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Various papers on abnormal milk |
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Analyst,
Volume 18,
Issue January,
1893,
Page 1-21
C. W. Heaton,
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摘要:
VARIOUS PAPERS ON ABNORMAL MILK. (Rend at the Meeting, Novem6er 2nd, 1892.) No. 1, by C. W. HEATON. On August 9th, 1892, I received from the Inspector of the Parish of St. Martin’s- in-the-Fields, a sealed sample of milk.. He stated that his deputy had seen the milk2 THE ANALYST. drawn that morning from the udder of a cow. The results of analysis were as follows :- Specific gravity ... ... ... 1031.43 Solids, non-fatty ... ... ... 8.39 per cent. Fat ... ... ... .._ ... -86 ), Total ... ... . . . . . . ... 8.65 )9 Ash ... ... ... ... ... -79 7 ) Chlorine in Ash ...... ... *20 ) was ... ..* ... ... 1IOO ,, The creamseparated in the lactometer The sample was, of course, obtained by partial milking, and according to law it could Yet, what analyst, in ignorance of the facts, could not be said to be adulterated.* possibly certify that such a milk was genuine 5 This case seems to me to illustrate the inefficiency of the Food and Drugs Act in its Surely, it would be better to insert in a schedule, the minimum strength The vendor could, of course, dilute Milk below present form. which was to be held as representing genuine milk.or skim his milk down to this standard, but that is abundantly possible now. a certain strength ought not to be sold without special description. It must be remembered that, to quote the words of the twelfth report of the Local Government Board, “ the Sale of Food and Drugs Acts are not designed to prevent the sale of poor articles, but that of adulterated articles.” No. 2, by B. DYER, Sc.D. During the milking trials at the Essex Agricultural Society’s Show at Harlow, this year, the writer met with a sample of abnormal milk which was of some interest.The cow yielding it was under four years old. She was milked dry on the eve of the show in the presence of the writer’s colleague, Mr. Rosling. On the next morning she was again milked dry, and the morning milk was weighed and sampled for analysis. It weighed 164 lbs. It was observed at the time of milking, that the cow was restless and nervous, and the attendant who milked her observed that she “ held up ” some of her milk, The milk when analysed gave :- Total solids ... ... ... 10.85 Fat .. ... ... ... 1.85 Solids-not-fat ... ... ... 9.00 Ash ... ... ... ... O W * It was decided, so far back as 1877, t.hat milk should be sold “ whole.” A fine of &lo was inflicted (THE ANALYST, vol, i., p.82:. in a erne where the defendant lrsd sold “ fore ” milk for genuine milk. -S.-Edit.THE ANALYST. 3 On the afternoon of the second day, being curious t o investigate further a case in which milk of such abnormal quality was yielded by a cow in good health and condition, the writer had her milked out again. This time the milk was normal and of good quality, shewing :- Total solids ... ... ... 12-75 Fat ... ... ... ... 3.64 Solids-not-fat . . , ... ... 9.1 1 The milk obtained at the trial milking was like pnrtially skimmed milk, and it is to be presumed that the strange deficiency of fat was due to the ‘‘ holding up ” of the richer part of the milk. It is well known that the (I strippings ” are richer in fat than the main bulk of the milk, but not that so great a proportion of fat is liable to be withheld, as was the case here.The main interest is centredjn the fact thatthe cow normally yielded good normalmilk; and the case serves to show that even an appeal to the cow may be sometimes misleading. Not only should a cow be milked ‘‘ dry,” but she should be milked carefully and without any unusual excitement, if a correct sample of her yield is required, No. 3, by A. SMETHAM. For several years past i t has been the custom of the Altrincham Agricultural Society to award prizes at its annual show for the best cow for dairy purposes, and in order to estimate the relative merits of the animals exhibited, the judges have awarded points for the appearance (frame, etc.) of the cows, and have then left the final award to me, the award t o be made by granting points for appearance of cow, quantity of milk produced and for the weight of the butter-fat and of solids-not-fat yielded during the trial.This year four cows were entered for competition, a i d below I give the figures relating to each :- No. Weight of Mllk. Total Solids. Fat. Ash. Sp. Gr. 545 16 10 14-88 5.73 -68 1.031 9 516 8 4 12-79 3-31 -80 1,0347 547 6 6 19-50 11.06 -53 1.0266 54s 13 6 16.06 7.37 .’72 1.0378 The cows were milked dry a t eleven o’clock in the morning in the presence of stewards, and they were again milked for the purposes of adjudication a t 4 o’clock in afternoon. I t was the milk obtained in the second milking which I examined.lbs. om. per cent. per cent. per cent. the the Although I was not present when the samples were taken I am assured that care was observed to prevent any tampering with the milk, and that, after weighing, the samples were immediately bottled in presence of the judges and forwarded t o me. Indeed, the conditions under which the trials take place, practically preclude the4 THE ANALYST, possibility of any tampering, for the milking is performed in view of the public as well as of the judges and stewards. It is also in the interest of each exhibitor to obtain as much milk as possible from his cow, as points are given for quantity as well as quality. All the cows exhibited were shorthorns, but the only one which gave abnormal milk was the one numbered 547 in the catalogue.This was a three-year-old non-pedigree shorthorn, which had had her first calf three weeks before the show and had been liberally fed on a compound feeding cake and bean flour in addition to her ordinary rations. The milk marked No. 548 was from a cow which had had her second calf two months previous to the show, while that marked No. 545 was from a cow which had only calved one week. In considering these resdts it must be remembered that the milk was obtained from four picked cows from one of the best dairy districts in England, and that the conditions of a show yard are not such as conduce to a normal flow of milk ; but, nevertheless, they are interesting as showing within what limits pure milk from shorthorns may vary. No. 4, by H. D. RICHMOND.A sample of the evening milk from a farm in the West of England had the low specific gravity of 1.0300; this caused a suspicion of watering, but on analysis the figures found were :- Specific gravity ... ... ... ... 1.0300 Total solids ... ... ... ... 12.32 Fat ... ... ... ... ... ... 3.70 Solids-not-fat ... ... ... ... 8.62 From that date for the succeeding five weeks a sample was analysed from every The weekly arerages are as follows :.- churn received from this farm. Morning Milk, /-. / Week Ending. Sp. Gr. T.S. Fat. S.-N.%. A.-- on ug. A W ... !.23!2 12-21 2-68 8.63 Sept. 3 ... 310 12-47 3.91 8.56 ,, 10 ... 310 12-59 3.92 8.67 ,, 27 ,,, 305 12.30 3.84 8.46 ,, 17 .,. 305 12.30 3.68 8.62 Evening Milk. Sp. Gr. T.S. Fat. S -N.-I?. !.Q2cJ5 13.64 4.97 8.57 297 12-56 4.18 8.38 303 12.90 4-41 8-49 306 12.75 4.15 8.60 302 12.94 4-26 8-68 / 1- Of the total of 160 samples, no less than 16 fell below 8.45 per cent.of solids-not-fat, The milk was supplied by a herd of 60 cows, who yielded an average quantity of GO and a further 14 fell between 8.45 per cent. and 8-5 per cent. of solids-not-fat. gallons a day, a very small quantity for the time of year,THE ANALYST. 5 On the 37th of August the whole of the cows were milked in the presence of witnesses, and samples were taken, as soon as the cows were milked, after the milk was cooled, and on the arrival of the milk in London ; the analysis of these three series of samples differed only in the second place of decimals ; the results were :- Sp. Gr. T.S. Fat. S.-N.-F. 17 cows ...... 1.0300 12-32 3.97 8.35 24 ), ... ... 