity of aqueous methylic and ethylic alcohols being almost idpntical.Geissler’s vaporimeter will, however, now give a higher result, the higher the more methylic alcohol is present, this alcohol having a lower boiling point than ethylic alcohol, or, at the same temperature, a higher vapour tension. On the other hand, the oxidation process will yield a lower result, since the meth- ylic alcohol, when completely oxidised by sulphuric acid and potassium dichromate, yields only water and carbonic anyhydride, which, of course, is not estimated volumet- rically. This process will therefore indicate only the ethylic alcohol present in the mixture, and the difference between the strength thus found and that derived from the specific gravity, gives a rough indication of the proportion of methylic alcohol present.When pure aqueous alcohol is oxidised in this manner in a closed flask, it will be found, on opening the flask after cooling, that, if anything, a slight vacuum has been produced in the flask.If, however, any appreciable amount of methylic alcohol is present, it will be found that, on opening the flask, a slight escape of gas takes place, owing to the carbonic anyhydride produced. I n this diluted spirit the alcohol is now determined.THE ANALYST.5 For details of the method of oxidation, I must refer you to the work on wine, by Dr. Thudichum and myself (page 207). Should the presence of methylic alcohol be indi- cated by this process, the remainder of the half-ounce may be employed for confirmation by other tests, such as production of methyl aniline-violet, or oxahte of methyl.The method, however, will, 1 think, be found valuable chiefly as yielding very strong negative evidence, and when once one gets accustomed to it, it is very easily worked, much more so than might perhaps appear from my description of' it. I n conclusion, I will give two experiments, showing the working of the process. Firstly. A pure whisky, when treated as above, gave the following results for the Strength by specific gravity .........9 83 per cent. A portion of the same whisky was now adulterated with 10 per cent. of ordinary diluted final distillate :- ,, ,, vaporimeter ........... 9.75 ,, ,, ,, oxidation ............... 9.75 ,, methylated spirit, and again tested. The final diluted distillate now gave :- Strength by specific gravity .........10.08 per cent. ,, ,, vaporimeter ............ 10 45 ,, ,, ,, oxidation ............... 9.50 ,, The differences between the three estimations are, as will be seen, so great, that we are justified in concluding that as small an addition as 2 or 3 per cent. of methylated spirit would be distinctly recognisable, and that, at all events, as much as 5 per cent. could not possibly be overlooked.B.-TESTINQ FOR EOUSEL OIL. From time to time, B certain amount of commotion is produced in the public mind, by alarming statements regarding the presence of fousel oil in spirits, and it's alleged maddening effect on consumers of such spirits, and, analysts have even been found certifying certain spirits t o have been adulterated with fousel oil. Now in the first place I am not aware that any perfectly trustworthy evidence exists of the alleged injurious effects of fousel oil, and secondly I believe it is utterly absurd t o suppose that any spirit is ever in any proper sense of' the word, adulterated with fousel oil.Nevertheless the subject is an interesting one, and as I have not seen any process described for the detection and approximate estimation of the small quantities of fousel oil, such as are usually found in spirits, I venture to bring the following method, which I have employed for years past for this purpose before this society, without wishing t o claim any special novelty for the process.Fousel oil, as is well know. -, consists of a mixtiire of various of the higher homologues of ethylic alcohol, all or most of which, when