摘要:

DECEMBER, 1915. Vol. XL., No. 477. THE ANALYST. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. AN ordinary meeting of the Society was held on Wednesday evening, November 3, in the Chemical Society’s Rooms, Burlington House. The President, Mr. A. Chaston Chapman, F.I.C., occupied the chair. The minutes of the previous ordinary meeting were read and confirmed. Certificates of proposal for election to membership in favour of Messrs.A. S. Carlos, B.Sc., A.I.C., and E. K. Rideal, B.A., Ph.l)., A.I.C., were read for the second time ; and certificates in favour of Messrs. Thomas Featherstone Harvey, 69, North Road, West Bridgford, Nottingham, chief analyst to Messrs. Boots’ Pure Drug Co., Ltd. ; Cyril Hubert Manley, B.9. (Oxon), A.I.C., 292, Iffley Road, Oxford, assistant to Mr.W. W. Fisher, M.A., F.I.C. ; Gary1 Cameron Roberts, M.A. (Cantab.), A.I.C., Watling Chambers, Canterbury, analytical chemist ; and Frank Thomas Shutt, M.A., D. Sc. (Toronto), F.I.C., Experimental Farm, Ottawa,, Canada, Dominion Chemist, were read for the first time. Messrs. A. W. Crossley, D.Sc., Ph.D., F.R.S., F.I.C. ; D. J. Davies, B.Sc.; M. 0. Forster, D.Sc., Ph.D., F.R.S., F.I.C.; Herbert Jackson, F.I.C.; J. C. Philip,M.A., D.Sc., Ph.D.; W, J. Pope, M.A., D.Sc., LL.D., F.R.S., F.I.C.; F. I. Richardson, B.A. ; and G. H. Warburton, were elected members of the Society. The following papers were read : (6 Note on the Melting-Point of Salicylic Acid, and a test for the presence of Para-Hydroxybenzoic Acid,’’ by Henry L.Smith, B.Sc., F.I.C. ; and ‘( The Persistence of Hydrogen Peroxide in Milk,” by Edward Hiuks, B.Sc., F.I.C. A number of exhibits of glass and porcelain apparatus and of filter-paper, of English manufacture, were shown by Messrs. Baird and Tatlock, Ltd., London, Messrs. Townson and Nercer, Ltd., The British Laboratory Ware Association, Messrs. Doulton and Co., Ltd., and Messrs. W. and R. Balston, Ltd.482 HINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK OBITUARY. WE greatly regret to record the death, on November 16, of Professor Raphael Meldola, D.Sc., LL.D., F.R.S., F.I.C., an honorary member of the Society. An obituary notice will appear in a forthcoming issue of the Journal.

ISSN:0003-2654    

DOI:10.1039/AN9154000481

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

482 HINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK. BY E. HINKS, F.I.C. (Read at the Neeting, November 3, 1915.) CONSIDERABLE attention has, during recent years, been given to the determination of the catalytic activity of milk, and to the question of the usefulness of such deter- mination for the purposes of milk control, Various methods have been proposed, and are in use, for effecting this determination.Faitelowitz (ANALYST, 1910, 35, 526) shows that while the catalase of milk destroys hydrogen peroxide, the peroxide at the same time destroys the catalase, and consequently the rate of destruction of peroxide is not necessarily a measure of the amount of catalase. If the concentration of the peroxide is high, the destruction of catalase has a considerable influence upon the rate of destruction of peroxide, and a measure of the amount of catalase present can be obtained only by continued additions of small quantities of peroxide and observing the rate of destruction of the peroxide under these conditions.I n this communication, when a figure for catalytic activity is given, this has been determined by Koniag’s iodimetric method as used by Revis (ANALYST, 1910, 35, 359), and is numerically the number of C.C.of FT Thiosulphate corresponding to the peroxide destroyed by the catalytic activity of 100 C.C. of the milk in two hours at 37’ C. In this method the concentration of the peroxide used is high. The following experiments, in which the persistence of hydrogen peroxide has been studied, have a bearing both upon the determination of catalytic activity and upon the detection of peroxide in milk.The length of time during which hydrogen peroxide at various concentrations persisted in different milks was first studied. Known quantities of peroxide were added to milk which was then allowed to stand at laboratory temperature, and the peroxide present at stated intervals was estimated iodimetricalIy, the procedure following that used in Koning’s method for the catalytic activity determination (Zoc.cit.). Owing to occlusion of iodine by the casein the precise end-point of the titra- tion is difficult to determine, and although the results of analysis are given to the third place of decimals this third place is hardly a significant figure.It was found that the peroxide was destroyed rapidly at first, that the rate of destruction diminished, and that if the concentration of peroxide was highHINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK 483 Per Cent. Per Cent. Peroxide added ... 0.200 0.197 After 1 hour 0-158 0.146 ,, 1 day ... 0.100 0.100 ,, 2 days ... 0.076 0.110 9 , 3 9 , ... 0.097 0*107 9 , 4 9 9 ...0.097 - 9 , 6 9 ) ... - 0.103 99 3, ... 0-092 0.103 9, 9 9 9 ... 0-090 - ,, 11 3, ... 0.090 0.101 >, 13 9 , ... 0.090 - ,, 3 weeks ... 0.087 0.099 $9 4 9 9 ... 0.092 0.098 ¶, 5 9 , ... 0.086 0.096 Peroxide present- ... enough to withstand the first rapid destruction, the residual peroxide remained constant in amount over long periods. The following example as typical of the results that were obtained may be given.I n this case the peroxide concentration was high : Per Cent. Per Cent. Peroxide present- After 6 weeks ... 0.087 0.102 9 ) 7 ?, ... 0.087 0*101 ,, 8 ,, ... 0.090 0.104 ,, 9 ,, ... 0.091 0.100 ,) 11 ,, 0.091 0.102 ,) 13 ,, ... 0.091 0.102 ,, 15 ,, ... 0.088 0.098 ,, 17 ,) ... 0.096 0.101 ,, 23 ,, ... 0-082 0.092 ,, 30 ), ...0.081 0.088 ,, 39 ,, ... 0.079 0.084 ,, 56 ,, ... 0.066 0-081 ,, 67 ,, ... 0.073 0.089 ,, 87 ,, ... 0.070 0.087 ... MILK I. Peroxide added, 0.5 per Cent. Peroxide Present. ... ... ... 0.37 per cent. ... ... ... 0.21 ,, ... ... ... 0.20 ,, . ... ... ... 0.185 ,) ... ... ... 0.183 ,, ... ... ... 0.181 ,, ... ... 0.182 ,) ... ... ... 0-182 )) ...484 HINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK I t wiIl be seen that in this milk, though the initial concentration of peroxide was only 0.2 per cent., peroxide was still present in comparatively large amounts after a very considerable length of time in portions A and B: at the end of one year upwards of 33 per cent. of the peroxide added was still present.The influence of the age and condition of milk upon the persistence of peroxide added to it is markedly shown in this experiment.The portions A and C had cata- lytic activities of 32 and 158 respectively. Neglecting the differences introduced by the different concentrations of peroxide used in the experiment and in the catalytic activity determination, and also the influence of temperature, calculation from the catalytic activity figures shows that A would reduce the peroxide concentration by 0.05 per cent.and C would reduce it by 0.27 per cent. (absolute) in two hours. In A and B the peroxide concentration was high enough to stand this first rapid action by catalase : in C it was not. As a result, whilst the peroxide persisted in A and B for more than eighteen months, and was still present at the time of writing, in the case Qf C none remained after one hour, though A, B, and C were actually all portions of the same milk, and the initial concentrations of the peroxide were approximately Unqualified statements to the effect that any given quantity of peroxide will or will not persist for a given time, and can or cannot be detected after a given time, are, though frequently met with, valueless.* As is to be expected from the known equal.MILK VI. Catalytic Activity, 39. Peroxide added, 0-1 95 per Cent. Peroxide present. Portion kept at- 17" C. -- 0.170 0.082 0.052 0.035 0.032 0.030 0.020 3-015 none - 27" C. 0.165 0.104 0.103 0-105 0.111 0.1 11 0-111 0.038 none - 37" c. 0.143 0.113 0.113 0.113 0.116 0.116 0.114 0.116 0.119 - Ortol Reaction. 17" C. Alone.+ + + + faint faint - With fresh milk. + + + + + + Portion kept st- 27" C. ~ With fresh milk. + + + + + + 37" c. With fresh milk. + + + + + + * From the results of those experiments that mere performed with perfectly fresh milk, it would appear that it would be unusual if 0.1 per cent. of peroxide were to persist for twenty-four hours even if added to the milk immediately after being drawn, strained, and cooled.HINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IK MILK 485 0.044 MILK IV.Catalytic Activity, 61. Peroxide added, 0.19 per Cent. 0.024 Peroxide present . . . Reactiorzs- (a) Milk alone 1:: I P” 0-082 (b) With peroxide added 0.071 (c) With fresh milk added {i Portion kept at 15’ C. after- 10 Mins. 0.148 Hours. 1 1 Day. -..--- I- 3 Days. 0.015 + trace + + trace + + + 4 bays. 0.008 + trace + + inc’d + + + 6 Days, 0.004 - - - trace - - - trace - 8 Days. none - - - trace - - - - - Portion kept at 27” C.after- 10 Mins. 11 Days. none Peroxide present . . . Reactions - i 0 i! (a) Milk alone ( b ) With peroxidej LO IP added ( c ) With fresh {: milk added 0.139 6 Hours. I 1 Day. I 3 Days, 0-070 faint - - faint faint - + + + 4 Days 0.070 - - - - faint -.+ + + 6 Days 0.066 - faint - - faint - + + + 8 Days, 0.065 trace trace trace trace + + + - - rise that takes place in the catalytic activity of milk on keeping, a most important factor in the behaviour of milk towards hydrogen peroxide is its age. I t will be shown later, in connection with the peroxidase reactions, that if the milk has not been heated it is sometimes possible to infer that hydrogen peroxide has been added, though at the time of testing it is not present.Peroxide was added in known quantities to milk, portions of which had been brought to, and were subsequently kept at, different temperatures. The results of several such experiments are given in the tables, the quantities of peroxide remaining in the various portions being estimated after the intervals stated.The influence of temperature was then studied. * For an explanation of these letters see p. 487, under “The Peroxidase Reactions.”486 HINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK 10 Mins. 0.150 Within the range of temperatures studied, the effect of a rise of temperature is to lengthen the time during which the peroxide persists.I t is to be noted, however, that during the first few minutes the rate at which peroxide was destroyed was greater at the higher temperature. Thus in ten minutes in all cases more peroxide had been destroyed in the portions kept at the higher temperatures, but at the end of six hours this condition had been reversed. I t might be expected that, at any rate up to 3 7 O C., the higher the temperature the greater would be the catalytic activity, and the results obtained at the end of ten minutes indicate that this is so, The ultimate result, however, must be due to a resultant of destructive effects of the catalase on the peroxide and of the MILK 111.Catalytic Activity, 70. Peroxide added, 0.196 per Cent. _. - __ . .- __ ._ - - - - - 6 Hours. 1 Day.2 Days. 3 Days, 0.070 0.053 0.046 0.050 ----- trace I 1- 10 Mins Peroxide present.. . Raac tions- ... I 0.162 ( a ) Milk alone { b ) W i t h peroxide added ... (c) With fresh milk added ... ... I + + + Portion kept at 15" C. after- trace + + + ! I i Hours 0.055 1 Day. 0.015 + + + 6 Days, ' 7 Days. none - - - f + + Peroxide present . . . React ions- I0 (a) Milk alone B I p (b) With per- oxideadded ( c ) R7ith fresh milk added {i Port,ion kept at 27" C.after- I 4 Days. 1 6 Days. I 7 Days. I - I-' 0-042 ' 0.034 I 0-008 - 9 faint 1 faint I i - + / + I + ' + I - I - - - + J + I - l 9 Days. noneHINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK 487 MILK V. Catalytic Activity, 132. Peroxide added, 0.10 per Cent. ! Portion kept at 14" C. after- I- I I 10 Mins. I_- I _ _- Peroxide present .. . Reactions- (a) Milk alone B -I: ( b ) With peroxide{! added ( c ) With fresh fg milk added Ip 0.076 3 Hours 0.003 Portion kept at 27" C. after- LO Mins 0-065 6 Hours. 0.006 1 Day. peroxide on the catalase. If the latter action is enhanced by a rise of temperature to an extent equal to or greater than the former, then there would be, at an elevated temperature, at first a more rapid destruction of peroxide, due to increased cata- lytic activity, followed by a less rapid destruction, due to disappearance of catalase.If this be the correct explanation of the results obtained, it would follow that in a method for the determination of the catalytic activity in which an excess of peroxide is employed for a period of some hours, an elevated temperature would be likely to result in a lower figure being obtained.The reverse would occur if the catalytic activity were high enough to reduce quickly the effective concentration of the peroxide.* The Pdroxidase Reactions. Orthomethylaminophenol sulphate ('( ortol "), benzidine, and paraphenylene- diamine have been used for the detection of hydrogen peroxide in milk.They are also used for the detection of previous heating of milk. The reactions of these reagents with the milk to which peroxide had been added were accordingly observed during the course of these experiments, the reactions being noted as positive or negative against the letters 0, B, and P in the tables, these letters denoting the reagents in the order named above.The reactions depend upon the simultaneous presence in the milk of hydrogen peroxide and a peroxidase. As in the case of catalase, hydrogen peroxide destroys peroxidase, and a negative reaction may consequently be due not to the absence of peroxide, but to the absence of peroxidase, which has been caused either by previous heating of the milk or by the peroxide which is being tested for, The reaction8 were * In a few cases the catalytic activity figure was determined at two temperatures.In only one case did an elevated temperature result in a higher figure, and this was a case in which the catalytic activity was somewhat high.488 HINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK therefore tried with the milk under examination (a) alone, (b) with a fresh addition of peroxide, (c) with the addition of fresh milk; (b) and ( c ) being applied only when a negative reaction was obtained with (a).C. H. La Wall (ANALYST, 1909, 34, 160) found that the reaction with benzidine disappeared at an earlier stage, after addition of peroxide, than that with para- phenylenediarnine, and concluded that different enzymes were involved in the two cases.The present experiments do not confirm this. The ben- zidine reaction is extremely brilliant and sensitive, but is much affected by the conditions under which the test is performed. Strong positive reactions are obtained only when the peroxide is carefully added and not intimately mixed with the milk, the best condition being that in which the peroxide is floated on to the surface of the milk and allowed to diffuse.In the case of a milk which already contains per- oxide this condition is unattainable, and the brilliancy and certainty of the reaction are much diminished. The ortol reaction is adversely affected by the presence of excess of peroxide, and is, perhaps, rather less sensitive to a very small amount of peroxidase ; the paraphenylenediamine reaction is not affected by a considerable excess of peroxide, and is, on the whole, probably the most generally applicable of the three.Numerous trials, in addition to those detailed above, were made with different concentrations o€ peroxide, and no evidence was obtained that the reactions are due to different enzymes, due allowance being made for the susceptibility of the reagents, especially benzidine, to the coditions existing.It may be here observed that with colour reactions of this nature, in which time is also a factor, distinct positives and distinct negatives form sharp contrasts, but as the peroxide or per- oxidase disappears, there comes a time when it is doubtful whether the reaction should be classed as positive or negative. That a negative reaction may be due to the absence of peroxide or of peroxidase or of both may be seen from the tables.For instance, in the case of Milk IV., in the portion kept at 27" C., the reactions with the milk alone at from four to eleven days were all negative or nearly so, although approximately 0.07 per cent. of peroxide was present ; with fresh milk added the reactions were all positive ; the peroxidase had thus been destroyed, while the peroxide persisted.I n the portion kept a t 15" C., at four days there was little peroxids left, but sufficient peroxide and peroxidase to give the reactions ; at later periods the reactions were all negative, with the exception of a few doubtful ones, with milk alone, with fresh peroxide added, and with fresh milk added, showing that the peroxide and the peroxidase had both disappeared.I n the c a ~ e of Milk III., at the end of four days the portion kept at 15' C. the peroxide had disappeared, and consequently negative reactions were obtained with the milk alone and with fresh milk added ; positive reactions were given with fresh peroxide, however, showing that the peroxidase had not disappeared.In the portion kept at 27" C. the exact reverse had occurred, the peroxide being still present and the peroxidase having disappeared. In Milk V., which had received a small original addition of peroxide, after one day the portion kept at 14' C. contained peroxidase but no peroxide; that kept at 27' C. contained neither. These three reagents are not equaHy applicable in all circumstances.HINKS: THE PERSISTENCE OF HSDROGEN PEROXIDE IN MILK 489 Owing to this destruction of peroxidase by peroxide it is thus necessary, when testing for the presence of the latter, to add some fresh milk as well as the reagent used, in order to insure the presence of peroxidase.Also, although peroxide may not be actually present, it may at times be inferred that it had at one time been present, provided that the milk had not been previously heated.This possibility of the milk having been previously heated must always be considered in relation to these tests for peroxide, though the addition of fresh milk will be effective in such a case. Conversely, the possibility of the milk having received an addition of poroxide must be considered when these reactions are used for the detection of previous heating, since a, “peroxidised” and n heated milk will, in certain circumstances, react in exactly the same manner.DISCUSSION. THE PRESIDENT remarked that under even the best conditions the study of enzyme action was beset by many difficulties, and Mr. Rinks was to be congratul- ated on having, in face of such complications as were met with in the case of milk, approached so nearly to a, definite conclusion.Mr. C. REVIS said that the fact of the persistence of hydrogen peroxide was well known to those concerned with the practical handling of milk, I t was, indeed, one of the almost insurmountable difficulties connected with certain processes for sterilising milk with hydrogen peroxide. When such processes first came into use, it was considered that it would be quite easy to add sufficient hydrogen peroxide to destroy all the organisms, and that the hydrogen peroxide would not persist, but would itself be destroyed by the organisms or by the organic matter, leaving a sterile liquid, in which there would be no injurious substance left, I t was found, however, that if hydrogen peroxide was added in sufficient quantity to bring about sterilisa- tion, a pronounced taste was produced in the milk, and the addition of some cata- lase, which would destroy the hydrogen peroxide after sterilisation had taken place, was found to be necessary.He was pleased to find that Mr. Hinks had used Koning’s method of measuring catalytic activity. I t was an excellent method, but, judging from the literature, apart from the original author, Mr.Hinks and he were the only two workers who had used it. The gasometric method was exceedingly difficult to obtain good results with. Dr. Harden and Miss Lane-Claypon had used it in their experiments in the best possible manner. In Koning’s process there certainly was some occlusion of iodine by the casein, but if the experiments were carried out in a, comparative manner, with the necessary precautions, the results were excellent.It was important, in an investigation of this kind, that the milk used should be, as in some of Mr. Hinks’s experiments, obtained direct from the COW, because the catalase, or peroxydase, or whatever it was that destroyed the peroxide, did not arise from one source alone. According to some authorities, these destructors of peroxide were present in milk in the udder, this conclusion being based on the fact that freshly drawn milk was in many cases capable of destroying hydrogen peroxide.Thie, however, did not necessarily mean that the milk in itself contained catalase. Grimmer had made glycerol extracts of mammary tissue, and490 HINKS: THE PERSISTENCE OF HYDROGEN PEROXIDE IN MILK had found these to have a strong catalytic activity.There was no doubt that the cellular elements which were present in milk always had a strong catalytic activity, and he had recently obtained evidence that these cellular elements might be actually dissolved in the milk itself whilst in the udder. Unfortunately, however, the bacteria occurring in milk also produced a good deal of catalase, and it was these multiple sources of catalase which complicated all experiments.If both natural catalase and bacteria were present, the result all depended upon the quantity of peroxide added and the temperature employed. If so much peroxide were added that all bacteria were destroyed, then natural catalase alone came into action, and if it were destroyed before the peroxide was completely used up, then peroxide remained. If bacteria were not destroyed, the excess peroxide was gradually de- stroyed as bacterial catalase developed.The course of the action was also greatly modified by the type of bacterial development which took place. I n Mr. Hinks’s three cases the partial destruction of peroxide occurring in experi- ment ‘(A’’ would be due to the catalase of the milk, and so also in experiment B,” since in theinterval of twenty-four hours there would be but a slight multiplication of bacteria, but in experiment C ” the bacteria would have multiplied enormously, producing sufficient catalase to complete the destruction of the peroxide immediately.Mr. W. PARTRIDGE remarked that neither Mr.Rinks nor Mr. Revis had men- tioned whether, as a matter of fact, hydrogen peroxide was used at all for preserva- five purposes. Its use under certain restrictions was provided for in the Milk and Cream Regulations, but he had never found it in milk or cream or seen any cream labelled as containing it. Mr. Hinks’s experiments might perhaps be the means of removing an injustice hitherto suffered by certain oxidising disinfectants, the action of which was supposed to be due to organic peroxides.From the fact that such disinfectants were found to have as strong an action after being left in contact with organic matter as before, it used to be assumed that there wag no peroxide present ; but Mr. Hinks’s experiments clearly showed that peroxide could exist and remain in presence of organic matter. Mr.REVIS said that hydrogen peroxide was never used for preserving milk. The PRESIDENT thought it probable that the increase in catalytic activity which occurred after a few days’ rest was due to bacterial growth. With regard to the question of the presence of catalase in milk as drawn from the udder, he did not Bee any reason why it should not occur in solution, apart from any cellular elements, as in preserved yeast prepared by Buchner’s method, where there was not any question of cellular dements.In the experiments with Milk V. and Milk VI., of which the catalytic activity was 132 and 39 respectively, he should have expected a consider- able difference in the quantity of hydrogen peroxide destroyed during the first ten minutes.I t was, however, approximately the same in both cases, which seemed curious. Mr. RINKS said that generally speaking one would expect the destruction of peroxide to correspond to the catalytic activity, but there were many disturbing influences, though as a rule these followed very much the same course. Milk V. was certainlynot very fresh. Mr. Revis had mentioned that hydrogen peroxide was never used in milk, but attempts had been made to use it. There was a great differ-FORMIC ACID AS A REAGENT IN ESSENTIAL OIL ANALYSIS 491 ence as regards persistence between 0.1 and 0-2 per cent. No unqualified statement could be made as to how long it would last, but he should think that probably, even with perfectly fresh milk, 0.1 per cent. would not last twenty-four hours, while 0-2 per cent. would probably last for a long time. Koning’s method, of course, did not measure the actual quantity of catalase present or the actual catalytic activity, but merely yielded an empirical figure. This would vary if the temperature or the time were altered, but when obtained under the same conditions it was very useful for com- paring different samples of milk. As to whether catalase did or did not exist in milk drawn under sterile conditions he was not prepared to speak positively; but when a sample taken immediately after milking showed a, figure of 32, and when this only rose to 34 after forty-eight hours, and then rose rapidly, it would seem reasonable to suppose that the catalase was there to start with.