305 12SO 4.2 1 s.59 19 3, ... ... 2 95 12.40 4.1 2 8.28 As these samples were strictly authenticated, and the possibility of water being added is precluded, I have no hesitation in accepting the other low samples as genuine ; that they were so was further shown by the practical identity of the figures for milk- sugar, casein, albumen and ash in the authenticated and unauthenticated low samples. The average of seven analyses during the week ending August 27th, was :- Water , . . ... ... 87.25 Fat ... ... ... 4.32 Milk-sugar ... .. 0 ... 4.21 Casein c . . ... ... 2.91 Albumen .... ... ... -42 Salts ... ... ... -77 99.88 At the time when the low samples occurred, the cows were out to grass, and, owing to the bad season the pastures were extremely bare ; I recommended an addition of saccharine matter to the food, and this was commenced in the week ending September 3rd, and in the week ending September 10th three samples were submitted to analysis with results as follows :- Water ...... ... 87.49 Fat ... ... ... 3.91 Sugar ... ... ... 4.43 Albuminoids ... ... 3.40 (difference) Salts ... ... ... *77 100.00 The average solids-not-fat had risen from S.42 per cent. in the week ending August 27th to 8-63 per cent. in the week ending September loth, or a rise of a 2 1 per cent. ; the sugar had concurrently risen from 4-21 per cent. to 4.43 per cent., a rise of 022 per cent. Other samples from farms in the same district have been found as low as 8.4 per cent, in solids-not-fat, and a similar deficiency in sugar has been found.I n all the samples received from this farm the fat calculated by means of the milk- scale has been found to be about -2 per cent. in excess of that actually estimated ; aG THE ANALYST. deficiency in sugar, lowering the average density of the solids-not-fat, would partially account for this, but the difference is greater than would be due t o the deficiency found. As BBchamp (Comptes Rendus, 1873, 2d. Xemestre, 436) has described alcohol as a normal constituent of milk, I attempted to estimate this, After making 100 C.C. alkaline with baryta and passing a current of carbonic acid to remove the excess, I distilled 20 C.C. and found the density of the distillate to be 1.00005 and 1*00007 in two experiments; alcohol, then, if present at all is not insufficient quantity to account for the low specific gravity. Vieth (THE ANALYST xiv.69.) has drawn attention to Recknagel’s observation that the specific gravity of milk rises for some hours after milking, and has supple- mented his researches ; the average rise is -0013 ; it is possible that this rise had for some reason not taken place in the milk from this farm. From my analyses of milk this year, I can draw the following conclusions :- i. During the months of June, July, August, and September of this year, the solids- not-fat have been fully -1 per cent. below the average. ii. This deficiency is due t o a lowness in the amount of milk-sugar, and is probably attributable to the condition of the pastures due to the bad season. iii.Authenticated samples have given as little as 8-28 per cent. of solids-not-fat (average milk of 19 cows) ; two unauthenticated samples having been lower than this, viz. : 8.22 per cent. and 7.92 per cent. iv. During these four months the fat calculated by means of the milk-scale has been in excess of that estimated, the average of results (excluding this abnormal farm) has been -07 per cent. too high. [This farm has been excluded as the great number of samples would destroy a true average.] KO. 5, by W. F. Loim This milk was taken August 17th 1881, from a cow 9 years old and apparently in very good condition. The cow was milked in my presence and was milked dry, at the usual time of milking. The cow had calved at Christmas, and i t was receiving a daily feed of Indian meal and cotton cake on coming up to bc milked.The milk had $n impleasanti saline taste, especially when cold. It yielded the following results :- I. 11. Total Solids .. , ... ... 8.82 8.83 Fat ... ... ... 2.84 2 * i 3 Solids-not-fat ... ... ... 5.9s 6-10 Ash ... ... ... -93 -95 Chlorine in Ash.. , ... ... 2 6 6 *2G8 The cow was some-time nfterwarcls killed for food and was said to be healthy.THE ANALYST. 7 DISCUSSION. Mr. A. J. de Hailes drew attention to the results of analysis of certain samples examined by him. He had found Specific Gravity 1026.00 1028*00 1026.50 1031.00 1031.50 Total Solids 11-90 11.33 10-27 14.54 13-95 Fat 4-1 i 3.45 2.80 4.i7 3-93 Solids-not-f a t 7-73 7-88 7-47 9-77 10-06 Ash 0.59 I n all these cases Mr. de Hailes stated he had seen the cows milked. stated that he put them on the board because they were abnormal samples.He subsequently I n reply t o a question put by Mr. H. Droop Richmond, Mr. de Hailes stated that the gravity was taken with a specific gravity bottle. Mr. Cassal thought that while the discussion was of undoubted importance to the Society, it went to show the necessity for the re-consideration by the council, or, perhaps, by the whole OF the Society, of the definitions given to the articles dealt with by public analysts under the Sale of Food and Drugs Acts. Everything depended upon definitions. Mr. Heaton had contributed a note referring to what he called ‘‘ poor but genuine milk.” He (Mr. Cassal) would like to ask Mr. Heaton, Mr. Richmond, or any who made a speciality of milk analysis, what they meant when they said ‘‘ genuine milk.” The only definition with which he was acquainted was this,-that “ milk is a liquid yielded by the lacteal glands of the cow.” He did not consider that this was a definition which could possibly be accepted by scientific men.It ought surely to be obvious that the lacteal glands of a cow could be made to yield all sorts of remarkable liquids. By ill-treating a COW, by starving her, by improperly feeding or poisoning her, that cow could be made to yield various things, but those things were not milk. He had had samples of so-called milk, containing considerable amounts of pus and blood. Would Mr. Heaton say that a liquid consisting partly of pus and blood was “genuine milk” because it was extracted from the udder of a cow ? He declined to accept the analysis of Mr.de Hailes, or analyses such as that of which Mr. Henton had given details, as representing, in any sense, the composition of the article known as “milk,” simply because it was alleged that the fluids axalysed had been extracted from the udders of one or more abnormal cows. He invited the serious attention of the Society to the desirability of laying down a scientific plan upon which to work, based upon the many thousands of analytical results which had been obtained in reference to the natural product in question, and which showed its normal composition to vary between certain limits. It was well known within what limits natural milk varied and what was the “ nature, substance, and quality” of that which the purchaser had a right to get when he asked for milk, and he contended that it should be laid down in any future Act OF8 THE ANALYST.Parliament relating t o the adulteratioii of food, that, taking milk as an example, in cases where samples of so-called milk differed in composition from the well-known normal composition of milk, and were therefore not of the ‘‘ nature, substance, and quality ” of milk, it should be incumbent upon the person who sold these articles to prove that they had been produced in a legitimate manner. Rational definibions to be applied t o other articles of food would also have to be agreed upon. The matter was one of vital importance. Mr. de Hailes agreed with Mr. Cassal’s remarks with reference to definitions. I n his opinion there was no branch of trade in which such a rule of thumb method obtained, as in the milk trade.Everything that came from the udder of a healthy cow was called milk. The first variety could command the higher price, and the inferior could be sold at a lower price. Why should there not be two varieties