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“.HE ANALYST’. SEPTEMBER, 1894. THE LATE C. R. ALDER WRIGHT, B.Sc. (VICT.), D.Sc. (LoND.), F.R.S. IT is with feelings of the deepest regret that we have to record the somewhat sudden decease, at the comparatively early age of forty-nine years, of an old and much esteemed member of the Council of the Society of Public Analysts, Dr. Alder Wright, which took place on July 23. I n his early life it was intended that Dr. Wright should follow the profession of an engineer, and for this object he received a special training; but, feeling a strong attraction towards chemistry, he eventually forsook the former pursuit, and devoted hie attention t o the latter, in which he was soon destined to make his mark. A survey of Dr. Wright’s professional career shows it to have been one of excep- tional activity.In 1866, whilst yet a student at Owens College, Manchester, he Contributed a paper to the Chemical Society on the ‘( Action of Light on Sensitive Photographic Papers.” Having completed his college career, he became chemist to the Runcorn Soap and Alkali Works, and in 1867 read a valuable paper before the Chemical Society describing his experiences in this capacity. He next became assistant in the laboratory of St. Thomas’s Hospital, and about this time contributed a number of letters to the ChemicaZ News on the various methods of testing alkalies, and on other subjects of interest from a technical point of view. He also published the results of a large number of investigations on bodies of the most diverse nature, some of which he had made independently, others in conjunction with Matthieson and others.Amongst these are included his valuable researches on the alkaloids of opium and of the aconite family. As exhibiting the mathematical bent of Dr. Wright’s mind may be adduced the series of nine voluminous papers, which appeared for the most part in the Philosophical Magazine, “ On the Determination of Chemical Affinity in terms of Electromotive Force.” I n 1873 he contributed a paper to the Chemical Society on “ The Rydrogm occluded by Pal!adium,” a d , later GE in the same year, a series of papers on “ Isomeric Terpenes.” I n 1875 Dr. Wright delivered a lecture at the Royal Institution on ‘( The Chemical Changes accompanying the Smelting of Iron in the Blast-furnace,” which bears evidence of the large experience he had gained in the research laboratory and works of Sir Lowthian Bell. Then follows a series of papers, commencing in 1878, which were communicated to the Chemical Society on “ Researches on some Points in Chemical Dynamics,” followed by a paper in 1880 on ‘‘ Notes on Manganese Dioxide.” He was elected a fellow of the Royal Society in 1881, to which he communicated papers in 1889 and 1892 on Ternary Alloys.” I n 1884 Dr. Wright read a paper before the Society of Arts on “Cupro-ammonium Solutions, and their use in Waterproofing Paper and Vegetable Tissues,” and in the following year gave a course of three Cantor Lectures on the ‘‘ Manufacture of Toilet194 THE ANALYST. Soaps.” Amongst his published works are a treatise on (‘ Metals, and their Industrial Applications,” which appeared in 1878, and the one on ( ( Animal and Vegetable Fixed Oils, etc. ,” which appeared quite recently.

ISSN:0003-2654    

DOI:10.1039/AN8941900193

出版商:RSC    

年代:1894

数据来源: RSC

摘要:

194 THE ANALYST. THE QUANTITATIVE SEPARATION AND ESTIMATION OF THE ALKA- LOIDS OF COCOA. BY WILLIAM E. KUNZE.* THE term “alkaloids,” according to the most recent views on the constitution of these bodies, should be reserved for those substances of a basic nature which are found ready-formed in plants, and which are constitutionally derivatives of pyridine. Since theobromine and caffeine are xanthine derivatives, they entirely differ in chemical constitution from the alkaloids proper. They should, consequently, be separated from these and included with the nucleins, which form a subdivision of the proteids. I t is a matter of some difticulty to find a generic name for these two bodies which, whilst being precise, clear, and not too cumbersome (cocoa-xanthines ?), shall sufficiently define their isolated position and sharply distinguish them from the alkaloids, For this reason the author has retained their old designation (alkaloids) in the present paper.The variety of the methods which have been proposed from time to time for the estimation of these bodies, their number, and the fact that every fresh itivestigator has propounded a new process, affords distinct evidence that there has not existed, up to the present time, a thoroughly reliable method for their determination. The following is a short resumd of the methods which have been hitherto proposed : 1. Weigmann’s Method.-2O grammes of cocoa are rubbed up with hot water, boiled from a quarter to half an hour, made up to 1 litre, and allowed to settle. 500 C.C. of the clear liquid are precipitated, boiling, with ferric acetate, filtered, the filtrate concentrated by evaporation, 6 per cent.of its weight of H,SO, added and precipitated with phosphotungstic acid. The precipitate is washed with dilute H,SO,, and the amount of nitrogen which it contains estimated; from this the quantity of theobromine deduced. 2. Mulder’s Method-10 grammes of cocoa are rubbed up with water, boiled for EL quarter of an hour with magnesia, and evaporated to dryness, the dried mass exhausted with chloroform, and the latter distilled off. The residue from the chloroform is dissolved in hot water, filkered, evaporated to drymss, the residue remaining weighed, ignited, and again weighed. The difference between the two weighings gives the quantity of theobromine.The chloroform extract also contains the theine. For its separation from the theobromine Weigmann suggests the follow- ing modification : the mixture of cocoa and magnesia is first extracted with benzol (in which theobromine is almost insoluble), the solution evaporated to dryness, the residue shaken out with hot water, the filtrate evaporated to dryness, and the residue weighed as theine. (Schmidt-Pressler has also pointed out the difference in solubility of the two * Abridged from the original, which appeared in Freseniub’s Zed. f. Analyt. Chem., 1894, p. 1.THE ANALYST. 195 alkaloids in benzol, and called attention to the possibility of their separation in this way.) 3. WoZfram's &!ethod.-lO grammes of cocoa, or 20 to 30 of chocolate, are treated for a considerable time with boiling water, aminoniacal lead acetate is then added in slight excess, the mixture filtered hot, and the precipitate washed with hot water until the acidified filtrate, after cooling, no longer gives a precipitate with sodium phosphotungstate." To the filtrate, which, when excess of lead acetate has been employed, is perfectly brilliant, a solution of caustic soda is added, the whole evaporated to 50 c.c., strongly acidified with H,SO,, and filtered.The theobromine is separated out of the filtrate by the addition of sodium phosphotungstate in con- siderable excess, with stirring and gentle warming, allowed to become cold, the precipitate filtered off, and washed with a 6 to 8 per cent. H,SO, solution. The washed residue is decomposed by warm barium hydrate solution, the excess of baryta removed with H,SO,, the filtrate neutralized with barium carbonate, filtered hot, and the residue washed with hot water.The united filtrate and washings are evaporated in a platinum dish, dried and weighed. The residue is ignited, the ash treated with ammonium carbonate, the liquid evaporated, and the residue dried, and weighed. The difference between the two weighings gives the quantity of theobromine. 20 to 25 gramrnes of cocoa, or 50 grammes of chocolate, are, after removal of the fat, digested on the water-bath for some hours with 50 C.C. of 4 to 5 per cent. H,SO,, the solution filtered, and the theobromine precipitated by sodium phosphotung- state in excess. The precipitate, which is contaminated with proteids, is allowed to settle for twenty-four hours and filtered off, washed with 8 to 94- per cent.H,SO,, and dissolved in sodium carbonate solution. The slightly alkaline solution is evaporated to dryness, quartz sand being added, and the residue extracted with amylic alcohol on the water-bath at a temperature of 80" to 90" C.; the solution evaporated in a platinum dish, and the residue dried and weighed. It is then gently ignited and again weighed, the difference giving the theobromine. 5. Frojanozuski's Method.-A weighed quantity of cocoa in powder is extracted with petroleum spirit to remove fat, well rubbed up with powdered glass and water, mixed with a weight of magnesia equal to that of the cocoa, and dried at a tempera- ture of 60" to 70" C. The dry mass is sprinkled with alcohol and rubbed to a fine powder, boiled with 50 C.C.80 per cent. alcohol under a, reflux condenser for half an hour, this operation being again repeated with another 30 C.C. alcohol for a quarter of an hour. The extracts are united and filtered boiling hot into a beaker, and evaporated on the water-bath; the residue is brought on to a filter with petroleum spirit and washed with alcohol, until the washings run off nearly colourless. The residue on the filter is then weighed, and i+5s of the weight of the alcohol used in washing added as a correction of the solubility of the alkaloid in this fluid. 6. Zipperer's Method.-The beans, from which the fat has been previously removed by petroleum spirit, are extracted three tinies with 80 per cent.alcohol, the extracts united, calcium hydrate added, and the whole evaporated to dryness on * The sodium phosphotungatate is prepared by dissolving 100 grammes of sodium tungstate and 4. Legler's Method.-This is essentially a modification of Wolfram's. 60 to 80 grammes of sodium phosphate in 500 C.C. of water acidified with nitric acid.196 THE ANALYST. the water-bath. The dry residue is extracted with boiling chloroform in a Soxhlet apparatus. The chloroform extract is evaporated to dryness, and the residue dissolved in boiling water, filtered, and evaporated to dryness in a platinum dish, dried and weighed; 0.89 per cent., representing water, is deducted from the weight found. 7. Suss’s Method-6 grammes of an intimate mixture of equal parts of cocoa and quartz sand are extracted for ten hours with petroleum spirit, boiled for half an hour with 200 C.C.distilled water and 6 grammes of freshly prepared pure lead oxide, strained, the residue squeezed, and the fluid thus obtained filtered. The cocoa residue is again twice boiled, each time with 100 C.C. distilled water for a quarter of an hour, and similarly treated. The nearly colourless filtrate is evaporated down to 10 C.C. and shaken out three times with chloroform, 100 C.C. being used each time (time of shaking, three minutes). The bulk of the chloroform removed by distilla- tion, and the remainder evaporated to dryness in a weighed glass vessel. 8. Diesing’s Method.-The chocolate, after previous removal of the fat by petroleum spirit, is extracted with chloroform for four hours in a Soxhlet, the residue from the evaporation of the chloroform boiled with water several times, and to these solutions the water is added in which the fat had been boiled.The united fluids are then evaporated to dryness in a platinum dish and the residue weighed as pure theobromine. 9. Bell’s Method.-20 grammes of cocoa are repeatedly digested with benzol, filtered, and the united filtrates distilled; the fatty residue boiled with water, allowed to cool, and filtered. This process is repeated twice, so that the alkaloid may be completely extracted by the benzol. The aqueous extract is then evaporated to dryness, and the residue purified first by solution in water, then in benzol. I n this way an alkaloid resembling theine is obtained in white silky crystals.The cocoa, after the treatment with benzol, is rubbed up to a magma with water, sand, and 10 grammes of calcined magnesia added, and the mixture, after being dried in the water-bath, repeatedly treated with alcohol. After removing the alcohol by distilla- tion, the residue containing the theobromine is brought into a glass, dried, and weighed; the last traces of fat and of the other alkaloid removed by treatment with hot benzol, the latter being separated (?) and weighed. The residue insoluble in benzol is twice treated with a little ice-cold water, and in this way the theobromine obtained by decantation is a perfectly pure and white powder, containing a trace of inorganic matter. As even cold water in some cases (lj dissolves a portion of the theobromine? it is advisable to evaporate the aqueous extract to dryness, and if a small quantity of crystals are found, to treat it with water once more(?). “If the whole residue, obtained by extracting the cocoa and magnesia mixture with alcohol, be submitted to a nitrogen estimation, and the nitrogen found calculated to theobromine, a greater and probably more exact percentage amount of the alkaloid would be obtained.” Criticism of the above Nethods.