ISSN:0003-2654    

DOI:10.1039/AN9154000482

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

FORMIC ACID AS A REAGENT IN ESSENTIAL OIL ANALYSIS 491 FORMIC ACID AS A REAGENT IN ESSENTIAL OIL ANALYSIS. BY WM. H. SIMMONS, B.Sc. (Read at the Meeting, December 1, 1915.) THE action of formic acid on some of the alcoholic constituents of essential oils was examined by Bertram and Walbaum as long ago as 1892 (J. f. prakt. Chem. II., 45, 598 et Seq.), but its use as a reagent for the quantitative analysis of essential oils appears to have been first suggested by Schimmel (Half-Yearly Report, April, 1901, pp.47-49) for the estimation of citronellol in Otto of rose, in which by its means they found 26 to 29 per cent. Satie (Amer. Perf., 1907, p. 12) applied the method to the analysis of geranium oils, and in 1912 (Half-Yearly Report, October, 1912, p. 43) Schimmel unsuccessfully attempted to use it for the ,estimation of citronellic aldehyde in citronella oils.The process is based on the fact that geraniol is very largely converted into terpenes by treatment with formic acid, whilst citronellol is esterified to citronellyl formate; it is carried out by heating a mixture of 1 vol. of oil with 2 vols. of I00 per cent. formic acid under a reflux condenser for one hour on a boiling-water bath, washing the esterified oil with brine until free from soluble acid, rendering it neutral to phenolphthalein, and then saponifying it with excess of alcoholic potash, and titrating back excess of potash with standard acid.Then the percentage of citronellol may be calculated from the formula, : Per cent. citronellol = Weight of esteritied oil taken-(number of C.O.2 KOH absorbed x 0.014). Number of C.C. KOH absorbed x 0.078 x 100492 8IMMONS: FORMIC ACID AS A In. a paper before the British Pharmaceutical Conference in July, 1913, on the “ Compositionof the Alcoholic Constituents of Geranium Oils” (Year-Book of Plzarrn., 1913, pp. 565-8), I showed that by this process one obtains : 1. Incomplete decomposition of geraniol.2. Incomplete esterification of citronellol. 3. An apparent citronellol ” content of about 14 per cent. for prtlmarosa oil, probably due to (1) 4. A much larger proportion of oitronellol in Bourbon than in African geranium oils, the quantities being respectively 44 to 57 per cent., and 32 to 43 per cent. And that further it is immaterial whether the mixture is heated on a boiling- water bath or boiled on a sand-bath, though in the latter case considerable bumping occurs. Beyond reducing this bumping, no effect is produced by adding 2 grms.anhydrous sodium formate to the mixture. Further experiments on the subject have since been made by Schimmel (Hslf-Yearly Report, October, 1913, p. 64), who confirm the incomplete decomposition of geraniol by formylation, but find that with freshly prepared citronellol the results obtained by the formylation process are too high, though they decrease as the preparation ages.Umney (Perf. and Ess. Oil Record, 1914,5, 51) has also examined four different samples of commercial citronellol, which showed 9794 to 99.7 per cent. by acetylstion, but 96.6 to 119.8 per cent. by formylation.Umney has, further, returned to the subject of formylation of Otto of rose (Perf. and Ess. Oil Record, 1913, 4, 328-9), and concludes that the percentage of citronellol, determined in this way, in the finest French, Bulgarian, and Anatolian Otto of rose, varies between 32 and 39 per cent. Since the publication of my previous results with geranium oils some two years ago, I have had the opportunity of examining some fifty further samples of Bourbon geranium oil, including practically all the most important brands, and several African oils, and find that the proportion of citronellol in Bourbon oils invariably lies between 45 and 57 per cent., all, with the exception of six, being under 65 per cent., while in African oils it is between 32 and 43 per cent., thus confirming the previous results.I have since extended my investigations on the effect of formylation on various other essential oils arid their alcoholic constituents, and give in Table I. the results obtained by formylation in the usual way for one hour with 2 vols. of 100 per cent. formic acid and 1 vol. of oil. To make $he figures complete, I have also included my already-published results for geraniol, citronellol, and palmarosa oil. The results with menthol and peppermint oils being so promising, I tried reducing the quantity of formic acid to I volume of acid to 1 volume of oil, in case treatment with the larger quantity was too drastic, and the results are given in Table II,, compared with those obtained by acetylation.Inability to obtain 100 per cent.formic acid owing to the war has prevented experiments on these lines being carried further for the present, but as 85 per cent. formic acid is still available, I have made one or two experiments to determine whether this was of any use for the purpose, and the results obtained are given in Table III., compared with thoee already found with 100 per cent. acid.REAGENT IN ESSENTIAL OIL ANALYSIS 493 Acctylated Alcohols.~ ~~ Geraniol ... ... ... ... Ci tronellol ... ... ... Mixture of geraniol and citron- ellol .in equal proportions .... Geranium oils : Bourbon (56) ... ... Asian ... ... ... Corsican ... ... Trappe de Staouelii . . . . Palmarosa oil ... ... ... Ginger-grass oils (2) ... ... Linalol ... ... ... ... Ter pineol ... ... ... Rosemary oil ...Sandal-wood oil (East India& * ' Menthol ... ... ... ... Peppermint oils : American ... ... ... Japanese ... ... ... African (16) ... ... Formylatcd Alcohols. TABLE I. I I Per Cent. Calculated as- Acetylttted Alcohols. Per Cent. Calculated as- ! Per Cent. - 99.6 100.4 ::: - 66-7-79 -5 68-4 69.8 71.5 91.4 48-8-49.2 68.5 67 -6-75 *8 - - 92.0 - 55.3 51.2 Calculated as- Geraniol 9 9 - Geraniol 9 9 9 9 P ? 9 9 PI Lidkol - - San talol - Menthol 1 s Forrnylated Alcohols.Per Cent. 13.7 83.4 47.3 32 -0-42 -3 63.9 30.3 27.9 13.9 15.4-15.9 22.0 3.0 14.9 63.6 99.5 51.6 44.7 44 *0-57 02 Calculated as- Ci tronellol. ....... - 9 9 9 9 > > 9 9 9 ) 2 9 9 ) 3 9 9 9 Linalol. Terpineol. Borneol. Sant alol. Menthol. 9 9 8 9 TABLE 11. I I American peppermint oil (1) ...9 9 9 3 9 9 (2) *.' Japanese dementholised oil ... 55.3 55.0 49.1 Menthol 9 3 9 ) 52.8 I Menthol. 52.3 46.4 j ,',' TABLE 111. With 100 Per Cent Formic ! With 85 Per Cent. Formic Acid. i Acid. -. .- ..... . I I__. I I Per Cent. I Calculated as- 1 Per Cent. I Calculated as- American peppermint oil ... Bourbon geranium oil ... 52.3 51.7 Menthol Ci t r onellol 52.0 I Menthol.49.0 Citronellol. * Or calculated as citronellol 101.6 per ccnb.494 BOLTON AND REVIS: RECENT ADVANCE8 RELATING TO THE The results show that terpineol is almost completely decomposed by formyla- tion; geraniol and linalol are both converted into an appreciable quantity of ester, while santalol is only very partially decomposed, and citronellol, menthol, and the borneol in rosemary oil may be approximately estimated by the PrOCeSB.The use of formic acid as a reagent is undoubtedly of value in the examination of geranium oils and-if the right conditions as to strength and proportion of acid and duration of heating can be determined-enables an accurate measurement of the proportion of menthol in peppermint oils to be made; it appears also to offer advantages over the ordinary acetylation process for this purpose. The heating of the mixture on a boiling-water bath ensures a more Vniform temperature than is possible when boiling on a sand-bath, and no addition of sodium acetate or formate is necessary. As soon as 100 per cent. formic acid is again obtainable, it is hoped to define the conditions under which menthol can be satisfactorily determined by formy lation. I desire to acknowledge the help of my former assistant, Mr. L. V. Shatwell, who has carried out many of the estimations recorded in this paper.

