摘要:

JANUARY. 1913 . Vol . XXXVIII. No . 442 . Aluminium Antimony . Argon . Arsenic . Barium . Bismuth . Boron . Bromine . Cadmium . Casium . Calcium . Carbon . Cerium . Chlorine . Chromium Cobalt . Columbium Dysprosium Erbium . Europium . Fluorine . Gadolinium Gallium . Germanium Glucinum . Gold . Helium . Holmium . Copper . Hydrogen . Indium . Iodine . Iridium . Iron . Krypton . Lanthanum Lead . Lithium . Lutecium . Magnesium Manganese Mercury . THE ANALYST . INTERNATIONAL ATOMIC WEIGHTS. 191 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0=16 . . A1 27.1 . Sb 120.2 . A 39-88 .As 74-96 . Ba 137.37 . Bi 208.0 . B 11.0 . Br 79.92 . Cd 112.40 . Cs 132-81 . Ca 40.07 . c 12.00 . Ce 140.25 . C1 35.46 . Cr 52.0 . Go 58.97 . Cb 93.5 . Cu 63-51 . Dy 162.5 . E r 167.7 . Eu 152.0 . F 19.0 . Gd 157.3 . Ga 69.9 . Ge 72-5 . G1 9.1 . Au 197.2 . He 3.99 . Ho 163.5 . H 1.008 . In 114.8 . I 126.92 . Ir 193-1 . Fe 55-84 . Kr 82-92 . La 139.0 . Pb 207.10 . Li 6-94 . Lu 174.0 . Mn 54.93 Hg 200.6 . Mg 24.32 0=16 . Molybdenum . . Mo 96.0 Neodymium . . Nd 144.3 Neon . . . Ne 20-2 Nickel . . Ni 58.68 Niton (radium emanation) N t 222.4 Nitrogin . . Osmium . . Palladium . Phosphorus . Platinum . . Potassium . Praseodymium . Oxygen . . Radium" . Rhodium . Rubidium Ruthenium Samarium Scandium Selenium .Silicon . Silver . Sodium . Strontium Sulphur . Tantalum Tellurium Terbium . Thallium . Thorium . Thulium . Tin . Titanium . Tungsten Uranium . Vanadium Xenon . . . . . . . . . . . . . . . . . . . . . . . . . I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N os 0 Pd P P t K P r Ra Rh Rb Ru S& sc Se Si Ag Na Sr S T& Te Tb T1 Th Tm Sn Ti W U V Xe 14.01 16-00 31.04 39.10 190.9 106.7 195-2 140.6 226.4 102.9 101.7 150.4 44.1 79.2 28.3 107.88 23-00 87-63 32.07 85 -45 181.5 127.5 159.2 204-0 232.4 168.5 119.0 48.1 184.0 238.5 51.0 130.2 Ytterbium (Neoytterbium) Yb 172.0 Yttrium . . . Yt 89.0 Zinc . . . Zn 65-37 Zirconium . . Zr 90. 2 PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS OBITUARY. WE regret to record the death on December 11 1912 of Mr. H. de Mosenthal, technical secretary to Messrs. Nobel Dynamite Trust Go. Ltd

ISSN:0003-2654    

DOI:10.1039/AN9133800001

出版商:RSC    

年代:1913

数据来源: RSC

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2 PROCEEDINGS OF THE SOCIETY OF PUBLIC ANATJPSTS PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. THE monthly ordinary meeting of the Society was held on Wednesday evening, December 4, in the Chemical Society’s Rooms, Burlington House. The President, MY. L. Archbutt, 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. S.Elliott, A.I.C. ; T. R. Greenough, B.A., A.I.C. ; H. Lowe, M.Sc. ; J. P. Ogilvie ; and J. A. 5. Sutcliffe, A.I.C., were read for the second time; and certificates in favour of Messrs. John Augustus Goodson, F.I.C., Assistant Chemist to the Sudan Govern- ment in the Wellcome Research Laboratory, Gordon College, Khartoum ; John C.White, A.I.C., Tudor Lodge, St. James’s Road, Upper Tooting, Assistant Chemist to Messrs. Price’s Patent Candle Go., Ltd. ; and Frederick William Skevington, 87 and 89, Aldgate, E., assistant to Messrs. G. H. Ogston and Uoore. The following papers were read : ‘‘ The Detection of Adulteration in Linseed Oil,” by G. D. Elsdon, B.Sc., and Herbert Hawley, M.Sc.; “ The Estimation of Citric Acid in the Presence of Certain Other Acids,” by Lionel Gowing-Scopes ; (‘ The Value of the Guaiacum Test for Bloodstains,” by Herbert S. Shrewsbury, F.I.C.; “The Determination of Nitrates and Nitrites in Sewage Effluents,’’ by Arnold Higginson; and “Alcoholysis and the Composition of Cocoanut Oil,” by G. D. Elsdon, B.Sc. The President announced the Council’s nominations of officers and Council for 1913 as follows : President .-L.Archbutt, F. I .C. Past-Presidents (limited by the Society’s Articles of Association to eight in number).-Edward J. Bevan, F.I.C. ; Bernard Dyer, D.Sc., F.I.C. ; Thomas Fairley, F.I.C.; W. W. Fisher, M.A., F.I.C.; Otto Hehner, F.I.C.; R. R. Tatlock, F.I.C.; E. W. Voelcker, A.R.S.M., F.I.C. ; J. Augustus Voelcker, M.A., B.So., Ph.D., F.I.C.Vice-Presidents.-G. Embrey, F.I.C. ; J. T. Hewitt, M.A., D.Sc., Ph.D., F.R.S. ; W. H. Willcox, M.D., B.Sc., M.R.C.P., F.I.C. Hon. Treasurer.-Edward Hinks, B. Sc., F. I.C. Ron. Secretaries.-A. Chaston Chapman, F.I.C. ; P. A. Ellis Richards, F.I.C. Other Members of Council.-R. M. Clark, B. Sc., F.I.C. ; J. Connah, B.Sc., F.I.C. ; J. Evans, F.I.C.; G. T. Holloway, A.R.C.Sc., F.I.C.; G. D. Lander, D.Sc., F.I.C. ; T. Macara, F.I.C. ; G. W. Monier-Williams, M.A., Ph.D., F.I.C. ; C. Revis ; H. Silvester, B.Sc., F.I.C. ; F. Wallis Stoddart, F.I.C. ; A. R. Tankard, F.I.C. ; John White, F.I.C.

ISSN:0003-2654    

DOI:10.1039/AN9133800002

出版商:RSC    

年代:1913

数据来源: RSC

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THE DETECTION OF A.DULTERATION IN LINSEED OIL 3 THE DETECTION OF ADULTERATION IN LINSEED OIL. BY G. D. ELSDON, B.Sc., A.I.C., AND HERBERT HAWLEY, M.Sc., A.I.C. (Read at the Meeting, December 4, 1912.) ONE of us and another, Liverseege and Elsdon (J. Soc. Chem. Ind., 1912, 31, 207) recently described a modified form of the Livazhe test, which was capable of giving quantitative figures for the oxygen absorbed by oils on exposure to the atmosphere.The close relationship existing between the iodine value and the figure thus obtained was pointed out, but we have since found that this is of more importance than at first appeared to be the case. We thought that an indication of the purity of a linseed oil might be obtained by finding the relationship between the oxygen absorbed and the iodine value; but, although this relationship is close, we found that the differences between linseed oil and other oils in this respect were not sufficient to detect small adulterations.The finding of a figure which would have a fixed relationship to the iodine value seemed to promise good results, and it appeared to us that further figures might be obtained by an analysis of the oxidised residue obtained in the above process.For this purpose extraction with ether on quantitative lines naturally suggested itself, the oxidation products of oils being insoluble in this solvent. The difficulty, however, of transferring the hard paste to an extraction thimble, and the readiness with which the finely divided litharge passed through the paper into the flask, complicated this method to such an extent that it was finally discarded in favour of drying on Adams’ coils.2.5 grms. of the oil are accurately weighed out into a small, wide-mouthed flask, and transferred by means of ether (using a, small funnel) to a 25 C.C. graduated flask- those which are used for roughly taking specific gravities serve admirably. The solution is then diluted to the mark with more ether, and the whole thoroughly mixed.Five C.C. of this solution are then transferred by means of a carefully-dried pipette to an Adams’ coil (the fat-free strips made by Schleicher and Schull for the estimation of fat in milk), care being taken that the solution is uniformly distributed over the whole paper. After drying, by whatever method (see below), the strip is rolled up and placed in a Soxhlet fat-extraction apparatus and extracted with ether (sp.gr. 0.720) for three hours. At the end of this time the ether is evaporated, a little absolute alcohol added, and the flask dried in the steam oven for two hours; it is then cooled and weighed. Drying in the Air at Laboratory Temperature.-The first experiments were made using the above process, and allowing the oil-saturated strips to dry in the air of the laboratory for varying lengths of time, the extraction then being carried out as described above.I t will be seen from this table that the drying proceeds rapidly during the first week, then more slowly, and is practically constant after a fortnight, the extract then showing a slight tendency to increase.The method was accordingly abandoned. Some results obtained in this way are giwn in Table I.4 26.0 33.4 100.6 36.8 ELSDON AND HAWLEY : TABLE I. 20.2 20.6 29.8 - 100.8 101.2 29.6 30.0 Oil. Oil. Linseed oil A ... ... 9 , B ... ... Colza oil ... ... A + 20 per cent. colza . . . A + 20 per cent. whale.. . ~ ~ ~ ~ ~~ Linseed oil A ... .. ,, B ... Colza oil ..... Linseed oil A with~20 per cent. colza, . ... Extract per Cent. Iodine Value. (Wijs.) 2 Hours. 4 Hours. 8 Hours. 17 Hours. 41 Hours. - - 194 14.0 13-6 13.2 10.0 9.4 179 19.0 17.6 16-2 13.2 10.4 99 100.6 100.2 - 74-0 40.0 176 21.0 19.0 18.8 14-8 11.0 185 21.2 - - - - 176 1 - Extract per Cent. 1 Week. I 2 Weeks. 1 3 Weeks. The reason for this increase in the extract is not particularly obvious, but it would seem to be intimately connected with the loss in weight which occurs in the above-mentioned Livache process after the maximum gain has been reached.Possibly a portion of the oxygen is loosely combined, and after the maximum quantity has been absorbed some slight decompoaition takes place, substances soluble in ether being formed, and oxygen or some other gas being evolved.Drying in the Water Oven.-Although the figures obtained by drying in the air are fairly concordant, the time required is obviously too long for a laboratory test. Our final modification shortens the process considerably, s t the same time giving concordant results. The oil is distributed on the coils as described above, and these are allowed to dry in the air overnight, the drying being then continued in the steam oven for varying lengths of time.The strips are folded three times, and so arranged on their edges in the oven that the whole of the surface is exposed. The extraction of the dried coils is then carried out in the usual manner, In carrying out this method it is necessary to have a fairly large oven (12 inches cube), and to place the strips at the bottom and well away from the door, the shelves being removed to give plenty of air-space above the coils.Some results obtained by this method are shown in Table 11. The process is as follows : TABLE 11.THE DETECTION OF ADULTERATION IN LINSEED OIL 5 It will be observed that the addition of 20 per cent. of either whale or colza oil to the linseed oil A makes a considerable difference in the extract; but, owing to the variation in the extract8 obtained from different linseed oils, this cannot be made use of as a quantitative test (cf.Table 111.). In Table 111. are given the results of the examination of several pure oils and6 ELSDON AND HAWLEY : known mixtures, together with the iodine values (Wijs), modified Livache figures, and Zeiss butyro-refractometer readings at 25" C.It will be seen from Table 111. that a close relationahip exists between the iodine value and the extract obtained by the method described; this relationship, however, becomes even more marked when the values are plotted as in the diagram. A consideration of the results shows that the point produced by plotting the iodine value of a pure linseed oil against the extract should fall to the left of the dotted line.Now, in the case of many mixtures of the oils the iodine values and the extracts might be quite passable when taken alone, yet, when plotted in this way, the point would fall to the right of the dotted line, and the oil would be shown to 'be suspicious and to require further examination. Thus the linseed mixtures con- taining 20 per cent.respectively of cottonseed, colza, seal, and whale lie well outside the line, so that, although these might be passed as genuine linseed on either the extract or the iodine value alone, yet, when they are considered together, the oils are Been to be obviously adulterated. TABLE 111. ____ Oil. ... ... .. Linseed ... ?, ... .... ... . . I 9 , ...... ... . . I 9 , ... ... ... ... 9 9 ... ... ... ... 19 ... ... ? 9 ... ... ... ... ... ... ... . . . ... 9 , 9 9 ... ... ... ... 9 , ... ... .., ... ... ... Colza ... ... ... Linseed + 20 per cent. colza ... ,, +20 per cent. whale ... ,, + 20 per cent. cottonseed ... . , + 20 per cent. seal.. 1.. Iodine Value (Wijs. ) 192 174 194 179 183 188 183 180 176 181 99 176 185 179 181 Livac he (Modified).- 13 *3 17.4 14.6 15.5 16.3 15.3 15.2 13.8 15.2 13.5 14.9 15.1 16.3 - Extract per Cent. 2 Hours. 14.0 19.2 14.0 19.0 17.4 15.2 17.6 18.6 18.8 18.0 100.6 21.0 21.2 19.4 31.6 Zeiss . 25' C. 82.2 79.0 83.0 79.6 80-6 82.4 80.3 80.8 78.9 80.8 66.0 79.7 79.4 - - The following equation has been calculated from the curve for the maximum If I is the iodine value, then the maximum permissible extract of a linseed oil.extract for that oil is given by- Extract = 81.9 - 0.35 I. It is suggested that the routine examination of linseed oils be restricted to the determination of the iodine value, and the extract as described above, by which means decisive information as to the purity or otherwise of any sample may be obtained. CITY AXALYST'S LABORATORY, BIRMINGHAM.THE DETECTION OF ADULTERATION IN LISSEED OIL 7 DISCUSSION.lfr. L. M. NASH thought that the authors might perhaps have chosen better examples of adulterants than they had mentioned. Soya oil, sunflower oil, perilla oil, and wood oil, were more likely to be used, and would be less easy to detect by specific tests. AD admixture of 20 per cent. of colza oil would be shown at once by its effect on the viscosity.Mr. R. BODMER said that, in examining samples oE linseed oil by the bromine addition method, he had found that erratic results were sometimes obtained, owing apparently to differences in the mode of working. The method as laid down by Messrs. Hehner and Mitchell consisted in dissolving the oil in cooled ether, adding the bromine, and then, after allowing the precipitate to subside, washing four times with 10 C.C.of cooled ether ; while Dr. Lewkowitsch, in an early edition of his book, recommended washing with alcohol and acetic acid. The results obtained by the two modes of procedure were in his (the speaker’s) hands quite different, and yet the figures laid down by the respective authors for linseed oil were the same.Evidently, in order to insure concordant results, the mode of procedure must be absolutely uniform. Dr. RIDEAL remarked that the results would probably have been more interesting had they embraced smaller admixtures-say 10 per cent.-of the foreign oils. The positions of the crosses on the authors’ diagram were somewhat difficult to under- stand. In the case of pure linseed oil one would expect the ratios between the iodine value and the percentage of extract to fall into a straight line, or at any rate that the number of crosses inside and outside the line would be the same.Mr. E. R. BOLTON remarked that, in the case of an oil containing a considerable proportion of oxidisable substances, some of the extractable matter would probably be retained by the oxidised oil, just as in the Adams’ process for determining fat in milk some of the fat was liable to be held back by the casein.Mr. CRIBB said that possibly the difficulty to which Mr. Bolton had alluded might be avoided by the use of thinner paper. The very thin l1 Japanese” paper used for press-copying answered well, allowing the oil to be spread in a much thinner film. The PRESIDENT said that he had found Messrs. Hehner and Mitchell’s process to be a very valuable one, though he quite agreed with Mr. Bodmer that it was necessary to work under uniform conditions. The question as to what conditions were the best for obtaining uniform results appeared still to need investigation, and he thought that this was a matter which might usefully be taken up under the Society’s Analytical Investigation Scheme. Mr. N. EVERS, in the absence of the authors, said that most of their determina- tions had been made in duplicate, the duplicate results agreeing fairly well. The film of oxidised oil undoubtedly prevented some of the non-drying oil from being extracted-in fact, if that were not the case, the results obtained by extraction would be quantitative.