of milk ? Dr. John Muter said he had always understood that, supposing a certain process were used-say the paper-coil process, or sowething which was known to be equally good- commercial mixed milk was a substance which should contain not less than 11 $ per cent. of total solids, and 3 per cent. of total fat. This seemed to him to be a verygood definition of milk. He agreed with Mr. Cassal, and did not see that it followed, because an analyst occasionally received abnormal samples, that such definition should be affected.For one sample of an abnormal character (supposing all the cows in England were milked at one time), there would be thousands and thousands above the standard; the solitary exception only went to prove the rule. He objected to people bringing up extraordinary analyses for the purposes of defence in adulteration cases, as was occasionally done. A man, for instance, might go into Court and swear that he once analysed a so-called milk, or even two or three so-called milks, with extraordinary results ; and he might give evidence for the purpose of defeating another public analyst who had worked on the recognised standard ; and this, most unfortunately, was sometimes done. Instead of correcting blunders, such a man was trying to undo all the standards and to give milk dealers in England the power of adulterating milk to a certain extent, depending on the standard of abnormality.The Society should not take oflEicial notice of odd or abnormal samples. The question was-what were the constituents of average normal milk in England? He believed that the present standard of the Society could not be improved upon. He thought that the figures brought forward in the various papers had a purely academic interest, since no public analyst would think of condemning samples of milk having the composition of the abnormal samples described. It had also been laid down very clearly by Mr. C. Estcourt, in a paper read some years ago before the Society, that the solids-not-fat should not be the sole criterion in judging of milk, but that other data should also be taken into account.From the point of view of the administration of the Act, the results recorded Mr. Allen concurred with Mr. Cassal and Dr. Muter.THE ANALYST. 9 by the authors of the paper were almost without significance at any rate, there was no fear of injustice being done to vendors. He thought that gentlemen who had found abnormal figures were quite justified, when called for the defence, in stating candidly that they had occasionally met with some samples of such composition which they believed to be genuine : but it was a pity that they did not go on to tell the whole truth, and say that such samples were of such rarity that the probabilities in favour of the milk in question being adulterated enormously out-weighed, by, perhaps, 10,000 to 1, the remote chance of its being genuine, and that the analyst who had an opportunity of examining the milk when perfectly fresh was more likely to be right than those who examined it at a later period.It was a great scandal that the Court should often be misled by evidence of the kind, and wrong-doers should consequently escape. Mr. de Hailes, in reply to a question put by Mr. Alfred H. Allen, stated that the samples had not been taken from a herd of cows, but from single animals. Mr. A. W. Stokes referred to the results of analysis of some milks yielded by a herd of thirty-one cows during three months. The President asked Mr. Stokes whether he had any personal knowledge of how the samples were taken.Mr. Stokes said he had not seen the cows milked. Mr. Stokes thought, until some legal standard could be fixed, it was unwise to publish the results of confessedly abnormal samples. These were used in law courts as samples of genuine normal milks. Even in Dr. J. Bell’s book on food not a single reference was made t o the many hundreds of thousands of milk analyses made by other analysts on ordinary samples, but the pages of THE ANALYST have been ransacked to find every recorded abnormal analysis. It might be well for the Society to revise, in full committee, the present standards, and to invite a11 those who had experience of well- authenticated cases differing from the normal to detail them, but not for publication. There is a feeling in the trade, even by those who wish to raise the standard, that occasionally the innocent suffer, Mr.H. Droop Richmond could not agree with some of the remarks made by Mr. gtokes, namely, that there was a general feeling in the trade that the standards of analysts were too high. Several representative meetings of the trade had been held, and the unanimous opinion expressed at these was that the standards of the Society of Public Analysts were too low ; they admitted of a very considerable quantity of separated milk being mixed with and sold as genuine milk, a practice which was largely adopted by unscrupulous dealers; and the general sense of the meetings was that the standards should be raised, in order to prevent this fraud being committed. He (Mr. Richmond) worked with a high standard, and he found that nearly all his milks came up to it, and he made complaint in those rare instances in which they did not do so, with the result that the quality soon improved.He believed it possible that in the cases mentioned by10 THE ANALYST. Mr. Stokes the cooler may have leaked, and this was possible without the knowledge of anyone. As Mr. Stokes had no means of satisfying himself on this point, his very numerous low samples could not be considered as authenticated, even if the reputation of a farmer were considered snfficient guarantee of the genuineness of ‘milk which, perhaps, passed through half-a-dozen different hands. Such yenzcine low samples might suit the unscrupulous dealers before referred to, but they would not bear looking at from an impartial point of view.Mr. Stokes remarked that if, as Mr. Richmond said, the cooler leaked, it only did so in the morning and never in the afternoon, through the three months’ series of analyses. Mr. Richmond drew attention to the fact that the low gravity of Mr. de Hailes’ samples was an abnormality. He was under the impression that there was only one definition of milk-the norma2 secretion of the mammary glands of the cow. He thought some definition, such as the one he had given, which was a reasonable one should be inserted in the Sale of Food and Drugs Act. He also thought that a clause should be inserted to the effect that all milks below a certain composition should be considered suspicious, and the onus of proving the genuineness of such milks should be borne by the vendor, as had been previously suggested by another speaker.He would consider it sufficient proof of a milk being normal if the cows, milked on some convenient date, as soon after the samples were taken as possible, yielded milk below the Society’s standard. Mr. Alfred H. Allen said that in Manchester a system was carried out according to which, when a milk was found adulterated, the vendor was informed of the fact, and invited to allow an Inspector to visit his farm and see the cows milked, with a view to taking another sample of milk, and comparing it with that previously analysed. Dr. Bernard Dyer said that the quotation of cases of abnormal milk should be of no use at all in defending cases under the Act, In bringing his note forward he did so as an illustration of what even a normal cow in normal health, under certain conditions might do, and to show that even an appeal to the cow herself might be fallacious or misleading if made under unusual conditions, as, for instance, if she were milked by strange hands or in presence of a group of strange witnesses.Mr. E. J. Bevan thought it would be a matter of considerable interest if those gentlemen who had analysed such abnormal milks would tell the Society whether, in the future, if such samples came under their notice, they proposed to regard them as adulterated o r not. It seemed to him that, as those gentlemen who were taking part in the discussion were speaking to a Society of public analysts and not one of milk vendors, such a question was not at all an improper one to ask.Mr. Benedict Kitto said that his predecessor was sent a sample of milk one day and he rdx~ned it aq having had SO much water added. The Inspector believed the analystTHE ANALYST. 