ISSN:0003-2654    

DOI:10.1039/AN9154000491

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

494 BOLTON AND REVIS: RECENT ADVANCE8 RELATING TO THE RECENT ADVANCES RELATING TO THE COMPOSITION AND ANALYSIS OF EDIBLE OILS AND FATS.* BY E. RICHARDS BOLTON AND CECIL REVIS. THE marked development in the oil industry during the last few years, while it has led to a concomitant development of industrial processes, has certainly not been accompanied by a parallel extension of our analytical knowledge on the purely chemical side of oils and fats.I t is not too much to say that we are still very dependent on the almost rule-of-thumb methods which have prevailed in this department of analytical chemistry up to the present time ; nor, unfortunately, is there much promise as yet that any more scientific methods are likely to come into use. This is a natural result of the highly complex character and overlapping con- stitution of the natural fatty products. For this reason it has seemed advisable to collect the work of the last few years under a number of separate headings, rather than to attempt to show the inter- relation of the work as a whole.These headings are : (a) Constitution and Composition of Natural Glycerides. (b) Hydrogenated Fats.(c) Analytical hfethods. (a) Constitution and Composition of Natural Glycerides.-What little addition to our knowledge has been made in this direction has resulted chiefly from the study of the hydrolysis of known glycerides by various agents, and from attempts at the * This is the third of a series of articles dealing with recent advances in certain branches of analytical work.Others will follow at intervals.-EDITOR.COMPOSITION AND ANALYSIS OF EDJBLE OILS AND FATS 495 synthesis of such glycerides, and from the study of the meltingpoints of both fats and fatty acids. The saponification of triolein by alcoholic potassium hydroxide has been investi- gated by Fortini (Chem. Zeit., 1912, 36, 1117). The speed of reaction during frac- tional saponification being studied, the results show three distinct phases in the chemical process.He deduces from his findings that these phases correspond to the successive degradation into diglyceride, monoglyceride, and fatty acid. These results, however, only confirm the earlier experiments of Geitel and Lewkowitsch. With these experiments must be contrasted the results of Griin and Correlli (Zeitsch.angew. Chem., 1912, 25, 665 ; ANALYST, 1912, 37, 256), who have examined the hydrolysis of tripalmitin with concentrated sulphuric acid. In their experiments no trace of the formation of monoglyceride was obtained, the products of the reaction being always free fatty acid, dipalmitin and unchanged triglyceride. Similar results were obtained with tristearin. They infer from these experiments the formation of diglyceride sulphuric acid ester, and an a P-distearin sulphuric acid ester has been prepared by them, though this could not be isolated from the reaction mixtures, which is easily explained by the great instability of the ester in the presence of water.The synthesis of natural glycerides from the point of view of the phase rule has been investigated by Kremann, Schoulz, Klein, and Kropsch (Monatsh., 1912, 33, 1063 ; 1913, 34, 1291 ; and 1914, 35, 561).The ternary system, (1) tristearin- tripalmitin-triolein, (2) tripalmitin-stearic acid-palmitic acid, and (3) tristearin-stearic scid-palmitic acid, have been studied. The work has entailed the determination of the freezing-points of a very large number of mixtures of these substances, but whilst the results obtained are largely of theoretical interest, they appear to throw a, certain amount of light upon the probable composition of the hard and soft fats which are chiefly composed of the above-mentioned glycerides.An attempt at the direct synthesis of glycerides has been made by Bellucci (Gazz, Chim. ItaJ., 1912 42, ii., 283) by :heating equal molecular proportions of palmitic, oleic, and stearic acids with glycerol at high temperatures and greatly reduced pressure.The for- mation of glycerides under these conditions proceeds along very similar lines to those followed when the synthetic agent is the lipase of castor oil seed. While these three acids vary greatly in the speed with which they are changed into glycerides, the general course of the reaction is of an exactly opposite character to that obtained by Fortini (Zoc.cit.) in his experiments on saponification. Before leaving the subject of glycerides mention may be made of the suggestion of Bomer and Lirnprich (Zeitsch. Unters. Nahr. Genussm., 1913, 25, 354 ; ANALYST, 1913, 38, 214), that in describing mixed glycerides the following nomenclature, which enables isomeric glycerides to be described graphically without confusion, should be employed : CH;OH.a position CH*OH. ,G ,, I I CH;OH. 7 ,,496 BOLTON AND REVIS: RECENT ADVANCES RELATING TO THE The a and y positions are of equal value when only two fatty acid radicles are present in the 8ame molecule. The decomposition of fats and fatty acids by the action of moulds has been made the subject of investigation by Spieckermann (Zeitsch.Unters. N a h . Genussnz., 1912, 23, 306, and 1914, 27, 83). Under the action of moulds (penicillium, asper- gillus, and rnonilia) the glycerides are hydrolysed to glycerol and fatty acid, by means of a lipase which appears to be extracellular, the glycerol is almost com- pletely converted into carbon dioxide and water by the mould, a certain proportion of the fatty acid being absorbed by the cells, probably in the form of a soap solution.The fatty acids show very varying resistance to the action of the moulds- stearic and arachidic acids being but slightly attacked, while myristic and lauric acids were almost completely decomposed and absorbed. The residual fatty acids unabsorbed by the moulds show distinct evidence of change ; for instance, the iodine value of oleic acid is reduced, while that of the saturated fatty acid is often increased.These results are of distinct interest in connection with the question of rancidity and accounts for the fact that the oils and fats of the coconut group, which have a large content of lauric acid, are peculiarly susceptible to rancidity when acted upon by moulds.Some interesting papers have been published in connection with the melting- ppints of fats which throw some light on the anomalies observed in such determina- tions. That of Le Chatelier and Mlle. Cavaignac (Conzpt. rend., 1913, 156, 589), working with a coconut oil product and with ‘( stearine,” shows that the change of state at the melting-point does not really differ from that of chemical compounds in general, and is a strictly reversible phenomenon, but often takes place exceedingly slowly.The variation between tho melting-point and solidifying-point of fats, as commonly determined in analyticaI work, is, therefore, solely the result of the com- paratively rapid way in which such determinations are made.The solidification temperature, as a rule, shows much greater departure from the true value than does the meltingpoint. Griin (Berichte, 1912,45,3691) has brought forward more evidence in support of the theory that glycerides exist in two modifications, and deduces from his results the reasons for the variability in the melting-point of fats prepared by different pro- cesses, and has also prepared some of these modifications which appear to uphold his contentions.The general results of his investigations are to be taken as supporting the view that the final condition of a glyceride is the result of an equilibrium between those modifications which, in Bome cases, may only be attained slowly. Somewhat, similar results ‘have been obtained by Smits and I36khurst (Proc.K. Akad. Wetensch., Amsterdam, 1912,15, 681), who have shown the existence of two such crystalline modifications when working with tristearin. Arising out of the above results there appears ground for the opinion of Twitchell (J. Id. und Eng. Chem., 1914, 6, 864; ANALYST, 1914, 39, 448) that the: lowering of the solidifying-point in mixtures of fatty acids is of no value as an indi- cation of their composition, while the lowering of the meltingpoint is.According to Bonzio and Gastaldi (Gazz. Clzim. Ital., 1912,42, ii. 92), the position of the double links of the oleic acid series can be ascertained by-a determination ofCOMPOSITION AND ANALYSIS OF EDIBLE OILS AND FATS 497 the iodine value, as when this linkage is distant from the carboxyl groups the value obtained agrees with that required by theory, while if it be in the 2 : 3 position the results are too low, evidently due to intramolecular action taking place during the process.Attention may be drawn to a method originated by Arnold (Zeitsch. Unters. Nahr. Genussm., 1912, 23, 129 ; ANALYST, 1912, 37, 203) for the determination of the molecular weight of small quantities of fatty acids by saponification with alcoholic potassium hydroxide. The formulae given by him appears to give very satisfactory results. (b) Hydrogenated I+’ats.--It is not too much to say that the process known generally as the hydrogenation or g g hardening” of fats has made almost a revolution in the history of fats and oils.Not only has this effected the production of new fatty substances hitherto quite unknown and almost unthought of, but has also brought before the analyst an entirely new series of problems of a most difficult character.The old analytical landmarks have in many cases disappeared, and the amount of sure ground at his disposal is by no means large. Though the process of introdxing hydrogen into unsaturated oils and fats may be said to start from the year 1896, it was only in 1903 that the first effective patents became commercially used, and the full development of such processes is in the distant future.Since 1903 an enormous number of patents and modifications of the original process have been published, and it is quite impossible within the scope of such an article as this to do anything but touch lightly upon the work of the last few years.The developments which had taken place up to the year 1913 have been fuliy dealt with by Ellis in a paper read before the New York section of the Society of Chemical Industry ( J . SOC. Chem. Ind., 1912, 31, 1155). The chief developments from a commercial point of view have centred round the finding of the most suitable catalyst for the production of tho change and the temperature at which the process can be most economically worked. Among catalysts which have been proposed are platinum, palladium, nickel oxide, nickel carbonyl, cobalt, copper, iron, and a mixture of some of these ; and, quite recently, Bergius (Zeitsch.angew. Chem., 1914, 27, 522) claims that the change can be brought about without any catalyst at all under a high pressure of hydrogen at high temperatures.At this present moment, however, nickel appears to be the favourite catalyst, though the method by which it is employed varies con- siderably, and is the chief subject of the greater number of patents which have been taken out. The catalyst is usually made by the preparation of its oxide from a nickel salt and the reduction of the latter in hydrogen, the object being to obtain the nickel in a very finely divided state.The question of the details and cost of the catalytic hydrogenation of fats is dealt with in a paper by Bontoux (Zes Natihes Grasses, 1914, 7, 4194). The process has also enabled such oils as whale oil to be used, and the product is becoming known commercially as ‘‘ artificial tallow,” a large factory having been erected at Fredrickstad (Board of Trade Journal, 1913, May 29; see also Chenz. ,Zed,, 1914,.38, 392). I t also appears that (Thompson, Amer. Perfumer, 1914, 9, 139) in the United States, compound lards are now almost entirely hydrogenated cotton-seed oil. The questions of the digestibility of the hydrogenated fats, and of the possible498 BOLTON AND REVIS: RECENT ADVANCES RELATING TO THE danger to health from traces of the catalyst, have not yet been satisfactorily settled, and it is not improbable that any decision adverse to their production would meet with considerable opposition both on account of their extreme utility and of their value as substitutes for animal fats.Some experiments have been carried out by Lehmann (Chem.Zeit., 1914, 38, 798), who finds that commercially hardened oils contain from 0.07 to 6 mgrms. of nickel per kilo, and has carried out a number of feeding experiments both on animals and on human beings, which appear to show that no ill effects result from the consumption of these fats. Offerdahl-Larvik (Ber. deutch. Pharrn. Ges., 1913, 23, 558) goes so far as to state 0.5 grm.of nickel per day is not harmful. The question has, however, lost a little of its interest, as the removal of the catalyst is ever so much more perfect at present than it was originally, which, while satisfactory from the point of view of the consumer, cannot be regarded in the same light by the analyst. The nickel is undoubtedly held by the fats in the form of nickel soaps.The chemical changes accompanying hydrogenation have been little investi- gated. As would be expected, the iodine value diminishes, while the melting-point and the solidifying-point rise, and, as the process may be stopped at any stage, a whole series of products may be obtained from the same original fat, varying, in the case of such an oil as ootton-seed, from substances but little different outwardly to the original oil, up to a hard product almost resembling marble.According to Norman and Huge1 (Chem. Zeit., 1913, 37, 815; ANALYST, 1913, 38, 432)) hydroxyl groups are split off during the hardening process, and acids such as arachidic and behenic acids are formed during the treatment of marine animal oils. Though theoretically the process consists of the introduction of hydrogen atoms into the unsaturated linkages of the glyceride, it is highly improbable that the process is actually so simple, and Leimdorfer (Seijensieder Zeit., 1913, 40, 1317) is of the opinion that the “steariae” of the hydrogenated fat is different to natural ‘‘ stearine,” and is probably an allotropic modification, the speed of saponi- fication being greater than in the case of the natural fat.I t is evident, to anyone working with these fats, that their general character and microscopical appearance differ markedly from that of natural fats. With the above-mentioned molecular changes which take place on hydrogenation, there also occurs the disappearance of those substances which are the cause of reactions so charaoteristic of certain natural fats.Bomer (Zeitsch. U?Aws. Nahr. Genzcssm., 1912,24,104 ; ANALYST, 1912, 37, 452) states that the Halphen, Baudouin, and other colour reactions are rendered negative by hydrogenation, and this is undoubtedly so in the case of Halphen’s reaction ; the chromogenetic substance appears to be almost entirely destroyed before any appreciable quantity of ‘( stearine ’’ is formed.Kreis and Roth (ibid., 1913, 25, 81 ; ANALYST, 1913, 38, 160), however, state that the nitric acid-resorcinol test is not nullified, and holds good for the oil after treatment. According to Stiepel (Siefensicder Zeit., 1912, 39, 953), the octobromide test, which is so useful in exami- nation for marine animal oils, is rendered practically useless by the process of hydrogenation.The only test which is available with the same certainty after treatment as before is the phytosteryl-acetate test, which has accordingly assumedCOMPOSITION AND ANALYSIS OF EDIBLE OILY AND FATS 499 even more importance than it has hitherto done, and on which account great interest attaches to the digitonin methods of performing the test, reference to which is made in Section (c) on Analytical Methods.