oxidised by means of sulphuric acid and potassium dichromate, yield their corresponding acids and these latter are much more readily separated than the alcohols.Upon this fact the method is based. An amount of spiiit containingfrom one to two grammes of alcohol, previously distilled if necessary, is oxidised in a closed flask by means of sulphuric acid and potassium dichromate, care being of course taken to have an excess of this mixture in the flask.I usually digest the mixture in the flask for two hours in a water bath. When cool the flask is opened, the excess of dichromate present reduced by zinc, and the acids produced are distilled off (see the work previously quoted). The acid distillate ie now neutralized with a standard solution of normal soda, the aolution is6 THE ANALYST.evaporated to a small bulk and transferred to a retort. An amount of normal sulphuric acid equal to one twentieth of the normal alkali used is now added, and the contents of the retort are distilled to dryness in an oil bath ; the temperature being allowed to rise t o about 130 deg. C. Water is now added and a further addition of one twentieth pro- portion of normal acid is made, after which the contents are again distilled t o dryness. These two distillates may be collected separately, but I prefer to collect them together.It is advisable to add some water to the dry residue in the retort, and again distil to dryness repeating this addition of water and distillation three times after the se9ond addition of acid.The acid distillate which contains all the acids higher in the series than the acetic acid, together with a proportion of this latter, is now neutralised by means of pure carbonate of barium, the solution is boiled, filtered, evaporated to dryness, the residue dried at 130 deg. C. and weighed. The amount of barium contained in the salt is now estimated in the usual way by conversion into the sulphate.We now have the necessary data for calculating the amount of fousel oil contained in the spirit under examination, on the assumption that it consists either of amylic alcohol or of any other alcohol that may be supposed to be the chief impuritT- present. The real amount present cannot of course be obtained without a knowledge of the exact nature of the acids produced, but even this can be accomplished according to Ducloux (compts.r6nd. lxxviii. p. 1160), by submitting the mixture of acids t o fractional distillation, and estimating the proportion of acid which does over with each fraction. I n conclusion I will give the analyses of a few spirits by the foregoing process. A sample of Scotch whisky, strength 54.5 per cent.by weight in volume was found to contain 0*108 per cent. amylic alcohol (Ba in ,Io acid 53.49 per cent.) The same spirit submitted to a process of purification gave no trace of fonsel oil. (Ba in & acid, 63.73 per cent.) A sample of cape smoke,” strength 35.75 per cent. by weight in volume was found to contain by weight in volume 0.089 per cent. amjlic alcohol. (Ba in :o acid, 33.39 per cent.) A sample of common “samsho,” strength 21-51 per cent. by weight in volume, contained 0.04 per cent. amylic alcohol. A sample of fine “ samsho,)’ strength 24.49 per cent. by weight in volume, contained 0.033 per cent. arnglic alcohol (Ba in Ib acid 53.42 per cent.), calculating in each case the proportion of amylic alcohol to 100 ethylic alcohol we get. Scotch whisky for 100 ethylic 0.19 per cent. amylic alcohol. Fine 7 , > 7 ,, 0.13 7 9 ,? (Ba in :o ticid 53-46 per cent. 7, 9 7 Cape smoke ,, ), 0.24 Common samsho ,, 0.18 7 ) 9 7 A brief discussion ensued. SOCIETY OF PUBLIC ANALYSTS. DATES of Meetings in the present Sear :- Nay 3rd. June 14th. November 15 th. We have grcat pleasure in announcing that the above meetings will, by the courtesy The Chemical Society,” be held in the MEETING Booaa of that Society, Burlington of Ilouse, Piccadilly, W.