11 in that case to be wrong, because the farmer declared-and there were circumstances surrounding the case which showed the probable truth of the statement-that the milk was not watered. Of another sample sent after a short interval, the analysis was returned as being that of a very poor milk, but probably genuine. I n the latter case the Inspector was tolerably certain that the milk was watered, because when he took the sample the man was reluctant to serve him, whilst in the former case it was just the reverse. The reason for the poorness of the milk in the first case given by the vendor in Court was that the cow had been affected by a blizzard, a period of most severe weather which lasted for 10 days or longer; and, after hearing Dr.Dyer’s statements as to the great differences in the quality of the milk yielded on two successive days by a cow at a cattle show, he could conceive that this farmer’s cow might have been so affected by the sudden blizzard that it gave an abnormally poor milk on this particular occasion. The President remarked, as Mr. Smetham had very pertinently observed, an animal placed in a show, or under conditions that were likely to excite it, could not be expected to field normal milk. He considered, therefore, that important conclusions could not be drawn from some of the samples referred to that evening.Dr. Dyer had ’ given a very cogent explanation as to the reason for the abnormality of the milk which he had analysed, namely that the cow was excited, and yielded, on one occasion, exceptional milk. I n Mr. Richmond’s figures the differences from normal milk were so small that no cautious Public Analyst would have declared the samples to be adulterated. Not so, as regards Mr. Heaton’s sample. He (the President) would have liked to have had full information concerning this sample. They knew only that it was sent by an Inspector, who stated that the Sub-Inspector had seen the cow milked. Coming to the results of Mr. Lowe it seemed evident that the cow was diseased. The ash was altogether out of proportion to the solids-not-fat, and Mr.Wynter Blyth had observed this in certain diseases. No doubt it was very interesting that diseased cows might yield such CI fluid, but he could not see how this concerned them as Public Analysts. He would like to ask Mr. de Hailes in what condition were the cows, the milk of which he had referred to 1 It was an extraordinary thing, that in one single herd there should be so many cows yielding milk below the ordinary standard. Exceptional samples were undoubtedly some- times met with that point had been agreed upon years ago-but exceptions surely were not so very common that from a herd of 30 cows many of the animals were found to yield milk of the nature described by Mr. de Hailes. Analysts ha.d experience of immense numbers of milk and he (Mr. Hehner) could not but look upon the sudden appearance of so many abnormal samples with a great deal of suspicion.He had already expressed his surprise a t some remarks that had been made by Mr. Stokes. He thought that; a Public Analyst who brought matters before them which affected both the general public, and the agricultural interests of the whole country, would most carefully weigh his remarks. He was astonished to hear Mr. Stoke8 bring12 THE ANALYST. forward his results and then admit that the samples upon which the remarks were based were furnished to him by someone else who was, or might be, deeply interested in having these, to say the least, suspicious samples passed as genuine milks. The9 had from Dr. Vieth and Mr. Richmond the experience of the Aylesbury Dairy Company, where a process of considerable selection was going on, and they found that not one sample in 100,000 examined fell below, to any notable extent, the limit adopted by this Society; while Mr.Stokes asserted, that such exceptions were not only not rare, but frequent. By careful selection of the cows a great deal could be done, and he believed it was the duty of Public Analysts to teach the public and farmers to select their cows so that the public got a fair value for their money. It had been shown that if Public Analysts condemned milk with less than 8.5 per cent. of solids-not-fat, such milk disappeared from the market, and he believed, if they insisted upon 8.6 or even 8.8 they would soon get it, while if they always attached so much importance to the so-called lowest milk, they were not doing their duty to the public who had no one but the Public Analysts to advise them as to what milk ought to be.If a person purchased milk, he expected t o obtain milk of fair composition and quality. The milk-consumer is distinctly prejudiced if the milk- man sold milk containing only 8.0 per cent. of solids-not-fat. He refused to accept sttch a fluid as genuine milk. As regards other articles to which Mr. Cassal had referred, such as butter, he did not see how at present any definition of composition from a chemical point could be made. He could not see, with his present knowledge of the subject, how anyone who obtained a smaller proportion of soluble or volatile fatty acid in his butter was prejudiced, as the quality of butter did appear to be independent of the composition as regards soluble and insoluble fatty acids. He did not therefore think that a rigid definition of butter could at present be fixed upon.But in the case of milk the urgency for such a definition was very great. He thought Dr. Muter's remarks on this subject were much to the point, A limit by which milk should be judged had been carefully fixed by the Society and had since been confirmed by tens of thousands of analyses. It was certainly well for Public Analysts to know that there were occasional exceptional milks, but they should not help in depressing the limits upon the basis of occasional abnormal samples. For a Public Analyst to make the most of these abnormal milks, to hold' them up as the milks by which the whole milk-supply should be judged and regulated appeared to him a grave scandal.Such persons were counteracting the good done by the general body of Analysts. At the same time it should be distinctly understood t,hat Public Analysts had absolutely no interest t o get up cases against milkmen. Abnormal milks were the products of abnormal animals, and must always be considered in the light of their experience as exceptional and rare. They could be of no influence upon the mixed milk of herds of cows as sold by milkmen and used by the public.THE ANALYST. 13 The Analysis of Rubber Goods. R. Henriques. (Chem. Zeit., xvi., 1892, 1595,1596, and 1623,1626, and 1644, and 1645.