(c) Analytical Methods.-The past few years have not been prolific of methods of great interest in connection with the analysis of oils and fats, the published work having been directed rather towards the improvement and refinement of existing methods. I n connection with the specific gravity of oils, Ransome (J. SOC. Chern. Ind., 1912, 31, 672; ANALYST, 1912, 37, 410) has drawn attention to the fact that this figure may be considerably altered by the presence of free fatty acids, particularly in connection with olive oil.A comparative study of the Hiibl and Wijs method for the determination of the iodine value of oils and fats has been made by Auguet (Ann. Fa&@., 1912, 5, 459), who confirms the superiority of the Wijs method, and at the same time elucidates some of the causes of the discrepancies between the two methods.In spite of the debt which we owe to the Hub1 method for the early recorded iodine values, it would be of advantage if the Wiis method mere the only recognised one for carrying out this test. The Bellier test for the detection and estimation of arachis oil has been the subject of critical study by Evern (ANALYST, 1912, 37, 487), who, following on the lines of Adler (Zeitsch.Unters. Nahr. Genussm., 1912, 23, 676) and of Franz (Dis. Uunchen., 1910), has succeeded in clearly pointing out the weak points of the original method, and has evolved a, practical and satisfactory procedure €or con- ducting this well-known and useful method. The error seems to have chiefly arisen through a mistaken idea that the precipitates of arachidic and lignoceric acids were insoluble in 70 per cent.alcohol. Later, however, Luers (Zeitsch. Unters. Nuhr. Genussm., 1912, 24, 683), using the method of Franz and Adler (Zoc. cit.), has shown that in certain samples of olive oil, containing abnormally high proportions of myristin, a misleading result, pointing to the presence of arachis oil, may be obtained, but that an increase in the quantity of acetic acid will obviate the difficulty.Kreis and Roth (Zeitsch. Unters. Nahr. Genussm., 1913, 25, 81), however, sound a note of warning, which is very necessary at this time, with regard to the impossibility of applying Bellier’s test to (( hardened oils,” and have themselves proposed a method whereby the difliculty may be overcome.A great number of papers have been published in connection with Tung oils, the growing demand for which has necessitated a greater care in the examination of the commercial product. Most of these centre round the ‘( heat polymerisation test,” and many so-called standard methods have been put forward, chiefly from American sources ; see Browne (Chem.News, 1912, 106, 14 ; ANALYST, 1912, 37, 410), and the recommendation of the New York Produce Exchange (J. Xoc. Chem. Ind., 1912, 31,997) and Potsdamer (ibid., 1913,32,542).* The nature of the body formed during this test has been investigated by Wolff (Chem. Zeit., 1913,37,1376), who shows that the jelly is not a homogeneous substance, but that the setting is due to the solution of * See also specification for South China wood oil, issued by the Association of Exporters and Dealers of HongKong, in which details for carrying out sonie of the tests are given.500 BOLTON AND XEVIS: RECENT ADVANCES RELATING TO THE the altered portion of the oil in the unaltered part followed by the final gelatinisation of the solution.The chemical transformations which take place have also been investigated by Folkin ( J .Rzw. Phys. Chem. SOC., 1913, 45,2$3), and in this connec- tion attention may be drawn to an interesting paper by Morrell (J. Chem. SOC., 1912, 101, 2082) on the behaviour of elaeo-stearic acid. The analysis of both Chinese and Japanese wood oils has been made the subject of a very careful investigation by Chapman (ANALYST, 1912, 37, 543), who has suc- ceeded in placing the matter in a much more satisfactory condition.Some further work has been published by Ware and Schumann (J. SOC. Chem. Ind., 1914,33,1017 ; ANALYST, 1914, 39, 557). Gastaldi (Chem. Zeit., 1912, 2, 758) has published an investigation into the actual cause of the Halphen colour reaction for cotton-seed oil, and concludes that im- purities in the amyl alcohol employed axe responsible, He shows that a great variety of substances could be used instead of amyl alcohol, and particulary recom- mends the use of pyridine, whioh undoubtedly greatly improves the sensitiveness of the test, particularly if carried out in closed tubes.He goes so far as to state that 0.25 per cent. of cotton-seed oil can be detected.Utz (Chem. Rev. E’ett-Id., 1913, 20, 291), proposing to use pentachlorethane instead of carbon disulphide as the sulphur solvent, has been attacked by the former author, who states that his test is still further improved by a reduction in the quantity of carbon disulphide, the liquid being heated to 140° C. These refinements of the original Halphen test are not without value, as the increasing use of “hardened” cotton-seed oil calls for this greater delicacy, the chromogenetic substance being largely destroyed in the process of hydrogenation.The excessive quantity of carbon disulphide generally employed will be appreciated when one considers a test proposed by Milliau (ANALYST, 1912, 37, 101), who has ingeniously taken advantage of the delicate Halphen reaction with kapok oil, conversely to detect minute traces of carbon disulphide in commercially 6 c extracted ” oils.This test is carried out by distilling 50 grms. of the oil with 10 C.C. of pure amyl alcohol ; 1 C.C. of kapok oil is added to the first 4 C.C. of the distillate, which, together with a few mgrms. of sulphur, are heated in a sealed tube for one hour in a water-bath.The writers have found it possible to detect as little as 0.02 per cent, of carbon disulphide by this means, and when the amounts are small have even made approximate estimates of the quantity by comparison with standards prepared from oils con- taining known quantities of carbon disulphide. Norman (ANALYST, 1912, 37, 508) has put forward a rapid method for obtaining acetyl values, whereby he claims to obviate errors caused by esterification of acetylated fatty acids when dissolved in alcohol.Simmons (ANALYST, 1915, 491) has carried out some useful work on the formylation of essential oils and their alcoholic constituents, and he compares the figures obtained with those yielded by acetylation. A consideration of his figures and data open out a new field of investigation in the examination of fatty oils, the method being likely to give information similar to the acetyl value in a more expeditious manner.A simple method is given by Arnold (ANALYST, 1912, 37, 203) for the determination of the molecular weight of small quantities of fatty acids by titration with potassium hydroxide, and weighing the soap after a special method ofCOMPOSITION AND ANALYSIS OF EDIBLE OILS AND FATS 501.drying. The author claims to obtain molecular weights within two units of theory. Bolton, Richmond, and Revis (ANALYST, 1912, 37, 183), have applied the Reichert- Meissl, Polenske, and Kirschner tests to a series of mixtures of coconut and palm kernel oils with butter fat, in the presence of other fats and oils.The figures they have obtained show that the quantity of butter fat in margarine can be estimated within about 1 per cent. in the presence of either coconut or palm kernel oil, or both together. They express the opinion that the relationship between the Polenske and Kirschner values is both more constant and more sensitive than the relationship between the Polenske and Reichert-Meissl values as first put forward by Polenske.A table was tentatively constructed by them, in the hope that it would be critically examined by other workers, which, in fact, has just been done by Cranfield (ANALYST, 1915, 439), as the result of an extensive investigation. This author, in the course of a. series of feeding experiments, obtained butters which gave Reichert-Meissl, Polenske, and Kirschner values covering an extensive range from nearly the lowest to almost the highest figures commonly found.The average results agree well with the relationship proposed by Bolton, Richmond, and Revis (Zoc. cit.), and tha author puts forward the relationship T-- as a constant, varying between 1-97 and 2.98, but generally between 2.2 and 2.8. This he hopes to further investigate, but, as the matter stands at present, the death-knell of profit- able adulteration of butter by means of either coconut or palm kernel oil, has been sounded.The great similarity in constitution between coconut and palm kernel oil has rendered it an almost impossible task to estimate the proportion of these fats in mixtures, more especially in the presence of other fats.Burnett and Revis (ANALYST, 1913, 38, 255) have devised a method by which they believe some help is given in the solution of this problem, the process being quite independent of the presence of other fats. turbidity tem- perature ” of an alcoholic solution (of certain atrength) of the barium salts of the insoluble volatile acids, as obtained when determining the Polenske value.Some very useful work on Egyptian butter, samna, and ghee, is recorded in a paper by Trimen (ANALYST, 1913, 38,243), who gives constants for a large number of samples of these products. He applied many of the lately proposed methods, and adds his conclusions and criticisms of their value. His figures for the Reichert- Meissl value of pure ghee confirm those of certain other observers, and tend to prove that the low figure unfortunately put forward by Kesava-Menon (J.SOC. Chem. Ind., 1910, 29, 1428), for one sample only, must be regarded as strangely abnormal. The author has applied the AvB Lallement method to some forty samples, and obtained in every case minus values for b - (200 + c), thus showing that Lallement’s statement applies to butter made from the milk of the buffalo and the sheep, as well as to that made from cow’s milk; but he points out that, in oases where large minus values were obtained, he was able to add large quantities of coconut oil and produce a mixture which still gave a minus value.He concludes from this that the writers’ commendation of the AvB Lallement process (Allen’s RM-K It consists of a determination of the502 THE COMPOSITION AND ANALYSIS OF EDIBLE OILS AND FATS ‘‘ Commercial Organic Analysis,” fourth edition, vol.ii., 288) is not justified. This is a little unfortunate, as such commendation was never directed towards this useful process as a means of detecting coconut oil, since the presence of 5 per cent. of this oil is readily disclosed by the relationship of the Polenske and Kirschner values, but rather to its value for the detection of other animal fats in butter-a problem of muoh greater difficulty. The existence of an official method for estimating glycerol in fats has, like all standard methods, the unfortunate effect of leading every analyst into the same groove, and sadly hampering analytical enterprise in the direction of improved methods.The method of Zeisel and Fanto of converting the glycerol into isopropyl- iodide has been shown by Lewkowitsch (ANALYST, 1903, 28, 108) to give low results. Willstlitter and Madinaveitia (ANALYST, 1912, 37, 571) claim to have improved this method, though the figures they cite are still somewhat below that required by theory. A very simple method has been described by Bertram (ANALYST, 1913, 38, 275), who treats the glycerol solution with excess of KOH, adding a 10 per cent.solution of copper sulphate till a permanent precipitate is formed. An excess of potassium iodide solution is added after acidification with acetic acid, and the liberated iodine titrated with & sodium thiosulphate solution, each molecule of sodium thiosulphate corresponding to two molecules of glycerol.Langheld and Zeileis (ANALYST, 1913,38,273) have proposed a method for the analysis of mixtures of certain lower fatty acids by fractional moist combustion with chromic acid, and measurement of the GO, evolved at certain temperatures. Formulae are given for calculating the proportion of acetic, isobutyric, isovaleric, and methyl-ethyl-acetic acids.Bomer (ANALYST, 1913, 38, 204) has isolated the saturated glycerides from lard by repeated fractional precipitation and crystallisation from ether, and finds that tristearin is absent, thereby showing a striking difference from mutton and beef fats. This observer contradicts the statement of Kreis and Hafner (ANALYST, 1914, 29, 259) that heptadecyldistearin is present, and he identifies the insoluble glyceride as palmitodistearin, and from this suggests that it is a-palmitodistearin, that obtained from mutton fat being 6-palmitodistearin.Bomer has made use of his experimental results to detect the presence of beef fat in lard and for the solution of similar problems. A method for the detection of adulteration of linseed oil has been worked out by Elsdon and Hawley (ANALYST, 1913, 38, 3), whereby the oil is dried” on paper under standard conditions, and the paper extracted by ether in a Soxhlet apparatus.The test is simple and novel, and appears to give indication of crude adulteration, but the information is, after all, no more than could be obtained by a consideration of the ordinary analytical (‘ constants.” The insoluble bromide value (sometimes known as the hexabromide test), origin- ally worked out by Hehner and Mitchell (ANALYST, 1898,23,313), has since then been the subject of many researches.Of recent years, under this Society’s Analytical Investigation Scheme, most valuable work has been carried out by Gemmel (ANALYST, 1914, 39, 297), who has exhaustively examined the sources of error in various methods of carrying out the process, Similar investigations, though on a, less exten-FOOD AND DRUGS ANALYSIS 503 sive scale, were carried out by Sutcliife (ANALYST, 1914, 39, 28). Gemmel (LOG c&) criticises Sutcliffe’s conclusions, and the latter replied to the criticism (ANALYST, 1914, 39, 388). In view of the useful work which these observers have recorded, their points of variance are of minor importance. Halphen’s qualitative modification of this test often affords most useful informa- tion in cases of unknown oils, and helps in the detection of rape oil; but in this con- nection it should be borne in mind that, as pointed out by the writers (“ Fatty Foods,” 43), beef fat, lard, butter fat, and shea butter give precipitates. As already mentioned in section (b) the phytosteryl acetate test has assumed much greater importance on account of the possible use of hardened vegetable fats as adulterants of animal fats. This method, always somewhat tedious, has been decidedly simplified by the employment of digitonin, first proposed in its application to fats by Marcusson and Schilling (Chew. Zeit., 1913, 37, 1001 ; ANALYST, 1913, 38, 458). The pitfalls of this simple application of the test have been well pointed out by Klostermann (Zeitsch. Unters. Nahr. Gertzcssm., 1913,26,443 ; ANALYST, 1914,39, 32), who has elaborated the process in such a manner that the free phytosterol and phytosteryl esters may be separately estimated.