ISSN:0003-2654    

DOI:10.1039/AN9133800003

出版商:RSC    

年代:1913

数据来源: RSC

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8 ELSDON : ALCOHOLYSIS AND THE COMPOSITION OF COCOANUT OIL. BY G. D. ELSDON, B.Sc., A.I.C. INVESTIGATION CARRIED OUT UNDER THE SOCIETY’S ANALYTICAL INVESTIGATION SCHEME. (Read at the Neeting, December 4, 1912.) THE full details of the process of alcoholysis were first published by A. Haller in 1906 (Compt. rend., 1906,143, 657 ; ANALYST, 1907,32,52), but the same idea had been previously used by Fox and Wanklyn, who, some years before (ibid., 1884, 9, 73), described a method for the analysis of butter which depended upon the formation of ethyl butyrate on heating with alcoholic potash.The method of Hailer has been used for determining the composition of various oils and fats, and the following papers have bee3 published on these lines : (( Alcoholysis of Cocoanut Oil,” Haller and Youssoufian (ANALYST, 1907, 32, 53) ; L( Alcoholysis of Castor Oil,” Hailer (J.Soc. Chem. Ind., 1907, 26, 328); ‘( Alcoholysis of Linseed Oil,” Haller (ibid., 1908, 27, 234) ; ‘‘ Alcoholysis of Japan Wax,” Tassily (ibid., 1911, 30, 907) ; (‘ Alcoholysis of Cottonseed Oil,” Meyer (Chem. Zeit., 1907, 31, 793) ; l 4 The Deter- mination of the Composition of Complex Lipoids by Alcoholysis,” Fourneau and Piettre (ANALYST, 1912, 37, 463).In none of these cases, however, has the method been made quantitative, and it was therefore suggested to the author, through the medium of the Analytical Investigation Scheme, that an examination of the process should be made with special reference to its quantitative applications, with a view, if possible, of finding a method for distinguishing between cocoanut oil and palm-kernel oil.The results obtained from the alcoholysis of cocoanut oil are given below; palm-kernel oil is at present being examined, and the author hopes to publish the results in due course. In the case of cocoanut oil it is proposed to describe the process used and the results obtained under two headings: (1) Alcoholysis, and (2) the composition of cocoanut oil.1. ALcoHoLYsIs.-For these experiments methyl alcohol has been used exclu- sively, on account of the fact that the methyl esters of the fatty acids have lower boiling-points than the corresponding ethyl esters. The process, which consists in boiling the oil with excess of methyl alcohol, will now be described in detail. It has been shown by Patterson and Dickinson (1.Chem. SOC., 1901, 79, 280) that when any ester is heated with excess of another alcohol the two alcohols change places, and the acid of the ester combines solely with the alcohol in excess. Thus, on heating ethyl tartrate with excess of methyl alcohol, ihe whole of the ethyl tartrate is transformed into methyl tartrate. From this it was surmised that ‘‘ pure ” com- mercial methyl alcohol might be used in place of the absolute alcohol used by Haller, as any higher alcohols present 8s impurities would not be transformed into esters in he presence of such a large excess of methyl alcohol, and the effect of such substancesALCOHOLYSIS AND THE COMPOSITION OF COCOANUT OIL 9 as acetone would merely be to assist alcoholysis.In all the experiments described in this paper this commercial alcohol has been used with satisfactory results. The alcohol was prepared for use as follows : '( Pure " commercial methyl alcohol was dried over lime for several days with the help of a shaking apparatus ; it was then roughly filtered and distilled from the water-bath, the fraction 65' - 72" C. being collected.A current of dry hydrochloric acid gas was then passed through the distillate until it had increased by about 2 per cent. of its weight. The Process of AZcohoZysis.-The process used is based on that of Haller (Zoe. cit.), and is as follows : Five hundred grms. of dry coconut oil were placed together with 1200 C.C. of methyl alcohol (obtained AS described above) in a conical flask, and the whole heated on the water-bath until it had become clear, this process taking ten to fifteen hours ; it was then heated for about ten hours more to make sure that the reaction was complete.The mixture, on cooling, deposited a large quantity of esters, and these were removed as completely as possible by means of a separating funnel; the alcoholic layer was then poured into at least an equal volume of water, and the whole extracted four times with ether, the ethereal solution being added to the separated esters.The alcoholic layer was disregarded. The ethereal solution of esters was then twice washed with a dilute solution of sodium carbonate, and then twice with water in order to remove hydrochloric acid, and alcohol ; it was then dried over fused sodium sulphate.The ether was finally removed by heating in a water-bath until nothing further distilled. The esters obtained from two such experiments (representing 1 kgrm. of cocoa- nut oil) were then fractionally distilled in quantities of about 250 grms. at a time, under a pressure of 14 mm., the corresponding distillates obtained in the different distillations being mixed together and finally weighed.The receiver was changed during the progress of the distillation at a temperature midway between the boiling- points of two consecutive esters. For convenience of reference a table of the melting and boiling points of the methyl esters of the chief fatty acids likely to occur in oil and fats is given below : Name. Methyl n. butyrate ,, n. valerate ,, n.caproate ,, n. caprylate ,, n. caprate ,, n. laurate ,, n. rnyristicate ,, n. palmitate ,, n. stearate ,, oleate Boiling-Yt. C. Meltgg-Pt. C. 760 mm. 16 mm. - 102 - - 117 - - 150 52.5 - 40.5 194 83.0 - 18.0 224 114.0 + 5.0 - 141.0 + 18-0 - 167.5 28-0 - 196.0 38.0 - 214.5 - - 212.5 The individual fractions thus obtained, whose weights will be roughly propor- tional to the quantities of the various methyl esters present in the oil, are then refractionated until a fraction is obtained of constant boiling-point.I n this way the10 ELSDON : various constituents of the oil are isolated as their methyl esters, and the individual esters can then be identified by physical and chemical means. The separation of methyl oleate from methyl stearate requires a special process, as the boiling-points of the two are so nearly alike.I t is carried out, as described by Haller, by cooling the mixture in ice, and filtering the solid methyl stearate from the liquid methyl oleate. This part is one of the weak points of the process, as it is by no means easy to separate them in this way; and, indeed, complete separation is an impossibility. The Results obtained.-From the experiments carried out it has been concluded that the process of alcoholysis is a suitable one for determining the qualitative com- position of an oil, and that it also gives considerable information in regard to the quantities of the constituents present ; the process, however, is much too lengthy for use as an ordinary laboratory test, and would seem to be chiefly of theoretical interest.The quantitative results have not been encouraging, but the process probably gives results within about 5 to 10 per cent. of the true value-that is to say, it should decide between 35 and 45 per cent. for the content of lauric acid in cocoanut oil. 2. THE COMPOSITION OF COCOANUT OrL.-The composition of cocoanut oil has been the subject of various papers, but the results given by the various workers, while having much in common, show greater divergences than would be expected from the variation in the composition of different samples.It has been shown by Jensen (ANALYST, 1905,30,397) that cocoanut oil contains no butyric acid and but little caproic, the volatile acids being mainly capric and caprylic. Paulmyer (J. SOC.Chem. Ind., 1907, 26, 881) found that the fatty acids of cocoanut oil consisted of capric, 20 per cent. ; lauric, 40 per cent. ; myristic, 25 per cent.; palmitic, 11 per cent. ; and oleic, 5 per cent. ; together with capric and caprylic acids; while Caldwell and Hartley (ANALYST, 1909, 34, 274) found by a different method at least 60 per cent. of lauric acid. Haller and Youssoufian found, by the method of alcoholysis, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, and oleic acids.They did not give any quantitative results, but they stated that lauric and myristic acids predominated, whilst palmitic, stearic, and oleic were present in relatively small quantities. It will be found that these results of Haller have been largely confirmed by the results obtained by the author, and which are given below.The sample of cocoanut oil used in the experiments described in this paper had the following analytical constants, and was in all respects a fair average commercial sample. The figures obtained are in close agreement with those obtained by Haller on the sample used by him : Saponification equivalent ... ... ... 25.84 Iodine value (Wijs) ...... ... ... 8.71 Melting-point ... ... ... ... ... 24' C. Reichert-Meissl value ... ... ... ... 7-71 Zeiss at 40' C. ... ... ... ... ... 34-90 One kgrm. of the oil was used for alcoholysis, and from this 976 grms. of estersALCOHOLYSIS AND THE COMPOSITION OF COCOANUT OIL 11 were obtained. as described above, and the following fractions were obtained : These were fractionally distilled under reduced pressure (14 mm.) Boiling-P t .63" to 76" C. 76" ,, 100" C. 100" ,, 128°C. 128" ,, 153°C. 153' ,, 182" C. 182' ,, 204' C. 204' ,, 216OC. Weight. 16.5 grms. 85.0 ,, 92.5 ,, 442.0 , l 206.0 ,, 66.5 ,) 67.5 ,, Corresponding to- Methyl caproate ,, caprylate ,, caprate , l laurate ,, myristicate ,, palmitate ,, stearate and oleate These various fractions were then refractionated, and each ester was obtained in the pure state, or as nearly pure as the quantity of the matter would allow.They were then examined by physical and chemical means, and each ester mentioned above identified with certainty. About 20 grms. of methyl oleate were obt'ained, but the subsequent purification was difficult. No indications were obtained of the presence of any other fatty acids but those mentioned.From a consideration of these results, the composition of the fatty acids of cocoanut oil would appear to be somewhat as follows, but, as already stated, the figures are rough, and must only be taken as an indication of the relative amounts present : Ctiproic acid Caprylic acid Capric acid Lauric acid Myristic acid Palmitic acid Stearic acid Oleic acid ... ... ... ... 2 per cent. ... ... ... ... 9 ,, ... . . I ... ... 10 ,, ... ... ... ... 45 ,, ... ... ... 20 ,, ... ... ... ... 7 ,, ... ... ... ... 5 ,, ... ... ... ... 2 ,, 100 per cent. In conclusion, it is with great pleasure that I acknowledge the valuable assist- ance which I have received from Mr. A. Chaston Chapman and Dr. J. Lewkowitsch, both in connection with the above work and with that on palm-kernel oil at present being carried on. Part of the cost of the investigations has been defrayed by a grant from the Society. CITY ANALYST'S LABORATORY, BIRMINGHAM.

ISSN:0003-2654    

DOI:10.1039/AN9133800008

出版商:RSC    

年代:1913

数据来源: RSC

摘要:

12 GOWING-SCOPES THE ESTIMATION OF CITRIC ACID THE ESTIMATION OF CITRIC ACID IN THE PRESENCE OF CERTAIN OTHER ACIDS. BY L. GOWING-SCOPES. INVESTIGATION CARRIED OUT UNDER THE SOCIETY’S ANALYTICAL INVESTIGATION SCHEME. (Read at the Meeting, December 4, 1912.) UNTIL quite recently the only method available for the estimation of citric acid consistedin precipitating the acid as tricalcium citrate. I t has been shown, how- ever, by 0.von Spindler (Chem. Zeit., 1903, 27, 1263)’ that this method is quite unreliable. DenigBs (Revue Ginha1 d u Luit, vol. iii., p. 385) devised a method by which the citric acid is oxidised to acetone-dicarboxylic acid, and precipitated as an insoluble mercury compound. This process has been examined by M. Beau (Annales de Chim. et de Phys., 1899, 18), L.Robin (Ann. de Chim. anal., 1904, 9, 453), and E. DesmouliBrB (BUZZ. d . Sciences Pharmacol., 1910, 17, 588). L. Robin states that DenigBs’ test has not proved satisfactory in his hands, and proposes a method based on the precipitation of citric acid as cadmium citrate. E. DesmouliBrB finds DenigB’s test useless for quantitative purposes. M. Beau, however, appears to have obtained satisfactory results, and his modification appears in Barthel’s ‘‘ Milk and Dairy product^.^' In addition to these methods, M.Spica (Chem. Zeit., 1910, 34, 1141) proposed to precipitate the acid as calcium citrate, digest with strong sulphuric acid, and to measure the carbon monoxide evolved, D. S. Pratt (U.S. Dept. of Agriculture Bureau Chem. ; through Chem. Eng., 1912, 15, 72) oxidises to.acetone, distils into mercuric sulphate, boils with this reagent, and weighs as an addition product. The present investigation was undertaken to examine critically Beau’s modification of DenigBs’ method. The principle on which the process is based is that when citric acid is oxidised with potassium permanganate, acetone-dicarboxylic acid, carbon dioxide, and water are formed.C,H,07 + 0 = C,H,O, + GO, + H,O. Acetone-dicarboxylic acid on treatment with excess of mercuric sulphate gives a white precipitate of mercury dicarboxysulphoacetone. The precipitate, which is insoluble in water, is dissolved in hydrochloric acid, excess of ammonia added, as well as a known quantity of Fv potassium cyanide, and then titrated with & silver nitrate, using potassium iodide as indicator.Beau precipitates the casein in milk with DenigAs’ mercuric sulphate reagent, filters, and estimates the citric acid in the filtrate in the following manner : 100 C.C. of the filtrate are oxidised with a 1 per cent. solution of potassium permanganate, the liquid is heated to boiling; the flame is then removed and permanganate solution added drop by drop, the flaskIN THE PRESENCE OF CERTAIN OTHER ACIDS 13 being shaken after each addition.The liquid soon becomes turbid, after which a yellowish-white precipitate forms. The addition of the potassium permanganate is, however, continued until the precipitate sinks rapidly to the bottom and the supernatant liquid is perfectly clear. To reach this point about 5 to 10 C.C.are required. A slight excess is of no disadvantage, for otherwise the oxidation is apt to be incomplete. The precipitate has a coffee-brown colour on account of small quantities of manganese dioxide, but this can be removed by heating the liquid until it boils, removing the flame, and adding small amounts of hydrogen peroxide until the precipitate is quite colourless.Generally 5 to 10 drops of hydrogen peroxide are required for this. The precipitate is then filtered off, dis- solved in hydrochloric acid, and titrated as above. These directions were followed, with the exception that instead of titrating, the precipitate was filtered through a Gooch crucible, and dried to constant weight. The results varied considerably. The effect of adding standard amounts of reagents, boiling for a definite time, and filtering, etc., was tried, but the results continued to vary for some undetermined reason.Other oxidising agents were experimented with. Nitric acid either did not oxidise the citric acid to acetone-dicarboxylic acid or kept the precipitate in solution. Potassium bichromate gave a precipitate of an ochreous colour, but it was readily oxidised further and its use was abandoned.0. von Spindler (Chem. Zeit., 1904, 28, 15) has used potassium bichromate successfully as a qualitative test, and states that the precipitate contains chromium as well as mercury. Bromine proved useless, as also did ferric chloride. Ammonium persulphate and hydrogen peroxide gave pure white precipitates, which separated well from boiling solu- tions ; but when employed quantitatively conflicting results were obtained, the ratio weight of precipitate weight of citric acid taken approximating to 3.5.It was found that hydrogen peroxide oxidised the precipitate at 100' C., and even at lower temperatures the results were unsatisfactory. A number of experiments were made at temperatures varying from 16" to 53' C., the same amount of citri'c acid being used in each case.The precipitates were filtered, dried, and weighed at hourly intervals. The weight of the precipitate gradually increased to a maximum, then fell fairly rapidly, and when kept at a temperature of 53' C. in the course of a few days entirely disappeared. It appears that the precipitate is no sooner formed than it is oxidised again, and this happens before the whole of the citric acid is precipitated. These experiments explain the reason of the variable nature of Beau's results (Zoc.cit.) ; when the manganese dioxide is removed with hydrogen peroxide part of the precipitate is oxidised to acetone. Hydrogen peroxide having proved a failure, the use of potassium permanganate was further investigated, and for the removal of manganese dioxide several substances were tried in place of hydrogen peroxide ; some, such as oxalic acid, were too powerful reducing agents and decomposed part of the precipitate, whilst others were not strong enough to remove the manganese dioxide.After many trials fairly good results were obtained with a solution of formalin." The citric acid was oxidised at 100' C. with potassium permanganate until the precipitate was slightly brown, formalin was14 GOWING-SCOPES : THE ESTIMATION OF CITRIC ACID added, and the mixture boiled until the precipitate appeared quite white.The following weight of precipitqte weight of citric acid taken table gives the ratio for several sets of experiments made : _ _ . . Citric Acid alone.I n the Presence of other Acids. First Set. Second Set. Third Set. 3-55 3.83 3-57 3.65 3-85 3.48 3.50 3 a84 - - 3.77 - Acid. I Ratio. Succinic acid . . . ... 3.94 Tartaric acid . . . ... 5.29 Lactic acid .... 3.93 Citric acid alone . I . 3.92 (control experiment) The other acids used were present to the extent of about three times the weight of citric acid. I t will be seen that the ratio varies from about 3.5 to about 3.9, a variation sufficient to cause a fairly large error.I t appears that the reason is due to the oxidising action of the precipitated manganese dioxide on the precipitate. Attempts to dissolve and reprecipitate, to prepare halogen derivatives, or to titrate the solution with iodine were unsuccessful. Better results were obtained by titrating the hydrochloric acid solution with potassium bromate, but, these varied considerably.Incidentally it was found that methylene blue formed an excellent indicator for bromine, acting in the same manner as it does with iodine, as was first shown by Sinnat (ANALYST, 1910, 35, 309). As acetone-dicarboxylic acid is a strong reducing agent, it is possible that solutions of the precipitate might reduce ferric chloride, but this was not the case, or at any rate the oxidation was too slow to be of any use. Unsuccessful attempts were made to prepare derivatives, using for this purpose phenylhydrazine and its derivatives-semicarbazide, sodium bisulphite, etc.I t was thought that the small quantity of nitrous acid in Wiley’s mercuric nitrate solution was affecting the results, and the solution was therefore treated with potassium permanganate till a, precipitate was formed which was removed. The oxidised solution was then added to some citric acid, and the whole was heated to boiling ready to add permanganate to oxidise the citric acid and so obtain Denigds’ precipitate.Instead of the liquid remaining clear when boiled a white precipitate rapidly formed.Further investigation proved that the cause was the manganese nitrate formed in the oxidised Wiley’s solution, and much better results were obtained by using a mixture of manganese nitrate and mercuric nitrate in a nitric acid solution. This is the principle on which the method now proposed as an alternative to DenigBs’ method is based. In order to ascertain what proportions of manganese nitrate, mercury nitrate, and nitric acid to use, experiments were made in which the proportion of two of the reagents was kept constant and that of the third varied.As it seemed probable that the nitric acid would have a solvent action on the precipitate, this was varied first. The citric acid taken was about 0.027 grm., the manganese nitrateIN THE PRESENCE OF CERTAIN OTHER ACIDS 15 1.25 grms., and the mercuric nitrate 0-95 grm.The mixture was made up to 200 C.C. and boiled under a reflux condenser for three hours, filtered through a Gooch crucible, and the precipitate weighed. The variation in the factor for different amounts of nitric acid is shown in the curve. In the same way the manganese nitrate was varied while the citric acid and the nitric acid were kept constant.The amount of nitric acid taken corresponded to the maximum precipitate on the curve. In a like manner the mercuric nibate was varied. When, how- ever, the citric acid was varied, it was found that the larger the amount of citric Both results are shown by curves. acid taken the smaller the precipitate. This seemed to suggest that the mercury reagent should bear some relation to the amount of citric acid present.As the amount of citric acid present is generally unknown, the only way appeared to be to add neutral mercuric nitrate until the precipitate formed just dissolved, and, as the curves showed that about equal quantities of the various reagents should be present, amounts of manganese nitrate and nitric acid equivalent to the amount of mercuric nitrate were added, and the whole was diluted so that each constituent was present to the extent of 1 per cent.The mixture was then boiled for three hours, precipitated, filtered, dried, and weighed in the usual manner. By adopting this procedure, consistent results, as shown in the following table, were obtained :16 GOWING-SCOPES : THE ESTIMATIOW OF CITRIC ACID Weight of Citric Acid taken.0.0028 0.0112 0.0196 0.0280 0*0055 0.0083 0.0153 0.0236 Weight of Precipitate obtained. 0*0170 0.0684 0.1217 0.1700 0-0347 0.0503 0.0932 0.1412 Factor. 0.164'7 0-1637 091612 0.1647 0.1585 0.1 650 0.1642 0.1671 Experience gained by using this method showed that if large quantities of the reagent were used better results were obtained.Experiments were then made to see if this was the cause of the fall in the factor, as the citric acid was increased in the earlier experiments. Three grms. of each of the reagents, mercuric nitrate, man- ganese nitrate, and nitric acid, were used for each experiment. The citric acid was varied and the solution made up to 300 C.C. and boiled for three hours. Constant results were obtained, which were in excellent agreement with those obtained by the previous method.They are given in the following table : Weight.of Citric Weight of Precipitate Acid taken. obtained. 0.0027 0.0138 0.0202 0.0160 0.0840 0.1220 Factor. 0.1 688 0.1643 0.1656 In the next series 2 grms. of each reagent were taken, the citric acid was varied as before, and the solution was diluted to 200 C.C.The results obtained again agreed well with the foregoing, and this strength of solution was ultimately adopted. A reagent containing mercuric nitrate, manganese nitrate, and nitric acid was prepared in the following manner : Fifty-one grms. of mercuric nitrate and 51 grms. of manganese nitrate were covered with about 68 C.C. strong nitric acid. About 100 C.C.of water were added, and when the salts were dissolved the volume was made up to 250 C.C. and filtered. Ten C.C. were taken for each estimation, correspond- ing with 2 grms. of each ingredient. The estimation is carried out as follows: A quantity of the substance, containing not more than 0.04 grm. nor less than 0.001 grm. of citric acid, is exactly neutralised with :i alkali, using phenolphthalein as indicator.Ten C.C. of the reagent are added, and the whole diluted to 200 C.C. The mixture is boiled under a reflux condenser for three hours, filtered through a weighed Gooch crucible, and the precipitate well washed with cold water. Usually there is a deposit on the sides of the flask which may be removed by adding 1 or 2 C.C. 1 per cent. nitric acid, and rubbing with a rod.The precipitate is washed first by decantation and then in the crucible, and is dried in theiwater-oven for five hours, when the weight will be found to be nearly constant. Further drying usually only reduces the weight by less than 1 mgrm. The precipitate is white, with a slight cream tinge, if it has been prepared properly. If it is at all yellow, basic salts have formed, and the estimation will beIN THE PRESENCE OF CERTAIN OTHER ACIDS 17 The following table gives the results obtained by using pure citric acid, the high.exact amount being determined by titration : Weight of Citric Acid taken. 0.0027 0.0055 0.0083 0.0125 0.0080 0.0159 0-0240 0.0312 0.0144 0.0144 0.0144 0.0144 0,0173 0.0172 0.0140 0.0140 Citric Acid found (using Factor 0 -01 66 7).0.0027 0.0054 0.0084 0.01 24 0.0083 0.0159 0-0241 0-0308 0.0147 0.0145 0.0141 0.0140 0,0172 0,0172 0.0142 0.01 40 Difference. o*oooo - 0~0001 + 0~0001 - 0*0001 + 0.0003 k 0~0000 + 0.0001 - 0.0004 + 0*0003 + 0*0001 - 0.0003 - 0.0004 - 0~0001 rt o*oooo + 0.0002 k 0~0000 Weight of Precipitate. 0.0162 0.0325 0-0502 0.0744 0-0497 0.0956 0.1447 0.1850 0.0880 0-0868 0-0848 0-0838 0.1034 0.1030 0.0853 0.0838 Factor.0.1667 0.1692 0.1653 0.1680 0.1610 0.1663 0.1657 0.1687 0.1636 0.1659 0.1698 0.1719 0.1673 0.1670 0.1642 . 0.1670 Average factor : 0.1667. I t will be eeen that there is a good agreement between the weights of citric acid taken and the weights found. The error in no case is as much as 0-5 mgrm. 1.t is of interest to note that the factor 0.1667 corresponds exactly to one-sixth of the weight of the precipitate.Experiments to try the smallest amount of citric acid that could be accurately determined by direct weighing gave the following results : Weight of Citric Acid taken. Weight of Precipitate. Difference. Weight of Citric Acid found. 0.0005 0.0011 0.0022 0.0008 0.0012 0.0021 + 0.0003 + 0.0001 - 0.0001 0,0046 0.0070 0.0125 I t will be seen that quantities less than 1 mgrm.give high results. Hence the Anything less than 3 mgrms. requires The experiments below were carried out to ascertain if the estimation could be limit must be placed at about this figure. very careful working. made in the presence of other acids :18 GOWING-SCOPES : THE ESTIMATION OF CITRIC ACID Acid.Tartaric ... ¶, Y, . .. ... Succinic ... Maiic ... LGtic ... 9 , ... ... Y 9 ... ... ... $ 9 9, ... Oxalic ... Benxoic ... Salicylic . . . Phosphoric 0*0150 0.0150 0*0300 0.0150 0.0150 0*0300 0.0150 0.0150 0.0150 0.0150 0.0240 0.0480 0.0150 0.0150 0.0150 0*0150 Weight of Acid taken. Citric Acid taken. 0.0144 0.0172 0.0172 0.0144 0.0140 0.0140 0.0143 0,0144 0.0156 0.0140 0.0173 0,0173 0.0144 0.0140 0-0140 0.0140 Citric Acid found.0.0145 0.0169 0.0167 0.0143 0.0136 0.0137 0~0200 0.0163 0.0204 0,0155 0.0215 0.0296 0.0142 0-0138 0.0173 0.0147 Differelm. + 0~0001 - 0.0003 - 0.0005 - 0*0001 - 0.0004 - On0O03 + 0-0057 + 0*0019 + 0.0048 + 0.0015 + 0.0042 + 0.0122 - 0~0002 - 0.0002 + 0.0033 + 0.0007 Weight of Precipitate. 0.0872 0.1014 0*1004 0.0858 0.0818 0.0822 0.1202 0.0976 0.1223 0.0932 0.1292 0-1774 0.0850 0.0827 0.1038 0*0880 In presence of tartaric, succinic, oxalic, benzoic, phosphoric, sulphuric, and acetic acid's accurate results are obtained, but with malic, lactic, and salicylic acids the results are approximate.Salicylic acid gave a salmon-coloured precipitate, which is probably a nitro compound ; with tannic acid a voluminous orange-brown precipitate was obtained.The percentage of mercury estimated by Volhard's ammonium sulphide method varied from about 72.5 to 74.0. The nitric acid determined by the phenolsulphonic acid end Kjeldahl methods was about 4 per cent. I t is interesting to note that the precipitates obtained by Beau's modification of Denigbs' method gave 72.5 per cent. of mercury and 3 to 4 per cent.of nitric acid. This seems to suggest that the precipitate is very similar, if not the same. These results do not correspond to any simple formula. The precipitates persistently retained traces of manganese, as shown by the colour method, and also possibly traces of uncombined mercury and nitric acid. It is very soluble in hydrochloric acid, also in strong sulphuric acid and nitric acid.Drying seems to render the precipitate less soluble. Soluble haloid salts, as well as many other salts, readily dissolve it, this being the reason that it cannot be reprecipitated from a hydrochloric acid solution. When properly prepared, it is easily filtered and washed, and does not show any tendency to pass through the filter. It dries rapidly, and could probably be dried to a constant weight at 110" C.in three hours. I t has been found that three hours is about the minimum time for boiling, but if boiled much longer basic compounds tend to separate. When heated, the precipitate suddenly decomposes. CONCLUSIONS. 1. I t is shown that Beau's method is unreliable, due to the addition of hydrogen peroxide to remove manganese dioxide, and that no other oxidising agent can beIN THE PRESENCE OF CERTAIN OTHER ACIDS 19 used. The manganese dioxide formed cannot be removed without oxidising or reducing the precipitate. I n hot solutions, manganese dioxide slowly oxidises the precipitate. 2. The precipitate cannot be dissolved and reprecipitated. Halogen, phenyl- hydrazine, and other derivatives could not be prepared. 3. I t has been found that a mixture of equal weights of mercuric nitrate, manganese nitrate, and nitric acid react with citric acid, yielding a precipitate after prolonged boiling which is exactly six times the weight of citric acid taken. The reaction has been studied, and a method for the accurate estimation of citric acid is given, together with details of the preparation of the reagent, The maximum error in the table is +0*0003 and-0.0004. Good results have been obtained in the presence of tartaric, succinic, and other organic acids, but malic and lactic acids gave high results. In conclusion, I have to thank Mr. H. D. Richmond for the interest he has taken in the work and for allowing part of the early work to be done in his laboratory, also Mr. A. N. Gates, who has assisted me in the investigation.

ISSN:0003-2654    

DOI:10.1039/AN9133800012

出版商:RSC    

年代:1913

数据来源: RSC

摘要:

IN THE PRESENCE OF CERTAIN OTHER ACIDS 19 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Estimation of Benzaldehyde and Oil of Bitter Almonds. F. D. Dodge. (Eighth Int. Con. App. Chem., 1912, vol. 17, 15-20.)-1n the estimation of benzal- dehyde by the bisulphite method results sufficiently accurate for technical work may be obtained as follows : The aldehyde (0.15 grm.) is dissolved in 25 C.C.of sodium bisulphite solution, and the flask corked and allowed to stand for one and a half to two hours in ice-water, after which the liquid is titrated while still cold with FG iodine solution with starch as indicator. Simultaneously a blank estimation is made with 25 C.C. of the bisulphite solution, and the difference between the results calculated into benealdehyde.One C.C. of iodine solution = 0.0053 grm. benzaldehyde. At best the results are only approximately correct, and only the free aldehyde is estimated in a natural oil. This .also applies to the precipitation of the benzaldehyde as hydrazone, whilst in the oxime method of Bennett (ANALYST, 1909, 34, 14) the presence of hydrocyanic acid apparently causes irregularities in the titration.Good results were obtained with artificial benzaldehyde by the use of a 2.5 N solution of potassium hydroxide in a method based on Cannizzaro’s reaction : 2C6H5COH 4- KOH = C,H,COOK -j- C,H,.CH,OH, especially when the mixture was allowed to stand for twenty-four hours at the ordinary temperature instead of being heated before titrating the excess of alkali with standard acid. The objection to the method is that an error of only 0.05 C.C.of the alkali solution amounts to 1 to 2.5 per cent. of benealdehyde. In the case of20 ABSTRACTS OF CHEMICAL PAPERS the natural oil the results were not satisfactory. A substance with a characteristic pleasant odour was isolated from the natural oil by removing the hydrocyanic acid by distillation with lime and ferrous sulphate, dissolving the residue in ether, precipi- tating aldehydes with sodium bisulphite, filtering off the crystals and washing them with ether.The ethereal extract when washed with sodium carbonate solution and evaporated an vucuo left about 0.2 per cent. of a heavy yellow oil, with an aroma which probably influences that of the oil. Under the same conditions artificial benaaldehyde yielded only traces of oil without characteristic odour.I t is suggested that the presence of the new body may account for the superiority of the flavour of the natural oil. C. A. M. Essential Oil of Cocoa. J. S. Bainbridge and S. H. Davies. (Proc. Chem. SOC., 1912, 28, 253.)-The authors have isolated, from 2,000 kilos of cocoa-nibs, 24 C.C.of a mixture of esters (formed during the fermentation of the cocoa-bean) with the true essential oil, which they regard as the aroinatic principle of cocoa, and which consists chiefly of a d-linalol. Octoic and other fatty acids were also present in the oil, together with small quantities of an unidentified nitrogenous compound. A. R. T. Examination of Honey. G. Armani and J. Barboni.(Ann. Lab. Chim. Cent. delle Gabelk, 1912, 6, 85-107.)-The presence of 10 per cent. of artificial honey may be detected by means of benzidine acetate with much more certainty than by the tests of Ley or Fiehe. The reagent is prepared by dissolving pure benzidine in sufficient dilute acetic acid to give a saturated solution. About 2 grms. of the honey are dissolved in about 10 C.C.of water and treated with 1 C.C. of the filtered reagent. In the presence of artificial honey a pronounced yellow coloration is produced, the intensity of which increases with the proportion of adulterant, so that it is possible to make an approximate colorimetric estimation of its quantity. This reaction is not due to the presence of nitrites, but is probably produced by oxymethyl-furfural in the artificial honey.Tables are given showing the analytical results and the colorations obtained in various tests in the analysis of a large number of samples of pure honey and mixtures of various origin. C. A. M. Effect of Kiln-Drying at 14Q" F. on the Composition of the Hop. H. V. Tartar and B. Pilkington. (J. Ind. and Eng. Chem., 1912, 4, 839-840.)-The temperature at which hops are dried varies from about 70" to 140" F., the lower figure being more generally employed in Europe, and the higher in America. It is usually stated that at the higher temperatures soft resins are converted into hard, and valuable essential oils are lost.The authors, however, do not confirm this, and adduce many figures to show that the composition of the hop is almost identical whether samples are merely air-dried or dried at a temperature rising from 120" to 145" F.The resins were determined by methods previously described by the authors (ANALYST, 1912, 37, 191) and Siller (ibid., 1909, 34, 485), tannin by Chapman's method (ibid., 1908, 33, 95 ; and 1909, 34, 372), and wax by precipitating it from its solution in ether and wepighing on a tared filter.Physical examination showed thatFOOD AND DRUGS ANALYSIS 21 the difference in the aroma of the air-dried and kiln-dried samples was hardly perceptible, different judges varying somewhat in their opinions. H. F. E. H. Detection of Vegetable Oils in Margarine. L. Settim and L. Maurantonio. (Ann. Lab. Chim. Cent. d e l b Gabelle, 1912, 6, 203-206.)-The greater proportion of the vegetable oils in margarine may be separated by heating 150 C.C. of the sample with about 200 C.C.of 95 per cent. alcohol with continual stirring, then allowing the mixture to cool, and decanting the alcoholic layer. The residue left on distillation of the alcohol will contain only minute quantities of (‘ oleomargarine,” and may be used in the special tests for cotton-seed oil, arachis oil, etc.C. A. M. Estimation of Casein and Lactose in Milk. R. Malenfant. (J. Pharm. Chhz., 1912, 6 , 390-397.)-1t is recommended that the casein be precipitated by means of alcohol acidified with acetic acid, the lactose being then estimated in the solution separated from the casein by filtration. Twenty-five C.C. of 65 per cent. alcohol and 3 drops of glacial acetic acid are placed in a flask, and 10 C.C.of the milk are added; the mixture is shaken for forty seconds, and, after the lapse of a further fifteen minutes, the coagulated casein is collected on a weighed filter and washed with 50 per cent. alcohol. The filtrate and washings are collected in a 100 C.C. flask, diluted with water to the mark, and the lactose is estimated in a portion of this solution by titration against Fehling’s solution.The casein is now washed successively with boiling 95 per cent. alcohol, boiling acetone, and ether, then dried for seven hours s t 100” C., and weighed. The casein thus obtained contains a quantity of insoluble salts, and the actual quantity of casein present is found by multiplying the weight by 0.925.w. P. s. Interference of Hydrogen Peroxide with the Milk Tests for Formalde- hyde. H. D. Gibbs. (Philippine J. of Sci., 1912, 7, 77-78.)-€3oth the Hehner and Leach tests for formaldehyde in milk fail in presence of hydrogen peroxide, though a positive result can still be obtained with the Rimini reaction. Mixtures of formalde- hyde and hydrogen peroxide in milk were made with varying dilutions, the formalde- hyde varying from 1 in 20,000 to 1 in 200,000, and the peroxide from 1 in 350 to 1 in 3,000, and in practically all cases only a brown, yellow, or roddish-brown colour was obtained, instead of the characteristic purple or violet.As showing that the failure of the tests is not entirely due to the reaction between hydrogen peroxide and formaldehyde before the application of the test, some of the mixtures which failed to give the characteristic colour were treated with sodium hydrogen sulphite and sulphur dioxide, and immediately tested with positive results. With even larger excesses of the peroxide this treatment was effective.A milk preservative called u Soldona,” containing formaldehyde and hydrogen peroxide, is now on the market, presumably designed with a view to the interference above described, H.F. E. H. Total Solids of Milk. A. Splittgerber. (Zeitsch. Untersuch. Nahr. Genussm., 1912, 24, 493-507.)-1n the case of a complex material like the solids of milk, it is a22 ABSTRACTS OF CHEMICAL PAPERS matter of some difficulty to ascertain at what point of the drying process (as carried out in the usual way at a temperature of 100OC.) the water has been eliminated completely, as the continued loss in weight of the solids on prolonged drying is, in part, due to the decomposition of certain of the constituents.The author has there- fore carried out a considerable number of experiments with the object of discovering the decompositions which milk constituents undergo when heated singly or together for many hours.The results obtained show that the alterations which take place in milk solids on prolonged heating are brought about almost entirely by lactic acid. Although this acid, when alone, volatilises fairly readily, it combines with certain milk constituents, such as casein, albumin, and lactose, and the greater part of the amount of the acid present becomes non-volatile unless the milk solids are heated for a considerable length of time, a portion of the acid being then liberated gradually and volatilised. This loss in weight, due to the volatilisation of lactic acid, does not take place to any appreciable extent during the first hour of the drying process, but after several hours it is plainly observable.At the same time, a, drying period of one hour does not result in any marked decomposition of the various milk constituents.When heated for two hours or more, casein, mixtures of lactose with phosphates, and mixtures of casein with lactose and phosphates, undergo considerable alteration, whilst milk-fat, citric acid and its salts, albumin, and lactose, are scarcely, if at all, affected. It is also shown that when milk solids are dried until constant in weight, the weight found does not correspond with that of the sum of the con- stituents; the two weights agree more closely when the solids are dried for one hour at 100" C.The above-mentioned action of lactic acid affords an explanation of the low results which are obtained when the total solids of sour milk are estimated gravimetrically.w. P. s. Detection of Saccharin in Vermouth. R. Guareschi. ( A m Lab. Ckim. Cent, delle GabeZZe, 1912, 6, 185-196.)-1n most products saccharin may be detected by extraction with petroleum spirit after acidification with sulphuric acid, and tasting the white residue. In the case of vermouth, however, other substances which dis- guise the taste are also extracted.The following method is therefore recommended : From 300 to 500 C.C. of the sample are concentrated to about 150 to 200 c.c., acidified with 5 C.C. of dilute (1 : 3) phosphoric acid, and extracted with three successive por- tions of 150 C.C. of a mixture in equal parts of ether and petroleum spirit (boiling below 70" C.). The extract is washed and distilled, and the residue heated with a few C.C.of potassium permanganate solution to oxidise and destroy coumarin, vanillin, glycyrrhizic acid, etc., whilst leaving the saccharin unattacked. After com- plete oxidation the liquid is acidified with phosphoric acid and filtered. These operations are repeated two or three times, and finally, on evaporation of the liquid, a white residue will be left in which the saccharin may be identified by the usual reactions.C. A. M. Methods for the Estimation of Saponin. M. Korsakoff. (Compt. rend., 1912, 155, 844-846.)-The method for the estimation of saponin established by Christophson is based on its precipitation in the form of a barium compound. TheFOOD AND DRUGS ANALYSIS 23 author has tested this method, hydrolysing the barium compound with sulphuric acid and titrating the dextrose produced. Purified saponin yields, on hydrolysis with 3 per cent.sulphuric acid at 105" C. for one hour, 60-16 per cent. of dextrose. On precipitating 2 grms. of saponin with baryta water, and hydrolysing the precipitate, only about 1.1 grms. of saponin were calculated from the dextrose produced, whilst a considerable further quantity was found in the mother-liquors.Moreover, when this method was applied to the extract of Saponaria ojicinalis, the saponin calculated from the dextrose obtained by the hydrolysis of the barium precipitate was nearly double that calculated from the sapogenin obtained. Hence, not only does the baryta method not precipitate the whole of the saponin, but from natural extracts it also precipitates bodies other than saponin which yield sugar on hydrolysis.A second method, proposed by Kruskal, is based on the formation of an unstable magnesium compound of saponin, the extraction of the glucoside from this by boiling alcohol, and its precipitation on cooling. Here, again, the author finds that only a portion of the saponin separates from a solution in 95 per cent.alcohol on cooling. The following improved method is now described: The plant to be analysed is dried and finely powdered; the powder is exhausted several times with boiling 60 per cent. alcohol. The alcoholic extract is filtered, the alcohol distilled off, and the residue evaporated on the water-bath with calcined magnesia. The magnesium compound is powdered end then extracted with boiling 80 per cent.alcohol; the liquid is filtered and the saponin precipitated by ether. The precipitate formed is dissolved in 3 per cent. sulphuric acid and hydrolysed for an hour in the autoclave at 105" C. The sapogenin produced is filtered off and washed until the washings are neutral ; it is then dissolved in absolute alcohol, the alcohol is evaporated, and the weight of sapogenin is deter- mined whence the equivalent of saponin may be calculated. J.F. B. Iodine Titration Method for the Estimation of Tin, especially in Connec- tion with the Estimation of Tin in Canned Foods. H. A. Baker. (Eighth Int. Cong. App. Chem., 1912, vol. 18, 35-38.)-The tin sulphide obtained in the usual way from 100 grms. of the canned food (digestion with nitric and sulphuric acids, and precipitation with hydrogen sulphide) is dissolved in hydrochloric acid with the addition of potassium chlorate ; a few pieces of aluminium foil are then added to the boiling solution to eliminate all the chlorine, and the tin is reduced to the metallic state by the addition of about 1 grm.of aluminium foil, this and subse- quent operations being carried out while an atmosphere of carbon dioxide is main- tained above the surface of the liquid.The mixture is again heated, when the tin dissolves to form stannous chloride, and, after the addition of a quantity of air-free water, the solution is titrated with i& iodine solution, using starch solution as indicator. Although the precipitate of tin sulphide may contain foreign substances such as lime, phosphorus, silica, lead, and even traces of iron, these will not inter- fere with the subsequent iodine titration.w. P. s. Estimation of Higher Alcohols in Wine. T. von Fellenberg. (Mitt. Lebensmittelunters. u. Hyg., 1912, 3, 231-235 ; through Chem. Zentralbl., 1912, II., 1851.)-The author has applied to wine the reaction which the higher alcohols give24 ABSTRACTS OF CHEMICAL PAPERS with salicylic aldehyde and concentrated aulphuric acid.Although the quantity of higher alcohols in wine gives no measure of its genuine character, the values obtained give some idea of the quantity of higher alcohols to be expected in the brandy perpared from it. For the estimation, 50 to 60 C.C. are distilled over from 100 C.C. of wine. The distillate is placed in a flask of 400 C.C.capacity, together with 0.5 C.C. of sulphuric acid (1 : 1) ; after five minutes it is made distinctly alkaline with sodium hydroxide, treated with 20 C.C. of & silver nitrate solution, and heated for thirty minutes under a reflux condenser. Then about two-thirds are distilled off, and the distillate is made up to 100 C.C. Five C.C. of this distillate are treated in a 100 C.C.flask with 1 C.C. of a 1 per cent. solution of salicylic aldehyde and 4 C.C. of water. A standard is similarly made up with 5 C.C. of a solution containing 3 9.c. of higher alcohols (Rose's test) per 1,000 C.C. of absolute alcohol and diluted to contain the same amount of alcohol as the liquid under examination. To both flasks are added 20 C.C.of concentrated sulphuric acid, the flasks are shaken round, and after standing for forty-five minutes, 50 C.C. of sulphuric acid (1 : 1) are added; the two liquids are then compared in the colorirneter. Swiss wines, according to district, showed average values of 2.99 and 3-32 parts of higher alcohols per 1,000 of alcohol, from which it would appear that the official Swiss standard limit for cognacs of 1 per 1,000 is very low.J. F. B. Colour Reaction of Wine. T. von Fellenberg. (Mitt. LebensmitteZunters. u.. Hyg., 1912, 3, 228-231 ; through Chem. Zentralbl., 1912, II., 1850-1851.)-Schaffer found a colour reaction with wine similar to that of phloroglucinol with vanillin and hydrochloric acid. According to the author, besides tannin, a constituent of the wine is concerned in it which has neither acid nor basic character, and is probably an unsaturated alcohol.This body gives with vanillin and hydrochloric acid a strong red coloration with a bluish tone, resembling acid-fuchsin. It was isolated by making the' wine distinctly alkaline with sodium hydroxide and shaking out with ether (20 C.C. of ether for 10 C.C. of wine). The residue of the ether extract is treated with 2.5 C.C.of concentrated hydrochloric acid and a little vanillin, and is shortly after- wards diluted with 2.5 C.C. of 20 per cent. hydrochloric acid. After ten minutes the coloured solution is compared in a tube with a standard solution of acid-fuchsin (the latter substance dried at 100" C.), and the coloration is expressed in terms of mgrms. of acid-fuchsin per litre.With seven samples of Bernese wines the values ranged from 3-3 to 11.8. The reaction is of little value in the analysis of wines, but indicates the presence of an apparently new constituent of wines. J. F. B. Estimation of Glycerol in Sweet Raisin Wines. B. Bardach and S. Silber- stein. (Chem. Zeit., 1912, 36, 1401-1402.)-Although the usual method of estimating glycerol in wine yields only approximately correct results, it is employed very generally, and the quantity of glycerol found to be present in genuine wines is normal.I n the case of sweet raisin wines, however, the amount of glycerol obtained by the method is abnormally high. This is due to the fact that raisins yield an aqueous infusion which, although free from alcohol, gives a considerable quantity of substance which counts as glycerol; this substance is not glycerol, but a mixture of nitrogenousFOOD AND DRUGS ANALYSIS 25 organic matters with inorganic salts.The ratio of glycerol to alcohol in such wines is, therefore, usually found to be much too high, and the estimation is of little use, if any, as a criterion of the quality of the wines.w. P. s. Investigations on Lead Precipitates from Wines ; Estimation of Pentoses and Methylpentoses in Grapes and Wines. T. von Fellenberg. (ilIitt. Lebens- mittelunters. u. Hyg., 1912, 3, 213-227 ; through Chem. Zentmlbl., 1912, II., 1850.)- Natural wines contain considerable quantities of matters which are precipitated by basic lead acetate, but not by ordinary lead acetate, whilst these bodies are present in artificial wines only in small quantities.Basic lead acetate in excess tends to redissolve the precipitate, and basic lead nitrate is preferable. For its preparation, 400 C.C. of basic lead acetate solution are precipitated with 50 grms. of ammonium nitrate dissolved in a little water; the precipitate is washed with cold water, dissolved by heating with 3 litres of water and filtered; the excess of the salt separates on standing over-night and the mother-liquor serves as the reagent.For the estimation, 30 to 40 C.C. of wine are heated under a reflux condenser for five minutes with 0.5 grm. of animal charcoal, then neutralised earefully with 0.3 to 0.5 grm. of precipitated chalk, heated for on3 minute, cooled, and filtered.Pre- liminary tests are then made with lead acetate solution (190 grms. per litre) to ascertain what quantity of this reagent is required for precipitation, 2-5 C.C. of the wine filtrate are diluted with water to 5 C.C. and treated with increasing quantities of lead acetate, beginning with 0.15 C.C. The filtrates from these tests are tested until one is found which gives no further precipitate with a drop of lead acetate. Then 12.5 C.C.of the wine filtrate are treated with the ascertained proportion of lead acetate and diluted to 25 C.C. The liquid is filtered, and 10 C.C. of the filtrate (= 5 C.C. of wine) are treated in a tube of 40 C.C. capacity with 20 C.C. of the solution of basic lead nitrate, heated to 70" to 75" C. for five minutes and centrifuged for three to five minutes, After pouring off the clear liquid, the precipitate is stirred up with 7 C.C.of absolute alcohol, 7 C.C. of dry ether are added, and the mixture is again centrifuged. The liquid is poured off and the precipitate transferred with a little ether into one of the author's specially designed centrifugal tubes, in which it is centrifuged for three minutes at a speed of 1,200 revolutions, and its volume then read off.With twenty- four samples of natural wines the volumes ranged from 0.210 to 0.518 c.c.; grape marc wines showed only slightly lower values, but heavily diluted and fortified wines gave very small values. Examination of these basic lead nitrate precipitates showed that they contained succinic acid together with some sulphurous acid, inositol, pectin, pentosan, methylpentosan, and, for red wines, a trace of colouring matter.The pectin or parapectin of grapes contains methylpentose as well as pentose, but the quantity of these derived from the pectin is only a small portion of the total pentoses and methglpentoses. Grapes contain pentoses and methylpentoses both in the free state, not precipitated by basic lead nitrate, and in the form of pentosans and methylpentosans precipitated by that reagent.The grape-juice contains principally methylpentose, whilst the marc contains more pentose. Commercial dried-grape wines contain very little pentose and methylpentose ; marc wines contain the two sugars in a different ratio from natural wines. J. F. B.26 ABSTRACTS OF CHEMICAL PAPERS Deteetion and Estimation of Xanthin Bases in Cocoa, Tea, and Coffee, and their Preparations.S. Camilla and C. Patusi. (Giorn. Farm. Chim., 1912, 61, 337-385 ; through Chem. Zentralbl., 1912, II., 1581.)-For the detection of small quantities of xanthin bases, the basic substance is isolated in any convenient manner, and treated with a, few drops of very concentrated potassium hydroxide solution; saturated potassium permanganate solution is then gradually added. Reduction of the permanganate, with gas evolution, and the characteristic smell of carbylamine, show the presence of xanthin bases. To estimate theobromin and caffein, 10 grms. chocolate or cocoa are boiled for thirty minutes with 150 C.C. water and 50 C.C. sulphuric acid, made up to 500 C.C. and filtered hot; 250 C.C. of the cooled filtrate art3 neutralised with magnesium oxide, evaporated to 80 C.C. on the water-bath, and extracted for two to three hours with carbon tetrachloride in an apparatus described in the original paper. Caffein, a little theobromine, and fat, if any is present, pass into solution. The solution is evaporated to dryness with paraffin, the residue boiled several time8 with dilute sulphuric acid, the solution mixed with the liquid remaining in the extraction-apparatus, evaporated to dryness with 5 grms. magnesium oxide, and boiled up four or five times for ten minutes with separate quantities of chloroform of 100 C.C. each. The xanthin bases are obtained in sufficient purity on boiling off the chloroform. If the residue is coloured, it is dissolved in water and treated with potassium permanganate; the xanthin bases are then extracted froin the pink solution with chloroform. The method has been successfully applied to tea, raw and roasted coEee, and coffee substitutes. 0. E. M.