-In Legler’s method (No.4) no directions are given as to the nature of the solvent to be used for the extraction of the fat, and this is by no means a matter of indifference, since the alkaloids are soluble in some of these; and, moreover, as Diesing has shown, the solubility of cocoa-fat in the The amount of the latter is determined by incineration.THE ANALYST.197 different solvents varies. Diesing distinctly prefers petroleum spirit to ether or chloroform. Amylic alcohol is an extremely unpleasant liquid to use on account of its physiological effects. Trojanowski’s method (No. 5) is faulty, owing to the necessity of having to make a correction for the solubility of theobromine in the wash-liquid. Moreover, Trojanowski has not used a correct solution-factor, the solubility of theobromine, according to other observers, being only about a tenth of that which he gives, namely, 1 : 12,500 or 16,600. From the author’s experiments it is 1 : 7,100 (absolute alcohol at 20” C.). Zipperer’s method (No. 6) is not clearly described; there is no exact statement of the quantities to be used; and there are also other obscurities, to which must be ascribed the low results which he obtained in comparison with those of the author.Suss evidently came to the conclusion by comparative experiments that the methods of Zipperer and Diesing gave results below the truth. He perceived that the method they employed (direct extraction of the alkaloid with chloroform) was the cause of this; he therefore altered the method of procedure to that of shaking out the alkaloid from its aqueous solution. I n this way he obtained nearly twice as much alkaloid as Zipperer and one and a half times as much as Diesing. After Bell (No. 9) had demonstrated the presence of another alkaloid in cocoa besides theobromine, and Trojanowski had also called attention to the presence of some other body, of which, from lack of sufficient material? he was unable to ascertain the real nature, and after Schmidt had fully identified it with caffeine, it became apparent that the majority of workers had entirely overlooked its presence, and contented themselves with the estimation of the theobromine alone (Mulder, Wolfram).Zipperer expressly insists on the removal by petroleum spirit of the caffeine along with the fat, and his results, therefore? represent pure theobromine, that is, providing the whole of the caffeine is removed in this way. He, however, like the others, entirely neglects to estimate the caffeine. Diesing has remarked that in the extraction of the cocoa-fat a part of the caffeine is also removed; he therefore directs the fat to be boiled in water, and this solution added to that containing the bulk of the alkaloid.He overlooks the fact that it is caffeine which goes over with the fat, and erroneously calls his residue pure theobromine. Since both caffeine and theobromine are precipitated by sodium phosphotungstate, and as they contain different amounts of nitrogen, TVeigmann’s method must lead to incorrect results. I n the methods of Legler, Suss, and Trojanowski the caffeine passes either partially or completely into the fat solution, and escapes detection. The objection to Mulder’s method, as stated above, is that the alkaloid obtained is regarded as pure theo- bromine. This niust be taken with a limitation, since, according to the length of time of the extraction with petroleum spirit, the caff’eine may be wholly or only partially extracted.According to this, the correctness of the methods of Suss, Trojanowski, Zipperer, and Legler hinges on the fact as to whether the caffeine is partially or totally removed by the petroleum spirit. I n the methods of Mulder, Wolfram, and Diesing the results are not reckoned upon pure theobromine, but on a mixture of the two alkaloids. The method of Bell, and Weigmann’s modification of Rfulder’s, possess points of importance. Weigmann’s method must be totally rejected.198 THE ANALYST. - 0.115 - - - The author gives the following results, which he has obtained from the same sample of cocoa examined by the different methods : -- N found=O.0203 grammes, reck- oned as theo- bromine. difference.Estimated by Ditto. Ditto. Coloured deeply Method. - - - 1. Weigmann ., not decoloriz- able by washing with alcohol. Coloured, car- bonized on heating. Not absolutely colourless. Slightlycoloured. A little ash. 2. Mulder mod. by Weigmann 3. Wolfram .. 4. Legler 5. Trojanowski .. 6. Diesing .. 7. Zipperer .. 8. suss ... .. Grammes Found. 11 Expressed in per cents. I Grammesl Total of,",:^ 1 Alka- loids. 10 I - I 10 ~ 0.059 10 ' 10 - 20 ' 1 10 10 3 -.- - 0.215 1 - 0.0785, - 0.564 ! - 0.124 0.0235 0 -054 - Theo- bromin6 0.652 0.475 2.15 0.3921 5 -64 (! !) 1.24 0.235 1.80 Remarks. f E i . I The differences in these results are striking, varying, as they do, from 0.235 per cent. (Zipperer) to 5.64 per cent. (Trojanowski). I n the determinations by the methods of Zipperer and Legler the theobromine has evidently escaped the solvent action of the alcohol.The author's results obtained by the methods of Zipperer, Diesing, and Suss agree closely with those obtained by Suss, who obtained from 3 grammes of cocoa the following amounts : Zipperer 0.7 to 0.8% Theobromine. suss 1.4 ,, 1.46 9 ) Diesing 1.0 ,, 1-1 9 , The analysis by Trojanowski's method gives most improbable results. The author considers that in any rational method of analysis of the cocoa alkaloids the total quantity of the two together should be first ascertained, one of the bases should then be isolated from this. If, during the fat extraction with petroleum spirit, a partial solution of the theobromine is not to be feared, there yet remains the possibility of small traces being carried over mechanically.The principal reason, which demands that the total amount of the two alkaloids should be first ascertained, lies in the difficulty of removing the caffeine without losing some traces of the theobromine; and, besides this, there is no criterion to judge when the whole of the caffeine is removed during the fat extraction. The common fault of all theTHE ANALYST. 199 methods hitherto proposed is that they entirely neglect the estimation of the caffeine, which is a body of no less importance in its physiological effects than theobromine. I t has become the rule to estimate the value of such food substances as tea, coffee, cocoa, etc., by the amount of alkaloids which they contain; possibly also the relative proportions of the two alkaloids in a cocoa might give some clue to its origin. With reference to the influence of cocoa-fat on the estimation, the author has proved that petroleum spirit, either pure or holding cocoa-fat in solution, dissolves caffeine in considerable quantity ; Siiss has shown that theobromine is absolutely insoluble in these fluids, but he found that small quantities of this body were carried over mechanically in the fat extraction.The author found that the cocoa alkaloids could be readily extracted by a solution of the caustic alkalies with formation of the respective salts, and that the bases were reprecipitated on the alkali being converted into carbonate. He thought that in this way there might be founded a satisfactory process for the estimation of the alkaloids, but the concomitant saponification of the fat proved an insurmountable obstacle.Evidently for a process of this nature to succeed, the fat must be first removed; for this purpose various solvents were tried : benzol, toluol, xylol, chloroform, methyl alcohol, benzyl alcohol, etc., none of which proved suitable, since they all dissolved more or less caffeine or theobromine. The attempt to devise any process which required the previous extraction of the fat was abandoned. Though the two methods-extraction and precipitation-are equally correct in principle, the latter method is to be preferred in practice, because no solvent is known which will dissolve the alkaloids without simultaneously taking up other substances, and also because with the small quantities of material usually employed the necessary purification of the alkaloid, either by re-crystallization or taking up in another solvent (shaking out), is certain to lead to loss of material unless the work is carried out with the greatest possible care.The method of determination may be either : 1. Direct weighing ; 2. By difference (loss on ignition) ; 3. Weighing a definite (metallic) compound ; 4. By titration. No. 1 presupposes the purity of the residue; by No. 2 any non-volatile con- stituent can be deducted; the platinum compounds alone fulfil the conditions of constancy required by No. 3, and permit of a, ready control by igniting, and weighing the residue of platinum, The general method of titration proposed by Barth, which depends on the dissimilar reactions of the alkaloids with litmus and phenolphthalein, is inapplicable in this case, since theobromine docs not behave towards these indicators in the same way as the other alkaloids.The greater number of the proposed methods prescribe direct weighing ; two determine by loss on ignition, one by a nitrogen estimation. Direct weighing possesses the advantage that one has the actual body in hand, which can, when necessary, be identified and tested for purity; but the before-mentioned difficulties in the way of obtaining the alkaloid free from foreign admixtures, and the loss likely to ensue during its purification, considerably detract from its value. In testing a method for correctness, it is no satisfactory evidence to show that it yields higher results than previous methods ; it must rather be denionstrated that the200 THE ANALYST.- method is absolutely quantitative and includes no sources of loss or error. This can only be proved by test experiments. In the present case, on precipitating a known quantity of the alkaloid with phosphotungstic acid, regeneration of the alkaloid, etc., the quantity found must exactly correspond with the amount taken. When it has been found that this is so, an investigation must be made to discover if the other bodies present exercise a disturbing influence on the process. In order to determine this, a second control experiment must be made, which shall represent as completely as possible the actual conditions of working. With this object in view the author has made parallel determinations in which a known mixture of the two alkaloids was employed.The difference in the two determinations must, if the process is to be credited with success, exactly represent, the quantity of the added material. From the above considerations a rational process for the estimation of the cocoa alkaloids ought to be founded on the following principles : I. The estimation, which may be divided into two phases : 1. Determination of the total alkaloids collectively. 2. Their quantitative separation. 11. Previous extraction of the fat is not permissible. 111. The total amount of the alkaloids must be estimated by weight. IV. The method of estimation must be controlled for exactitude in its various stages and in its whole course by parallel experiments. V. The alkaloids must be separated in such a form as will permit of their subse- quent identification, I n the author’s method water is em-plcyed as the solvent, since alcoholic fluids and chloroform are excluded on account of the subsequent difficulties in purification, and in order that the fatty and alkaloidal solutions may be kept quite separate.Acid and alkaline solutions were inadmissible, the former because the conversion of the alkaloids into their respective salts might hinder the transference to another solvent, the latter on account of saponification difficulties. The author intended, first of all, to bring the alkaloids into solution with boiling water, then to evaporate the solution to dryness with the addition of a binding material to retain the disturbing admixtures (colouring matters, sugar, etc.), and then exhaust the residue with a suitable solvent.Taking into account the conversion of caffeine into caffeidine, which ensues on long boiling with caustic bases (e.g., Ba(HO),), and the decomposition of theobrornine on being evaporated with CaO (Diesing), the author made choice of MgO on account of its lesser basicity. Suss has controverted this statement of Diesing’s, and to all appearance correctly, for the author found the destruction of the theobromine only partial ; he points out that in an estimation conducted according to Zipperer’s method the small quantity of theobromine obtained from the residue which contained calcium hydrate points to its partial decomposition, or to the formation of an insoluble calcium compound.He considers that chloroform is to be preferred to amylic alcohol as the solvent. An experiment in which a weighed quantity of theobromine was evaporated to dryness with MgO and extracted with chloroform in a Soxhlet, showed considerable loss, probably owing to the formation of a magnesium compound. On account of the solubility of MgO in boiling chloroform, this fluid could not be used in this condition. Hence the author was obliged to abandon this method and attemptTHE ANALYST. 