ISSN:0003-2654    

DOI:10.1039/AN9154000494

出版商:RSC    

年代:1915

数据来源: RSC

摘要:

FOOD AND DRUGS ANALYSIS 503 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Deteetion and Estimation of Benzoic Aeid in Foods. K. Baumann and J. Grossfeld. (Zeitsch. Untersuch. Nahr. ‘Genussnz., 191 5, 29, 387-409 ; through Chem. Zmztr., 1915, ii., 202-203.)- Several methods for the detection of benzoic acid were investigated, and Mohler’s method was found to be the most trustworthy (cj.Halphen, ANALYST, 1908, 33, 420; Von der Heide and Jacob, ibid., 1910, 35, 166). The following procedure is recommended for the estimation, of benzoic acid in various animal foods. In milk : 100 C.C. of the sample are mixed with a few C.C. of phenolphthalein solution and concentrated potassium carbonate solution is added until a permanent pink coloration is obtained ; the mixture is then diluted to 200 c.c., 20 C.C.of 20 per cent. calcium chloride are added, the mixture is heated for fifteen minutes on a waterbath, cooled, diluted to 250 c.c., and filtered. Old milks tend to yield a turbid filtrate, but this dces not interfere with the process. A quantity, say 175 c.c., of the filtrate is transferred to a 200 C.C. flask, a few drops of copper sulphate solution are added (to remove any sulphide present), followed by 10 C.C.of sodium phosphotungstate solution (200 grms. of sodium tungstate and 120 grms. of sodium phosphate per litre), and the mixture is diluted with sulphuric acid (1 : 3) to the mark. After standing for eighteen hours, the mixture is filtered, 100 C.C. of the filtrate are percolated for six hours with carbon tetrachloride, the latter is then504 ABSTRACTS OF CHEMICAL PAPERS drawn off, mixed with an equal volume of neutral alcohol containing phenolphtha- lein, and the solution titrated with TG alkali solution.Under these conditions, milk free from benzoic acid requires 0.1 C.C. of the alkali solution for neutralisation ; allowing for this correction, the quantity of benzoic acid present is found from the equation : x= 0.03486 (n - 0.1) grm., where n= C.C.of Fa alkali solution used. In fats, etc. : 50 grms. of the fatty food, such as butter or margarine, are melted in a beaker, dissolved in benzene, the solution is washed into a separating funnel with ether (any insoluble portion may be left in the beaker), and shaken with 20 C.C. of warm potassium carbonate solution after the addition of phenolphthalein ; if the red coloration disappears, more of the potassium carbonate solution must be added.The aqueous layer is now drawn off into the beaker, and the fatty layer is washed several times with warm water. The united extracts are then treated with 20 C.C. of calcium chloride solution, evaporated until all odour of benzene has disappeared, the solution next transferred to a 200 C.C.flask, and the process continued as described under milk. The amount of benzoic acid present is calculated from the equation : x= 27.88 (n - p ) mgrms., where p is the number of C.C. of & alkali solution used by 100 grms. of different fats free from benzoic acid. For lard the correction is 0.05 c.c., for butter 0.50 c.c., and for palm oil 0.30 C.C.w. P. s. Note.-An almost similar method has been previously described by Revis (ANALYST, 1912, 37, 346) for the detection of benzoic acid in milk. He also points out that in the case of fats ‘‘ violent shaking I’ with the alkali is necessary for the removal of the benzoic acid.-ED. Caffeine in Java Tea. J. J. B. Deuss, (Chem. WeekbZad, 1915, 12, 938-943.) -The amount of caffeine in twenty-nine samples of Java tea, was estimated by van Romburgh and Nanninga’s method of extraction with chloroform, the extracted alkaloid being weighed and the result controlled by the refractometer reading of the aqueous caffeine solution. The proportion ranged from 2.68 to 5.58 per cent., and the conclusion is drawn that 3 per cent.of caffeine may be taken as the minimum pro- portion of caffeine in good Java tea.In the case of certain samples of good quality with low caffeine content (e.g., 2.85 per cent. in Java orange pekoe) the leaves came from Chinese plants or hybrids. C. A. M. Detection of Citric Aeid in Wine. E. Baier and P. W. Neumann. (Zeitsch. Untersuch. Nahr. Geizussm., 1915, 29, 410-411 ; through C‘hcm.Zentralbl., 1915, ii., 205-206).-The test depends on the formation of the mercury salt of acetone- dicarboxylic acid. Twenty-five C.C. of the wine are neutralised, acidified with acetic acid, then shaken for ten minutes with the addition of 3 grms. of blood-charcoal (free from calcium carbonate), and filtered. To 10 C.C. of the filtrate is added 1 C.C. of DenigBs’ reagent (5 grms.of mercuric oxide dissolved in 20 C.C. of sulphuric acid and 100 C.C. of water), the mixture is boiled, cooled, filtered if any precipitate has formed, and 1 per cent. potassium permanganate is added drop by drop until manganese dioxide begins to precipitate; the precipitate is then dissolved by the addition of hydrogen peroxide. The solution exliibits a white turbidity, or a precipitate forms,FOOD AND DRUGS ANALYSIS 505 i Cat0 oil, I if the wine contained citric acid.The precipitate may be identified as the acetone- dicarboxylic acid salt by collecting it on a filter, washing it with cold water, dissolving it in 3 C.C. of 10 per cent. sodium chloride solution, and adding a few drops of very dilute ferric chloride solution. A raspberry-red coloration, due to the formation of the corresponding iron salt, is obtained.w. P. s. Pili Oil. Long Nuts. I Short Nuts. C ~ l ~ ~ m ~ a n g - Oil. Increase in the Total Solids of Milk after Separation of the Cream. (Ann. Chim. anal., 1915, 20, 209-212.)-The increase in the total solids G. Tellera. of milk after separation of the cream may be calculated by means of the formula- r‘ 1 0 0 - 9 - loo’ where r represents the dry total solids-not-fat of the original milk, g the fat removed with the cream, and r’ the dry fat-free solids of the soparated milk. As a rule, the actual result agrees with the calculated amount within 0.25 per cent.in the case of samples of milk taken from the farm, but with commercial samples the increase varies in an irregular manner.If a commercial separated milk gives a dry residue decidedly in excess of the maximum found by Formenti (10.17 per cent.), it must be regarded as of abnormal composition. C. A. N. Sp. gr. a t 15O-C. ... ... ... ,, 30’ C. ... ... ... Butyro-refractometer reading at Iodine value (Hanvus) ... ... Reichert-Neissl value . . . ... Acid value ... ... ... ... Saponification value . .. ... ... ... 30’ C. ... ... I 0.9203 0.9188 60-61 80.78 7 *34 7-06 192.02 63-64 76.14 2.10 0.30 212.01 1 0-9067 54-54.2 61-25 3.3 2.70 192.6 - 0.9067 54-54.2 59.61 2.2 3.13 186.8 The oils of Aleurites moluccana (“lumbang bat0 oil ”) and A. trisperma (“ lumbang brtnuoalag oil ”) have excellent drying properties. They may be distinguished from506 ABSTRACTS OF CHEMICAL PAPERS each other by the fact that the former is soluble in four parts and the letter in its own volume of absolute alcohol. C.A. M. Detection of Phytosterol in Animal Fats by Bomsr's Method, using Digitonin to precipitate the Phytosterol and Cholesterol. B. Kuhn, F. Bengen, and J. Werwerinke. (Zeitsch. Umters. Nahr. Genussm., 1915,29, 331-329 ; through Chem. Zentr., 1915, ii., 50-51).-The separation of the phytosterol and cholesterol from the fat by precipitation with digitonin (cf.Windhaus, ANALYST, 1910,35, 256 ; Klostermann, ibid., 1914, 39, 32) may be carried out rapidly by adopt- ing the following procedure : The mixed fatty acids obtained from 50 grms. of the fat are melted and treated with digitonin solution ; after standing for one hour at 70" C., the mixture is diluted with 20 C.C.of chloroform, the precipitate collected on a filter, washed with chloroform, then with ether, and dried for ten minutes at 100" C. Ths precipitate is then separated from the filter, heated with acetic anhydride, the hot solution mixed with four times its volume of 50 per cent. alcohol, cooled, the pre- cipitate collected, washed with 50 p3r cent. alcohol, and then recrystallised from alcohol in the usual way. In the case of animal fats, almost pure cholesteryl acetate is obtained after the first crystallisation ; should the fat contain vegetable oils, the presence of these is generally indicated at this stage.w. P. s. Determination of Volatile Esters in Citrus Oils and Extracts. A. R. Albright and C. 0. Young. (J. Anter. Chem.SOC., 1915, 37, 2382-2387).--In essential oils containing aldehydes the condensation of the aldehydes with semi- carbazide is recommended as a general procedure preliminary to the determination of the saponification value by alkali. The semicarbazones are not hydrolysed during the saponification of the esters, and the resinification of the aldehydes is prevented. The procedure recommended in the case of lemon oils is as follows : The terpene fraction is first removed from 100 grms.of the oil by distillation under diminished pressure (2-5 MM.), in a three-bulb Ladenburg flask, at a rate of 18 to 20 drops per minute, and distillation is continued until tho limonene ceases to come over. The residual oil is then distilled with a current of steam until the volume of distillate amounts to 200 C.C.This operation is regulated so as to last for at least thirty to forty-five minutes, and the volume of liquid in the flask is kept as nearly as possible constant by heating with a flame. The proportion of aldehydes having been determined in a previous operation, the calculated quantity of semicarbazide hydrochloride in the form of a concentrated solution is added with an equivalent amount of crystalline sodium acetate.When an insufficient amount is used the end-point is not sharp. One hundred C.C. of 95 per cent. alcohol are added, the mixture is shaken and allowed to stand for ten to fifteen minutes. Citral semicarbazone may separate. The solution is then made neutral to phenolphthalein, 50 C.C. of $ alcoholic potassium hydroxide are added, and the mixture is boiled under a reflux condenser for two hours. I t is cooled rapidly and the excess of alkali titrated with $ hydrochloric acid.A large amount of phenolphthalein must be used. I n the case OE lemon extracts, 400 grms. of the sample are distilled from an ordinary flask until the volume is reduced to 50-75 C.C.BACTERIOLOGICAL, PHYSIOLOGICAL, ETC.507 Steam is then passed through until no more volatile oil comes over. The combined distillates are treated in the same manner as the steam-distillate from lemon oils, the amount of semicarbszide hydrochloride being calculated st the rate of 0.75 grm. per grm. of citral. The distillation with steam before saponification is necessary because lemon oils contain a non-volatile residue of resinous matter, which itself possesses a, considerable saponification value, and which cannot be credited &S linalyl or geranyl ester. Experiments made on the sapmification of pure linalyl acetate, under the conditions described above, showed that the saponification equiva- lent only corresponded to 78.4 per cent. of the actual quantiby, whereas saponification under optimum conditions should come to an equilibrium at 85.5 per cent. There is therefore a loss of about 7 per cent. in carrying through the operations. The per- centage of ester calculated from the saponification value should be multiplied by the empirical factor 1.28. J. F. B.