ISSN:0003-2654    

DOI:10.1039/AN9133800019

出版商:RSC    

年代:1913

数据来源: RSC

摘要:

26 ABSTRACTS OF CHEMICAL PAPERS BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Experiments on Antigen and Antibody Actions : Differentiation of Proteins (Kidney, Liver, and Cancer Proteins). E. Rosenthal. (Zeitsch. j'. Immunitatsforsch. u. experam. Therap., 1912, 15, 37-48; through Chem. Zentralbl., 1912, II., 1848.)-By means of the epiphanin reaction it is possible to detect in guinea-pigs specific antibodies of the kidney protein by immunising with the kidney of another animal.This detection can also be made when the organism is induced to secrete antibodies by the breaking down and resorption of its own kidney parenchyma. Experiments carried out in accordance with these results yielded, however, a negative result when tried with guinea-pig's liver. According to this, the liver apparently possesses no antigen characters, or else the method, for some unknown reason, is not suitable for the detection of liver antibodies.Specific antibodies directed against tumour protein can be detected in guinea-pigs after previous immunisation with tumour material from the human subject or mice. Likewise in the serum from cancerous mice antibodies are present directed against mouse tumour protein, which apparently in a small degree also reacts towards human tumour antigen.J. F. B. Estimation of Creatine, Creatinine, and Mono-amino Acids in Certain Fishes, Mollusea, and Crustacea. Y. Okuda. (Bighth Int. Cong. App. Chenz., 1912, vol. 18, 275-281.)-For the estimation of the creatine and creatinine, the finely-divided flesh was extracted with three successive quantities of water atBACTERIOLOGICAL, PHYSIOLOGICAL, ETC.27 55" C., each extraction lasting one hour. The extracts were boiled, filtered, and the filtrate evaporated under reduced pressure to a smell volume. The two bases were then estimated in this solution by Foiin's method. A second portion of the flesh was extracted with water as above described, The soluble proteins were removed by coagulation and precipitation with phosphotungstic acid and sulphuric acid, and after the excess of the two latter had been removed by means of barium hydroxide, the monoamino acids were estimated by the formaldehyde titration method.The following results were obtained, the figures expressing grms. per 100 grms. of dry substance : Creatininc, Mono-amino Acid- Nitrogen.Kind of Fish, etc. Creatine. Bonito ... .. 2-011 0.481 0.072 Tunnyfish Salmon Snapper Carp ... Shark Lobster Crab ... Cuttlefish Clam Porgy ... ... 1.800 ... ... 1-525 ... .. 3.327 ... ... 2.020 ... ... 3.242 ... ... trace ... ... trace ... ... trace ... ... trace - ... ... 0.232 0.041 0.182 - - 0.069 0.308 - 0.369 0.194 0.663 - trace 0.608 trace - trace 0.485 trace - w.P. s. Chemical and Bacteriological Study of Fresh and Frozen New Zealand Lamb and Mutton. A. M. Wright. (J. Xoc. Chem. Id., 1912, 31, 965-967.)- The changes in lamb *and mutton when exposed to temperatures of 2O to 19" F. for varying periods up to one hundred and sixty days are described at length. The methods followed for the estimation of moisture, ash, fat, and total nitrogen, were those described in U.S.Department of Agriculture, Bureau of Chemistry. Bulletin 107, revised ; the coagulable proteose, peptone, meat-base, and ammoniacal nitrogen, being determined as in the author's previous paper (ANALYST, 1912, 37, 193). Changes Dzce to Pzctrefactiolz.-Portions of finely-minced lamb and mutton were inoculated with infusions from putrefying meat, and examined at the end of two, four, seven, and fourteen days.The initial stages of putrefaction were marked by the transformation of insoluble into soluble proteins, and of coagulable proteins into proteoses, peptones, meat-bases, and ammonia. There was found to be a progressive increase in the amount of soluble matter, the total soluble nitrogen rising from 21.7 per cent.of that in the fresh meat to 75.5 per cent. after fourteen days. The most striking evidence of putrefactive change is given by the figures for ammoniacal nitrogen, which rise from 0.8 to 53 per cent. of the total nitrogen present, The changes due to ripening both in the presence and absence of bacterial infection were also studied, thymol and chloroform being used in the latter series.In the former case incipient decomposition commenced on the third day, while in presence of antiseptics enzymic changes ensued involving the increase of organic extractives, total soluble nitrogen, meat-base nitrogen, proteose and peptone nitrogen, for the first four to five days, after which no more change occurred.28 ABSTRACTS OF CHEMICAL PAPERS Changes Due to Cold Storage.-There was a loss of moisture amounting to from 2.5 to 3.5 per cent., an increase in the amounts of proteose, peptone, and meat-base nitrogen, and a decrease in coagulable nitrogen, whilst ammoniacal nitrogen remained unchanged. These changes were similar to those occurring during the ripening of meat in absence of bacterial interference, the maximum change taking place in the lamb about the sixtieth day, and in the mutton between the ninetieth and one hundred and twentieth days.The changes in chemical composition were probably due to enzyme action, and the meats remained in the same condition bacterially as when freshly killed. When the freezing and subsequent thawing were carried out slowly, there was no rupture or alteration of the structure of the tissues. The free acidity of the fat remained practically unchanged.H. F. E. H. Estimation of Lipoids in Blood-Serum. L. Grimbert and M. Laudat. (Compt. rend., 1912, 155, 974-976.)-The authors propose the following simplified scheme, which has been proved to yield accurate results and afford valuable clinical evidence: Twenty C.C. of serum are treated with 100 C.C. of 95 per cent.alcohol to coagulate the proteins ; after twelve hours' contact the precipitate is exhausted hot with a further quantity of alcohol in Kumagawa and Suto's apparatus. The alcoholic extracts are evaporated to a small bulk, and the residue, dried at 50' C., is exhausted with dry ether. The ethereal solution, when filtered through asbestos and evaporated, contains in the crude form the whole of the neutral fats, pre-existing fatty acids, phosphoric and other lipoids, and cholesterol. The extract is first saponified by heating for three hours with 50 C.C. of alcoholic potash per 0.2 grm.of extract, After evaporating the alcohol, the fatty acids are liberated by nitric acid and extracted by ether. The aqueous portion contains the phosphoric acid from the lipoids.The fatty acids are dried for an hour at 50" C., redissolved in dry ether ; the solution is filtered through asbestos, evaporated, and the residue is dried in the oven for four or five hours to fix the pigments in an insoluble form. The residue is dissolved in light petroleum, the solution evaporated, dried at 50' C., and the mixture of fatty acids and cholesterol is weighed.This mixture is treated according to Kumagawa's method for the separation and estimation of the cholesterol. The liquid containing the phosphoric acid is evaporated in a large crucible on the water-bath, and calcined a t a moderate heat to destroy the organic matter. The residue is extracted with a little very dilute nitric acid ; the liquid is filtered, and collected in a centrifuge tube of 50 C.C.A large excess of molybdate reagent is added; the liquid is left at rest for two hours, then for four hours in an oven at 40" C., and centrifuged. The clear liquid is decanted off, and the precipitate is washed first with dilute molybdate and then with a little water. The weight of phosphomolybdate divided by 2.3 gives the quantity of lipoids expressed in terms of distearo-lecithin.From the total fatty acids weighed above must be subtracted the oleic acid combined with the cholesterol, and the stearic acid combined with the lecithin. The factors are : Pure cholesterol, x 0.73 ; and lecithin, x 0.689. The residue represents the acids of the fats and the pre-existing fatty acids, which The precipitate is dried and weighed in the tube.BACTERIOLOGICAL, PHYSIOLOGICAL, ETC.29 for all practical purposes may be taken together. Typical examples are given which illustrate the increased percentages of the above constituents in pathological sera as compared with normal. J. F. B. Mett's Method for Determining the Activity of Pepsin and the Acidity- Maximum of Peptic Digestion. J. Christiansen. (Biochem. Zeitsch., 1912, 46, 257-287.)-As described originally by Mett (Arch.Anat. Plzysiol., 1894, 68) the method consists in filling capillary tubes with egg albumin, coagulating the albumin by immersing the tubes for one minute in water at a temperature of 95' C., and then placing portions of these filled tubes in the pepsin solution to be tested, the latter being maintained at a definite temperature for twenty-four hours.At the end of this time the tubes are removed, and the extent to which the albumin has been dissolved from the tubes is measured and expressed in millimetres. The author finds that the method is quite suitable for comparing the activity of one pepsin with another, provided that certain precautions are taken in carrying out the test. In the first place, egg albumin varies in its behaviour towards pepsin, and the solubility is affected to a considerable extent according to the temperature at which the albumin has been coagulated.I t is recommended that the tubes-about 40 cm. long, and having an internal diameter of about 1.5 mm. (the diameter, however, is of little consequence, but the measurement given is most convenient)-are filled with filtered albumin, and immersed in a large vessel filled with water at 85" C., and allowed to remain in the water until the latter has cooled to the ordinary temperature.When thus prepared, about 10 mm. of the albumin should be dissolved from both ends of a portion of the tube when placed in pepsin solution (0.3 per cent. of Armour's pepsin in TG hydrochloric acid) for twenty-four hours at 37" C.I n practice it may be necessary to vary the initial temperature of coagulation a few degrees, so that different albumins may give this rate of solubility in pepsin solution. The stock tubes may be kept for six months without alteration if the ends of the tubes are sealed with shellac. The author finds that, for low concentrations of acid, the digestion is proportional to the time of contact, and that after some time the hydro- chloric acid inhibits the action of pepsin ; comparative tests should, therefore, not be prolonged for more than twenty-four hours.It is essential that the temperature during the digestion should be maintained as constant as possible, an alteration of a few degrees affecting the rate of digestion to a 'considerable extent.In the case of human pepsin, the digestion proceeds most rapidly when the concentration of the hydrochloric acid in the solution is from 0.020 to 0.033 N, whilst for (' animal " pepsin the maximum concentration lies between 0.050 and 0.075 N. w. P. s. Gold Bromide Test for Semen. A. de Dominicis. (Vrtljschr. f. ger. Ned. ZL. ofentl. Sanitiitswesen, 1912, [III.], 44, 294 ; through Chem.Zerttralbl., 1912, II., 1789.)-A trace of fluid human semen is treated on a glass slip with concentrated gold bromide, and a cover-glass placed upon i t ; it is then carefully heated, and allowed to cool. With a magnification of 300 to 400, numerous garnet-coloured, cruciform, or square crystals, due to the presence of cholin, and also the elongated yellowish crystals produced by the semen may be seen.Fabrics are stretched30 ABSTRACTS OF CHEMICAL PAPERS upon glass slips, extracted with a few drops of distilled water, and the aqueous extract treated as above; if the semen (human) is not too fresh, numerous rect- angular nut-brown crystals are obtained, the recognition of which by the reaction offers no difficulty. These crystals are due to the modification, with time, of the cholin ; this can be shown by the extraction of human semen with alcohol, the residue obtained yielding, after a certain time, similar crystals.The modification of cholin which yields these crystals cannot be detected in any other manner. 0. E. M. Estimation of Skatol and Indol Together in Faxes. C. Moewes. (Zeitsch. exper. Path.u. Ther., 1912, 11, 555 ; through Chem. Zentl-albl., 1912, II., 1702.)-A mixture of the feces with water in the proportion of 30 to 200 is steam- distilled with 1,000 C.C. of water, 200 C.C. of the distillate extracted with 50 C.C. of light petroleum, and 10 C.C. of the extract precipitated with 1 C.C. of a 2 per cent. solution of dimethylaminobenealdehyde in 20 per cent. hydrochloric acid.The solution of the resulting dye in 4 C.C. of water is compared in a Plesch chromo- photometer with a 1 in 100,000 test solution of equal parts skatol and indol. The results vary between 0.008 and 0.024 grm. skatol + indol per 100 grms. feces. 0. E. M. New Rapid Method for the Bacteriological Examination of Water and its Application for the Testing of Springs and Filter-Beds.P. T. Muller. (Arch. Hyg., 1912,75,189-223 ; through Chem. Zentralbl., 1912, II., 1847.)-One hundred C.C. of the water to be examined are placed in a measuring cylinder with 5 C.C. of formalin and 5 drops of ferric chloride solution, mixed and allowed to settle for fifteen to thirty minutes. The clear liquid is poured off and the precipitate is treated with 5 drops of a concentrated alcoholic solution of gentian violet; it is then transferred to a specially-shaped centrifuge tube, and, after dipping for about a minute in the boiling water bath, it is centrifuged for a short time.0.02 C.C. of the precipitate is trans- ferred by means of a serological pipette to a microscope slide. The author employs a slide which has been etched in such a manner that a square of exactly 1 cm.remains clear. The precipitate is placed in the middle of this square and evenly spread by a platinum wire loop. The preparation is dried over a small flame, and, thus fixed, is covered with a drop of cedar-wood oil and examined without a cover-glass with an immersion-objective and the organisms counted. With waters containing 9,500 to $40,000 organisms per c.c., 99 per cent.of the organisms are pre- cipitated by a single treatment with ferric chloride ; highly infected waters should be suitably diluted before treatment. I n testing spring waters the number of organisms found by this method was always higher than the number of colonies counted on plate cultures. When this method showed a water containing comparatively few organisms, cultivation on gelatin plates likewise showed only a few colonies.On the other hand, waters which showed only a few colonies on plate cultures showed sometimes fewer and sometimes far more organisms by the precipitation method. Deep bore waters were found both by plate cultures and by organism-counting to be nearly sterile. The method is applicable for the rapid control of the efficiency of sand filter-beds. J. F. B.ORGANIC ANALYSIS 31 Yoghurt and Yoghurt Preparations. C. Griebel. (Zeitsch. Untersuchb JWar. Genussm., 1912, 24, 541-557.)-The author has examined various solid and liquid preparations which are sold for making Bulgarian or Turkish sour milk (Yoghurt) ; these preparations are supposed to contain the micro-organisms which, when cultivated in milk, convert the latter into Yoghurt. It is essential that the preparations or cultures should contain the Bacillus bulgaricus in an active condition, and the author describes the biological methods by which this bacillus may be identified together with the streptococci and diplococci which occur with it in true Yoghurt. Of sixteen liquid preparations examined, three were practically valueless, whilst only two out of six solid preparations were of any use ; three of the latter did not contain B. bulgaricus in an active state. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9133800026

出版商:RSC    

年代:1913

数据来源: RSC

摘要:

ORGANIC ANALYSIS 31 ORGANIC ANALYSIS. Detection of Cane-Sugar. S. Rothenfusser. (Zeitsch. Untersuch. Nahr. Genussm., 1912, 24, 558-570.)-Results of further experiments on the detection of small quantities of cane-sugar in the presence of other sugars by the method described previously by the author (cf. ANALYST, 1912, 37, 493) are recorded. Par- ticular attention has been paid to the influence of other substances on the test.The following were found to have no interfering action : Alcohols and higher alcohols, aldehydes, organic acids, yeast constituents and decomposition products, organic esters, terpenes, preservatives, etc. The test may be applied to musts, dry wines, milk, honey, biscuits and infants’ foods ; in the case of certain sweet wines, however, some substance other than cane-sugar is present, and yields a positive reaction with the test.The nature of this substance has not been ascertained. Milk and materials which contain dextrins should be treated with acetone and filtered before the process is applied, w. P. s. Estimation of Cyanogen Compounds in Gas Liquor. F. Weisser. (Chem. Zeit., 1912, 36, 1285-1287.)-Arnmonium cyanide is estimated from the difference between total cyanogen and cyanogen existing as ammonium ferrocyanide.Total cyanogen is determined as follows : The gas liquor (500 c.c.) is shaken in a litre flask with 50 C.C. caustic potash solution (1 : 1) and 50 C.C. of a 10 per cent. solution of ferrous sulphate, and the flask is heated on the water-bath for least an hour. The contents of the flask are then cooled and made up to the mark, and the solution, in which all the cyanide now exists as ferrocyanide, is filtered from the precipitate of iron sulphide and hydroxide.An aliquot portion (100 c.c.) of the filtrate is made strongly acid with hydrochloric acid, and the ferrocyanogen precipitated as ferric ferrocyanide by addition of 5 C.C. of 10 per cent. ferric chloride solution.After twelve hours the precipitate is filtered off, washed with a little cold water, and decomposed by means of dilute caustic potash. After boiling, the solution of potassium ferro- cyanide is filtered from the separated ferric hydroxide, acidified with sulphuric acid, and evaporated to dryness. The residue is gently ignited, taken up in dilute (1 : 1) sulphuric acid, and the iron is reduced with zinc and titrated with i& permanganate.One C.C. Ferrocyanide is estimated by the permanganate= 0.00156 grm. CN.32 ABSTRACTS OF CHEMICAL PAPERS followingimethod, which depends on the assumption, said to be sound, that all the iron in filtered gas liquor exists as ammonium ferrocyanide : A measured portion of the filtered liquor is evaporated to dryness, and the residue is ignited and then discolved in concentrated hydrochloric acid with addition of a few drops of nitric acid.Dilute (1 : 1) sulphuric acid is added, and the solution evaporated to fuming. After cooling and addition of more sulphuric acid, the iron is reduced by means of zinc, and titrated with permanganate. Thiocyanate is determined as follows : The gas liquor (50 c.c.) is diluted with an equal bulk of water and evaporated on the water-bath to about 30 c.c., to expel ammonia and hydrogen sulphide.The solutio'n is made up to 100 c.c., and the thiocyanate in 20 C.C. is determined colorirnetrically by addition of 10 C.C. of a 6 per cent. ferric chloride solution containing 10 per cent. of hydrochloric acid, followed by dilution to 500 c.c., filtration and comparison of 100 C.C. with a standard containing the same amount of free acid.As the intensity of colour is affected by the concentra- tion of acid, the preliminary elimination of ammonia must not be omitted. One C.C. T& permanganate = 0.00284 grm. (NH,),Fe(CN),. G. C. J. Ethylene Dibromide as Cryoseopic Solvent. E. Moles. (Zeitsch. f. physik.Chem., 1912, 80, 531 ; through Chem. Zentralbl., 1912, II., 1527.)-Ethylene dibromide is found to be as hygroscopic as nitrobenzene. The pure, perfectly dry substance melts at 9.975" C., and its cryoscopic constant is 12.5 (calculated, 12.35). 0. E. M. Use of Hydrosulphite in Volumetrie Analysis [of Dyestuffs]. I. W. Siegmund. (Monatsh. f. Chem., 1911, 33, 1431-1445.)-After investigating the various forms in which sodium hydrosulphite may be kept as a relatively stable solution suitable for use in volumetric analysis, the author has selected the following mixture as the best : One litre of water, 10 grms.of sodium hydrosulphite, con- centrated B.A.S.F. powder, 15 C.C. of acetone, and 35 C.C. of ammonia, sp. gr. 0.91. The solution is stored in a three-necked Woulfe's bottle under a layer of paraffin oil, the bottle being permanently connected with a burette which can be filled by opening a cock.The liquid in the burette is protected from the air by a column of toluene. The titration flask has a cork with four holes : one of these carries a tube drawn out at the point and connected with the delivery end of the burette; through another passes a thermometer ; whilst the remaining two serve for the passage of a current of carbon dioxide, generated in a Kipp's apparatus, through the flask, to expel the air before titration.The carbon dioxide is freed from oxygen by passing it through a washing bottle containing a solution of ferrous sulphate, Rochelle salt, and excess of ammonium carbonate. The titration flask stands in a water-bath which can be heated if necessary.For standardising the hydrosulphite, a solution of ferrous ammonium sulphate is employed which has been oxidised by permanganate and sulphuric acid; this solution should contain 2 grms. of iron per litre and the hydrosulphite should be restandardised before each series of determinations with 30 C.C. of the iron solution. The standardisation must be done in the cold, since the bisulphite developed would reduce the iron salt if heated; a few drops ofORGANIC ANALYSIS 33 thiocyanate are used as an indicator.The author has applied the method for the estimation of solutions of dyestuffs of the azo, nitro and triphenylmethane groups ; the results agree well with the theoretical values for the pure compounds.The dyestuffs are dissolved in the proportion of about 2 grms. per litre, and 25, 50, or 100 C.C. of the solution are measured out into the titration flask. To the measured dyestuff solution are then added, for 50 C.C. of the dyestuff, 10 C.C. of a 20 per cent. solution of tartaric acid, and the mixture is boiled for a few minutes to expel the air. The flask is then placed in position in the water-bath and a current of carbon dioxide is passed through, whilst the temperature is adjusted at 70" to 80' C.Titration is effected at this temperature, the flask being agitated frequently and time being allowed for the hydrosulphite to exert its full effect. J. F. B. Methoxyl Estimations with Hydriodic Acid in Presence of Phenol. F. Weishut. (Moizatsh.f. Chem., 1912, 33, 1165-1172.)-By the condensation of the methylic ester of P-hydroxynaphthoic acid with anisic aldehyde, the author obtained a body which gave low results for methoxyl when treated by Zeisel's method, owing to its tendency to resinification. The addition of acetic anhydride, as recommended by Herzig for diflicult cases of this nature, made very little improvement.It was found, however, that by performing the distillation in presence of phenol, the quantity of methyl iodide produced was in satisfactory agreement with the theoretical value. The author has made similar determinations of methoxyl groups in a range of other substances which fail to give satisfactory results by the ordinary method. Most of these substances only part with the whole of their methoxyl when heated for seven to fourteen hours with fuming hydriodic acid of sp.gr. 1.96. When treated by the author's method, with 2 to 3 C.C. of phenol in 10 C.C. of hydriodic acid of sp. gr. 1.7, most of these difficult substances gave perfectly satisfactory results in the normal time of one and a half hours. One of the substances tested-tetramethylellagic acid-required fuming hydriodic acid to produce the above result, even when phenol was used ; whilst another-methyl nitroanisate- had to be heated with phenol and fuming hydriodic acid for five and a half hours before decomposition was complete.All the others (ten in number) behaved normally when phenol was employed. In carrying out this method there are placed in the distillation flask first the substance (about 0-2 grm.), then the melted phenol, and lastly the hydriodic acid.The author recommends that whenever normal values are not obtained by Zeisel's method in the ordinary way, the operation should be repeated with the modification above described. J. F. B. Estimation of Total Fatty Acids in Cottonseed Foots. F. N. Smalley. (Eighth Int. Gong. App. Chem., 1912, vol.11, 31-35.)-The author recommends the following modification of the official method of the Inter-state Seed-Crushers' Association, which he finds to give more trustworthy results than any other method tried. About 8 to 10 grms. of the well-mixed sample are saponified in a small extraction flask with alcoholic sodium hydroxide on a water-bath, the liquid being subsequently heated with occasional stirring until all alcohol is driven off.The soap is washed34 ABSTRACTS OF CHEMICAL PAPERS out into a beaker with about 400 C.C. of hot water, and digested on a water-bath till solution is complete. Dilute sulphuric acid is added in slight excess, and the heating continued on the water-bath till the layer of fatty acids has melted and become clear. The liquid is then cooled and filtered from the cake of fatty acids, and the acids washed with cold water till free from traces of sulphuric acid.The fatty acids are then allowed to dry by standing (preferably) overnight. The fatty acids on the filter-paper are transferred back to the original beaker, and the whole dissolved by the addition of 100 C.C. of petroleum-ether (boiling-point not exceeding 50' C.), boil- ing for a few minutes on the electric hot plate to assist solution.The solution is filtered through dry paper, and the residue treated with successive smaller portions of petroleum-ether till the fat is all dissolved. If only two such extractions are given, the residue in the filter-paper should be extracted in a Soxhlet apparatus. The solvent is evaporated and the residue of fatty acids heated to constant weight.A. R. T. Estimation of Total Fatty Acids in CottonseedFoots. F. N. Smalley. (Eighth Int. Cong. App. Chem., 1912, vol. 11, 27-29.)-The following is recommended as a rapid factory method for the estimation of total fatty acids in foots, soap-stock, or similar materials, and consists in determining the iodine value, from which the fatty acids can be calculated by means of a factor.Half a grm. of the well-mixed sample is treated with carbon tetrachloride (5 c.c.) and Wijs' iodine solution (20 c.c.) with the usual precautions. After complete solution of the material the mixture is allowed to stand for thirty minutes, when the titration is carried out with thiosulphate in the usual way. The iodine value of the sample, multiplied by 1.24, gives the percentage of fatty acids present.The method yields good results when the soap-stock is not more than one week old ; after this time, the iodine value falls, and low results for fatty acids are obtained by the use of the factor. A. R. T. Experiments on the " Cold Test " of Oil. A. Lowenstein and L. Beolio. (Eighth Int. Cong.App. Chem., 1912, vol. 11, 17-26.)-The '' cold test " as employed for these experiments was substantially that outlined in Bulletin 99, p. 66, Bureau Chem., U.S. Dept. AgricuZture. (Further information on the test is contained in Bulletin No. 105.) A pad of hair-felt was used to insulate the testing-bottle during the test. To determine the effect of the presence of water in the oil, samples were prepared containing 0.05, 0.10, 0-20, and 0.30 per cept.of water, the oil and water being vigorously shaken until uniformly mixed. Forty C.C. of these oils were placed in duplicate 4-ounce oil bottles, and exposed to a temperature of - 2" F. for eighteen hours. The results showed that the influence of water is in the direction of bringing the flowing-point of the oil towards the freezing-point of water.Tallow, having a high cold test (70" F.), gives a reduced reading proportionate to the water present ; while in the case of neatsfoot oil, with a cold 'test below that of the freezing-point of water, the temperature is raised. The disturbances are small with small quantitiesORGANIC ANALYSIS 35 only of water, and it would appear that samples should be tested as received unless excessive quantities of water or foreign solid impurities are present.The next points tested were whether, where the oil is first frozen solid, the oil should be stirred while freezing or allowed to remain at rest, and whether the oil should stand for a definite time after freezing. An apparatus was devised to deter- mine how much air was stirred into the oil during agitation, and from the results obtained the conclusion is drawn that concordant results for the cold test cannot be obtained unless an empirical method, rigidly followed out in all its details, is employed.After freezing, most oils should stand two hours (tallow oil, lard oil, etc.), though for certain types of oil one hour would be sufficient. The bath containing the oils for this test should have a temperature of 30” F. below the flowing-point of the oil.Experiments were also carried out in order to determine whether any different results were obtained in the “ cloud test” (Bulletin 99, p. 66, Bureau Chem., US. Dept. of Agriculture) when a jacketed test-tube was employed instead of directly placing the oil in the bottle in contact with the freezing mixture.The air-jacketed tube method takes much time, and the results are practically identical with the simpler method. A. R. T. Detection of Marine Animal Oil (Thran) in Other Oils and Fats. C. Stiepel. (Seifensieder Zeit., 1912, 39, 953-954 ; through Chem. Zentralb., 1912, IL, 1751.)-In criticism of Marcusson and Huber’s modification of the insoluble bromide test (Seifensieder Zeit., 1911, 38, 249) for the detection of marine animal oils in other fats and oils, it is pointed out that the (‘ hexabromide ” value of linseed oil is considerably reduced, whilst the ‘‘ octobromide ” value of marine animal oil is eliminated by heating the oils.There is also a simultaneous decrease in the iodine value, which in the case of many marine animal oils falls considerably below 100.A negative result in the ‘‘ octobromide ” test cannot, therefore, of itself be regarded as conclusive of the absence of marine animal oil. For example, the new product neutraline, which has been reported by several chemists to consist of horse fat, or a mixture of that fat with hoof oils, has been found by the author to be a deodorised marine animal fat.C. A. M. Detection of Mineral Oils in Oleins of Wool Fat. L. Settimj. (Ann, Lab. Chim. Cent. delle Gabelle, 1912, 6, 197-201.)