ISSN:0003-2654    

DOI:10.1039/AN8760100004

出版商:RSC    

年代:1876

数据来源: RSC

摘要:

THE ANALYST. 7 ON THE ANALYSIS OF BUTTER. Read at an Ordinary illeeting of the Society of Pu6Zic Analysts, held XarcJt 1 Sth, 1076. BUTTER diffcrs from all other fats inasmuch as it contains a notable proportion of ftitty acids other than oleic, stearic, palmitic, and their congeners. If we analyse the pure glycerides of these latter acids we obtain, by the taking up of three molecules of water during saponification and subsequent liberatior: of the acids, amounts which almost exactly approximate themselves to theory.There is no process in the whole range of analytical chemistry more accurate in the hands of those who know the importance of never trust- ing to the eye to decide whether vessels, &., are free from fat, but of invariably drying every article used, and extracting it afterwards with ether.If precision is to be attained, the principles of mineral analysis must not be applied. Fat precipitates cannot be treated as if they were barium sulphate, and expense in the shape of such articles as ether and absolute alcohol must not be spared. I am entitled to put this point strougly before public analysts, because of the experience in fats possessed by myself and my assistants owing to our having been specially thrown into this branch of analysis some years ago.Unfortunately, with a laudable desire no doubt t o introduce simplified processes, Messrs. Angell & Hehner have touched dangerous ground, and proposed the washing of fatty acids on a filter, with hot water, taking it for granted that because no fat was visibly coming through, they could manipulate thus in safety.I will venture t o say, however, that every one of the few chemists who have been called upon t o work in fats for com- mercial or scientific purposes, would agree with me that such a process is in the highest degree dangerous. Not only should fatty acids never be trusted out. of the vessel in which they are precipitated until they are finally transferred to the weighing capsule, but also every rod, beaker, and even the filter paper used t o pass the washings, should be dried and extracted with n suitable solvent.Mr. Angell, himself, evidently feels the difficulty, because in his book he gives a special instruction that ‘‘ great care must be observed in the washing.” I hold that. processes requiring SUC~J.delicate care are not suitable for use under a penal statute ; and, indeed, I go further and say, that with even the highest precaution, a constant loss of at least 5 centigrams t o 1 decigram is made in every analysis on this principle, using 5 grams of fat. By accurate methods, such as it will be m y aim to point out in this paper, the following pure. glycerides can be so nearly analysed to theory as to be made to show :- Tristearin ..................................9-5-70 Triolein .................................... 95-52 Tripalmatin .................................... 95.27 and no process of washing on a filter erer could come within, at the nearest, half a per cent. of these results, except by an accident. A very striking case in point is aflorded by Messrs.Angell & Hehner. After giving analj-ses of tallow, lard, and cocoa butter (the latter two being, by the way, about ‘5 per cent short of the ordinary yield), they intro- duce an analysis of palm oil, in which they admit a deficiency, but fancy that it is accounted for by colouring matter. Now palm oil is a specialty of ours, one of my staff having for six months done nothing else almost, and I can assure you that there is no palm oil in the market yielding so low an amount of fatty acids by at least 2 per cent.lndeeti it is a fact that commercial palm oil always yields over theory owing to free acidity, and the most highly colourcd samples give no appreciable loss of weight when BY DR. JOHN D/IUTEB, F.C.S.8 THE AXALYST.- the colour is destroyed by heat, Xere, therefore, is the decigram loss in 5 grams Plainly manifest. Besides the glycerides already referred to, butter contains tributyrin in considerable proportion, with small traces of tricaproin and tricaprylin. I have not yet SuficientlY separated these traces for estimation, as their fractional liberation from barium is very troublesome ; but of this much I am certain, that they are only present to a very small amount.That this is so may be proved by supposing a butter t o yield 88 per cent. of insoluble acids (oleic, stearic, and palmitic, the latter two being present i n the proportion of the so-called Margaric acid of older writers). This will represent 92.14 per cent. of glycerides, leaving 7.86 for glycerides of the soluble acids.I f the latter were all tribu- tyrin it would give a soluble acidity of 6.88, but in practice this does not come out. Taking a butter yielding an amourit nearly like 88, we have- Insoluble acids ............ 87-96 equal to 92.10 glyceride soluble acids (as butyric) ............ 6*72 ,, 7.69 ,, --a - Total ............ 