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APRIL, 1912 Vol. XXXVII., No. 433. THE ANALYST. OBITUARY. WE deeply regret to have to record the deaths of Mr. Arthur E. Ekins and Mr. John Pattinson, former Vice-presidents of the Society. Obituary notices will appear in the next number of the Journal. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. THE Monthly Meeting of the Sociaty was held on Wednesday evening, March 6, in the Chemical Society’s Rooms, Burlington House. The President, Mr. 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. M. E. Balston, M.A., H. A. Caulkin, B.Sc., F.I.C., and C. R. Wilkins, B.Sc., were read for the second time, and certificates in favour of Messrs. Reginald Freeman Easton, 38, Edith Road, West Kensington, W., assistant to Mr. G. Cecil Jones, F.I.C., and Leonard Goodban, A.I.C., 43, Addison Gardens, W., assistant to Mr. Frederick Davis, were read for the first time. Miss M. Gazdar, B.Sc., A.I.C., and Mr. H. Hawley, M.Sc., were elected members of the Society. The following papers were read : L L Standards for Malt Vinegar,” by A. Chaston Chapman, F.I.C. ; The Estimation of Ammonia in Carbonated Waters,” by G. D. Elsdon, B.Sc., and Norman Evers, B.So. ; “ A Note on B New Preservative for Milk, Cream, etc.,” by George A. Stokes; ‘( The Phosphomolybdate Estimation of Phosphoric Acid in Soils,” by S. J. M. Auld, D.Sc., Ph.D., F.I.C. ; and “ A Method of Estimating Calcium Carbonate in Soils,” by Herbert S. Shrewsbury, F.I.C.

ISSN:0003-2654    

DOI:10.1039/AN9123700121

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年代:1912

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122 ARNAUD AND HAWLEY: NOTES ON THE DETERMINA.TION OF B 42 8 0.5 2 1.0 &4 G NOTES ON THE DETERMINATION OF BUTTER FAT AND COCOANUT OIL IN MARGARINE. -- I BY 3’. W. F. ARNAUD, F.I.C., AND H. HAWLEY, RI.Sc. (Read at the Meeting, February 7 , 1912.) THE method suggested by Cribb and Richards (ANALYST, 1911,36,327) for calculating from the Reichert and Polenske figures the percentage of cocoanut oil and butter fat in margarine mixtures yields excellent results with comparatively large proportions of cocoanut oil, but with quantities under 20 per cent. (the Polenske being below 2.5) the correction applied to the Reichert and Polenske figures is too great. With the aid of the following formulae and of the subjoined curve, deduced from the analysis of a variety of mixtures, the corrected Polenske figure may be obtained and the percentage of cocoanut oil calculated : R 10 P=(P--P”)- - +T.P = corrected Polenske figure. P’ =found Polenske figure. P=Polenske figure of margarine fat free from cocoanut oil and butter T = correction ascertained from curve. (about 0-4). loop Percentage of cocoanut oil = - 17.6 2.0 1.5 1.0 0.6 The butter fat is then found by the following method : R = ( R - R ) - Beichert due to cocoanut oil - T. R = corrected Reichert-Meissl figure. R = found Reichert-Meissl figure. R = Reichert-Meissl figure of margarine free from butter and cocoanut oil T = correction ascertained from curve. (about 0.6). 100R Percentage of butter fat = ~ 25BUTTER FAT AND COCOANUT OIL IN MARGARINE 123 The percentage of butter fat in any margarine mixture may be coufirmed by the Kirschner process, for which purpose the following formula is recommended : K = (IT-0.5) --p in which 10' K = corrected Kirschner figure.K = found Kirschner figure. 0.5 = Kirschner figure of butter-free margarine. P = found Polenske. 100 K Percentage of butter fat = I__ 23 ' DISCUSSION. Mr. c. EL CRIBB said that Mr. Richards and he had referred in their paper to the question of an allowance for the Reichert and Polenske figures of margarine fat in mixtures, but in the mixtures then dealt with there was never less than 20 per cent. of cocoanut oil and 20 per cent. of butter, so that the correction would be very small, and it seemed scarcely worth while to make it ; but when the proportion of margarine might be as high as 90 per cent. it became necessary to take the correction into account. Mr. E. R. BOLTON said that due regard must be had to the composition of the margarine. Margarine nowadays often contained notable quantities of lard, and, although lard itself had a very low Reichert-Meissl value, it exercised, when mixed with other fats, a curious altering effect on the volatile fatty acids.