ISSN:0003-2654    

DOI:10.1039/AN9154000503

出版商:RSC    

年代:1915

数据来源: RSC

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BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 507 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Digestive Activity and Composition of Different Fractions of the Pancreas.-I. J. H. Long, M. Hull, and H. V. Atkinson. (J. Amer. Chem. SOC., 1915, 37, 2427-2430.)-Preparations of minced pancreatic tissue were treated in a large laboratory centrifuge, having eight tubes of about 75 C.C. capacity each, and rotating up to 3,500 revolutions per minute.Generally only four of the tubes were charged with the finely minced mass, and rotated for forty-five minutes at a rate of 3,000 revolutions per minute. The mas9 gradually separated into three layers : at the bottom a mass of protein substance more compact than the original material; above this a distinct liquid layer nearly d e a r ; at the top a layer con- sisting largely of fat, with some protein and water.The proportions varied according to conditions; generally the lower layer amounted to 50 per cent. or more; in some cases the liquid and top layers were about 25 per cent. each. The three fractions have been examined separately in the case of pancreatic tissues from the hog, ox, and sheep, and the localisation of phosphorus, nitrogen, amylase, and trypsin, has been studied.The percentage of phosphorus in the fat was in all cases low, and the analyses seemed to indicate a, uniform composition of the fat in all the layers ; it would appear that the lipoid fraction cannot be more than 7 or 8 per cent. of the fat in any case. The amylase was located chiefly in the liquid fraction; it was only present in any considerable amount in the pancreas of the hog.The tryptic power was in all cases low, but the greatest activity was always found in the bottom layer, and the lowest activity in the liquid fraction. The liquid portions showed a slight acid reaction, substantially the same in all cases. J. F. B. Nephelometric Estimation of Purine Bases, including Uric Acid, in Urine and Blood.S. S. Graves and P. A. Kober. ( J . Amer. Chem. SOC., 1915, 37, 2430-2447.)-Salkomski’s reagent for purine bases has been modified to meet nephelometric conditions, and will precipitate santhine, hypoxanthine, guanine, adenine, and uric acid quantitatively in solutions containing as little as 0.0002 per cent. concentration. The reagent, as modified, consists of : 50 C.C.of ammoniacal silver508 ABSTRACTS OF CHEMICAL PAPERS nitrate solution (26.0 grms. AgNO, per litre, with sufficient ammonium hydroxide- e.g., 26-27 C.C. of sp. gr. 0.90, to prevent the separation of silver oxide); 8 C.C. of ammonium chloride solution (16.5 grms. NH,CI. per 100 c.c.) ; sufficient ammonia (usually about 9 c.c.) to redissolve any silver chloride formed ; an excess of ammonium hydroxide equal to 5 C.C.of sp. gr. 0.90 ; and lastly, water to make up 100 C.C. This reagent, after filtration, will keep indefinitely in stoppered bottles. In order to preserve the precipitates in perfect- suspension and prevent agglutination before t h s nephelometric readings can be taken, the use of a protective colloid has been adopted ; egg albumin is employed for this purpose, and certain optimum conditions for its use are prescribed.The reagent precipitates uric acid, together with the purine bases, and the uric acid may be eliminated, before precipitation, by oxidation with manganese dioxide prepared from potassium permanganate by the action of alcohol. Acting in a slightly alkaline medium the separation of the uric acid by this means is perfect, and takes place in three to four minutes, without any actiorP on the purine bases.The solution containing the mixture of uric acid and bases is neutralised, and 10 c.c., containing about 0*001 grm. of the substance, are treated with 0-1 C.C. of 6 per cent. ammonium hydroxide (1 part of 0.90 ammonia to 3 of water) ; 1 C.C. of a suspension of manganese dioxide is then added.This is made from 25 grms. of potassium permanganate in 500 c.c., washed on a filter, and sus- pended in 500 C.C. of water. After shaking for three to four minutes, the solution of purine bases free from uric acid is filtered; if necessary, 1 C.C. of a 4 per cent. solution of sodium acetate may be added to flocculate the manganese. The estima- tion of the uric acid is made by difference between reedings obtained with t h e original solution and one oxidised as described above.I n the analysis of urine it is necessary to make a preliminary separation of the uric acid and purine bases from the large proportion of inorganic salts present. This is effected by Salkowski’s reagent : 5 C.C. of urine and 5 C.C. of the modified reagent are mixed in a graduated tuhe and centrifuged for one to three minutes.The supernatant liquid is poured off, 10 C.C. of hydrochloric acid (1 : 100) are added to the residue, and the tube placed in boiling-water for two to five minutes. The contents are cooled and the volume made up to 15 C.C. The solution is centrifuged and the clear liquid drawn off for analysis. Uric acid is used as a standard cloud for both determinations.I n the estimation of the purine bases by oxidation of the uric acid, the residual traces of silver must be removed. This is effected by employing a solution of lithium car- bonate saturated with sulphuretted hydrogen to make the medium alkaline before oxidation. The silver sulphide is filtered off with the manganese, and it is noted that the manganese also removes the whole of the excess of alkali sulphide.In thO examination of blood, 5 volumes of a 3 per cent. solution of sulphosalicylic acid is an excellent reagent for removing all coagulable protein ; 5 volumes of Greenwald’s reagent (5 per cent.) is equally efficient, and has the advantage of not giving a yellow colour with ammonia. J. F. B. Use of P-Napthalenesulphonic Chloride for the Recognition of Partial Hydrolysis of Flesh Protein.w. Lob. (Clzem. Zeit., 1915, 39, 369-37O0)-This reagent, introduced by Bergell (cf. Zeitsch. physiol. Chem., 1914, 89, 465), is veryORGANIC ANALYSIS 509 useful for detecting the degree of hydrolysis which has taken place in flesh and in meat extracts, and may be used to ascertain the freshness of meat, etc. An extract prepared from the fresh autolysed flesh or meat extract is treated with sodium chloride and acetic acid, the mixture heated, filtered, and the reagent ie added to the filtrate. The precipitate is then collected, dissolved in sodium hydroxide solution, and the nitrogen estimated in an aliquot portion of the solution by Kjeldtlhl’s method. About 0.04 grm. of nitrogen is obtained from 250 grms. of fresh flesh, and the quantity of nitrogen thus obtained increases as the flesh hydrolyses with age. W. P. S.

ISSN:0003-2654    

DOI:10.1039/AN9154000507

出版商:RSC    

年代:1915

数据来源: RSC

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ORGANIC ANALYSIS 509 ORGANIC ANALYSIS. Detection of Acetone by Frommer’s Test. N. 0. Engfeldt. ( B e d . klin. Woch., 1915, 52,458-459 ; through Chem. ZentraZbl., 1915, ii., lOO.)--Frommer’s test depends on the formation of a red-coloured compound when acetone is condensed with salicylaldehyde in the presence of alkali hydroxide. To detect acetone in urine, 10 C.C. of the latter are treated with 1 grm.of solid potassium hydroxide and, without waiting for the latter to dissolve, 10 drops of 10 per cent. salicylaldehyde solution (in alcohol) are added, and the mixture is heated to 70’ C. Should acetone be present, a purple-red zone develops at the junction of the two liquids; 0.05 mgrm. of acetone in 10 C.C. of solution may be detected in this way. The author finds that the reaction may be made more sensitive and capable of detecting 0001 mgrm.of acetone per 10 c.c., by mixing 10 C.C. of the urine distillate with 5 grms. of solid potassium hydroxide and 5 drops of concentrated salicylaldehyde solution in a test-tube, placing the latter in a water bath at 50” C., and heating the water gradually to boiling. As the potassium hydroxide dissolves, a crystalline mass is formed which is coloured bright-red, if acetone is present.Acetoacetic acid and hydroxybutyric acid also yield red compounds with the teat, but formaldehyde, wetaldehyde, formic acid, lactic acid, phenols, and alcohol do not interfere. w. P. s. Acid Potassium and Acid Sodium Phthalates as Standards in Acidimc- try and Alkalimetry. W. S. Hendrixson. (J.Amer. Chew. Soc., 1915, 37, 2352-2359.)-The use of the acid phthalates as standards for volumetric solutions was advocated by Dodge (ANALYST, 1915, 171) on account of the ease with which they are prepared in a stable, pure, and anhydrous form. The author has made a comparative investigation of vtqrioup methods of stsndardisation, using all pre- cautions, by means of weight-burettes, to secure the highest degree of accuracy in measurement.A standard solution of hydrochloric acid was thus prepared, based on the distillation of an acid of constant composition by the method of Hulett and Bonner (ANALYST, 1909, 34, 239). Titrations were made against a solution of pure sodium hydroxide in a current of air free from carbon dioxide in presence of phenol- phthalein, the alkali being run into the acid. All results were obtained in terms of weight, being calculated in terms of C.C.from determinations of specific gravity. The hydrochloric acid solution, prepared from the acid of constant boiling-point, was c a h l a t e d to contain 0.0036470 grm. per 1 C.C. Standardised gravimetrically as510 ABSTRACTS OF CHEMICAL PAPERS silver chloride, it showed 0.0036497 grm.Standardised by titration, it showed against benzoic acid (two preparations) 0*0036510 and 0.0036497 grm. ; against acid potassium phthalate 0.0036495 and 0.0036484 grm. ; against acid sodium phthalate 000036494 grm. Average of seven standardisations, 0.0036492 grm. Hence it follows that either of the phthalates may be used with a greater accuracy than is imposed by the limitations of the best volumetric apparatus.Acid potassium phthalate crystallises readily from water in the anhydrous form ; it is prepared by treating pure sublimed phthalic anhydride with slightly more than the calculated quantity of pure potassium carbonate, and recrystallising five times from hot water. The salt is dried in the oven for several hours, and its constancy in weight confirmed.Acid sodium phthalate is prepared in an analogous manner; it crystallises with ,tH,O, but is completely dehydrated without decomposition on heating at 120' C. to constant weight. J. F. B. New Colour Reaction for Papaverine. L. E. Warren. (J. Amr. Chem. SOC., 1915, 37, 2402-2406.)-By treating papaverine ferricyanide with Marquis's reagent (sulphuric acid containing a little formaldehyde), a blue colour is produced, which passes through violet and green stages to a dirty brownish-yellow. Sub- &antially the same reaction is observed by treating a mixture of the alkaloid and potassium ferricyanide with Marquis's reagent, but in this case the initial tint is greenish-blue.Many other oxidising reagents may be used instead of the ferri- cyanide, the shades of colour produced varying with the reagent employed.The reaction is best observed by intimately mixing a very small quantity of an oxidising agent, such as cerium oxide, phosphomolybdic acid, or potassium permanganate, with a very small quantity of papaverine, and stirring the mixture with a few drops of sulphuric acid containing a little formaldehyde. Of thirty-nine alkaloids tested, only one (an alkaloid from sanguinaria) gave colours in any way resembling those produced with papaverine.By using selenious acid as the oxidising agent, the sanguinaria alkaloid may be differentiated, giving an initial reaction of intense purplish-violet instead of a fugitive greenish-blue changing to deep blue, as with papaverine. J. F. B.Estimation of Total Sulphur in Rubber Products. A. Hutin. ( A m Chim. anal., 1915, 20, 214-216.)-From 1 to 2 grms. of the sample is treated with 30 c.c.of fuming nitric acid, added in successive portions of 2 to 3 c.c., and the mixture evaporated to a syrup on the water bath, and treated drop by drop with 2 to 3 C.C. pure sodium hydroxide solution. The alkaline liquid is then mixed with sufficient calcined magnesia to make a thick paste, evaporated to dryness at 140' C., and cautiously heated so as to avoid ignition of the mass. The friable residue is heated and stirred with water on the water bath, aud the extract and washings (about, 300 C.C. for 1 grm. of material) filtered, concentrated to 100 c.c., and acidified with hydrochloric acid, the carbon dioxide expelled, and the sulphuric acid precipitated with barium chloride. The final solution ought to be colourless, any coIoration indicating that the ignition was incomplete. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9154000509