94-68 ,, 99.79 total glyceride thus showing a deficiency of about -2 per cent, owing to the traces of higher soluble acids. The difference thus shown may be disregarded, as, although a little variable, it always comes within 07 per cent.Calculating therefore always as butyric, we come t o this fact- that no analysis of butter can be held to be complete unless both the soluble and insoluble acids be estimated, and they come, when added together, within a fair range of 94% alloming for possible experimental errors to, say, the extent of -3 to -5 per cent.in either direction, The process 1 adopt for the full analysis of butter is as foilows : - (1) 1500 grains of the butter are placed in a counterpoised porcelain dish, over a very low gas flame, and stirred with a thermometer at a heat not exceeding 230 deg.I?. until all the water is driven off, which is indicated by effervescence entirely ceasing, and the curd and salt settling perfectly down to the bottom of the dish, leaving the absolutely clear melted fat. The whole is then cooled and weighed, and the loss calculated to percentage of water. ThiE is the only method of absolutely and rapidly drying a fat, and the large quantity taken ensures a more perfect estimate of the true amount of water in the sample.I have proved by careful experirnent that the temperature of 230 deg. has not the slightest influence on butter fat. (2) The fat is melted at a gentle heat, and poured off as far as possible into a beaker, without disturbing the sediment, The remainder is poured on a weighed filter, placed over a beaker in the drying chamber, and, when all is through, the basin and filter are rinsed with petroleum spirit to remove all the traces of fat, and the filter being dried and weighed gives cztrd plus ash.(3) The filter after being weighed is placed in a weighed platinum crucible, and gently ignited. (4) The fat poured off from (2)-which mill generally bci about 1200 grains-if abso- lutely clear: is at once used for phpical and chemical examination ; but if not perfectly f're!: from spccks it must be filtered through a Swedish filter kept hot on the water bath, The processes necessary are, the taking of the specific gravity of the fat at 100 deg.F., and if that gives an adverse indication, the estimation of the total fatty acids of the butter fat both soluble and insoluble.This gives ash, called salt in the report.THE ANALYST. 9 FIRST.- 27ie “AttzkalDensity” at 100 dig. P.-This process was first publicly described by Nr. Bell, of the Inland Revenue Laboratory, in the Soiithwark Police Court. As employed by him, however, the results do not appear t o be those of actual density, no? do I consider that the precautions to ensure accuracy are quite sufficient, considering the rapid expansibility of melted fats by heat.I will give his process in his own words. ‘‘ The fat is taken out of the water bath and poured into the bottle until it is filled up to ‘( the neck. One person then takes the bottle and mother the residue of the fat, and (‘ both are brought t o exactly 100 dog. F., when the bottle is filled from the residue and (’ stoppered in the usual way.” Now I have tried this method but I find that, supposing the fat to be taken from the bath at, say, 200 deg., and each person cools his portion to 100, then the pouring in and stoppering will frequently, by a little want of care, cause the bottle to be closed when a part of its contents has gone below the 100, to the extent of 2 degrees ; because when fat is taken at 100 ‘‘ on the fall,’’ it will lose a degree of heat almost in a few seconds.At all events, the process can never be absolutely certain within one or two grains on the 1000 grain bottle. The results he gave in court embrace a range from 909-00 to 905.00, and these at once show that the actual density is not indicated. I take the actual density of a fluid to be the weight of any given volume of it, as compared with that of an equal bulk of distilled water at the same leurzpeyature. These results compare butter at 100 deg.with water at 60 deg. to 62 deg. F., and are not therefore actnal densities ; and 1 submit, that to get the true advantage of inequality of expansion, the water and butter must bufh be taken at 100 deg.F. The process I adopt is as follows :- A 1000 grain bottle is procured with rather a pear-shaped neck, and fitted with a thermometer stopper ranging from 32 deg. to 140 deg. F. The long mercurial bulb comes exactly down the centre of the bottle, and the scale is up above the stopper. The bottle is placed on the balance, and an accurate counterpoise prepared for it. It is then filled with recently boiled distilled water, at 95 deg.3’. The stopper is inserted, and the whole at once plunged up to the neck into a 12 oz. squat beaker partially filled with dis- tilled water at 103 deg. 3’. in which is placed a thermometer. As the temperature rises in the bottle, the water leaks out at the stopper, and in a few minutes (if the quantity of water in the beaker be properly regulated), a time arrives when the temperature of both thermometers equalise themselves at 100 deg.The joint between the stopper and the bottle is insta;r,tly wiped with a small piece of filter paper t o absorb loose water, and the bottle is lifted out, thoroughly cleansed and weighed. By repeating this three times the actual contents of the bottle at 1CO deg.F. is obtained, and the weight taken, before a fall of more than 5 degrees takes place. At first I let the bottle cool t o GO degrees so as t o avoid currents; but I found that it was better in practice to weigh at once, and quite as accurate. This weight of water is scratched on the bottle with a diamond, and 8111 is ready for the butter. The pure butter fat, prepared as already described, is taken from the bath and cooled to 95 dcg.F., it is then poured into the bottle, and the whole opera- rion repeated thrice, exactly asvith the water, and the mean of the three weighings thus obtaiued is divided by that oE the water. The contrivance of having a ‘‘ Yisiug-” fat heated by a “fa/Ziizg” water until the two equalize, is the height of accuracy, and more- over g b e s an appreciable rest in the variation of the temperature sufficient to enable the excess of fat which has leaked out t o be removed exactly at the required temperature.10 THE ANALYST.Mr. Bell stated in court that there was an analogy bctween the specific gravity and the per centage of iusoluble fatty acids, and here he is correct. The following are som of the figures he has given compared with the true results found by full analyses, the worst of which came to within -5 of the truth on tohe whole addition :- Mr.Bell’s ‘‘ Gravity” at 108 deg. compared with Mr. Bell’s comparative fatty acids working by the filter water at 60 deg. process and without the check of a full analysis. 