-The extreme difficulty of making a satis- tory analysis of rubber articles is well known, and the author has accordingly endeavoured to arrive at methods which, although not professing to solve all the problems presented, go a good way towards removing existing stumbling blocks.I n the first place, the sampling of rubber goods is not easy to effect, as commercial articles are not homogeneous. For example, in a sheet containing much siliceous matter, at one place as little as 1*4O/,, of SiO, was found, and in another no less than 28%. I n the case of soft rubber goods, therefore, the sample must be cut into tiny cubes, and these well mixed, and fairly large quantities taken for analysis; while with hard- rubber, division by means of a rasp is a convenient plan. The utility of an elaborate analysis of the ash of manufactured rubber has been much overrated, as on account of the alterations undergone by the mineral substances originally present during the process of incineration, the nature of these additions can with difficulty be deduced from the composition of the ash, whether obtained by simple incineration or by subsequent treatment with ammonium nitrate, carbonate and other reagents, designed to bring it into a uniform condition.The deter- mination of the inorganic constituents of rubber is best effected in conjunction with the estimation of the total sulphur. Methods for the determination of the latter are numerous, but the author having tried the recognised dry methods and the plan of dis- solving the rubber in an oxidising solution, such as nitric acid, has adopted a combination of the two. It is carried out as follows :-A small, but fairly deep, porcelain basin is covered with a funnel with a wide stem cut off short, and 20 C.C.of pure fuming nitric acid placed in it. Three to four grams of the rubber, cut into small pieces, are then gradually introduced through the stem of the inverted funnel, the operator waiting for the diminution of the reaction induced by each piece beforc putting in another. After solution has been completed, the dish is cautiously warmed on the water-bath, as a good deal of frothing may take place, the solution evaporated to a syrupy consistency, and the treatment with the acid repeated more than once if necessary. During the most violent part of the action of the acid the funnel stem may be covered with another smaller funnel, to prevent loss by spirting.Finally, to the concentrated solution is added 4 grams of a mixture of three parts of nitrate of potash and four of carbonate of soda, the whole warmed for some time on the water-bath and then fused in the basin, still covered by the funnel. Care must be taken that the melt be not too strongly alkaline, as otherwise the basin will be unduly attacked. When graphite is present in the rubber, prolonged fusion is inevitable in order to ensure its complete oxidation. The melt is treated with dilute hydrochloric acid, evaporated to dryness to render the silica insoluble, and taken up again with dilute nitric acid. Should the whole go into solution, it can be made up to a known volume, a portion taken for the determination of the sulphur, and the rest used for the estimation of the inorganic constituents of the rubber by the ordinary methods.I n the contrary case, the residue can only consist of silica, barium sulphate and lead14 THE ANALYST. sulphate. The latter is dissolved out with ammonium acetate, added to the main filtrate, and the analysis of the latter proceeded with as before. The silica and barium sulphate are separated by the usual means, and then, since barium sulphate has been recognized in the residue, the presence of barium in the filtrate will be a conclusive proof that the whole of the sulphur was left in the residue ; and, vice verscr, the presence of sulphur in the filtrate leads directly to the deduction that it cannot contain barium, and the work of analysis is by so much shortened.When the rubber contains little ash, and the total sulphur only is wanted, the quantity taken for analysis need not exceed 0.25 or 0.5 grms., and two evaporations with nitric acid, followed by fusion as described above, suffice. Carius' method is also available, but is, in the author's opinion, unsuited for the require- ments of technical analysis. Besides the total sulphur, it is important to know what quantity of the element is present as sulphur used for vulcanising, RS distinct from that present as sulphides and sulphates. The process of dissolving the rubber in oil of turpentine has many drawbacks, and is, at the best, inexact. The following is the plan adopted by the author in its place, Commercial kerosene is shaken with caustic soda to remove sulphur compounds, dried and distilled, the fraction coming over between 140" and 250" being collected.5 grams of the finely divided rubber, or 10 to 1 2 grams if it be low in ash, are placed in a weighed 250 C.C. flask, about 150 c c. of pnrified kerosene added, and the flask fitted with R con- densing tube and heated in an oil bath to 140", to 150", CO, until the pieces of rubber have lost all coherence and the insoluble portion is left as a powder a t the bottom. I n order to make certain that the temperature has not been so high RS to lead to the formation of sulphuretted hydrogen from the action of the sulphur on the kerosene, a second flask containing sulphur, and a similar quanity of the same kerosene, is heated in the same bath as the flask containing the rubber, and the evolution of sulphuretted hydrogen watched for by inserting a piece of lead paper in the neck.When solution is complete, the flask is put aside in a moderately warm place t o allow the insoluble portion to settle, the solution poured through a weighed filter, the residue washed a few times by decanta- tation, brought upon the filter, and the flask washed out with hot petroleum, without special pains being taken to remove the whole of the insoluble matter from its walls. The washing is completed with petroleum ether of low boiling point, and the flask and filter dried together at 110°C. and weighed. There is now no difficulty in determining the nmoiint of the sulphur in the insoluble residue and the form in which it is present, and this value deducted from that of the total sulphur already determined, gives the value for the free and vulcanising sulphur.It is possible that when the mineral matter incorporated with the rubber consists partly or entirely of oxidising bodies, such as red lead, or of metallic oxides or carbonates, a portion of the vulcanising sulphur may become changed in the rubber itself into sulphates, the author having found small quantities of calcium sulphate in a rubber containing lea4 oxide and chalk. It is not possible to tell in such a case whether the calcium sulphate has been One point needs notice.THE ANALYST. 15 added intentionally or has formed from the vulcnnising sulphur. The residue from the petroleum treatment is also available for the direct recognition of the inorganic con- stituents of the rubber, it being practicable to recognise the actual compounds that have been used, instead of relying on a fancy apportionment of acids and bases from the result of a.complete but undiscriminating analysis. The determination of the organic matter left undissolved by treatment with petroleum may be effected when the analysis of the inorganic constituents has been made, by heating a known amount of the total insoluble matter with sulphuric acid, and weighing the mixed sulphates, provided that the previous analysis has shown that no metal forming an easily decomposable sulphate is present. Should the inorganic matter be completely soluble in acids, that fact can be taken advantage of instead of the former method being used. This plan is especially useful when graphite is present, as it frequently is.Rubbers containing surrogate of one sort or another, may prove difficult t o dissolve in petroleum ; but their case is provided for by the methods for the separation of surrogates (v. i). Organic admixtures, such as fatty oils, paraffin and asphalt, are readily soluble in petroleum, while those diluents OP which cork and wood refuse are a type, do not seem to be used in modern rubber manufacture, and onlydrng on a precarious existence in text books. With regard to surrogates, scarcely anything more than a qualitative recognition of their presence has been hitherto attempted, in spite of their great commercial importance. They consist chiefly of the products of heating fatty oils with sulphur, or their treatment with sulphur chloride, although blown oils that are free from sulphur are also used.Rubber surrogates are generally yellowish elastic substances, which frequently possess a moist and oily feel. Two samples on analysis gave :- Water Sulphur Ash I 1 *OO% 6-1 7 5.5 1 11. 