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DOI:10.1039/AN9123700122

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年代:1912

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BUTTER FAT AND COCOANUT OIL IN MARGARINE 123 STANDARDS FOR MALT VINEGAR. BY A. CHASTON CHAPMAN, F.I.C. (Read at the Meeting, March 6, 1912.) DESPITE the numerous attempts which have been made to define malt vinegar and to lay down analytical limits for its composition, the present state of affairs in regard to that condiment can scarcely be described as satisfactory. It is clearly a much simpler matter to say what malt vinegar should be in terms of the materials used or the methods adopted in its production than to lay down chemical standards of composition. The latest pronouncement in this country appears to be contained in a letter addressed by the Assistant-Secretary of the Local Government Board to the Secretary of the London and Country Vinegar Brewers’ Association. In this it is stated that malt vinegar ‘( is derived wholly from malted barley or wholly from cereals, the starch of which has been saccharified by the diastase of malt.” Under the general definition of ‘( vinegar,” moreover, it is to be “ a liquid derived wholly from alcoholic and acetous fermentations; it shall contain not less than 4 grammes of acetic acid (CH,COOH) in 100 cubic centiinetres of vinegar ; it shall not contain124 CHAPMAN : STANDARDS FOR MALT VINEGAR arsenic in amounts exceeding 0.0143 milligramme in 100 cubic centimetres of vinegar, nor sulphuric or other mineral acid, lead, or copper ; nor sball it contain any foreign substance or colouring matter except caramel." On June 26, 1906, the United States Department of Agriculture issued a circular (No.19) giving definitions of various kinds of vinegar. I n this circular malt vinegar is defined as '( a product made by the alcoholic and subsequent acetous fermentations, without distillation, of an infusion of barley malt or cereals, whose starch has been converted by malt, is dextro-rotatory, and contains, in one hundred (100) cubic centimetres (20" C.), not less than four (4) grammes of acetic acid, not less than two (2) grammes of solids, and not less than two-tenths (0.2) gramme of ash; and the water-soluble ash from one hundred (100) cubic centimetres (20" C.) of the vinegar contains not less than nine (9) milligrammes of phosphoric acid (P205), and requires not less than four (4) cubic centimetres of decinormal acid to neutrttlise its alkalinity." Some time ago a certain firm of vinegar manufacturers, finding that their vinegar, although made strictly in accordance with the requirements of the United States Department of Agriculture-that is to say, wholly from barley malt and cereals, without the use of any sugar whatever-did not comply with the analytical require- ments of the Department, asked me, if I could, to explain the apparent discrepancy. On referring to the above definition, it will be seen that malt vinegar must be, among other things, dextro-rotatory ; and presumably any vinegar which did not comply with the definition in this respect would not be admitted into the United States under the description of " malt vinegar." Now, it so happened that, whilst the vinegar manufactured by the firm in question sometimes had a dextro-rotatory action on polarised light, it was very much more frequently appreciably lavo- rotatory.Thus, twelve samples which 1 examined, and which represented in the aggregate almost the whole of the vinegarmat that time in stock, were all laevo- rotatory, the rotations varying from -0.56" to -0.76' when examined in a tube 200 mm. long, using sodium light. Inasmuch as it was absolutely certain that no sugar of any description had been used in the manufacture of this vinegar, it became necessary to explain this Iaevo-rotation. I t was clear that certain laevo-rotatory constituents had been extracted from the grain during the manufacture of the vinegar, and a moment's consideration sufficed to show that these constituents could only be the proteins or certain of the products of their hydrolysis, such as the proteoses, peptones, and amino-acids. I t may be pointed out here that the vinegar in question contained an average of 0.085 per cent.of nitrogen, equivalent to 0.53 per cent. of proteins. I t is, of course, very well known that the naturally-occurring proteins are almost invariably strongly laevo-rotatory, and the same applies to many of the products of their hydrolysis, particularly the proteoses and peptones, the specific3 rotatory powers of these substances for sodium light varying from - 50" to - 80" in a 200 mm. tube, using sodium light. Asparagine, which occurs in malt wort, is slightly laevo-rotatory, and certain other of the amino-acids and amides are slightly dextro-rotatory. The important point, however, is that the more complex products of hydrolysis are those which are most strongly laevo-rotatory. I t is clear that, if it were possible so thoroughly to ferment away the carbohydrate constituents of malt wort as to leave practically nothing undecomposed, the protein matters presentCHAPMAN : STANDARDS FOK MALT VINEGAR 125 might quite well cause the resulting wash to exhibit a lzvo-rotatory action, and my first experiments were directed to ascertaining whether such was the case.It is, of course, the practice of vinegar manufacturers to carry out the fermentations of their worts in the presence of diastase, siiice by this means the malto-dextrins and