909.00 ................................. 85.30” { 99:J::; ...............................86.45 ................................. 86.87 906.52 ................................ 87-50 906.18 ................................. 87.85 905.75 ................................. 88 30 905.32 ................................. 88-76 9C.5.00 ................................ 89.15 The ‘‘ Actual Deosity ” at The actual insoluble acids 100 deg. as compared found submitted to the with water at the same check of full analysis.temperature. -91382 ................................. 87-47 -91346 ................................. 87.89 ‘9133’1 ................................. 37-98 *9 1290 ............................... 88.48 ‘91286 ................................. 88-52 *912’16 .............................. 88.62 ‘9 1276 ................................88.6 1 -91 258 ................................. 88-80 91246 ................................. 89.00 The whole nine examples by my process are corresponding to butters between 908 and 907 by Mr. Bell’s gra-rity, and the results shorn a much higher and more regular per centage of fatty acids. The regular loss on the filter process I have already referred to, is strikingly mltnifested by the following comparison.I happened t o have a butter which gave 9 1286 actual density, corresponding exactly to 907:,4 of Nr. Bell’s gravity, and so we see by the filter washing Mr. Bell makes that show 86.87, while on full analpis by my process it shows 88.52, or as nearly as possible the decigram in five grams difference, as seen in the palm oil experiment. While therefore we must admit the great correspondence of the density and acids when both are properly taken, it is to be noted that the moment you come to mix butter with other fats the whole thing is upset for quantitative purposes.The fats used for butter mixing are some of them of an ‘‘ actual density ” of ,90659 (dripping) to ,90294 (vegetable butterine,”) and therefore all we can say as regards specific gravity is that if a butter shows anything over -91 100 “ actual density,” it may safely be passed eyer without further analysis as being goo& SEcom.--l’he Total‘ Fatty Aci&.--About 10 grams (or 150 grains) of the butter fat at 100 deg.I?. are weighed by difference from a suspended tube into a clean dry 15 ounce flask, and 5 graius of Potassium Hydrate, with 2 fluid ounces of rectified spirit are added.The flask is placed in :2 basin with hot water, and kept boiling for a con- siderable time, until on adding water not the faintest turbidity occurs. Ten ounces of water are added, and evaporation continued (just short of boiling) until all traces of Alcohol are dissipated. The contents of the flask are then made up to 7 ounces, with nearly boiling water, and a good fitting cork having been introduced, through which just passes a tube 2 feet long and ending in a small funnel, 5 grammes of f u l l strength * This result is an extraordinary instance of the filter process.No such butter is to be found in nature.THE ANALYST. 11 Sulphuric Acid are poured in down the tube followed by some water.The whole is then agitated with a circular motion until the soap, which rises suddenly, is changed into a perfectly clear and transparent stratum of fatty acids. The flask and contents are then cooled down to 40 dg. F., till a perfectly solid cake of fatty acid forms. A few drops of cold water are run in to wash the tube, and the cork having been removed, a small piece of fine cambric is placed over the mouth of the flask, held in situ by an ordinary India rubber ring.The fat cake is caused t o detach itself from the sides of the flask by a gentle movement, and then the filtrate is decanted, without breaking the cake, into litre test mixer, with a good stopper. About an ounce of cold water is poured into the flask through the cambric, and the whole cake and flask rinsed out by gently turning round and the washings added to the filtrate.Six ounces of water at 120 deg. are now added through the muslin, which is then quickly detached, and the cork and tube inserted. The whole is again heated, this time to 200 deg., and kept constantly agitated with a circular, but not a jerky motion for five minutes. This agitation so divides the fat, that it almost forms an emulsion with the water, and is the only means of thoroughly and rapidly washing fatty acids without loss.I n practice no Butyric Acid comes off at 200 deg., but any trace that might do so, is caught in the long tube. The cooling and filtering are then again proceeded with as above described, (the filtrate being added to the contents of the test mixer,) and the washings are repeated alternately cold with 1 ounce, and hot with 6 ounces of water, until they do not give the slightest change to neutral litmus.After thoroughly draining the residual cake by letting the flasks stand upside down for some time, the cambric is removed and the flask is laid out on its side in the drying oven, with a support under the neck, until the acids are thoroughly fused, when they are poured while