-The acetic anhydride method devised by Marcusson (Mitt. Konig. Materialsprufungsamt, 1904,28, 469) is shown t o give good results only in the presence of considerable quantities of mineral oil. The following method is more sensitive and reliable : Ten C.C.of the wool fat olein are shaken with 40 C.C. of a mixture of 1 part of amyl alcohol and 2 parts of 96 per cent. ethyl alcohol in a 50 C.C. graduated stoppered cylinder. In the case of pure wool fat olein the liquid is clear at 20’ C., whilst in the presence of 5 to 30 per cent. of mineral oil (Russian, Galician, Texan, etc.) the liquid remains turbid at 30” C., and on cooling deposits a layer of the mineral oil.The volume of this deposit is approximately 10 per cent. of the quantity of mineral oil in the sample. C. A. M.36 ABST.RACTS OF CHEMICAL PAPERS Colour Reaction of Soya Bean Oil. L. Settimj. (Ann. Lab. Chim. Cent. delle Gabelle, 1912, 6, 461-465.)-0n shaking a mixture of 5 C.C. of soya bean oil with 2 C.C. of chloroform and 3 C.C.of a 2 per cent. aqueous solution of uranium nitrate, an intense lemon yellow emulsion is produced, whilst in the case of arachis, colza, cottonseed, maize, and sesame oils the emulsion is white, Olive oil usually gives a greenish emulsion, but some specimens give a slight yellowish tint similar to that produced by an oil adulterated with a small quantity of soya bean oil.The reaction with soya bean oil is sensitive, and the yellow coloration persists €or several days. C. A. M. Viscosity of Lubricating Oils. A. E. Dunstan and J. F. Strevens. ( J . SOC. Chem. Ind., 1912, 31,1063-1064.)-The authors advance the proposition that the viscosity of a lubricating oil can only be satisfactorily dealt with in the form of a temperature curve, so that the behaviour of an oil can be approximately predicted c p if the working conditions are known; and they further state that the viscosity of an oil should be expressed in absolute units of dynes per square cm.to allow of direct comparison. Ostwald's modification of Poiseulle's viscometer is the instru- ment employed (see Fig.). Filtered oil is run into the viscometer to the marks c, d.The apparatus is suspended vertically, with a delicate thermometer, in a bath of paraffin wax or suitable clear high-flash oil, which is stirred by a glass paddle by means of a hot- air motor. The apparatus should be shielded from draughts of air. After the viscometer has been immersed fifteen minutes at a constant temperature, the levels of the oil are accurately adjusted to the marks c, d, using a warmed pipette to withdraw any oil, when a rubber tube is attached to the top of bulb A, and the oil sucked up above the mark a. It is then allowed to flow ; and when the meniscus passes a the time (taken by a, stop-watch) is noted for the flow between a and b.The average of four or five determinations is calculated. The dimensions of the apparatus are : Capillary, C, 6 crns.x 1 mm. bore ; bulb A , 4 C.C. ; bulb B, 8 C.C. ; length over all, 15 crns. (made by Muller, Orme and Co., High Holborn). For lubricating oils it is advisable to take a series of readings between 70' C. and 200" C., and to plot a curve showing the variation of viscosity with the temperature. For the calibration of the instrument, a very viscous liquid should be used as the standard.The viscosity of pure phenol, which is a suitable fluid, is as follows : Temperature C. Viscosity. 25 0-0850 45 0-0404 50 0,0337 60 0.0253 70 0.0197 If the time of flow of phenol in the viscometer was t seconds, then the viscosity = K x time x density of oil, where K is a constant for the particular instru-ORGANIC ANALYSIS 37 Tern tern tnre C. merit. K only varies slightly with the temperature.Example : Temperature O C., 73.5; t = 130.5 seconds ; log K for viscometer= 5.0414 ; sp. gr. of oil, 0.877 ; then viscosity = K x t x d = 0.126. The results are of value as a means of obtaining the viscosity curve, and com- paring this with the curve given by an oil of high lubricating value for a particular purpose. The following are typical results : Ravison Standard Locomotive Crude American Rape Oil.Cylinder Oil. Cylinder Oil. Unrefined Oil. 70 80 100 115 130 150 170 180 190 198 A. R. T. 0.1460 0-9510 -_ - - - 0.6600 0.1620 0.0673 0.2630 0.2790 - - - - 0.0530 0.0327 - - .- 0.0219 0.0361 0.0574 0,0216 - - - 0.0139 - 0.0265 - - 0.0237 - - - 0.0187 - - __ Stearin of Wool Fat. E. Coen. (Ann. Lab. China. Cent. delle Gabelle, 1912, 6, 567-579.)-The '' stearin " of wool fat is obtained by pressing the distilled fat.Six samples examined by the author had a solidification-point above 48O C., and contained from 20 to 30 per cent. of solid unsaponifiable substances. The saponification value of the fats, excluding unsaponifiable matter, ranged from 157.9 to 168.5, with an average of 163 ; whilst the higher alcohols (expressed as cholesterol) in the unsaponifiable matter ranged from 18.7 to 27.3 per cent.(average 23 per cent.). The hydrocarbons differed from those in wool olein, consisting of a solid pasty mass with a somewhat high sp. gr. at 15" C. (0.924 to 0.936); a low iodine value (26 to 34) ; and a low specific optical rotation at 20" to 25" C. of + 11.7" to + 15.2'.In the case of four other samples the " stearin " melted below 48" C., contained less unsaponifiable matter (9 to 15 per cent.), and had saponification values ranging from 198.4 to 209.4. The hydrocarbons in the unsaponifiable matter (substances not combining with acetic anhydride) were liquid or semi-solid, and had an iodine value of 44.8 to 53.5, and an optical rotation at 20" to 25" C.of +12.1" to +21*2O. The presence of vaseline or paraffin wax in wool fat '' stearin " would thus be indicated by the chemical and physical characters of these hydrocarbons. C. A. M. Estimation of Paraffin Wax and Ceresin in their Mixtures. G. Armani and G. A. Rodano. (Ann. Lab. Chim. Cent. delle Gabelle, 1912, 6, 109-118.)- Paraffin wax may be sharply distinguished from ceresin by the difference in their critical temperature of precipitation from a solution in a mixture of equal parts of absolute alcohol and benzene.Exactly 0-1 grm. of the sample is dissolved in 10 C.C.38 ABSTRACTS OF CHEMICAL PAPERS of the boiling solvent in a test-tube, which is then closed by a stopper, through which passes a thermometer, and in which there is also a small opening to the outside air.This test-tube is surrounded by two other glass vessels to retard the cooling, and a note is taken of the temperature at which the solution becomes turbid. The results obtained with samples of pure paraffin wax and ceresin were as follows : Paraffin wax, Ceresin, per Precipitation per cent. ... 100 95 90 80 75 70 60 50 40 30 20 10 0 cent. ,.. - 5 10 20 25 30 40 50 60 70 80 90 100 temp.O C. ... 25" 27" 30" 36.5" 38" 40' 41.5" 43" 44-5" 47" 47.5' 48" 50" In the case of most paraffin waxes the critical temperature is about 25" C., but there are some soft kinds which show a temperature as low as 20" C. On the other hand, Java paraffin wax (m.-pt., 59" to 62" C.) has a precipitation temperature of 28" C. It is remarkable, however, that a mixture of ceresin with 10 per cent.of Java paraffin wax shows a precipitation temperature of 30" C. Other experiments indicated that the paraftin wax only influenced the precipitation temperature of the ceresin in so far as it diminished the quantity of the latter in solution. Virgin beeswax had a precipitation temperature of 23' C., but it had no appreciable influence on the critical point of paraffin wax or ceresin.Carnauba wax precipitated at 47' C., but, since it is not used in candle material in greater proportion than 2 per cent., its presence cannot materially affect the precipitation of the paraffin wax or ceresin in the unsaponifiable matter separated from candle wax. A quantitative estimation of the unsaponifiable matter followed by the precipitation test will afford an approx- imate valuation of the quantity of ceresin. If the precipitation-point is lower than 28" C.(thus including Java paraffin wax), ceresin cannot be present in the candle material. C. A. I!!. Shellac Analysis and the Detection of Small Amounts of Colophony in Shellac. E. F. Hicks. (Eighth Int. Cong. App. Chem., 1912, vol. 12, 115-121.)- Wijs's method of determining the iodine value gives good results, especially when used with the precautions suggested by Langmuir and White (ANALYST, 1912,36,464), but it has the drawbacks of being an indirect method and of being liable to underestimate the colophony.I n McIlhiney's method, which is based upon the solubility of rosin and insolubility of shellac in petroleum spirit (ANALYST, 1908, 33, 286), it is possible actually to separate and identify the rosin.In the author's experience, however, the petroleum spirit invariably dissolves resinous material from the shellac, and the amount separated from a pure sample may be as much as 2 per cent. I t is therefore necessary, when such small quantities are obtained, to prove, by means of Halphen's colour test (ANALYST, 1909,34, 108), that the residue actually consists of colophony.C. A. M. Determination of Sulphur in Fuels, especially Petroleum Products. I. C. Allen and I. W. Robertson. (Eighth Int. Cong. App. Chem., 1912, vol. 10, 25-31 ; also published by U.S. Bureau of Mines as Technical Paper 26.)-A review of existing methods, which are classified as follows : (1) Dry fusion with alkalis and sub-ORGANIC ANALYSIS 39 sequent oxidation with bromine; (2) dry fusion with alkalis and an oxidising agent ; (3) wet treatment with alkalis and oxidising agents ; (4) Carius' method and modifica- tions of it ; (5) burning in oxygen at atmospheric pressure ; (6) burning in a current of oxygen; (7) lamp methods; and (8) burning in a calorimetric bomb.The last method is applicable to all oils and combustible materials, is rapid and accurate, and is now used to the exclusion of a11 other methods in the laboratory of the Bureau of Mines.The application of lamp methods is restricted. to oils which can be burned in a lamp, and Conradson (Eighth Int. Cong. App. Chem., 1912, vol. 1, 133) has pointed out that the residue of unburned oil and the wick must be examined by a fusion method, as they retain sulphates and sulphonates.Methods (4) and (6) are accurate, but the latter requires much skilled attention, and the former is not free from danger to the operator. Method (5), due originally to Hempel, and advocated with modifications by Griife (Zeitsch. angew. Clzem., 1904, 17, 616), is inaccurate, because combustion is not always complete, and methods (I), (2), and (3), though excellent for coal rtnd coke, are not trustworthy for oils.G. C. J. Wood Turpentines-their Analysis, Refining, and Composition. L. F. Hawley. (Eighth Int. Cong. App. Chem., 1912, vol. 12, 41-100.-Five hundred grms. of the crude sample are distilled in a litre flask connected with a Hempel column dephlegmator (with thermometer) rtnd a condenser.The distillation should be carried on at a maximum rate of 2 drops per second, and the distillate collected in fractions of 10 to 12 per cent., when the temperature is changing slowly, or of 4 t o 5 per cent. when it is changing rapidly. As a rule, the whole of the turpentine substances will have passed over by the time a temperature of 180" C. (corr.) has been reached, just before the heavy oils begin to distil in quantity.Each fraction is weighed, and its boiling-point (cox), sp. gr., and refractive index determined. In the last estimation a correction of 0.00047 for each degree by which the temperature of the room differs from 15" C. is applied. These several results are then preferably plotted in curves against the total percentage weight of the fractions.Typical results obtained in the distillation of samples of old gum turpentine are shown in the following table : Temperature corr. tt 760 mm. C. 158.5 159.0 159.3 159.7 160.0 160.8 161-7 164-5 169-5 Residue Percentage Weight. Single Fractions. 9.5 11.0 11.0 12-2 11.0 12.8 10.0 10.5 6.8 5.0 ~ Combined Fractions 9.5 20.5 31.5 43.7 54.7 67.5 77.5 88-0 94.8 99.8 Sp.Gr. at 15" C. Refractive Index at 15". 0-8650 0.8651 0.8653 0.8655 0.8656 0.8660 0-8665 0.8675 0-8689 0.9450 1.4714 1.4715 1.4716 1,4720 1 *4723 14727 1.4734 1.4760 1.4780 1-494340 ABSTRACTS OF CHEMICAL PAPERS In the case of a wood turpentine, the first 70 to 75 per cent. might have consisted of a mixture of the same terpenes as those of gum turpentine mentioned above, the somewhat lower physical characters being attributable to the presence of smaller proportions of nopinene or camphene, or both.But between the points of the distillation of 75 and 95 per cent. the sp. gr. of the distillate decreased, while the refractive index increased. This indicated the presence of a substance of higher boiling-point and lower sp. gr. than '' pinene " (which here includes also camphene and nopinene).The terpene dipentene (b.-pt. 175" C. ; sp. gr. 0.849 at 15" C. ; [NJS~~OG. = 1.471) was isolated from this sample, and, in the author's opinion, a decrease in the sp. gr. as the distillation temperature approaches 175" C. is probably a, good indication of the presence of this terpene. The separation of the heavy oils from the dipentene was quite sharp, and the conclusion was drawn that this wood turpentine contained about 95 per cent. of terpenes, containing about 80 per cent.of " pinene " and 15 per cent. of dipentene, together with 5 per cent. of heavy oils of high b.-pt., probably non-terpenes. Special experiments showed that there was only a slight change in the composition of wood turpentine, whether by direct distillation or in a current of steam. Towards the very end of the distillation a slight polymerisation of the terpenes to substances of higher physical characters apparently occurred. The main differences between gum and wood turpentines are that the latter usually contain heavy oils, which are generally absent from the former. Even in the case of an old gum turpentine containing heavy oils, such as that described above, it is probable that these oils are of different composition. No dipentene has been found in seventy-five samples of gum turpentine examined. Its presence in wood turpentine may be due to the volatile oil in the original wood, or to trans- formation of some of the " pinene " by the high temperatures of distillation. Wood turpentines also usually contain light oils, for their removal during refining is difficult and requires a fractionating column. rosin spirits " are present in wood turpentine, and account for the odour and colour of the fractions, though they do not materially affect the distillation curves. With regard to the technical qualities, the volatility of a sample would be affected by large amounts of heavy oil, but would probably not be much decreased by proportions up to 10 per cent. The solvent action and drying properties of dipentene appear to be equal to those of (' pinene," and the small proportions of other ingredients in wood turpentine probably do not have much influence. Experiments on samples of refined wood turpentine showed that no great change in composition takes place on storage. I t is also probable that C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9133800031