201 the isolation of the alkaloids by shaking out with chloroform as proposed by Suss. This necessitated the removal of the colouring matters and other impurities which partially dissolve in that fluid. Treatment with PbO, animal charcoal, or basic ferric acetate, did not suffice to completely decolorize the aqueous solution.The author succeeded in effecting this object by the addition of animal charcoal and aluminium acetate, which, upon prolonged boiling, removed every trace of colour ; but traces of tannin and considerable quantities of sugar still remained in aolution. The filtrate was then evaporated to 10 c.c., and shaken out several times, each time with an abundance of chloroform ; on subsequent evaporation of the united extracts, the residue was not, however, obtained in the requisite state of purity, a brown greasy substance obstinately clinging to it. Probably some reaction took place between the aluminium and the theobromine, for in a control experiment the alkaloid could not be recovered quantitatively. As Mitscherlich has stated, theobromine is retained by animal charcoal; this was proved by direct experiment ; of the 0.0375 gramme taken only 0.0057 was recovered.I n this method of determination it is assumed that the alkaloids are contained in the cocoa in a form soluble in water ; should they be combined with tannin or with organic bases or acids, then it is questionable if they can be extracted by water alone. The precipitation methods offer the essential advantage that an acid medium, which has a more powerful solvent action, may be employed for extraction ; the presence of an acid also facilitates the subsequent preci- pitation. The best reagents for the precipitation are the double phosphates, sodium phospho-tungstate, -molybdate, -antimoniate. The precipitate thus obtained can be decomposed by an alkali, when it yields either the corresponding salt of the alkali, or the free alkaloid.When this is effected by NaHO a clear solution results ; on passing CO, through this the alkaloid is liberated, and a portion, beyond that which is soluble in the medium, is precipitated. The alkaloid may be also liberated by adding to the precipitate a magma of BaCO,. The precipitation was complete, for in the neutral- ized residue, obtained by evaporating the filtrate, no trace of alkaloid could be detected by the murexide reaction (chlorine water and ammonia). I n a control experiment where a known weight of theobromine was dissolved in about 5% H,SO,, the solution treated with phosphomolybdic acid, the precipitate dissolved in NsHO solution, this treated with CO,, and the residue obtained on evaporation boiled with chloroform under a reflux condenser, the alkaloid was recovered as a pure white powder, containing a minimum amount of ash, thus : Theobromine taken ...... ... ... ... 0,0605 gramme. Residue ... ... ... ... ... ... ... 0.0608 ,, Ash ... ... ... ... ... ... ... 0.0003 ,, Theobromine found ... ... ... ... 0.0605 .. In a second trial 0.053 gramme theobromine were taken, and 0.054 gramme theobromine + ash recovered. When the decomposition is effected by baryta water similarly satisfactory results are obtained. It is impossible to obtain the alkaloid absolutely ash-free, consequently in very exact determinations a weighed portion must be ignited and the ash deducted, not forgetting-its re-carbonation with ammonium carbonate.202 THE ANALYST.Phosphomolybdic acid was found to be the best precipitant, since the precipitate yielded is of a flocculent nature, and subsides more readily than those obtained by the other reagents. When NaHO is used to liberate the alkaloid, the extraction with chloroform is effected more easily than when Ba(HO), is employed. In the latter case the ash is lower, and is in such minimum quantity that it may be safely neglected. As the decomposition of the precipitate takes place momentarily, the author considers that no action on the caffeine is to be feared. To test the reliability of the process when other substances were present, the author made the following control experiments. The alkaloids from 10 grammes of cocoa were estimated, a, parallel experiment being made with the same cocoa to which a known weight of a nearly equal mixture of the two alkaloids was added. The following are the results obtained : 10 grammes of cocoa yielded .. . . . . 0.1195 gramme alkaloids. Ditto + 0.107 gramme alkaloids . . . ... 0.2255 ,, 1 , Added ... ... ... ... ... 0.107 ,, 9 9 Difference found . . . ... ... ... 0.106 ,, 3 , The exact details of the method are as follows : 10 grammes of cocoa are boiled for twenty minutes with about 150 C.C. of 5% H,SO,, filtered, and the residue thoroughly washed with boiling water. Excess of phosphomolybdic acid is added, and the whole kept warm for twenty-four hours, filtered off, and washed with approximately 5% H,SO, (800 to 1,000 c.c.). The filter and precipitate are brought, still moist, into a beaker, baryta water added, and GO, passed through until the whole of the barium is precipitated.The whole is then evaporated to dryness, dried, the residue carefully removed to a flask, in which it is exhausted with boiling chloroform under a reflux condenser. The chloroform solution is filtered into a small Soxhlet glass, such as is used in fat extractions, the fluid distilled off, and the residue weighed. The mixture of alkaloids thus obtained is invariably pure white, almost ash-free, and gives the murexide reaction. Zipperer found a sticky organic substance which clung persistently to the theobromine obtained by alcohol and chloroform extractions. The author has not found this to occur in quantity sufficient to afTect the accuracy of the analysis.The solution of the alkaloidal residue in ammonia is slightly opalescent, foams on boiling, and the theobromine obtained on separation (see further on) was not absolutely white. This may be caused by the body described by Zipperer, or by some other. It does not, however, interfere with the estimation, or with the subsequent separation of the two alkaloids, nor was there observed in the snbsequent treatment with ammoniacal AgNO, any blackening indicative of reduction, nor mas the recovery of the theobr,omine from the silver salt in any way interfered with by it. The coloured compound of silver and theobromine dissolves in dilute HNO, to a nearly colourless solution ; by subsequent neutraliza- tion, evaporation, and extraction with chloroform pure theobromine is obtained in beautiful crystals.Having now devised a reliable process for the estimation of the total amount of the two alkaloids, the next point was to find a similarly reliable one for their separation. The simplest would be a physical method, depending on the solubility of one and the insolubility of the other in some fluid such as benzol, petroleumTHE ANALYST. 203 spirit, etc. Experiments were made with these and many other liquids, but as no satisfactory results could be obtained in this way, the method was abandoned. The attempt to find a reagent which, while precipitating the one, should leave the other intact, failed, it being found that both behaved in a similar manner with the ordinary alkaloidal reagents. Phospho-antimonic, -tungstic, -molybdic acids, and bismuth- potassium iodide (more energetically with theobromine than with caffeine), preci- pitated both bodies.Iodine and potassium iodide, and gallic acid precipitated neither. The following reagents were also without effect on either alkaloid: alcoholic am- monium sulphide, iodic acid, iodine trichloride, ferrous and ferric chlorides, Millon's reagent, potassium xanthate, basic and neutral lead acetates, chromic acid mixture in the cold, disodium phosphate, potassium ferrocyanide, sodium carbonate, copper sulphate, basic copper acetate. In solutions of theobromine, bud not of cafeine, mercuric chloride produced a turbidity which formed very slowly; picric acid in EN1 solution yielded a gradual crystalline separation ; ammoniacal AgNO, solution gave, on prolonged boiling, a crystalline precipitate.A solution of either alkaloid, when treated with sulpho-molybdic acid, became, on boiling, of a dark-green colour, which spontaneously changed ti0 indigo-blue. Urea and uric acid also gave this last reaction, which may, therefore, be regarded as common to the whole group. The most powerful alkaloidal precipitants, the double phosphoric acids, act alike with the two bodies. The precipitate formed by picric acid with theobromine appeared to consist of a double chloride; on further investigation it did not prove suitable for effective separation on account of its solubility relations. The pre- cipitation with theobromine which takes place with either HgCI, or silver solutions is easily explained on comparing the constitution of theobromine with that of caffeine.The former possesses a labile H atom which can be replaced by one of a metal. In the conversion of theobromine into caffeine this is made use of as a stepping-stone, the metal atom being eventually replaced by a CH, group. Theobromine. CHS-N-GH I II CO C-N-CH, @-N-c=N I 1 >GO" Caffeine. CH3-N-CH As these metallic compounds were apparently likely to be suitable for effecting a quantitative separation, the properties of the lead and copper derivatives were also examined, but these were found unsuitable for the purpose, since they were both soluble. The mercury derivative only separated slowly, and in the condition of a fine powder; there remained, therefore, only the silver compound, and this was found completely suitable for the required purpose.AgNO,, when added to an ammoniacal solution of theobromine, gave at first a flocculent whitish precipitate, which redissolved on the addition of ammonia in excess. On prolonged boiling, as soon as the ammonia had been driven off, the solution became turbid, and eventually a crystalline body was precipitated, which the author considered to be the Ag substitution compound of theobromine. It was insoluble in204 THE ANALYST. water or dilute alcohol, easily soluble in ammonia or dilute HNO,. I t was found to contain no HNO,, and must therefore be a substitution compound and not an additive one ; 0.2174 gramme of the dry compound yielded 0,1083 gramme AgCl=0*0815 gramme Ag. Calculated for C7H7AgN,0, 37.63% Ag.Found 37.488% Ag. Schmidt has described a silver compound of theobromine containing 14 molecules of water of crystallization; that obtained by the author suffered no loss in weight on prolonged heating at 130" C. Caffeine, when treated under the above conditions, gave no reaction, and this is readily explained by its not containing a replaceable H atom. The method, therefore, seemed suitable for the separation of the two alkaloids. In order to ascertain the course of the process quantitatively, the author dissolved a known weight of theo- bromine in ammonia solution, heated to boiling, added AgNO,, and continued the boiling until the NH, was driven off and the precipitate ceased to increase, filtered off, washed the precipitate with boiling water until the washings were free from AgNO,, dried and incinerated filter and precipitate, and weighed the residual silver.Several unsatisfactory experiments showed that in order to ensure success a large excess of AgNO, must be used, and that the boiling must be continued until the whole is reduced to a few C.C. Under these conditions good results were obtained, as is shown by the following examples : 1. 