hot into a tared platinum capsule, dried and weighed.The film of fatty acid still remaining on the flask is rinsed out with ether, aad dried in a small weighed beaker, and the weight added to the whole. If any drops of water be observed under the fatty acids in the capsule after an hour’s drying, the addition of a fcw drops of absolute alcohol will quickly cause them t o dry off‘.If any trace of fat is on the cambric it should be also dried and extracted with ether, but with care not to break the cake at the last pouring off, this does not occur. The process is absolutely accurate, and the merest tyro cannot make any loss so long as he does not deliberately shake the melted acids against the cork, which he could not do if he practices a circular agitation while washing. The filtrate in the test mixer is now made to an absolute bulk, and in 200 c.c; the total acidity is taken with a weak solution of sodium hydrate.The solution I generally use represents -01 of N H, in each c.c., as it serves also for nitrogen combustions ; but a useful strength mould be decinormal soda, containing *004 Na H 0 in each c.c: The acidity found is multiplied by five, calculated t o H, SO, and noted as “total acidity as H2 SO:: 100 C.C.are next taken, and precipitated with barium chloride in the presence of a strong acidulation, with hydrochloric acid, well boiled and washed bp three decanta- tions, boiling each time; and, lastly, on a filter, till every trace of soluble barium is removed.The precipitate is dried, ignited, and weighcd as usual, multiplied by ten, and calculated t o H2 SO4, and noted as “total sulphuric acid.” Lastly, 100 C.C. are evapo- rated to dryness ovcr the water bath in a tared platinum dish holding 120 c.c., and furnished with a cover of platinum foil, also tared. When dry the dish is covered and heated eyer a bunsen till all fumes cease, and a fragment of pure ammonium carbonate12 THE ANALYST.having been added, the whole is again ignited and weighed. The amount of potassium sulphate found is multiplied by 10 and calculated t o H2 SO,, and noted as (‘ combined sulphuric acid.” The rest of the calculation is obvious to any analyst, but I give an example : Ten grammes taken. Total acidity as H2 SO, ............... 0.814 Total H2 SO, ...............4.9 Combined H SO4 ............... 4-4 4.9 - 4.4 = -5 free H2 80, 0.814- -5 = -314 acidity due to butter acids stated as H2 SO, -314 X 176 Then = -564 butyric acid in 10 grammes taken which equals 6-64 per cent. 9 s By this means we get the soluble acids indirectly by processes which are the every day work of nearly all commercial analysts.I have only t o remark that the barium sulphate should always be washed very carefully, and seeing that i t regularly weighs a little over a gramme, it is advisable to boil up with dilute hydrochloric acid after ignition and see that clear liquid gives no cloud with sulphixric acid. The following may be taken as fair specimens selected from a great mass of results by my process, and as a proof of the almost impossibility of error we have the check given by the totals found. I may also stzte, that another fact which speaks well is, that I have taken the same sample, one t o two months apart, without getting one-tenth per cent. variation in the amount of insoluble fatty acids 1.-A rich butter which by theory from the density should yield Soluble acids ...............7.05 Insoluble acids ............... 87.8 94.85 - was analysed twice and in each analysis two determinations of sulphates were made. 1 s t Analysis. 2nd Analysis. Soluble acids ......... 6-92 ... 6.89 ......... 6.85 ... 6.93 Insoluble acids ......... 81-66 ... 87-86 ........ 87.87 ... 87.87 94.78 94.75 94.72 91-80 - - - 11.-A poor butter showing by theory from density 88.8- Theory.Practice. Soluble acids ............... 6.10 ............... 5-77 Insoluble acids ............... 85 *8 ............... 88.95 94.90 94.72 Theory. Practice. 111,-A butter ahowing from density 89- Soluble acids ............... 5.94 .............. 5.76 Insoluble acids ............... 89. ............... 89.10 94:94 94.86 - ~ 1V.-A sample of butter purchased at the ssme shop and same price as the Southwark disputed butter, and showing a similar amount of insoluble acid- Soluble acids ............... Insoluble acids ..............V.-A sample of Belgian “ Butterine,” Soluble acids ............... Insoluble acids ............... Theory. Practice. 2.09 ............... 1-98 93.80 .............. 93.30 95-39 95.28 fro-m vegetable fat- Theory.Practice. 0-0 ............... 0-23 95.6 ................ 96.50 95.6 95.73 - ____ -THE ANALYST. 13 These are only a few of the mass of results I have, which I have selected to shorn my views of the composition of butter. They are each examples of a special class. No. I. being a first-class Aylesbury butter. No 11. an old low-class Dutch butter, kept six months, until quite unfit for food.No. 111. a butter which had lost all character, and was not distinguishable from a piece of tallow, although genuine Friesland eight months ago. No. IT. was evidently two-thirds foreign fat; and KO. V. was all vegetable fat, and the two-tenths per cent. of soluble acids are an experimental error. I intend, if able t o spare the time, t o ret’urn t o the subject at our next meeting, and answer the questions (1) What is the average composition of natural butter? and (2) How far may the butter be affected by time ? as it would take me too long now to quote the many results I have, I n the meantime, I may say that I have every reason, from my experiments, to take 88 as a fair standad of batter calculation, if