出版商:RSC    

年代:1915

数据来源: RSC

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INORGANIC ANALYSIS 511 INORGANIC ANALYSIS. Two Methods of Separation of the Metals of the Alkaline-Earth Group. A. G. Paterson. (J. *4mer. Chsm. Soc., 1915, 37, 2346-2352.bThe methods described for separations in qualitative analysis are based on the fact that, in the preeipitation of a mixture, the separation of the least soluble component is always completed first, and that if a relatively insoluble precipitate be treated with a reagent capable of forming a still less soluble compound by double decomposition, such exchange takes place completely. Method I.-A solution containing a mixture of salts of the alkaline-earth methods is treated with an excess of a mixture of ammonium carbonate and sulphate.Tho barium is precipitated as sulphate, and the strontium and calcium as carbonates.The liquid is brought to the boil and allowed to stand for twenty to thirty minutes with occasional stirring, in order to complete the reaction. Some magnesium may be precipitated. The mixture is filtered and the precipitate washed; the latter is removed from the filter with a minimum quantity of water, and boiled with 1.5 vols. of 1 per cent. acetic acid. The undissolved barium sulphate is filtered off, and the filtrate made slightly alkaline with ammonia, then treated with an excess of ammonium carbonate and oxalate together. The liquid is again brought to the boil, and allowed to stand for twenty to thirty minutes with stirring.This precipitate consists of calcium oxalate and strontium carbonate. It is filtered off, washed, and agitated vigorously with 1 per cent.cold acetic acid; the calcium oxalate remains, and thO strontium earbonate is dissolved. A small amount of magnesium may pass into solution as magnesium oxalate. The essential points for a, clean separation are the complete washing of the precipitates, and the digestion for about thirty minutes before filtering. Method I1.-This separation depends on the fact that the solubility of lead sulphate stands between that of barium sulphate and strontium sulphate. A portion of the mixture is first tested for barium by potassium chromate and the flame.The remainder is treated with ammonium chloride and sulphate, the mixture being brought to the boil. The precipitate consists of barium and strontium sulphates, with, perhaps, a little calcium sulphate ; most of the calcium remains in the filtrate.The precipitate is washed, transferred to a beaker, and digested with an excess of a normal solution of lead acetate ; the mixture is warmed for a few minutes, but must not be boiled ; it is then filtered. The whole of the barium sulphate remains on the filter with lead sulphate ; the strontium sulphate is completely decomposed.The sohtion contains strontium, calcium, and lead acetates. The lead is removed by sulphilretted hydrogen, and the strontium and calcium separated by Method I. It is noted that a separation of cadmium sulphide from copper sulphide may be effected on the same principle by digestion with lead nitrate, the lead displacing the cadmium. J. 2’. 13. Reagent for the Detection and Colorimetric Estimation of Aluminium.F. W. Atack. (J. SOC. Chem. Ind., 1915,34,936-937.)-The reagent used is a 0.1 per cent. aqueous solution of alizarin (red) S, the sodium salt of alizarinmonosulphonic512 ABSTRACTS OF CHEMICAL PAPERS acid. The solution is filtered before use, and is pale yellow in the presence of acids, but gives a purple coloration with alkalies.Detection of AZurrtinium.-To about 5 C.C. of the solution under examination is added 1 C.C. of the reagent and then ammonia until the solution is alkaline, as shown by the purple colour. The solution is boiled, cooled, and acidified with acetic acid, when a red coloration or precipitate remaining is conclusive evidence of the presence of aluminium. The red calcium, strontium, barium, zinc, and magnesium salts, and salts of other metals later than Group II., are readily soluble in acetic acid, and do not interfere with the aluminium reaction.The precipitate obtained with cobalt is not dissolved by acetic acid if a large quantity -of ammonia has been used; should cobalt be present (for detection of cobalt, cf. Atack, ANALYST, 1915, 414), an excess of ammonia must be avoided.The reaction with aluminium is not affected by the presence of phosphates or of chromium, and only by comparatively large amounts of iron. The test will detect the presence of 1 part of aluminium in 10 million parts of water. Colorimetric Estimation of AZu- milzizm.-From 5 to 20 C.C. of the solution (containing from 0-005 to 0.05 mgrm. of aluminium) are acidified with hydrochloric acid, 10 C.C.of glycerol and 5 C.C. of the reagent are added, the solution is diluted with water to 40 c.c., and then rendered slightly ammoniacal. After standing for five minutes, the solution is acidified with acetic acid, the latter being added until no further change in the coloration occurs. The mixture is then diluted to 50 C.C. and compared with a standard. Iron and chromium may be prevented from interfering by the addition of a citrate to the acidified solution before adding the ammonia.w. P. s. Detection of Free Carbon Dioxide in Water. L. W. Winkler. (Zeitsch. angew. Ckem., 1915, 28, 376.)-The presence of free carbon dioxide in moderately hard waters may be detected by adding two drops of 10 per cent. copper sulphate solution to 100 C.C. of the water; if free carbon dioxide is absent, the solution becomes turbid, but if the gas is present the solution remains.clear.If the clear solution is shaken with air, the carbon dioxide is expelled and a turbidity is produced ; if a turbidity does not develop under these conditions, the water contains a non- volatile acid (humic acid) or a large quantity of organic matter.The copper sulphate test fails, however, in the case of soft waters, but free carbon dioxide may be detected in these waters by adding ten drops of 1 per cent. alizarin solution (in alcohol) to 100 C.C. of the water. A blue-red coloration indicates the absence of free carbon dioxide ; a copper-red coloration, a small quantity ; a, reddish-yellow coloration, a moderate quantity; and a, yellow coloration, a large quantity of the gas.w. P. s. Estimation of Hydrogen in Gas Mixtures by Catalytic Absorption. E. Bosshard and E. Fischli. (Zeitsch. angew. Chem., 1915,28,365-366).-The hydro- gen is absorbed by a mixture of sodium oleate and metallic nickel ; the nickel is pre- pared by reducing nickel oxide in hydrogen at 340' C. The gas under examination should be freed previously from carbon dioxide, heavy hydrocarbons, oxygen (by ammoniacal cuprous chloride solution, and not by means of phosphorus), and carbon monoxide ; it is then passed into the absorption pipette, which contains concentratedINORGANIC ANALYSIS 513 sodium oleate solution mixed with 3 per cent.of its weight of reduced nickel, shaken with this mixture for three minutes, then passed into a second pipette containing a similar mixture, and, after the addition of 1 C.C. of alcohol to break down the foam, the residual gas is passed back in the measuring burette.The hydrogen is removed com- pletely from the gas by this treatment, whilst any nitrogen and methane which may be present are not absorbed. The results obtained for hydrogen agree well with those found by the ordinary explosion method.w. P. s. Composition and Analysis of Lime-Sulphur Liquors. J. Bodnar (Chem. .&it., 1915, 39, 715-716.)-The lime sulphur solutions employed as insecti- cides in agriculture, and prepared by boiling together water, lime, and sulphur, contain mainly calcium polysulphides and calcium thiosulphate with a small quantity of calcium sulphate; it is very improbable that calcium sulphite is present, since in aqueous solution this salt reacts with polysulphides and yields thiosulphate.Analyses of different lime-sulphur liquors showed that they contain per 100 C.C. : Sulphur as thiosulphate, 2.84 to 3-50 grms. ; as polysulphides, 10.20 to 16.29 grms. ; as sulphide, 2.84 to 3.61 grms. ; as sulphate, 0.1 grm.Concentrated lime-sulphur liquors are also on the market; these contain sulphur as polysulphides, 31-26 to 33-80 grms., and as thiosulphate, 1.85 to 1.92 grms. per 100 C.C. The author proposes a method for the estimation of the polysulphide, sulphide, and thiosulphate sulphur in lime-sulphur liquors which depends on the reactions shown in the following equations : (1) CaS, + 2AgN0, = Ag2S + S,.+ Ca(NO,), and CaS, + SAgNO, = Ag2S + s4 + Ca(NO& ; (2) CaS,O, + 2AgNO,= Ca(NO,), + Ag,S,O, and Ag2S,0, + H,O =Ag2S + H,so4. Ten C.C.of the sample are diluted to 100 c.c., and 10 C.C. of the solution are added to a, mixture of 50 C.C. of & silver nitrate solution and 20 C.C. of water ; after being shaken, the mixture is diluted to 100 c.c., and filtered. The filtrate is collected in 8 dry flask, which is then removed, and the precipitate washed with warm water, dried at 100" C., and weighed.Fifty C.C. of the filtrate are now mixed with 30 C.C. of ;v sodium chloride solution and 15 C.C. of FG sodium hydroxide solution, phenolphtba- lein is added, and the mixture titrated with TG sulphuric acid ; potassium chromate solution is then added, and the mixture titrated with Tv silver nitrate solution.The quantities of the various forms of sulphur present are then calculated from the following formulq the results expressing grms. per 100 C.C. : Thiosulphate sulphur, t , = 100 x 4(a - b) x 0.0016035 ; sulphide sulphur, s, = 100 x 2(25 + c - d ) x 0.0016035, where a = C.C. of =& sodium hydroxide solution, b= C.C.of & sulphuric acid, c = C.C. of & silver nitrate solution, and d = C.C. of & sodium chloride solution used ; poly- sulphide sulphur, p , = lOOe - 7*727(s + t/2), where e = weight of the precipitate. Sodium chloride is sometimes used in the preparation of the liquor, and in such cases its quantity must be estimated separately, and the corresponding quantity of silver chloride subtracted from the weight p .To estimate the sodium chloride, 20 C.C. of the 10 per cent. solution of the sample are rendered ammoniacal, hydrogen peroxide is added, the mixture boiled until the excess of hydrogen peroxide has been decom-514 ABSTRACTS OF CHEMICAL PAPERS posed and all free ammonia expelled, and the solution then titrated with =& silver nitrate solution.w. P. s. Nephelometric Estimation of Phosphorus. P. A. Kober and G. Egerer. (J. Amer. Chem. SOC., 1915, 37, 2373-2381.)-By a modification of the reagent of Pouget and Chouchak, a very sensitive test for phosphates, suitable for nephelo- metric determinations, has been obtained. The reaction is comparable in point of sensitiveness with Nessler's reaction, 1 mgrm. of phosphorus in 2 litres giving a very marked suspension, while the extreme limit of sensitiveness is 1 part in 20 millions.The reaction presumably depends on the formation of a phosphomolybdic acid com- plex of strychnine, and, by substituting hydrochloric acid for the nitric acid originally recommended, the authors have succeeded in preparing a stable and colourless reagent giving quantitative and constant results. The components of the reagent are sodium molybdate, strychnine sulphate, and hydrochloric acid.The sodium molybdate must be prepared from pure molybdic acid free from ammonia ; 35.5 grms. of this are boiled for about one hour with 50 C.C. of sodium hydroxide solution con- taining 400 grms. of 96 per cent. caustic soda per litre. The liquid is diluted to 84 c.c., and shaken until practically all the sodium molybdate is dissolved.A little talc powder is added, and the solution filtered and evaporated to dryness; the residue is extracted by grinding with 40 C.C. of 95 per cent. alcohol, and washed on a filter with several portions of 20 C.C. of alcohol, I t is dried at about 50" C. The strychnine solution is made by dissolving 2 grrns.of pure strychnine sulphate in hot water and making up to 100 C.C. when cold. Fifty C.C. of strong hydrochloric acid are diluted to 100 c.c., and 5 C.C. of this are again diluted to 100 C.C. and adjusted after titration; 24 C.C. of the acid should be equivalent to 30 C.C. of alkali. To prepare the reagent, 1.5 grms. of the pure sodium molybdate are dissolved in 2.5 C.C.of water, and 10 C.C. of the standard hydrochloric acid added while shaking ; the precipitate first formed should redissolve ; 1 C.C. of strychnine solution is then added, and the solution allowed to stand over night. I t must be filtered through an acid-extracted paper-e.g., C. S. and S., No. 575 or 589; ordinary filter- paper produces a cloudiness. A standard solution of potassium dihydrogen phos- phate is made up with 0-1 grm.of the salt in 2 litres of water, and 100 C.C. of this diluted to 1 litre serves as the standard for the nephelometer. For the precipita- tion, 5 C.C. of the reagent are added to a mixture of 30 C.C. of water with 5 C.C. of hydrochloric acid, and the solution shaken thoroughly; 10 C.C. of phosphate solution are then added slowly from a pipette, the solutions are mixed by gently rotating the flask, and the mixture is ready for observation after standing for three minutes. A number of readings have been made with the standard solution at various dilutions and curves plotted ; the use of the instrument and the relations exist- ing between the concentrations of turbidity and the readings are discussed.The completeness of a reaction may be tested by precipitating a standard solution and then diluting an aliquot portion of it, comparing it with the standard similarly diluted before precipitation.The divergence between the constants calculated from the two series of readings indicates the error due to incompleteness of reaction in dilute unknown solutions. In the present case a very fair agreement was found, indicating satisfactory conditions of precipitation for quantitative work.J. F. B.INORGANIC ANALYSIS 515 Estimation of Spelter Coating on Sheets and Wire. J. A. Aupperle. (Chem. Engineer, 1915, 22, 127-128.)-1t is suggested that the weight of the coating upon both wire and galvanised sheets should be expressed in ounces per square foot, and that the lengths of wire should be such that the area of the coated surface is equal to 5.079 Rquare inches.The samples of the sheet should also have the same area (2;t inches by 2$ inches), so as to obtain the final result without calculation. In dissolving the zinc, a, small amount of antimony chloride is added to the acid with the object of forming a thin film over the base of iron or steel and preventing its solution.Sheets.-Five samples (24 inches by 2a inches) are weighed together and immersed separatelyfor one minute in 100 C.C. of hydrochloric acid (sp. gr. 1-20), to which has been added 5 C.C. of antimony chloride solution, made by dissolving 20 grms. of antimony trioxide in 1,000 C.C. of hydrochloric acid (sp. gr. 1.20). The pieces are then washed and scrubbed under running water, dried with a cloth, and left for a few seconds in a warm place.The loss in weight of the five samples divided by 5 gives the weight of coating removed. Each grm. corresponds to 1 ounce of coating per square foot. Wire.-A small section of the sample is stripped with acid as described, and the diameter of the black wire measured to ascertain the length of wire required for the test. This may be found by reference to the subjoined table. The wire used in the estimation is cleaned with carbon tetrachloride, and treated in a tall glass cylinder with hydrochloric acid (sp. gr. 1-20> containing 2 to 3 C.C. of antimony chloride solution of the same strength as used on the sheets. After one minute’s immersion the wire is removed, scrubbed, dried, and weighed, as described above. For direct comparison with the weight of coating on galvanised sheets the loss in weight should be doubled, the sheets being coated on each side. Lengths of Wire to give Grms. of Coating Equivalent to Ouncesper Squa,re Foot. Gauge Number. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Diameter : Inch 0.340 0.300 0.284 0.259 0-238 0.220 0.203 0.1 80 0.165 0.148 0.134 0.120 0.1 09 0.095 0.083 0.072 0.065 0.058 0.049 Length for Test. Om’. 12.1 13.7 14-5 15.9 17.3 18.7 20.2 22.8 24.9 27.7 30.6 34.2 37.7 43.2 49.5 57.0 63.2 70.8 83.8 C . A. M.