0.1195 gramme theobromine yielded 0.0723 gramme Ag, equivalent to 0.1200 2. 0.1570 gramme theobrornine yielded 0.0942 gramme Ag, equivalent to 0.1564 3. 0.1432 gramme theobromine yielded 0.0870 gramme Ag, equivalent to 0.1444 4. 0.2394 gramme theobromine yielded 0.1435 gramme Ag, equivalent to 0.2382 5. 0.1165 gramme theobromine yielded 0.0698 gramme Ag, equivalent to 0.1159 6.0.1240 gramme theobromine yielded 0.0742 gramme Ag, equivalent to 0.1232 The quantity of theobromine equivalent to that of the silver found can be The result of experiments conducted with mixtures of the two alkaloids are gramme theobromine. gramme theobromine. gramme t heobromine. gramme theobromine. gramme theobromine. gramme theobromine. obtained by multiplying by the factor 1.66 (108 Ag = 180 theobromine). equally good : 0.1075 gramme theobrornine yielded 0.0645 gramme Ag, equivalent to 0.1071 0.0862 gramme theobromine yielded 0.0517 gramme Ag, equivalent to 0.0858 0.0911 gramme theobromine yielded 0.0543 gramme Ag, equivalent to 0.0901 0.0792 gramme theobromine yielded 0.0479 gramme Ag, equivalent to 0-0795 gramme theobromine. gramme theobromine. gramme theobromine.gramme theobromine.THE ANALYST. 205 Further experiments, in some of which the silver compound was collected and weighed in a tared filter, in others where it was dissolved in dilute HNO, and the Ag determined as AgC1, yielded equally satisfactory results. In order to shorten these somewhat tedious processes Volhard's volumetrical method was employed in the following manner. A measured quantity of AgNO, solution of known,strength was added to the solution of the alkaloids, and, after the precipitation and washing, the residual silver in the filtrate and washings was titrated by ammonium sulphocyanate solution, which had been previously titrated against the AgNO, solution." The actual titration was performed in the cold solution, with the addition of 5 C.C.of a cold saturated solution of ferric ammonium sulphate as indicator, and HNO,, which had been boiled until it was colourless. This method gives most satisfactory results ; it can be quickly performed, and possesses the advantage that the alkaloids can, when necessary, be recovered and subjected to further examination, For this purpose the silver theobromine is dissolved in dilute nitric acid, the solution neutralized and evaporated to dryness ; the caffeine solution, in which the titration took place, is also neutralized and evaporated to dryness. The alkaloids can then be easily extracted from the respective residues by chloroform. The author considers that he has completely solved the problem of the estimation of the cocoa-alkaloids, and that this result cannot fail to influence considerably the future technical valuation of cocoa and its preparations.W. J. S. Estimation of Citrate-soluble Phosphoric Acid in Basic Slag and untreated Mineral Phosphates. P. Wagner. (Chem. Zeit., 1894, xviii., 1153-1154. j-The author insists upon the necessity for a guarantee as to the degree of solubility of the phosphoric acid in basic slag, since, either on account of the low basicity of the slag-phosphate, or by reason of the presence of mineral phosphate as an adulterant, samples vary very much in respect of this solubility. Taking the manurial value of the basic slag found to give the best results in field experiments at 100, other samples of the same content of phosphoric acid, and of the same degree of fineness, gave yields represented by 80, 60, 50, and even 30.The best method of determining the solubility of the phosphate is by the use of a solution of acid ammonium citrate; and if the results are to be unimpeachable, the treatment with this solution should be preceded by a neutralization of the basicity of the slag by citric acid. For this purpose the basicity is first determined as follows : 5 grammes of the slag are introduced into a 500 C.C. flask, whichis then filled up to the mark with a 1 per cent. solution of citric acid and shaken for half an hour in a jigger; 50 C.C. of the filtered liquid are then titrated with soda solution, phenolphthalein being the indicator. For the actual analysis 5 grammes of the sample are placed in a 500 C.C. flask with 200 C.C.of water, and there are successively * The silver solution employed contained 5 grammes AgNO, in 100 C.C. ; consequently 1 C.C. = 0.03176 gramme Ag ; 14.7 C.C. ammonium sulphocyanate solution (A normal) =5 C.C. of the above silver solution =0'1588 gramme Ag, and 1 C.C. =0'0108 gramiue Ag.206 THE ANALYST. added (1) the quantity of 5 per cent. citric acid solution previously found to be necessary to neutralize the slag, (2) 200 C.C. of acid ammonium citrate solution (see below), and (3) water to the mark, The mixture is shaken in a jigger for half an hour and filtered; to 50 C.C. of the filtrate 100 C.C. of molybdic solution (see below) are added; the liquid is heated to 80" C., and after cooling the precipitate is filtered and treated as usual, The ammonium citrate solution is made by dissolving 160 grammes of citric acid and ammonia, equivalent to 28 grammes of nitrogen, in a, litre of water.The molybdic solution is prepared by dissolving 125 grammes of molybdic acid in a slight excess of 2& per cent. ammonia solution, adding 400 grammes of ammonium nitrate, diluting to 1 litre, and pouring the solution into 1 litre of nitric acid (1.19 sp. gr.). After having been allowed to remain at 35" C. for twenty-four hours the solution is filtered. If it be desired to save the half-hour requisite for determining the basicity of the slag, the analysis may be conducted as described above, with omission of the citric acid. In this case an acid ammonium citrate solution containing 150 gramrnes of citric acid and ammonia equivalent to 23 grammes of nitrogen must be used.The results are less accurate than when the slag is neutralized. A. G. B. Milk. J. Lehmann and W. Hempel. (Arch. Physiol., 1894, hi., 558, through Chern. Zeit.)-One of the best distinctions between human milk and COW'S milk resides in the nature of the casein. Casein from cow's milk contains 6.6 per cent. of calcium phosphate, whilst that from human milk contains 3.2 per cent. The mean ash content of casein from cow's milk is 7.2 per cent. The ash contains : Per cent., Per cent. Calculated on Anhydrous Casein. c&O ... 49.8 ... . . I ... ... ... = 3.20 K,O ... 0.9 ... ... ... ... ... = 0.06 Na,O ... 0.4 ... ... ... ... ... = 0.03 P,O, ... 45.0 ... ... 1.. ... ... = 2.92 so, ... 1.2 ... ... ... ... ... = 0.08 MgO ...2.1 ... ... ..I ... ... = 0.10 It appears that the whole of the phosphorus in the casein molecule is present in the form of a phosphoric acid, and two series of researches gave respectively 1.18 per cent. and 1.50 per cent. of P,O, in the casein molecule, It further appears that casein is a double compound of calcium casein and calcium phosphate in the proportion represented by the formula Cq(PO,),, Ca Casein. The proportion of calcium phosphate was not so high in another series of determinations. The mean ultimate composition of casein is, per cent. : Ash. C. H. N. P. S. 6-47 50.86 6-72 14.63 0.81 0.72 C. H. N. P. S. 54 7-04 15-06 0.847 0.771 The ash is nearly all calcium phosphate. The ash-free caRein contains, per cent. :THE ANALYST. 207 The authors do not doubt but that cow’s-milk casein and human-milk casein are two individual substances; for not only do they differ in content of calcium phos- phate, as shown above, but also in sulphur content, the casein of human milk con- taining 1.09 per cent.of this element. The mean results of the many analyses of cow’s milk and human milk made for the purposes of this research are as follows : Cow’s Milk. Per cent. Casein ... ... ... ... 3-0 Albumin ... ... ... ... 0.3 Fat ... ... ... ... ... 3.5 Ash ... ... ... ... ... 0.7 Water.. . ... ... ... ... 88.0 Milk-sugar . . ... ... ... 4.5 Human Milk. Per cent. 1.2 0.5 3.8 6.0 0.2 88.5 Care was taken that the women were healthy, and that their glands were fully milked. The coagulation of cow’s milk and woman’s milk by acids is characteristically different. Whilst the precipitated casein in the cow’s milk collects in flocks and sinks to the bottom of the vessel, that in human milk forms a coagulum which does not settle. This difference is traced to the fact that the proportion of fat to casein in the precipitate from cow’s milk is so much lower (1.16 : 1) than that in the precipitate from human milk (3 : 1). By the addition of fat to cow’s milk the behaviour of human milk when acid is added can be imitated. Dogiel’s statement that acids precipitate the casein in coarse flocks from salted human milk is not substantiated. I n order to make an artificial human milk which shall resemble the natural secre- tion as closely as possible, cow’s milk should be diluted with water until its casein content is identical with that of human milk, and cream, milk-sugar, and white of egg should be added until the mixture contains the proportions of fat, sugar, and albumin in human milk. The white of egg should be added in somewhat larger proportion if the suckling is to be fed from the first, since human colostrum, like that of the cow, is particularly rich in albumin. A. G. B. Determination of Silicon and Aluminium in Iron. L. L. de Koninck. (Stah1 und Eisen, 1894, xiv., 138, through Chm. 2eit.)-The metal is treated with nitric acid or aqua regia, and precipitated by means of ammonia or by ammonium acetate should manganese be present. The precipitate is dried, ignited, placed in a platinum boat and heated in a stream of hydrochloric acid, whereby ferric chloride is volatilized and a residue of alumina and silica, together with any titanic acid or chromic oxide that may be present, is left. The separation of the substances thus freed from the bulk of the iron is then effected by the usual methods. B. B.