associated with at least 6.3 of soluble acids.Rut I would not apply any charge of admixture to a butter which showed less than 89.5 insoluble with 5 soluble. You will notice that I give the standard of calculation andcondemnation differently, and I think this is the proper way, because if a butter really more than passes the utmost possible limit of the article, even when rendered quite unsaleable by decomposition, the admixture being then definitely proved, should be calculated on the fair ordinary standard.This is a point which has been rather lost sight of in milk, and I think we should consider it in fixing any fresh standards. As to any great change in butter by time, calculated to invalidate results of the standards 1 have given, I believe that when the supporters of that theory get rid of the filter-washing of fats, they will find that apparently enormous changes were due to the fact that now and then by chance they h l l y estimated their acids.They will also, I think, find, except in the very height of summer, a butter with less than 87 a naturitl curiosity. I t is worthy of note that as soon as admixture steps in, the total acids rise above 95 per cent.I have t o thankmy chief assistant Mr. De Koningh, an associate of this society, for his accurate work in the practical portion of my researches. Mr. Otto Hehner said that it was evident that the results obhined by Mr. Angel1 and himself prior t o the publication of their book, were too low in the percentages of fatty acids. Their expericnce, at that time, led them to assume a standard of 85-85, but they found since that 87 per cent.was the correct proportion. He considered that Dr. Muter’s method of obtaining and estimating the volatile acids was a complete confirmation of the process which they had introduced, while, at the same time, he admitted the superior accuracy of Dr. Muter’s method of manipulation. Dr. Dupr6 took exception t o several statements in the paper, and urged the following points :- FIasr.-That the specific gravity of the melted fat should be compared with water at 60 deg.F, or 62 deg. F, or at 4 deg. C. SEcom.-That the method of heating the fat to the required temperature was not, in his opinion, sufficiently refined. He considered it necessary t o keep it at the temper- ature in a water bath for at least ten minutes before weighing, in order t o ensure accurate results.THIRD .-The thermometer, he considered, should have an elongated bulb, reaching through nearly the entire length of the specific gravity bottle.14 THE ANALYST. FooaTxr.-That the loss on the basin and beaker used in the experiments which he had made on Hehner and Angell’s process, was less than that found by Dr.Muter. FIFrH.-That the mode of estimating the volatile acids was difficult, and three different estimations entering into the calculation, was more liable t o error. SIxrx-That the plan described by himself (Dr. Dupr6), at the previous meeting, namely heating the butter $at. with water in a closed tub t o 500 deg. F, at which temperature it breaks up into soluble and insoluble fatty acids and glycerine, the first of which can be readily estimated by standard alkali or conversion into barium salt, or secondly by hcating butter fat in a closed tub at 500 dcg.F with a standard solution of alkali, afterwards adding a corresponding amount of standard acid, separating the in- soluble fatty acids, and estimating the remainder of the acid by deci-normal soda solution, which acid of course corresponds t o the soluble acid produced from the butter fat.SEVENTH.-That the butter should be melted for scme hours before taking the fusing point, and that this should, in cvery case, be taken on a rising temperature. Mr. Wanklyn stated that in his experiments he has found traces only of butyric acid and Dr. Dupre’s experiments, which seemed t o giye different results, showed a loss in the total of more than 4 per cent. He had been led t o the conclusion that the amount of butyric acid increased with the age of the butter.Dr. h p r 6 pointed out that this loss only occurred in his earlier experiments, when the silver tube leaked, but in his more recent ones, which he should shortly lay before the society, the loss rarely exceeded Mr. Allen fully agreed with Dr. Muter’s method of stating the specific gravities and also with his directions t o dry at 230 deg. F., instead of 212 deg. Mr. Turner agreed with Dr. Muter as t o the difficulty of washing, and pointed out that the so-called alcohol process which had been associated with his name was really a process which had been applied t o the analysis of butter for a number of years past. Dr. Stevenson said that his experiments led him clearly to the opinion that the fatty acids increased in amount as butter became stale. After a few other remarks Dr. Muter, in replying, pointed out that he had estimated the free acidity of butter six months old and did not find it exceed - 2 per cent., which was within the limits of rariations of samples. He also pointed out two other alternative methods of indirect estimation of the soluble acids. (1) Neutralizing with volumetric potash and then evaporating, igniting and taking the alkalinity of the residue, and (2) a method which he now understood had been previously mentioned by Dr. Dupr6, using a standard alcoholic for saponification, and afterwards standard acid for separation of the fatty acids. The objections as yet to these two ways seemed to be (1) the tendency of neutral potassium sulphate to decrepitation and consequent loss, and (2) the difficulty of standard solution in spirit rapidly altering in strength. per cent.