0-S5°/0 6.40 0.80 The ash consisted of lime and alumina, together with a little oxide of iron and silica. After several attempts at estimating surrogates in the presence of rubber, including the use of various organic solvents and the application of the Hub1 method, the author arrived at the conciusion that alcoholic alkali was the best reagent for the piirp~se. Direct experiment showed that it was capable of dissolving surrogate completely, and that it had but little effect on vulcanised pure rubber, other than that of removing the superfluous sulphur.The chief drawback to its use is its tendency to leave a certain quantity of alkali in the undissolved rubber, which cannot be washed out, and thereby increases the weight of the insoluble portion. Digestion of the insoluble rubber with an acid is not advisable, as it is not perfectly effective, and much complicates the analysis of the inorganic portion. The phenomenon appears to be due to the formation of an alkaline salt with the rubber substance. The ash in the portion insoluble in alcoholic alkali is16 THE ANALYST. not, however, a direct measure of the amount of alkali that has been taken up by the rubber, as a part of it consists of sulphur as sulphato, so that it is necessary to determine the quantity thus present and correct back from SO, to S.The number and kind of estimations required may be gathered from the following analysis. PURE VULCANISED PAXA RUBBER. Ash 2 *soo/o Total sulphur 9.50 Residue from extraction 95.55 Ash in residue (calc. on original rubber) 9.21 Sulphur in residue , 9 4.35 Sulphur dissolved 7, 5.15 Sulphur in ash 77 1.25 SO, equivalent to sulphur in ash (calc. on original rubber) 3-10 Na&l in ash (by deducting original ash and SO,), (calc. on original rubber) 3.31 Corrected residue from extraction 92.24 1 Ez: matter So111ble portion 5.15 2-61 The extraction with alcoholic alkali is carried out by digesting 3 to 5 grams of the sample, cut into small pieces, with about ten times its weight of alcoholic soda, for 6 to 8 hours under a vertical condenser.The solution is turned out into a basin, diluted with water, which causes only a trifling precipitation, and evaporated until it no longer smells of alcohol, filtered through a weighed filter, washed, dried at 100°C. and weighed. The ash of the residue is determined on about 1 gram, ammonium nitrate being used to ensure the complete oxidation of the sulphur present. The portion of rubber substance that goes into solution may well consist of small amounts o€ vegetable fats that exist in commercially pure rubber, and possibly of a little unvulcanised rubber which has escaped the action of the sulphur, raw rubber being stated to be more readily attacked by alcoholic alkali than the vulcanised substance. The ’ last hypothesis is, however, not borne out by direct experiment, as it was found that raw rubber yields about the same amount of soluble matter as does vdcenised.The process is applicable to hard rubber, but the extraction takes place less readily. The results of analyses, on the lines given above, of rubber containing surrogate are quoted. The compositions deduced for two samples are as follows :- Caoutchouc Surrogate Sulphur Ash A. 41.32 51.68 5.10 1-90 B 84.43 8 31 4.26 3-00THE ANALYST. 17 What proportion of the sulphur belongs to the surrogate, and what to the vulcanised rubber cannot be determined by the method used. The analysis of hard rubber can, as mentioned above, be effected by the use of alcoholic alkali, but the deter- mination of the inorganic constituents by means of petroleum is not feasible, for hard rubber, unlike soft rubher, dissolves imperfectly therein.By substituting paraffin wax at a temperature of 300" C., solution can be effected, though there is a risk of loss of sulphur, and a certain amount of carbonisation is apt to take place if the temperature be unduly high. The author is engaged in devising methods for the discrimination of other rubber surrogates, such as fatty oils, paraffin wax, and asphalt. E, E. The Distillation of Butyric Acid. H. D. Richmond (Stax. Spey. Ag. Ital. xxiii. 5.)-The author disputes Duclaux's reasoning that the ratio between the amount of a solution of butyric acid which distils, and the acid contained therein, is expressed by a logarithmic formula ; he gives the following formula y=2*2Zx-O-O151~~ + 0.000031~ (where x = the amount of distillate from 100 C.C.and y = the quantity of butyric acid contained therein); from this he calculates that, were all the volatile acid in butter butyric, the quantity distilled when 110 C.C. are collected out of 140 C.C. should be 96.3 per cent., and when 50 C.C. are collected out of 75 c.c., 89.1 per cent. Actual experiments conducted as in the Reichert-Wollny process give 96.9 per cent and 89.6 per cent. respectively, using only a butyric acid solution, and 97.2 per cent. andS9.7 per cent. when 4.4 grammes and 2.2 grammes of well-washed butter acids are added ; the insoluble acids, therefore, exert no retarding effect on the distillation. The ratio between Eeichert-Wollny figures (5 grammes of butter taken, 110 C.C.distilled from 140 c.c.) and Reichert figures (2.5 grammes of butter taken 50, C.C. distilled from 75 c.c.) should be by the equation 2.167. Experimenting on butters he finds the following figures :- Ratio Riw 2.23 Percentage distilled R. W 86-45 9 , ,, R 77.5 These figures differ notably from those required by theory ; as the presence of volatile acids of higher molecular weight wodd cause the percentages to be higher than 96-3 per cent. and 89.1 per cent. and the ratio less than 2.167, he concludes that there is another volatile acid. He suggests the presence of lactic acid dissolved by the fat from the milk during churning. H. D. R. Some Analyses of Cacio-Cavallo. G. Sartori. (Stax. h$er. Ag. Ital. xxii., It is to some extent 337.)-" Cacio-cnvallo " is the typical cheese of southern Italy.18 THE ANALYST.made in Lombardy, but the chief centres of its production are Agro Romano, Albruzzi Puglie, Calabria, &c. As the chemical composition of this important type of cheese has not yet been studied, the author considered i t desirable t o obtain samples from different sources; of the different samples obtained, only two prepared at the Royal Agricultural School of Scerni, were considered typical. Of these, No. 1 was made with whole milk, and No. 2, with a mixture of separated milk with sheep’s milk containing S per cent. of fat ; the first was pale-yellow, and had a iiorma.1 odour ; the second was deeply coloured, and had a slight smell of the sheep. Water.. . ... ... Fat ... 0 . . ... Total proteids ...Ash (without NaCI) ... Sodium Chloride ... Total .. ... Pure Proteids ... Ammoniacal Nitrogen Amidic Nitrogen ... ... ... ... ... ... ... ... ... ... No. 1 ... 19.756 ... 36.706 ... 37.825 ... 2.340 ... 3.260 ... 99.887 ... 34.1 25 ... oo616 ... *665 -- No. 2 22.090 35.900 36,063 2-640 3-1 64 99.857 35,573 4503 609 - Reichert-Wollny figure of the €at ... 25.30 2S.71 The analyses were made according to tho author’s method for sheep’s milk cheese (Hilch-Zeit., 1890, 51, Annuario Lodi, 1890) ; the pure proteids were separated according to Stutzer’s method (ANALYST x. 75), with cupric hydroxide, and the nitrogen determined in the copper precipitate by Kjeldahl’s method. The author considers these results as only preliminary. €1. 1). It. The halysis of Steam Lard.A. Goske. (Chem. Zeit., xvi., 1892, 1560 and 1597)-The author has had experience in the analysis of steam lard in the works of A. Schijndorff & Cie., and the result of his observations is to show the futiiity of attaching the extreme importance to the indications afforded by the determination of the iodine absorption which is given to this criterion by some chemists. The usual assumption that ,z lard which gives the right iodine absorption must, if sophisticated, have been doctored by the addition of vegetable oil, and that consequently the qualitative disproof of its presence suffices with the determination of the iodine number, to place the sample beyond suspicion, is erroneous, because the proper consistency is not given to adulterated lard by the addition of vegetable oil, but by the incorporation of lard oil.