ISSN:0003-2654    

DOI:10.1039/AN9154000511

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年代:1915

数据来源: RSC

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516 ABSTRACTS OF CHEMICAL PAPERS APPARATUS, ETC. Application of Cryoscopy in Chemical Analysis. M. Drapier. (Compt. Tend., 1915, 161, 461-463.)-1t is pointed out that cryoscopic methods may often be employed for the estimation of a, component of a mixture in cases where chemical methods fail and other physical methods are not applicable on account of close similarity of constants. Case I.-A binary mixture of two bodies, A and B, such as might be isolated in fractional distillation where the boiling-points lie near together.Let A, in the pure form, serve as the cryoscopic solvent, then a solution of p grms. of the mixture in P grms. of pure solvent causes a depression in freezing-point proportional to the concentration of B in the mixture. This may be found by determining the depres- sion caused by dissolving p grms.of pure B in P grms. of A . Generally the fact that the weight P is increased by the weight of A in the mixture may be neglected ; when this is not the case, as when the mixture is poor in By the exact result must The author illustrates two hypothetical examples : be attained by successive approximations. Case II.-It may be necessary to estimate the mixture of A , B, C, etc.The depression caused by R of a solvent foreign to the mixture gives the relation where k is the cryoscopic constant of the solvent, proportion of A in a complex grms. of the mixture in P grms. x, y, x , etc., are the weights of A , B, C, etc., in R grms. of mixture, and M , H', W', etc., the respective molecular weights. Let MI = the mean molecular weight of the components B, C, etc.-that ia, the ratio of the weights of these bodies contained in R grms.of mixture to the number of their molecules ; the above equation then takes the form (1) A = ~ l o o k (-+T-x), x P J I M , The value of Nl may be calculated by making a cryoscopic determination of the mixture, using the pure substance A as the solvent. Then where k' is the cryoscopic constant of the substance A, and A' depression of freezing-point caused by dissolving T grms of the mixture in P grms.of A . Replacing the value of Nl calculated from (2) in equation (l), the expression becomes : P [ N look' 1 ' 100 k x A(P+z) A = . - . _ - -+ _____ whence M.P (UA - kA') k (MA' - look')' X=----..---- If the quantity x is negligible in comparison with P, the expression may be simpli- fied as follows : x= N.P (k'A- k A ) 100 kk' -' J.F. B.APPARATUS, ETC. 517 Reducing Power of Photographic Developers as Measured by their Single Potentials. F. C. FPary and A. N. Nietz. (J. Amer. Chem. SOL, 1915, 37, 2246-2263).-The reducing power of a developer may be expressed in terms of the concentration or partial pressure of the hydrogen produced in a platinised platinum electrode immersed in the developer until equilibrium is attained. This partial pressure may be determined from the difference between the potential (EHJ of a platinised electrode saturated with hydrogen at atmospheric pressure in contact with the developer, and the single potential (Ex) of an ordinary platinised electrode in the developer of the same composition.Then, at 25’ C., E H 2 - Ex= E = 0.05909 log. $, C where C’ is the hydrogen pressure to be measured. Several causes operate against the attainment of equilibrium in the determination of the single potential of the developer solution ; for instance, the influence of residual traces of oxygen in the system, and the slow diffusion of the hydrogen through the liquid into the electrode and into the space above the liquid.There appears also to be a sort of ‘‘ reaction-resistance,” inherent in the reducing agent itself, which in some cases (e.g., hydroquinone) delays equilibrium for several months, although in other cases (e.g., amidol) it is reached within a week. The apparatus was devised so that the developer could be dissolved in vacuo in oxygen-free water, and transferred t o the electrode cells attached to the same apparatus, which had also been evacuated and washed out both with nitrogen gas and with the developer.After filling, the cells were sealed up under vacuum and put aside for observations with the potentio- meter. Determinations of the hydrogen potential were made in a special apparatus containing the developer, through which a current of pure hydrogen gas was passed, while the electrode was suspended above the liquid and a platinum wire connection dipped below its surface ; equilibrium was attained within fifteen minutes.A large number of observations were carried out with typical developers of standard formuls. I n the case of hydroquinone, a developer of low reducing-power, equili- brium was not reached even after three months, but a mixture of hydroquinone and thiourea, which is a very powerful reducing agent, came to equilibrium rapidly at a high value, and subsequently fell to a lower value, at which it attained a second equilibrium.It is assumed that this second stage corresponded with the decompo- sition of all the thiourea present, and that the lower equilibrium represented that due to hydroquinine alone, The following values are given for reducing powers, taking hydroquinone as unity : Metol-hydroquinone, 2.7 ; amidol, 36.0 ; thiourea, 53-3 ; and reasons are given showing that these relative values are probably correct in 8 photographic sense.J. F. B. Thermostat for Moderate and High Temperatures. J.L. Haughton and E. Hanson. (Inst. of MetaZs, pp. 1-7, September, 1915.)-The apparatus first devised is shown in Fig. 1. The tube from the bulb leads, through a three-way tap, A , to the U-tube containing mercury ; another three-way tap, B, serves to connect the other limb of the U-tube with the air or with a second bulb, C, which is kept at a constant518 ABSTRA.CTS OF CHEMICAL PAPERS temperature by being immersed in a Thermos " flask filled with ice.A platinum wire, D, sealed through the wall of the U-tube and prolonged downward inside it, makes permanent contact with the mercury, whilst a similar wire, E, on the other side, at a, point where the tube is constricted, makes contact with the mercury as the latter rises in the limb, the contact being again broken as it, falls. The height of the wire, E, and the amount of mercury in the U-tube are so arranged that the pressure in the furnace bulb is slightly less than atmospheric, so that, should the bulb break, the current would be switched off.The three-way taps, though not necessary, ren- der the adjustment a matter of great ease; immersing the bulb, C, in ice neutralises IR.SPEC I PlCN. i FIG. 2. the effect of changes of room temperature. The mercury switch operates a relay which, through a resistance, cuts in or out a definite amount of the current supplied to the furnace ; the variations in current caused by the relay are just amply large enough to cover the range of accidental variations. The whole apparatus (furnaca, relay, etc.) is run off a 100-volt circuit.A more constant temperature may be obtained by constructing the furnace bulb as shown in Fig. 2. This is built into an electric furnace, the heating wire being wound on to asbestos paper wrapped directly round the bulb, and the inner tube containing the specimen is packed with asbestos in front of and behind the specimen. I t was found that a temperature of 305" C. could be maintained for two days with a variation of about 1". The furnace bulb may be constructed of glass for temperatures up to about 500' C. ; €or higher tem- peratures it should be made of silica,. I t was noticed that when a new bulb was used the temperature wag always inclined to rise for a few weeks, then fell graduallyREVIEW 519 and became steady. There is but little doubt that this effect was caused by the ageing of the glass, a phenomenon identical with the ageing of mercury thermometers. w. P. s. *@*+I+@

ISSN:0003-2654    

DOI:10.1039/AN9154000516

出版商:RSC    

年代:1915

数据来源: RSC

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REVIEW 519 REVIEW. THE BRITISH COAL-TAR INDUSTRY. ITS ORIGIN, DEVELOPMENT, AND DECLINE. Williams and Norgate, London. BY assembling in one volume the more important lectures and addresses delivered in this country on the title-subject, Professor Gardner has rendered a public service which is both timely and notable. Even to chemists, who are generally familiar with the English history of the coal-tar colour industry and its mournful progress of the last forty years, the volume offers unique opportunities of study, presenting, as it does, the valued opinions of our leaders in chemical thought.freed from the burdensome search through decennial indexes which would otherwise be necessary. More important still, however, is the fund of information now accessible to the general public, and which, being largely in the form of discourses, not always addressed to purely chemical bodies, should be attractive to the layman and easily assimilated by him.In fact, the Advisory Council for Scientific and Industrial Research, appointed last July by the Board of Education to administer &25,000 for the assistance of scientific research, might consider the allocation of 6350 to furnishing every Metr;ber of Parliament with a copy, particularly as this sum would be considerably diminished if the presentation were made conditional upon an undertaking to read the book.Not only is Professor Gardner’s idea, a fruitful one, but great wisdom and an admirable sense of proportion have been brought to its execution. There are four contributions from the lamented founder of the industry, beginning with the Cantor Lectures of 1868, which open the book, and concluding with his Hofmann Memorial Lecture; there are five from Professor Meldola, four from Sir Henry Roscoe, and one each from the late Mr.Friswell, Professor A. G. Green, Sir James Dewar, Mr, A. G. Bloxam, who dealt in an illuminating manner with Patent Law in relation to the Dyeing Industry, and Mr.I. Singer, who read the colour barometer in a, breezy and original manner before the Society of Dyers and Colourists in 1910. All these lectures, together with many others to which reference is given, are collected from journals issued prior to 1911, and there follow war addresses from Dr. F. M. Perkin, Sir William Tilden, Dr. Ormandy, Lord Moul ton, Professor Gardner, whose Edited by Professor WALTER M.GARDNER. 1915. Pp. 436. Price 10s. 6d. net.520 REVIEW lucid and broad-minded contribution is modestly abridged, Professor Frankland, Mr. J. W. Gordon discussing Patent Law reform, Professor Meldola, and Professor W. H. Perkin. Were it not that the moral is one of such sinister import, I should be tempted to call the volume a symposium of the British Coal-Tar Industry, and that is perhaps what the Germans, with that sense of humour happily peculiar to themselves, would label it.As this book is one which should be destined to appear in further editions, I would suggest to the editor that these include the speech of Dr. Carl Duisberg at the Perkin, Jubilee Banquet. This brief chapter on 66 Ourselves as Others See Us, by One of the Others,” would give just that touch of suuce tartare for which some digestions crave.Although it is not possible for cold print to depict the penetrating exuberance of the orator, the diagnosis which he made on that occasion is well worthy of wider notice, from more than one point of view. Equally illuminating, although for entirely different reasons, would be a judicious selection of wisdom quoted from the official report of the Aniline Dye Debate, which took place in the House of Commons on February 22, 1915; this, however, would involve much labour, which in these busy days it would be scarcely fair to call upon the editor to undertake. M. 0. FORSTER.

ISSN:0003-2654    

DOI:10.1039/AN915400519b

出版商:RSC    

年代:1915

数据来源: RSC