ISSN:0003-2654    

DOI:10.1039/AN8941900194

出版商:RSC    

年代:1894

数据来源: RSC

摘要:

208 THE ANALYST. EXTRACTS FROM THE EVIDENCE GIVEN BEFORE THE SELECT COMMITTEE ON FOOD PRODUCTS ADULTERATION, ON JULY 11, 18 AND 25. MR. RICHARD BANNISTER. 1. EVIDENCE REFERRINU TO THE WORK DONE AT SOMERSET HOUSE, AND THE RELA- 542. You have a lengthened experience in the Government laboratory?-I have been there for thirty-one years. 543. And in that Government laboratory you receive cases for analysis, or specimens for analysis, from different localities ?-Yes ; both for our ordinary official work and also for our work under the Sale of Food and Drugs Act. 544. Under the twenty-second section of the Sale of Food and Drugs Act ?-Yes. If you will allow me, I will tell you what we received last year. From the Customs Department we received 2,137 samples ; from the Admiralty, 73 ; from the Board of Trade, 557 ; from the India Office, 707 ; from the Post Office, 43 ; from the War Department, 18 ; from the Trinity House, 86 ; from the Stationery Office, 4 ; from the Office of Works, London and Dublin, 33; from the Colonial Office, 2 ; and references from magistrates, 71.545. That is under the Sale of Food and Drugs Act?-Yes ; and parochial samples 15, making together 3,889. 546. Of which how many were under the Sale of Food and Drugs Act ?-Seventy- one. Then, from the Inland Revenue Department we received 12,083 samples of tobacco ; beer for the estimation of drawback, 9,102 ; beer duty samples, 8,621 ; beers from public-houses, 2,820 ; tinctures, 5,575 ; naphtha, 773 ; miscellaneous, 5,392. TlON BETWEEN PUBLIC ANALYSTS AND THE REETEREES. 547.What is the total number of samples?-48,255. 548. I believe you have a tabie of specimens referred to you under the Sale of Food and Drugs Act from 1875 to 1894?-Yes. 549. Can you give us a brief analysis of that table?-Yes, I can. Samples of arrowroot, 4 ; beer, 5 ; bread, 7 ; brandy, 4 ; butter, 62 ; carbolic acid, 1 ; coffee, 26 ; cream, 1; flour, 3 ; gin, 6 ; ginger, 5 ; gingerbeer, 1; ketchup, 1; lard, 23; lemonade, 3 ; laudanum, 1 ; linseed-meal, 1 ; magnesia, 1 ; milk, 411 ; mustard, 8 ; sweet nitre, 4 ; oatmeal, 13; ointment, 1; peas, 2 ; pepper, 29; quinine, 4; rum, 3; soda-water, 1 ; tea, 3 ; vinegar, 14 ; water, 2 ; whisky, 28. 550. In those 678 specimens submitted to you, in how many did you agree with the previous analysis?-In the case of 474.551. And you disagreed in how many ?-In the case of 188 ; and 16 samples were sent up for a special purpose, which were not entirely sent up under the Sale of Food and Drugs Act strictly. 554. Milk and butter were really the two principal articles that were submitted to you ?-Exactly. 1609. I notice thak you mentioned two samples of water referred to you under the Sale of Food and Drugs Act : what water would that be?-That would be water referred to us under the Public Health Act by the magistrates. Total, 678.THE ANALYST. 209 1610. I notice that the Sale of Food and Drugs Act expressly excludes water ?- Yes ; we do not make a separate return of milk and water, but those samples were referred to us by the magistrates under the Public Health Act. 1611.With regard to the cases that you mentioned of your analyses differing from those of the public analysts, I think you said that in 474 cases you agreed, and that you disagreed in 188 cases : is that so?-Yes. 1612. Could you tell us whether this disagreement took place in the earlier stages of the working of the Sale of Food and Drugs Act ?-I have not got the returns for every year, but I think I have got the return for the last three or four years here ; and I looked at that, and thought that there was very little difference. 1613. Why I ask you is, that I notice in one of your reports it says that a year or two ago you had 47 samples submitted to you, and that you disagreed only in two cases, so that it occurred to me that the disagreement was lessened.-There is no doubt that it was up to a certain time.I think that last year there was a little difficulty about margarine; but, if I remember rightly, there was a steady decrease. 1614. That is to say, a steady decrease in the number of disagreements between Somerset House and the public analysts ?-Yes. 1615. I suppose it necessarily followed that some of the samples submitted to public analysts would be wrongly reported upon by them?-No doubt. 1616. But in the general working I presume you are of opinion that the public analysts have done their work efficiently?-I think that during the last six or eight years of the working of the Sale of Food and Drugs Act the work has been done remarkably well. 1617. And those differences that have cropped up between you have been differences rather more as to the interpretation of results than actual mistakes made? --Yes .1618. That is to say, that from the same analytical results two analysts, both working accurately and honestly, may, and very frequently do, arrive at different conclusions ?-They do. 1619. But, taking your figures from the last twenty years, the average differences between the public analysts and Somerset House have not amounted, as far as my calculation takes me, to more than, on an average, ten cases a year--1 dare say that is right. 1621. In the results which you have given us of samples that have been referred to you there were included samples from Scotland and Ireland, as well as from England, I believe ?-There were. 1622. But the Reports of the Local Government Board, as I understand them, only refer to samples taken from England under the Sale of Food and Drugs Act?- I cannot answer that question as regards their return; one return goes in for the whole of them.So far as the references are concerned, it goes in for England, Scotland and Ireland. 1623. But I have looked at it rather carefully, and I make out that the Local Government Board’s report refers only to samples from England. The average of the samples taken and submitted to the public analyst since the working of the Act would be about 25,000 per year, roughly speaking, I believe?-I should say quite that.210 THE ,4NALY ST. 1624. And you disagreed, on an average, with regard to one sample in 2,500?- That is in the reference. 1625. I would like to clear up one reply of yours here, in answer to question 556, which may be subject to misconception, although I think I understand it clearly. You stated that you disagreed in about one quarter of all the cases : you do not mean in one quarter of all the samples taken, but only in those submitted to Somerset House as a court of reference?-My answer had nothing to do with the others, so that I hope that my remarks cannot be misunderstood.1626. There were sixteen samples, you told us, sent up for a special purpose, not sent up under the Sale of Food and Drugs Act strictly; what were those sixteen samples?-I cannot give you the particulars of them, but they were samples arising out of previous examination ; they were not really confined to samples that had been referred by magistrates from the defendant, but were referred for some special information that the magistrate wanted.1627. You have had at Somerset House, outside the references that have come to you under the Sale of Food and Drugs Act, a, large experience with milk and butter samples ?-Yes. 1628. Would that be an experience as large and varied as that of the public analysts?-The experience would not be so large as that of the public analysts, because they are generally examining milk from morning to night. 1629. But Somerset House is not continually engaged in making examinations into a large number of samples of butter and milk?-We are continuously engaged in getting accurate results of examinations. 1630. But in a general way should I be overstating the case were I to suggest that the experience of the public analysts, so far as butter and milk axe concerned, is larger than that of Somerset House?-So far as the actual examination of samples is concerned, yes.1631. And of course the public analysts have their general practice, in addition to the work that comes to them in their official capacity ?-Certainly. 1632. They are analytical chemists with a private practice, many of them, I presume ?-Yes. 1633. There is going on, I understand, between public analysts an interchange of ideas, and experiences, and opinions in connection with analytical science ?-No doubt. 1634. And, therefore, would it be :fair to assume that they act upon their collective experience, or, to put it in another way, that the best information that the best of them may procure is placed at the disposal of other analysts throughout the country ?-That ia so to a large extent.1638. I suppose, from time to time, certainly since the passing of the Act, there has been a great improvement in the science of food analysis?-No doubt. 1639. And the public analysts have contributed very largely to this improve- ment ?--Certainly. 1640. Somerset House, I presume, gets the benefit of that improved knowledge acquired by the public analysts, and avails itself of the information ?-Yes ; but, of course, in our investigation of food analysis we always tty as much as possible to seeTHE ANALYST. 211 for ourselves, by direct experiments, the value of the results reported, and of the different methods of analysis. 1641. That means, naturally, that you do not necessarily accept in all cases the deductions, or improved results that the analysts announce as having been arrived at ?-Exactly. 1642.But in the case of Somerset House arriving at any improved result, or difering in their own minds from some new result, does Somerset House feel it incumbent upon itself to put itself into commz~nication with the public analysts, either to say: Here toe have discovered a new method that ought to be known through- out the country, or, W e have subjected this new methgd of yours to close investigation in our laboratory, and we do not agree with the results which you inform us YOU have arrived at ?-We do not make i t a general practice, but with some public analysts, they are in direct communication with us, and, of course, we interchange ideas and opinions about different methods of analysis. 1643.May I say, then, that there is a close intercommunication continuously being carried on between the public analysts of the country and Somerset House?- With sonw of the public analysts. 1644. But not with the Society of Public Analysts in its corporate capacity?- No. But I can give you a simple illustration of that : When poivrette was being largely used in the adulteration of pepper, one public analyst had a difficulty in separating it so as to show it to the magistrate, and I had the pleasure of showing him exactly how it could be done, and from that time forward the adulteration of pepper with poivrette has ceased completely. 1645. Because the public analyst received this information from you ?-He not only could say from its analytical nature that poivrette was there, but he could show the nagistrate its presence.1646. Showing the enormous advantage to the country from that revelation by Somerset House ?-Certainly. 1647. And, I suppose, that Somerset House deems it necessary that there should be this intercbnge of opinion between it and the public analysts ?-It is very desirable. 1648. And may I understand that it is being carried on on a systematic basis, or is it merely casual?-It is on a systematic basis with some members of the Society of Public Analysts. 1649. With those of the most repute, as far as regards reputation?-Yes, men of repute. 1650. And those men are in close communication with Somerset House?-Yes. 1651.Interchanging ideas and receiving suggestions from you, and conveying suggestions to you ?-Yes. 1652. Have you ever conveyed to the public analysts the details of the methods used by you, or of any standards or limits that you use?-As soon as we made an investigation into the composition of food products, we published the result of the investigation in two little manuals ; we made them general property. 1653. Such as Dr. Bell’s little work?-Yes. 1657. How many years is it since you issued a manual, do you think, from which the public analysts might gain the advantage of your improved experience ?-212 THE ANALYST. The years I cannot tell you, but you will see it from the two manuals from the title-page. 1658. But there is no systematic publication to which the public analyst can look for inspiration from Somerset House ?