出版商:RSC    

年代:1913

数据来源: RSC

摘要:

40 ABSTRACTS OF CHEMICAL PAPERS INORGANIC ANALYSIS. A c i d i t y and A l k a l i n i t y of N a t u r a l W a t e r s . J. Walker and S. A. Kay. (J. SOC. Chem. Ind., 1912, 31, 1013-1016.)-A practical application of Sorensen's method (Biochem. Zeitsch., 1909, 21, 131 ; 22, 352) for the determination of hydrion concentrations. A new and more convenient notation is proposed with the hydrion (or hydroxidion) concentration of pure water at the same temperature as unity. Thus, a water with a hydrion concentration of 1.36 x 107 at 18" C.is described asINORGANIC ANALYSIS 41 having a relative acidity of 2, or a relative alkalinity of 0.5, since the hydrion (or hydroxidion) concentration of pure water at 18" C. is 0.68 x 10 -7. An advantage of the method is that, whereas the hydrion concentration varies considerably with small changes of temperature, the relative acidity or alkalinity, as defined above, is nearly independent of the temperature at which the comparison is made.The method, therefore, is analogous to, andlshares the practical advantages of, that by which the specific gravities of dilute aqueous solutions are determined by comparison of their densities with that of water a t the same temperature-not necessarily a standard temperature.The following solutions are required : (1) A -:% solution of Na,RP0,.12H2O, made by dissolving 23.88 grms. of clear crystals picked from a supply of the '' chemically pure " substance, and diluting to 1,000 C.C. ; (2) a Tz solution of KH,PO,, made by dissolving 9.08 grrns.of the pure salt (specially recrystallised and dried at 100' C.), and diluting to 1,000 C.C. ; (3) a mixture of (1) and (2) in the ratio 612 : 388 ; and (4) a 0.1 per cent. solution of axolitmin (Kahlbaumj. The solution (3) is neutral. Of the water to be examined, 25 C.C. is tinted with a measured quantity of the azolitmin solution (1 C.C. is recommended as a convenient amount), and the tint compared with that of 25 C.C.of the neutral solution (3), to which an equal amount of azolitmin is added. If the sample proves to be decidedly acid, 25 C.C. of the acid phosphate (2) is measured out into a similar basin or Nessler cylinder, azolitmin is added, and alkaline phosphate (1) run in from a burette until a match is obtained, more of the sample being added to the other basin or cylinder from time to time to keep the concentration of the indicator in the two vessels approximately the same.In a second titration it is easy to secure almost exact equality of bulk in the two vessels. If the water sample is coloured, resort should be had to the compensation method of Walpole (Proc. PhysioZ. Soc., 1910, 40, 27) in the second titration. The acidity of the sample, corresponding with the composition of the phosphate mixture at the matching-point is given in Table I.: TABLE I.-FoR DECIDEDLY ACID WATERS. Volume of KH,PO, used=25 C.C. Acidity. 300.0 100.0 50-0 20.0 15.0 10.0 9.0 8.0 7-0 6.0 5.0 Volume of Na,HPO, required. 0.28 0.63 1-68 2.23 3.57 3.97 4.52 5-18 6-05 7.26 - Acidity. 4.5 4.0 3.5 3.0 2.5 2.0 1.8 1.6 1.4 1.2 (Neutral) 1.0 Volume of Na,HPO, required.8.07 9'16 10.5 12.3 15.2 19.2 21-4 24.2 27-7 32.7 39.4 If the sample is alkaline or nearly neutral, 25 C.C. of the alkaline phosphate is measured out, the indicator is added, and the acid phosphate is run in until a good42 ABSTRACTS OF CHEMICAL PAPERS match is obtained. volume of acid phosphate required, is given in Table 11. : The acidity or alkalinity of the sample, corresponding with the TABLE II.-FoR NEARLY NEUTRAL AND ALKALINE WATERS.Volume of Na,HPO, used = 25 C.C. Volnme of IiH,PO, required 20.0 - 15.0 0.24 10.0 0.75 9.0 0.91 8.0 1.11 7.0 1.39 6.0 1.77 5.0 2-35 4.5 2.72 4.0 3.15 3'5 3.74 Acidity. - - - - - - - (Neutral) 190 1.2 1.4 1.6 Alkaliiii ty. 3.0 2.5 2.0 1.8 1.6 1.4 1.2 1-0 - - - Volume of I<H,PO, reqnired.4-52 5.56 7.22 8-15 9.30 1098 12-9 15-8 19.1 22.6 25.8 If many samples, differing only slightly in acidity or alkalinity, have to be examined, it is convenient to prepare a series of standards covering the probable range of the samples. The paper includes a table, by reference to which such standards can readily be prepared in quantity by mixing solutions (1) and (2).If the standards are diluted with water, their relative acidity is increased, but the error introduced by the use of wet vessels is negligible. Cooling increases the acidity, but the separate effects of temperature on the standards and the sample almost exactly counterbalance each other. The temperature of the standards and the sample should be identical, but a difference between them of 5' C.only introduces an error of 5 per cent., or about 0.05 of a unit in the neighbourhood of the neutral point. The phosphate solutions remain unchanged in glass bottles for many months at least. The importance of the method described depends on the fact that it affords a measure of the actual acidity or alkalinity of a water, and not merely the potential acidity or alkalinity as given by ordinary titration.It is on this actual state of the water that its rate of action on metals depends. An example is quoted of a water which was rendered dangerously active towards lead by treatment with aluminium sulphate, though the amount of the latter used was equivalent to less than half the bicarbonate hardness of the water, which after treatment still possessed temporary hardness, and no free acid save carbonic acid, to excess of which its high relative acidity was due.G. C. J. Detection of Antimony in Alloys. R. Belasio. (Ann. Lab. Chim. Cent. delle Gabelle, 1912, 6, 501-503.)--From 0.5 to 1 grm. of the finely-divided alloy is treated with 2 C.C. of boiling concentrated sulphuric acid, and the mixture cooled, diluted with an equal volume of water, cooled and filtered from the insoluble lead sulphate.A few drops of the filtrate are heated in a porcelain basin with a crystal of sodium sulphite until the liberated sulphur dioxide has been expelled, after whichINORGANIC ANALYSIS 43 1 or 2 drops of a solution of 1 grm. of potassium iodide and 1 grm. of cesium chloride in 5 C.C. of water are added.I n the presence of antimony a stable rose-coloured precipitate of iodide of cesium and antimony is obtained. Under the same conditions bismuth gives a fugitive yellow coloration and a brown precipitate, whilst copper gives a light yellow precipitate. C. A. AT. Cadmium Nitrate in Quantitative Analysis. A. Vorisek. (Eighth Int. Cong. App. Chem., 1912, vol. 17, 91-102.)-A solution of cadmium nitrate may be used to separate ferrocyanides, ferricyanides, and sulphides, from the other anions precipitated as silver salts (chloride, bromide, iodide, cyanide, and thiocyanate). The solution of the salts is neubralised, an excess of 10 per cent.cadmium nitrate solution added, and potassium hydroxide solution run in until the reaction is faintly ilkaline, after which the excess of alkali is neutralised with a few drops of the cadmium solution or of dilute acetic acid, and the mixture diluted, heated on the water-bath for five to ten minutes, and filtered while hot.When ferricyanide is present, traces may pass into the filtrate, and to remove these it is necessary to boil the filtrate with a few drops of sulphurous acid solution and filter it again.Portions of the filtrate are then tested for cyanide (about four-fifths of which will remain in solution), and for chloride, bromide, and iodide. Thiocyanate is eliminated by means of mercuric, chloride solution. Precipitation of Tartaric and Citric Acids by Cadmizm.-A solution of cadmium nitrate in the presence of potassium hydroxide completely precipitates tartaric and citric acid from neutral solutions, the excess of alkali being neutralised as described above.The precipitate is filtered while hot, washed, and stirred with cold 5 per cent. acetic acid until disintegrated, after which the liquid is filtered and the solution of cadmium citrate and tartrate is evaporated nearly to dryness. The residue is taken up with water, the cadmium separated by means of hydrogen sulphide, and the filtrate evaporated to obtain the free citric and tartaric acid.C. A. M. Sensitive Reaction for Molybdic Acid. P. Melikow. (J. Rz~ss. Phys.-Chem.. Soc., 1912,44, 608 ; through Chem. Zeiztralbl., 1912, II., 1579.)-The residue obtained by evaporating the solution under examination on the water-bath is rendered alkaline with concentrated ammonia solution, and a 3 to 4 per cent.solution of hydrogen peroxide added; the presence of molybdic acid in the original solution is shown by a pink or red coloration due to ammonium permolybdate. If the liquid is then concentrated, and sulphuric or nitric acid added, a yellow solution of permolybdio acid is obtained. 0. E. M. Electro-Analysis with Light Platinum Electrodes. F. A.Gooch and W. L. Burdick. (Zeitsch. anorg. Chem., 1912, 78, 213-220.)-The total weight of platinum in the apparatus illustrated does not exceed 1 grm. The glass cell, of about 35 C.C. capacity, is constructed from the top of a thistle funnel, and rests in a brass spring support. A similar support of aluminium is used to support the cell on the balance pan. [In use the cell is pressed down into the stand as far as it will go, but is not so.44 ABSTRACTS OF CHEMICAL PAPERS figured, as parts of the apparatus would then be obscured.] The anode a is a piece of thin platinum-foil about 1 cm.square, welded to a platinum wire, zu', which penetrates the wall of the cell. The cathode c consists of a disc of gauze or foil, also about 1 square cm. in area, which is fused to the glass rod r.The wire zu" makes connec- tion between c and the source of current. As the use of such small electrodes implies a high current density, unless the electrolysis is to be a prolonged operation, the apparatus has been designed to deal with deposits with no pretence to be adherent. An essential part of the equip. ment, therefore, is a filter-tube, which is not figured, but which consists of a short piece of tubing to one end of which a disc of platinum-foil is fused.Before attaching the foil it is pierced with pinholes, and the burred side is turned away from the glass. Before commencing an analysis, this filter- tube is plunged into some asbestos pulp, its open end is connected to a pump by means of rubber tube, and the filter-tube thus prepared is dried and weighed together with the cell and the cathode with its connecting wire and glass rod support.The liquid to be electrolysed (about 15 c.c.) is next introduced into the cell, which is covered with an pw=i inverted funnel or split watch-glass, and the cathode is connected to gear which gives it a rotation of about 300 r.p.m. When electrolysis is complete the filter-tube is dipped into the electrolyte, its open end being connected to the pump, and the cell is repeatedly filled up with water, and finally with alcohol.The cell, cathode, and filter-tube, are then dried in an air-bath, and finally weighed. Several results with copper and nickel are given. With a current of about 1 amp. at 5 to 6 volts (N.D.,,,=50 to SO), 0.1 grm. of either metal may be deposited in twenty to thirty minutes with an error not exceeding k 0.5 mgrm.G. C. 5. Determination of Lead Sulphate and the Ultimate Estimation of " Sublimed White Lead " in Rubber. J. A. Schaeffer. (J. hd. Eng. Chem., 1912, 4, 836-838.)--" Sublimed white lead," as placed on the market, is a basic sulphate of lead of the average percentage composition : PbSO,, 78.5 ; PbO, 16-0 ; ZnO, 5.5.Commercial samples differ very little in percentage composition. The properties of the material, which consists of very finely- divided amorphous particles, are said to recommend it as a constituent of rubber mixinga. Its use is limited, however, in cases where specifications set a limit to the total sulphur content. There is reason to believe that its more extended use would be tolerated if ready means existed for differentiating between inert sulphur, existing as lead sulphate, and active sulphur, to which purchasers are anxious to set a limit.The following method has, therefore, been devised for estimating lead sulphate in rubber : The sample (2 grms.) is placed in the middle of a hard glass tube, about 8 inches by 1 inch, and gently heated, whilst a stream of carbon dioxide is passed through the tube.When the organic matter is all driven off, the dry residue is ground in a small agate mortar, transferred to a flask, which is filled with carbon dioxide, and decomposed by boilingINORGANIC ANALYSIS 45 with 25 C.C. of hydrochloric acid, a current of carbon dioxide being passed all the while to avoid risk of oxidising sulphide to sulphate.Twenty minutes’ boiling suffices to eliminate hydrogen aulphide and to bring nearly the whole of the lead sulphate into solution. The solution is diluted and filtered, and any residue is washed with hot water, ignited in a porcelain crucible, digested with hydrochloric acid, and the solution filtered and added to the principal solution.Lead sulphate equivalent to 0.1 to 0.2 per cent. on the original rubber may be recovered by this h-eatment of the (( insoluble ” residue. The combined filtrates are nearly neutralised with ammonia, neutralisation is completed by the cautious addition of sodium carbonate, and an excess of about 2 grms. sodium carbonate is then added. The solution is boiled for fifteen minutes, filtered, and the precipitate is washed.The sulphate in the filtrate and washings is then determined as barium sulphate, and calculated to sulphur and lead sulphate. Test analyses show that oxidation of sulphide to sulphate is not wholly prevented, that sulphate‘ sulphur equivalent to 0.1 per cent. may be found when none was originally present, and that 2.1 per cent- may be found when only 2.0 per cent.(equivalent to 19 per cent. of lead s~lphate) was present in the original sample. These numbers illustrate the extreme error of the method, which never gives results below the truth. Methods for the estimation of lead sulphate in rubber mixings which also contain calcium and barium sulphate will be dealt with in another paper. G. C. J. Detection of Nickel in Plated Articles. G.Silvestri and A. Cappelli. (Ann. Lab. Chim. Cent. delle Gabelle, 1912, 6, 119-120.)-Reichard’s methylamine hydrochloride test for nickel may be used for the detection of that metal in plated objects. If a fragment of nicked-plated iron is heated with a drop of hydrochloric acid and a crystal of methylamine hydrochloride, a blue coloration is produced, which disappears on cooling. Cobalt under the same conditions gives an azure blue colora- tion, but, unlike the nickel coloration, this persists after cooling.C. A. M. New Gasometric Method for the Estimation of Nitric Oxide : I. 0. Bau- disch and G. Klinger. (Ber., 1912, 45, 3231-3236.)-The new method for the estimation of nitric oxide in gas analysis depends on its oxidation by means of air, with the formation of nitrogen trioxide and the absorption of the latter in the form of nitrite by means of potassium hydroxide.Raschig has studied the oxidation of nitric oxide, and has found that it takes place in two stages. The first phase corre- sponds to the formation of the trioxide, and takes place with extreme rapidity; the second phase corresponds to the formation of the tetroxide, and requires an appre- ciable time for its completion.In order to limit the reaction to the first phase, it is only necessary to absorb the trioxide as fast as it is produced, so that an excess of oxygen cannot come into play. The reaction is then expressed by the equation 4N0 + 0, + 4KOH = 4KN0, + 2H,O. 4 vols. + 1 vol. = 0 vol. The operation is performed in a Fuller’s gas pipette into which a few sticks of moist potassium hydroxide are inserted and all the air is then expelled by mercury.A46 ABSTRACTS OF CHEMICAL PAPERS measured volume of the gas mixture to be analysed is introduced so that it surrounds the potash; next, a measured volume of air in excess is admitted, and the reaction allowed to take place. The residual gas is withdrawn and measured in the burette.Four-fifths of the observed contraction are due to the nitric oxide. The air used should previously be freed from carbon dioxide. The new method is perfectly accurate and very rapid, and the presence of other gases, such as nitrous oxide or hydrogen, which interfere with other methods, is quite immaterial. When the oxidation is performed in the reverse manner by admitting the nitric oxide to the excess of air standing in presence of potash, the results are inaccurate, because a mixture of trioxide and tetroxide is produced, with the absorption of a variable quantity of oxygen.J. F. B. Determination of Phosphorus in Commercial Acetylene. L. M. Dennis and W. J. O’Brien. (J. Ind. Eng. Chem., 1912, 4, 834-836.)-The paper deals really with the examination of commercial carbide rather than acetylene.For the estima- tion of calcium phosphide, the authors recommend a, modification of the method of Lunge and Cedercreutz, which depends on the generation of phosphine and its subsequent oxidation, by means of hypochlorite, to phosphoric acid, which is finally determined as magnesium pyrophosphate. A Kipp apparatus with 4-inch bulbs is used for the decomposition of the carbide, and its gas outlet is connected to two Friedrichs’ gas-washing bottles, arranged in series, and each charged with about 75 C.C.of a solution containing approximately 3 per cent. of actual NaClO. Before introducing the sample, sufficient brine is introduced into the Kipp apparatus to seal the end of the stem attached to the upper bulb.The apparatus is next connected to the gas-washing bottles and air swept out of the whole series by introducing hydrogen through the upper tubulure of the Kipp apparatus. The gas-washing bottles are temporarily disconnected, 50 grms. of carbide are introduced into the middle bulb of the Kipp apparatus, connection is again made with the gas-washing apparatus, and hydrogen is passed for a further five minutes.Sufficient brine is then introduced through the upper tubulure of the Kipp apparatus to enable the apparatus to function as a gas generator, and the cock between the apparatus and the gas-washing bottles is so adjustsd that bubbles rise through .the latter at a rate slightly faster than can be counted. Two hours serve for the decomposition of 50 grms.of carbide. When decomposition is complete, the acetylene remaining in the generator is driven through the absorption bottles by means of a, current of hydrogen. The contents of the gas-washing bottles are transferred to a, beaker, acidified with 10 C.C. of hydrochloric acid, boiled to expel chlorine, and rendered alkaline with ammonia, and the phosphate present is then precipitated with magnesia mixture.Carbide made from carefully-selected materials yields less than 10 mgrms. of magnesium pyrophosphate when tested in this way. Small quantities like this may be estimated with an error of 20.2 per cent., whilst the error attaching to determinations of quantities five times as large is about 21 per cent. It is usual to state results as C.C.phosphine per 100 C.C. acetylene. For this purpose it is necessary to determine the total volume of gas liberated by a definite weight of the carbide, and the most convenient method is that which depends on the loss in weightINORGANIC ANALYSIS 47 of an apparatus in which a weighed quantity of carbide is decomposed by brine, the apparatus including a calcium chloride tube, to deprive the escaping acetylene of moisture.G. C. J. Estimation of Potassium in Fertilisers, Soil Extracts, and Plant Ashes. w. A. Davis. (J. Agric. Sci., 1912, 5, 52-66.)-The platinum chloride method of estimating potassium is in many respects unsatisfactory, and has been largely superseded, especially in Germany, by the perchloric acid method of Wense and Caspari (cf.ANALYST, 1910, 35, 417). To obtain the best results, the perchlorate precipitate should be washed with 95 per cent. alcohol saturated with potassium perchlorate at the washing temperature. The presence of barium, magnesium and calcium chlorides and sodium phosphate are all shown experimentally to be without harmful effect, and these salts need not be removed. Potassium sulphate can be estimated direct, using a sufficient excess of perchloric acid without conversion into chloride by means of barium chloride; if, however, the sulphate is converted into chloride by the Stassfurt method, the exact precipitation of the sulphate is not imperative as with the platinum method.All uncertainty as to the atomic weight of platinum is eliminated by the use of the perchloric method.Full details as to the preparation and treatment of the precipitate are given, for which reference should be made to the original paper. H. F. E. H. Estimation of Water in Silicate Minerals and Rocks. M. Dittrich. (Zeitsch. anorg. Chem., 1912, 78, 191-200.)-Penfield's method may give results far below the truth unless the tube be wrapped, round with.platinum as Penfield directed, and the temperature raised to such a point that the platinum adheres to the glass.Many minerals and rocks fail to give up the whole of their water when heated alone in quartz or platin-iridium tubes, if the highest temperature employed is that of an ordinary blowpipe flame. If an electric furnace capable of giving a temperature of 1250' C. be available, heating alone in a quartz tube, with subsequent direct weighing of the water evolved, gives results agreeing with those obtained by the method of Dittrioh and Eitel (ANALYST, 1912, 37, 380).The former method has the advantage that a determination of carbon dioxide may be combined with it. On the other hand, it is not available in presence of fluorides, whereas the method of Dittrich and Eitel is, and, moreover, gives a residue which is immediately available for the determination of silica, alumina, etc.The criticism of Penfield's and other methods is supported by test numbere. G. C. J. Gravimetric Estimation of Zinc. H. Schilling. (Chem. Zeit., 1912, 36, 1352.)-It is proposed to substitute benzene-sulphonic acid for acetic acid in the precipitation of zinc as sulphide. The advantages of the modification are the more rapid subsidence of the precipitate, its more granular condition which determines more rapid filtration, and the fact that it exhibits no tendency to pass through the filter when washed with distilled water. The solution is freed in the usual manner from silica and from metals with sulphides insoluble in dilute mineral acids. I t is then boiled with a few drops of hydrogen peroxide solution, rendered alkaline with48 ABSTRACTS OF CHEMICAL PAPERS ammonia, and again treated with hydrogen peroxide to oarry down manganese with the hydroxides of the iron group. The precipitate is filtered off, redissolved, and reprecipitated to recover any co-precipitated zinc. The filtrates are united and an excess of potassium hydroxide added--that is to say, at least as much as is equivalent to the zinc present. Excess of benzene-sulphonic acid is next added, the solution heated to boiling, and a current of hydrogen sulphide led through it until it is quite cold. The application of the method to the separation of zinc from nickel and cobalt, calcium and magnesium will form the subject of another paper. G. C. J.

ISSN:0003-2654    

DOI:10.1039/AN9133800040

出版商:RSC    

年代:1913

数据来源: RSC

摘要:

48 ABSTRACTS OF CHEMICAL PAPERS APPARATUS, ETC. Apparatus for Estimating Dust in Gas. C. T. Nesbitt. (Chem. Netus, 1912, 106, 235.)-Two smooth, unribbed funnels, the edges of which fit closely, are clamped together in an apparatus consisting essentially of two wooden rings joined over the funnels by means of (1) a strip metal hinge, and (2) an ordinary screw- clip, by which the connection can be made gas-tight, Between the edges of the funnels a circular ring of thin rubber (about ,i3g inch wide) is placed, to prevent leakage.A piece of copper gauze is bent and placed in the back funnel so that its flat surface is flush with the edges of the funnel, and a filter-paper is placed on the rubber ring and gauze, when the other funnel is fixed in position and the whole clamped together.The first funnel is tared before use, about 100 litres of gas run through the apparatus, and, after drying, the funnel is weighed again. The filter-paper with the dust on it is burnt, and the weight of dust SO found, added to the increase of weight of the funnel, gives the total dust in the quantity of gas used. A satisfactory filter-paper is C. S. and S. No. 589 This rubber is best glued to the back funnel.Blue Band.” A. R. T. Simple Extraction Apparatus. L. Kalusky. (Zeitsch. Untersuch. Nahr. Genussm., 1912, 24, 623- 624.)-A small perforated cup provided with three legs (see figure) is placed in the extraction flask by means of the rod; this cup supports the thimble containing the substance to be extracted, and the flask is attached directly to the condenser by means of a cork.The upper end of the thimble rests against the neck of the flask. Ths quantity of solvent added to the flask should be such that it does not touch the bottom of the thimble. As the extraction is made at the boiling-point of the solvent, it is claimed that the rate of extraction of a constituent from a substance is more rapid than in the ordinary extraction methods. w.P. s. Prevention of Emulsification in Extractions by Immiseible Solvents. G. H. Meeker. (Eighth Inter. Cong. App. Chem., 1912, vol. 17,45-49.)-The apparatus described consists of a cylindrical separator into which dips a vertical shaft providedAPPARATUS, ETC. 49 near its lower end with two sets of propellers, one of which is adjusted so that it is completely immersed in the lower liquid, whilst the other revolves in the upper liquid.The propeller blades are of curvilinear outline, and, when the shaft is driven at a suitable speed by means of a cord connected with a motor, cause the upper liquid to be driven downwards, and the lower liquid upwards, so that fresh surfaces are continually brought into contact without sufficient interagitation being caused to produce an emulsion.The extraction of alkaloids by means of this apparatus has been found to be more complete than by the older '' shaking-out " method. C. A. M. Determination of the Permeability of Soils to Water. J. W. Leather. (Eighth Int. Cong. App. Chenb., 1912, vol. 15, 155-158.)-The rate at which water can flow through a short column of soil when a constant supply is maintained on the surface varies considerably with different soils.Some of the alkali lands in India, are highly impervious. To enable comparisons to be made with ordinary soils, the author has designed a special and somewhat elaborate machine (two illustrations are given in the paper) to fill soils uniformly into metal cylinders measuring 3 inches high by 2 inches diameter, and provided with a false bottom of brass wire gauze.Water is then poured on the surface, and after it has once commenced to flow from the lower surface the rate of flow is measured, the hydrostatic '' head " being main- tained within desired limits. H. F. E. H. Unusual Case of Specific Gravity. A. L. Hyde. (J. Amer. Chem. SOC., 1912, 34, 1507-1509.)-The author has noticed that when paranitrotoluene (sp.gr. 1.2856) is dissolved in carbon disulphide (sp. gr. 1.2660 at 20" C.) the resulting solution is lighter in gravity than pure carbon disulphide. This is contrary to the usual rule that, when a solid heavier than a liquid is dissolved in the liquid, the resulting solution has a higher specific gravity than the pure liquid. Thus, it was found that a solution of paranitrotoluene in carbon disulphide of 20.9 per cent. strength had a sp. gr. of 1.2370 at 20" C., and one of 53.0 per cent. a sp. gr. of 1.1988, and the decrease of sp. gr. is nearly proportional to the percentage of solid in solution. Further experiments have shown that the tendency of both carbon disul- phide and of paranitrotoluene is to increase the volume of solutions in which they are constituents, and where both are present an actual lowering of sp. gr. results. A. R. T.

ISSN:0003-2654    

DOI:10.1039/AN9133800048

出版商:RSC    

年代:1913

数据来源: RSC