ISSN:0003-2654    

DOI:10.1039/AN8760100007

出版商:RSC    

年代:1876

数据来源: RSC

摘要:

14 THE ANALYST. NOTES ON THE DETECTION OF ALUM I N FLOUR AND BREAD. BY J. ALFRED WANKLYN. THE want of a method for the estimation (or even of the detection) of the sulphuric acid which forms part of the alum put into flour and bread has been felt by analysts. Owing to the existence of sulphur in gluten to the extent of about one per cent., sulphuric acid makes its appearance in the ash obtained on calcining flour and bread, and, as I have shown, the sulphuric acid of the alum is overwhelmed by tbat naturally presentTHE ANALYST.15 in the ash of flour and bread. It is, therefore, to no purpose to make estimations of the sulphuric acid in the ash of dumed bread. From some experiments recently made in my laboratory, I have been led t o seek for the sulphuric acid in the cold aqueous extract of flour. The major part of the mineral matter of flour goes into the cold aqueous extract, whilst the total weight of the extract is only some five per cent. of the flour. Before determining the sulphuric acid in the extract I coagulate the soluble gluten and remove it by filtration.

ISSN:0003-2654    

DOI:10.1039/AN8760100014

出版商:RSC    

年代:1876

数据来源: RSC

摘要:

THE ANALYST. 15 DR. LETHEBY. WE hare to announce with extreme regret-a regret which r i l l be shared by our readers-the death, somewhat suddenly, of' Dr. Letheby. He had been unwell for some weeks, his complaint being we believe, inflammation of the lungs; but he was expected t o be present as a scientific witness in a case a t the Richmond Petty Sessions on the 29th inst. At the last moment, however,, a telegram was received notifying his decease.Dr. Letheby mas too well known in the chemical world, t o require any lengthened obituary notice at our hands. We may however, medon, that he was an early Member of the Chemical Society ; that he took his M.B. degree in 1843, became Ph.D., and N.L4. in 1858 ; that amongst the numerous appointments which he had held, were those of Medical Officer of Health, and Public Analyst for the City of London; and that he was the author of numerous scientific and hygienic works.He died in his sixtieth year.16 THE ANALYST. A NOVEL READING OF TI-IE SALE OF FOOD AND DRUGS ACT. AT Westminster, Henry Fielding, a milkman, of 15, Lower Symonds Street, Chelsea, appeared in answer to an adjourned summons, charging him with selling, to the prejudice of the purchaser, some milk which was not of the nature, substance, and quality demanded.Mr. Pemberton, barrister, appeared for the prosecution ; and Mr. Symth, solicitor, for the defendant. The adulteration was not i n dispute, but the summons being under the 6th section of the A dultcration of Food Act, and the inspector admitting that he purchased it solely for the purposes of analysis, it was asked whether the sale was to the prejudice of the purchaser.Nr. Pemberton said that i f he proved thet the article was not only diffe- rent from the article demanded, ’out inferior in quality, the purchaser was prejudiced and an offence committed. Mr. Smyt,h said i t was his duty t o subinit that the complainants had not proved their case.The proceeding was under a penal statute, and he was quite sure the magistrate would look at the statute strictiy and give effect to it strictly. The word L L plcjudice,” now appeared for the first time in an Adulteration of Food statute. He contended that i t was introduced to enable m y person buying food bonajde to have it analyzed, and to prevent an army of informers springing up.Mr. Pewberton contended that the purpose for which the articls was bought was no part of the inquiry. hh. Arnold said he could not tell what the Legislature intended by the words; but, as they were in the Act, they must have some meaning. Mr. Pemberton said that if any one paid more for an article than it was worth, it was to his “prejudice.” Mr. Arnold said it was a very nice point and required comideration.He had read the Act very ccrefullp since he had adjourned the case, but he should like to consider the matter further, as he was much struck by Mr. Pemberton’s argument that the prejudice of the purchaser must mean a loss to the pocket of the purchaser. He should adjourn the case and consider his judgment. Another summons, in which the same principle was involved, was also adj ourned.--Tiimes.TOWNSSON MERCER, (LATE JACESON & TOWNSON), Wholesale and Export Dealers and Manufacturcrs of Chemical and Scientific Apparatus, Graduated Instruments, and ‘Pure Chemicals for Analysis, &c. 89, BISHOPSGATE STREET WITHIN, LONDON. Apparatus arranged and Sole Agents for Prof. Wanklyn’s Test Solutions for Water Analysis.Sole Agents for England for Beckcr’s Chemical Balances. Illustrated Catalogue pose free on receipt of 3 stamps. JUST PUBLISHED. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS,’’ VoI. 1, 1876. Containing Chemical Papers read before the Society ; Original Art,icles ; Beports of the Society’s Xeetings, &c., &c. CLOTH, 2s. 6d. BY POST, 2s. loid. ELLIOT STOCK, 62, PATERNOSTER Row. ‘( This book should certainly be possessed by Public Ana1ystg.”- Chemist and Drzcggzst. THE ANALYST. Subscription-8s. 6d. per annum, post free. All communications, enquiries as to Advertisements, Post Office Orders, &c., to be addressed to G. W. WIGNRR, 79, Great Tower Street, London, E.C. Printed by ALFRED nooT, 7, Mark Lane. E.C., for the Proprietors; and Published by ELLIOT STOCK, 62, Paternoster Row, E.C.

ISSN:0003-2654    

DOI:10.1039/AN876010015b

出版商:RSC    

年代:1876

数据来源: RSC