-There is not.826. How do you make your standards known?-If any gentleman writes about it we send him word. 827. You do not communicate i t authoritatively to the public analysts ?-We do not consider that we have authority to do anything of the kind, because they are an independent body altogether, and they might think it was dictation. W e do not with- hold it, but we do not communicate it. 828. But it becomes known through test cases, does it not ?-Yes. 2. EVIDENCE RELATING TO MILK. 555. Will you tell us now with reference to the milk cases-will you give us the analysis of the milk cases that came before you? And 552. I notice that you have had a far larger number of milk specimens than of anything else.-Yes ; we had 411.I n 311 cases we confirmed the decision of the public analysts, and in 96 we disagreed, which is a percentage of disagreement of 23-5. 556. So that in not quite a quarter of the cases you disagreed with the public analysts of the country ?-Yes. 557. Could you refer this difference to any particular cause or condition?-I think that the difference is rather more in the interpretation of the results than in the actual mistakes made. 558. That is to say, that the analyses made by the public analysts were probably correct, but that their interpretation of the analysis differed from yours ?-We differed in the conclusions. 559. I n what way would this difference of interpretation arise?-It would arise when we came to the border-line between a genuine milk and an adulterated milk, or, as put in another way, between a good milk and a poor milk.560. That is to say, that a poor natural milk was occasionally mistaken for adulterated milk?-I think I have not made myself quite clear. It is practically impossible from the analysis of a sample to tell whether it is poor milk or an adulterated milk-that is to say, whether it has been a good milk adulterated with water, or a poor milk. 561. It really comes to this: that a naturally poor milk has been reported us ma adulterated milk ?-As a rule that is the case. 562. And that gives rise to the difference between you and the public analysts to a considerable extent ?-Mainly. 563. It accounts largely for the 96 cases in which you disagreed?-Yes. 564. Can you tell us whether you have any methods on which you rely for arriving at that conclusion ; any special tests?-The process that we use at Somerset House, after trying every process that we have known, or that has come before us, is what is called the maceration process.(The witness then described the process as laid down in Dr. Bell’s book.)THE ANALYST. 213 568. That is the process that you rely upon for estimating the natural condition of milk?-Exactly. Then, in the ezaminatiorrz of a sample, there are certain physical conditions which we have to take into consideration as well, and all these conditions, along with the result of the analysis, are taken together f o r the purpose of formiy a conclusion as to whether water has been added or not. 569. Are you able to arrive at a conclusion with moderate certainty as to whether the milk is a poor milk or watered milk?-We are not.570. That is to say, that you cannot distinguish between a rich milk which has been diluted and a milk coming from a poorly-fed or old cow ?-We cannot. 571. There are different methods of analysis which give somewhat different results, are there not ?-Yes, there are. perly. For instance, if the coil process be used it will, perhaps, give an increase of what is called butter-fat of perhaps 0.2. 581. So that when you have any analysis before you, or when the magistrate has any analysis before him, it is necessary that he should consider the method by which the results have been arrived at?-He ought to do so. 1707. Has he any opportunity of ascertaining this important difference of process?-There is no doubt about it that if we are coming to a small admixture of water i t is necessary that the method of analysis should be known.1708. But you do not, as a matter of fact, state on your certificates the process 583 and 584. Can you give us a description of some experiments that you made with 273 cows?-We obtained these samples of milk from different parts of the country and at different times of the year. You will see in the return that everything is given about the feeding of the cows, so that nothing can be said to the effect that the cows were ill-fed; and we sent one of our own reliable assistants down, so that he saw the cows milked out completely, and the milk was always under his super- vision until he got the samples, and had brought them to our own laboratory for examination, In that return we give 273 cases of individual cows, and also the results of the examination of 55 churns.(586) We examined all these samples by the maceration process, and we found that of non-fatty solids the lowest was 7.52, the highest 10.04, and the average 8.90; and so far as the fats are concerned the lowest was 2-43 in two cases, the highest 5.97, and the average 3.99. Then, from the 55 churns the lowest was 8.40, the highest 9.70, and the average 8.96; and of the fat solids the lowest was 2.89, the highest 5.61, and the average 4.00. 591. What is your standard?-When I am talking of the standard I ought to have a word presently about the difference between the standard and the limit.The standard that we are speaking of, and can call the standard for the present, is 8-5 solids-not -fat. Will you just define what you mean?-The difficulty about a standard and a limit arises in this way: Under the Adulteration of Foods Act, 1875, i t is laid down distinctly that if you have milk, or any other substance, from which nothing has been taken away, and to w h k h nothing has been added, however poor, it is genuine. In the case of milk, a, 1mge 572. Do those results vary widely?-Not if the examination is conducted pro- which YOU follow ?-NO. 593. You referred to a standard and a limit just now.214 THE ANALYST. quantity has to be sold in towns quite away from the place of production, and we do not know its origin; therefore, when we get a sample of milk of low quality, the analysts and ourselves (and I think it very proper that they should do it) fix a limit, so that if there is any milk that falls below that limit, it is for the person to prove or give conclusive evidence to the satisfaction of the court that water has not been added.1701. In your opinion, ought everything that passes from the cow be defined as pure milk ?-It is not a matter of opinion with me ; it is the interpretation of the law. 1702. And you interpret the Act in that way ?-Exactly. 1703. That it leaves you no option but to declare everything as pure to which nothing has been added, and from which nothing has been abstracted ?-That is the wording of the Act, and we are bound by that. 1704. Can you point out in the Act where that wording is referred to; I have looked through it carefully, and cannot quite follow it ?-The interpretation is from section 6 : ‘‘ No person shall sell to the prejudice of the purchaser any article of food, or any drug which is not of the nature, substance, and quality of the article demanded by such purchaser, under a penalty not exceeding $20,’’ and so on.1723. On this question of your construction of the Act, bearing on the point of poor milk being accepted as being pure milk, if a vendor of milk supplied what is termed fore-milk, which is almost free from cream, would you not consider that the purchaser would be prejudiced in such a case?-I think he would be, 1724. Would not the Act apply then?-I think that is for the magistrate to determine whether the Act applies or not.Personally, if I were buying that milk, I should think I was _pre judiced. 1725. Can you tell us whether that opinion has been held in courts of law ?-I cannot tell you. 1726. I think there have been cases where a vendor has been selling milk from a churn, where one purchaser has come to buy who has received practically the cream at the top through carelessness on the part of the vendor, and another purchaser has come and has received what is practically skim-milk; and I believe the courts have held that the purchaser has been prejudiced in the latter case?-Yes ; I should say that the court will settle it in that way. 1727. But still, at Somerset House you maintain the opinion that, notwith- standing that the milk is very poor, provided that it comes from the cow, it is a legal tender, if I may so use the word-it is saleable as a pure article?-I think it is scarcely right to say that we hold that opinion at Somerset House. I would rather put it in this way, that the interpretatiou of the law seems to be in that direction ; but so far as we at Somerset House are concerned, the only matter that we have to settle is to examine the sample of milk that comes before us.594. How is the limit (for milk) fixed?-It has been fixed on the part of the public analysts in this way : that when the Act of 1872 came into force they took the figures of Mr. Wanklyn, and Mr. Wanklyn’s jigares were 9.0 and 2.5 ; that is to say, 9.0 of solids-not-fat, and 2.5 of fat. 595. Then they adopted that as their limit?-They adopted that as their standard.Then in 1882 it had been found between those two years that by the method of analysis the solids-not-fat did not give a constant weight; and so in aTHE ANALYST. 215 paper read before the Society of Public Analysts on March 15, 1882, these facts were brought before the Society : (‘ I t can hardly be expected that anything very novel can be brought forward on a subject which has been so well ventilated, and which before all others has engaged the attention of public analysts, as milk analysis ” (the witness quoted from a paper on page 60 of THE ANALYST, vol. vii., to the end of the first paragraph, and then continued). Then the paper goes on, and it is shown distinctly that as soon as ever you dry to a constant weight of 9.0, in which the sugar of milk is present in a crystalline form, it comes down to 8.5 because it is anhydrous, and, therefore, when the drying is to a constant weight of 8.5, it is equal to the old 9.0.596. You have given the decrease of the solids-not-fat; would you give the increase of fat?-There is no increase of fat mentioned in the paper, and I shall be able to explain, if necessary, how that has come about. 597. You had better explkin that, perhaps ?-In going further with this paper, there is no diference at all given in the increase of fat, the fat remains at 2.5. 598. And the total solids-not-fat diminished ?-The solids-not-fat diminish from 9.0 to 8.5, and the explanation is given in a subsequent paper of Mr. Hehner’s; he finds that this is due to the fact that the milk-sugar that is present in the milk, when dried only for that time, does not give up its water of crystallization, but that as soon as it is dried to a constant weight then water is given up which is equivalent to about five-tenths of a per cent. 1714. Does not Mr. Hehner state in that very paper that whilst diminishing the solids-not-fat they transfer that half point diminished to solids that are fat ?-You have the book before you ; will you kindly tell me where that appears ? 1715. I t is at page 64; ‘‘ and in every instance do the modifications in the methods of analysis which I have examined tend to yield a lower amount of solids- not-fat, and a larger percentage of fat, than does the original (Wanklyn) method.”- The point which I raised was this, that there was no increase by the public analysts in the percentage of fat from 2.5 to 3.0 as suggested. 1716. I understood you to say that there was no increase of fat absolutely suggested?-No. The method of analysis that has been spoken of by Mr. Hehner is a different method from the Wanklyn method; it is one where you bring in the Soxhlet extractor, and that is well known to have a tendency to increase the amount of weight of that substance that is weighed as fat; but there is very little doubt that there is some thing there besides fat. (NOTE.-our readers are recommended to turn to the papers in THE ANALYST referred to by Mr. Bannister, page 60, vol. vii., and page 253, vol. viii., and to satisfy themselves how far Mr. Bannister’s statements are warranted by the contents of the papers in question.) (To be continued).