(Contrast the results obtained in the examination of American lard ; the AXALYST, Vol. xiv. 32.) TheTHE ANALYST. 19 following mixtures, all free from vegetable oil, give figures that approximate to that yielded by normal samples of lard, which is taken by the author as 60 :- Mixture. Iodine number Per cent. (calculated.) 60.5 Pressed Beef Tallow . , . Steam Lard ... ... Pressed Beef Tallow ... sg- 58-25 Steam Lard ... ... Mutton Tallow ... Steam Lard ... ... Pressed Beef Tallow Steam Lard ... ... Lard Oil ... ... 30 Pressed, Beef Tallow Lard Oil ... ... 40 E { 57.5 2} 59.75 Steam Lard ... ... E } 57.27 I n these mixtures the iodine number of pressed beef tallow is taken as 20, that of steam lard as 65, of mutton tallow as 40, and that of lard oil as 85.The corrective influence on the iodine number of the addition of lard oil to adulterated lard, of course increases the lower the temperature at which the oil has been pressed, and the more triolein it therefore contains. Thus a lard oil pressed at 34O C. had an iodine absorption of 70, and one pressed at 1 6 O C. one of 82.8, numbers approaching those given by most of the vegetable oils suitable for use in sophistication. The author having disposed of the claims of determinations, other than that of the iodine absorption to be considered certain criteria, proceeds to give the method of examination he adopts. The solidifying point is taken by gently melting the lard in a basin floating on water at a temperature of 50°-60” C., pouring it into a wide test tube up to a fixed height, surrounded by a bad conductor of heat, and observing the highest point attained in the act of solidifying as in Dalican’s method, a thermometer divided to 0 * 2 O C.being used. Some examples are quoted which show that butchers’ lard (Metxgerschmnlx) has a solidifying point of 28.6 to 29.9, and that pure steam lard ranges from 24.9 to 27.1, whiie the sophisticated lards vary from 29.8 to 36.6, there being a general ieadeiicy of the latter to be higher than genuine samples, A suspicious lard, with a solidifying point above 28” C. is then examined for the form of the crystals of “ stearin ’’ obtained from its solution in ether, 1 t o 1.5 of a gram of a suspicious sample, or 2 grams of a sample that has the proper solidifying point, are taken, dissolved in 10 c c.of ether in a test tube, the tube stoppered with a plug of cotton wool, and cryatallisation allowed to proceed in a cool place for about six hours. As soon as a layer has formed at the bottom of the glass, but nowhere else, the supamatant liquor, which should still be quite clear, is poured off and replaced by a few C.C. of a colourless oil such as arachis or cotton seed, a20 THE ANALYST. portion of the crystals picked out with a platinum loop, placed on a microscope slide and examined with a magnification of 300. The cryatltls first separating under these conditions ara almost wholly beef stearin, and by their msans a; little as 5 per cent. of beef tallow can be detected. Mutton tallow does not crystallise so well, and 15 par cent.is the minimum quantity that can thus be recognised. The macroscopic aspect of the crystals is some guide to the adulterant present. Beef and mutton stearin form thick solid crusts, while lard stesrin occurs in a, looser state of aggregation. The microscopic appearances are equally definite. BeeF stearin forms large tufts radiating from a cammon centre, the c9mpnsnt nesdles being partly straight and partly curved. Lsrd stearin, on the other hand, though crystallising in tufts, is built up of plates instead of needles. The recognition of a vegetable oil is performed by the aid of the phospho-molybclate test, the nitric acid reltction and the rise of temperature with sulphuric acid. As baef tallow som3times gives a blue or green colour with the first- mentioned reagent, like vegetable oils, it is necessary to test both the original lard and the oil expressed from it.Should the intensity of the colour b3 greater in the oil, it is clearly not due to the tallow. The same plan of separating the sample into a solid and a liquid portion, and testing both, is useful both for the nitric acid reaction and the rise of temperature with sulphuric acid. B. B. Analysis of Lard. C. Amthor and J. Zink. (Zeits. J. Aizd. Chenz., 1892, xxxi., 534-537.)-1n the following table the extreme and mean values of the numerous analyses of new and old samples of lard, tabulated by the authors, are given. The samples were rendered by the authors from different individuals and a t different seasons. New.Old. - , \ /- \ Highest. Lowest. Mean. Highest. Lowest. Mean. Melting Point of Eat ... ... 49-0 47.0 47.8 48.0 47.5 4'7.7 Solidifying Point of Fah , , . , ... 29.5 27.0 28.2 29.5 29.0 29.2 Melting Point of Fatty Acids . . . 45.0 42.5 44.1 47.5 45.0 46.2 Solidifying Point of Fatty Acids ... 39.5 37.0 38.3 49.5 40.0 40.9 Iodine Absorption of Fat ... ... 53.7 50.0 51.4 51.8 49.2 50.9 12 1, Fatty Acids .. 53.4 51.1 52.0 4'3.9 49.4 49% Acetyl Number ... .., ,,. 5*? 5.3 5.5 - - - Saponification Equivalent . . . ... 195.6 194.2 194.9 - --- - Hehner's Number . . . ... ... 96.1 94-7 95.4 -- - -- It is also stated that 0.0012 mgms. of KO13 are required to nentralise the free fatty acids in 1 grm. of the fresh fat and 0.0015 to neutralise those in the same quantity of-the old fat. The age of the fatty acids decreases their iodine absorption very considerably and, nsTHE ANALYST. 21 might be expected, exposure to air does so to a greater extent. Thus, a sample of fresh fatty acids gave an iodine absorption of 51 -61 ; after 42 days in a closed vessel this had fallen to 46.10, and in an open vessel to 44.34. The authors have their say in the controversy as to the conditions under which the iodine absorption of a fat should be determined (compare ANALYST, 1892, 199). They conclude that, for lard at all events, an iodine solution which has been kept (45 days) according to Hubl’s original method is preferable, and that the alleged necessity for a large excess of iodine does not exist ; constant results were obtained whether the iodine was 21*2 per cent. or S i per cant. in excess, or between these values, A. G. B. The Determination of Lime in Basic Slag. A. F. Holleman. (Chem. Zed., xvi., 1892, 14$1-1472.)-The conventional methods for the determination of lime in phosphates are not perfectly satisfactory when the phosphate is rich in iron and manganese, as in the case of basic slag. Both Classen’s and Jones’ process leave some- thing to be desired, but an accurate method can bs got by combining the two. The plan devised by the author is carried out as follows :- 50 C.C. of the acid solution of the slag, corresponding to 1 gram of the original substance, are evaporated to low bulk, 20 C.C. of a solution of neutral potassium oxalate (1:3)added, and digested on the water bath with vigarous stirring until the precipitate is pure white and free from clots, a result usually attained in about ten minutes. The precipitate is filtered and washed with hot water until oxalic acid is no longer recognisable in the filtrate. The filter paper is then perforated, the precipitate washed through, and the last particles dissolved off with hydrochloric acid (l:l), in which liquid the bulk of the calcium oxalate is also dissolved, about 15 C.C. of the strong acid being required for the purpose. The solution containing the whole of the lime is evaporated t o 25 c.c., 10 C.C. of dilute sulphuric acid (1:5) and 150 C.C. of 96 per cent. alcohol added. The calcium snlphate is filtered after standin? for thrpe hour;, washed with alcohol, and ignited and weighed in the ordinarymsnner. The test analysis on known mixtures and on basic slag are quite satisfactory, the results being appreciably better than those obtained by either nf the constitmnt methods used singly. B. B.