ISSN:0003-2654    

DOI:10.1039/AN8941900208

出版商:RSC    

年代:1894

数据来源: RSC

摘要:

216 THE ANALYST. CORRESPONDENCE. To the Editors of THE ANALYST. 4, New Court, Lincoln’s Inn, London, W.C. August 30, 1894. SIRs,-The following details of a prosecution for selling adulterated milk may be of The sample was analysed by me, and found to contain, as the mean of two very closely interest to your readers. colrcordant results : Total Solids ... ... ... ... 11.10 Fat ... ... ... ... ... 2-89 Solids-not-Fat ... ... ... ... 8-11 Ash ... ... ... ... .. 0.678 I certified that it contained 5 per cent. added water. When the case was heard, Mr. De Hailes gave evidence to the effect that, though the milk was of poor quality, it was not adulterated. The following is their analysis : The sample was referred to the Somerset House authorities. Non-fat ty Solids ... ... ... ...8-25 Fat ... ... ... ... ... ... 2.62 Water ... ... ... ... ... 89.13 They said : ‘‘ From a consideration of these results, and after making addition for natural loss arising from the change which occurred in the milk through keeping, we are of opinion that the milk, although of poor quality, does not afford conclusive evidence of added water. (Signed) ‘‘ R. BANNISTER, J. HOLMES.” As is almost invariably my experience, the fat found was considerably below that found by myself, and the solids-not-fat are consequently too high. When the Somerset House chemists analysed the milk, it was at least twenty-eight days old. Allowing for some natural loss in the solids-not-fat by decomposition, the fat would, according to their results, have been less than 2.62. Even 2-62 is below what Mr. Banni8ter informed the Select Committee was their standard for fat-viz., 2.75-and yet not a word is said in the certificate that the sample was deficient in fat. The County Council of Middlesex applied for an adjournment, but without success. I n view of Mr. Bannister’s statement to the Select Committee, that when a milk falls below the standards, the responsibility of proving it to be genuine should lie witb the vendor, i t seems to me to be a pity that he did not intimate as much to the magistrates.-I am, yours faithfully, EDWARD BEVAN. N O T I C E . IN recognition of the services of the late Dr. Arthur H. Hassall, Lord Rosebery has granted a pension of g50 per annum from the Civil List to Mrs. Hassall.

ISSN:0003-2654    

DOI:10.1039/AN8941900216

出版商:RSC    

年代:1894

数据来源: RSC