ISSN:0003-2654
DOI:10.1039/AN893180001b
出版商:RSC
年代:1893
数据来源: RSC
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The Italian Society of Analytical Chemists |
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Analyst,
Volume 18,
Issue January,
1893,
Page 21-21
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摘要:
THE ANALYST. 21 THE ITALIAN SOCIETY OF ANALYTICAL CHEMISTS. A society under the above title has been formed, and the inaugural meeting was held at Genoa on Aug. 27th, for the purpose of electing officers, framing bye-laws, and receiving scientific contributions. The provisional committee consists of Drs. Musso of Turin, Lon@ of Rome, Leone of Palerrno, Gnelfi of Genoa, nncl Alessi1ndr.i of Pavia. H. D. R.
ISSN:0003-2654
DOI:10.1039/AN8931800021
出版商:RSC
年代:1893
数据来源: RSC
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Reviews |
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Analyst,
Volume 18,
Issue January,
1893,
Page 22-24
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摘要:
22 THE ANALYST. REVIEWS. TRAITE GENERAL d’ANAL1’sE UES BEURRIH. Paris, 2 vols., 25 francs. By A. J. ~ ( ~ U N E . 108, Hue de Rennes, Eighteen years have elapsed since the first iiiethocl, based upon chemical principles for the analysis of butter fat, was published. The amount of literature which has mean- time been given to the world on this subject is enormous, and Mons. A. J. Zune bas undertaken a meritorious and arduous labour in collecting it, two volumes amounting to 800 pages being the result. The collection is most complete, the author having in the great majority of cases consulted the original papers. Perhaps he has gone rather too much into detail, even every insignificant contribution bearing upon the subject being noticed by him, the result being that he gives 9 distinct modifications of the process for estimating the insoluble fatty acids, and 14 for estimating the volatile fatty acids, each one being honoured by the author with the title of a distinct procidi.Thus we have the procSd& Hehner-Angell, Lechartier, Perkins, Reichert, Meissl, Munier, Caldwell, Allen, Crampton, Schmitt, Wollny, Mansfeld, Nilson and Sendtner, for the estimation of volatile fatty acids alone. The differences are often ridiculously small, and such as would suggest themselves to any intelligent operator, but M. Zune discusses and criticises them all with the utmost gravity. As a collection of work done on the subject, the work is most valuable, the author showing himself an acute and intelligent critic of work done by others. The same can hardly be said of his own original efforts to devise a method of butter-analysis. The method proposed by him consists in the saponification of 0.5 gramme of butter-fat with baryta under pressure, removing the products of saponification soluble in water, namely glycerine and the salts of butyric, caproic, etc., acids, together with the excess of baryta by means of hot water, the caprate and caprylate by petroleum ether, the salts of the oleic series with pure ethylic ether, and those of the palmitic series by boiling alcohol, the equivalent being determined in each case.Every practised chemist will see that this cannot possibly be done with accuracy upon half-a-gram of fat ; nor are the solubilities of the salts in the various solvents employed sufficiently satisfactory for good work.The author himself does not appear to have worked the process, for not a single statement of its results is givcn ; while in other methods he is profuse in such statements. Many chapters are devoted to the examination of butter-fat by physical means. The microscopical examination is very fully discussed, and many well-drawn figures are given, showing the appearance of various fats when crystallized from solvents, etc. ; but although the author strongly recommends miscroscopical examination, his own plates and drawings do not appear to the reviewer t o furnish a distinctive means of discrimination. There is an immense amount of padding in the work, and more or less irrelevant matter; but this may be forgiven an author who has been evidently determined to collect everything touching the analysis of butter.I n this task he has well succeeded. 0. H.THE ANALYST. 23 The CoaZ-Tar Colours : with special reference to their injurious qualities and the restric- A sanitary and medico-legal investigation, by Theodore Weyl, Translated by Henry Leffmann, M.B., Ph. D, tion of their use. with a preface by Professor Sell. Philadelphia; P. Blakiston, Son & Go. The existing information on the physiological effects of the coal-tar colours is largely the result of the investigations of the author, and chemists generally will welcome the appearance of the collected data in the English dress in which they are presented by Dr. Leffmann. The little work in question is not restricted to a description of the poisonous characters of the synthetical colouring matters prepared from coal-tar, but deals also, in outline, with the methods employed for their manufacture and the chemical nature of the products.The laws in different countries relating to the use of poisonous colours, and the legal enactments concerning the use of such colours for the preparation of food, are fully set forth. Perusal of these sections shows forcibly the far more stringent regulations which exist in foreign countries, under which the colouring of (( Demerara sugar” with a coal-tar dye, the nature of which was kept secret, would have been im- possible, The injurious influence of the existing law of this country respecting experi- ments on animals is also brought into strong relief. The typical reactions of the leading coal-tar colours are given at length, so that the analyst will usually be able to identify the substance with which he is dealing.The book under notice deals with a number of important facts which have never received full recognition in any .English work, and it will certainly be an indispensable addition to the library of the public analyst. The matter covers 150 pages, is well printed, and fairly free from errors. Dr. Leffmann deserves congratulation for his share in the production of a very useful volume. A. H. A. Olii Vegetali, Animccli e Minerali (Vegetable, Animal and Mineral Oils). By G. Gorini. Price, 2 lire (Is. 8d.). This little work is one of the well-known Hcepli Manuals of Science, Literature and Art. It is essen- tially an elementary work, but most of the chief points in the chemistry and industry of oils are touched upon.Second edition, by G. Fabris. Ulrico Hcepli, Milan, 1892. i n this volume of 216 pages a large amount of information is given. I n the analytical part the leading characters, both physical and chemical, of the chief oils are given in tabulated form; in some cases, notably in the table of refractive indices, the limits are too narrow, but generally the information is correct and up to24 THE ANALYST. date. A considerable amount of space is devoted to the discussion of the electrical con- ductivity of oil, which is later declared to be a method of little practical use for analytical purposes. We are glad to see that the presence of sulph~w in oils from the crzccijerm is not considered characteristic.For determining the safety of mineral oils most importance is attached to the appa- ratus of Salleron and of Grainer ; no mention is made of the Abel tester. It is, perhaps, too much to expect in a work of this order to find mention of all the latest researches, but we think that the work of Hazura and of Benedikt, on the chemistry of oils, and that of Salkowski, on the detection of raw oils in cod liver oil, should not have been ignored. This volume should be of great use to students and beginners, and though it lacks a comprehensive index, is greatly superior to the ordinary class of “ technical handbooks.” H. D. R. CATALOGUE OF SCIENTIFIC APPARATUS AND REAGENTS. Brady &. Martin, Newcastle- This is a fairly full and complete catalogue of Chemical and Bacteriological Apparatus, as well as of that appertaining to other Sciences. I t is printed on good paper, the numerous engravings of apparatus are very clear and distinct, and the whole is enveloped in a neat binding. Full and useful explanations are appended to much of the apparatus. on-Tyne. Altogether, it is superior to the ordinary run of such catalogues,
ISSN:0003-2654
DOI:10.1039/AN8931800022
出版商:RSC
年代:1893
数据来源: RSC
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