other comparatively stable carbohydrates are converted into fermentable substances, and so the maximum amount of alcohol, and subsequently of acetic acid, is obtained.I n the experiments described below I have therefore carried out the fermentations of the worts in question in the presence of active diastase-that is to say, the worts were not boiled prior to the introduction of the yeast. I n the first place, two worts having the same sp. gr. (1070') were prepared from the same malt, and were pitched with a small quantity of ordinary distillers' yeast, the temperature being kept within the ordinary limits of practice. The fermentations were started on December 4, and five days later the sp. gr. of each had fallen below 1000". The following results show the optical activities in a 200 mm. tube, using sodium light, of these worts on three different dates: No.1. No. 2. December 9 ... ... ... -0.40"' - 0.080 ,, 11 ... ... ... - 1.00" - 0.70" ,, 13 ... ... . . . -1.00" - 0.80" Two further experiments were then made with worts of rather lower sp. gr. (1050'), and employing the yeast actually used in the vinegar factory in question in place of the distillers' yeast used in the preceding experiment. The following results were obtained : No. I. No. 2. December I1 ... ... ... +0*54" - ,, 13 ... ... ... +0*04" + 0.20" ,, 14 ... ... -0.44" - 0.04" I t will be scarcely necessary to point out that these worts were not examined polarimetrically until their density showed that almost the whole of the carbohydrate matter had disappeared, and for that reason no considerable plus rotations are shown. These results show very clearly that, with a suficiently perfect fermentation, worts prepared from malt alone are capable of yielding liquids which are appreciably 1 zvo-rot at ory.I n the next place, experiments were directed to proving that the Izvo-rotation of these worts was in fact due to the presence of proteins and their products of hydrolysis. If such were the case, it should be possible, by the removal of these substances, to convert a lzvo-rotatory liquid into either an inactive or a dextro- rotatory one. I t is well known that, by the combined use, under proper conditions, of aqueous solutions of mercuric acetate and phosphotungstic acid, both the proteins and the majority of the products of their hydrolysis may be removed from organic liquids without effecting any change in the carbohydrates present.The mercuric acetate solution used in the following experiments consisted of a saturated aqueous solution of the salt; the phosphotungstic acid solution consisted of a 25 per cent. solution of the substance in water without the addition of mineral acid. I n the first place, the mercuric acetate and the phosphotungstic solutions were added to some126 CHAPMAN STANDARDS FOR, MALT VINEGAR fermented malt wort made in the laboratory, and having a rotation in a 200 mm. tube of -0.45". After filtering and making the requisite correction for the dilution due to the volume of the reagents eniployed, the liquid was Iound to have a rotation of +0*46". Similar experiments were then made with five samples of lzvo-rotatory vinegar, with the following results, the numbers under (a) representing the rotation of the vinegar prior to the addition of the reagents, and those under ( b ) the rotation after filtration : i 4 ( b) No.1 ... ... ... ... -0.63" + 0.02" ,, 2 ... ... ... ... - 0.60" inactive ,, 3 ... ... ... ... - 0.65" + 0*08" ,, 4 ... ... ... ... -0.63" -+ 0.13" ,, 5 ... ... ... ... -0.72" + 0.06" These results entirely bear out those obtained with the malt wort itself, and show that the lzvo-rotation of this vinegar is, in fact, due to the presence of proteins and the products of their hydrolysis. During the process of fermentation the amino- acids, and to a less extent the proteoses and peptones, will have been utilised by the yeast for its nutrition, and the residual nitrogen in the vinegar must consist largely of proteins and of their more complex hydrolytic products--that is to say, of those substances which exhibit the greatest degree of lmo-rotation.I may perhaps add that I have made experiments with the mercuric acetate and phosphotungstic acid solutions in the presence of a small quantity of lzvulose, and have found that when used under proper conditions these reagents bring about no change whatever in the rotation of that carbohydrate. This is borne out by experiments which have recently been made by Neuberg and Ishida (Biochem. Zeitsch., 1911, 37, 142- 169), who call attention to the errors which may result in the polarimetric estimation of sugar in natural products owing to the presence of lzvo-rotatory proteins and amino-acids. These authors have also made use of mercuric acetate and phosphotungstic acid, and have recorded a great many results to show that these reagents have no effect on the rotation of the carbohydrates present.The above results show very clearly that a genuine malt vinegar-that is to say, a vinegar prepared entirely from malt and cereals whose starch has been converted by diastase -need not necessarily be dextro-rotatory, but may be either lzvo-rotatory or optically inactive. As further showing the fallacy of insisting on dextro-rotation as an indication of genuineness, it is only necessary to point out that the unfermentable matter in many samples of commercial invert sugar is optically inactive, aad that even if a considerable proportion of invert sugar were used in the manufacture of the vinegar, the latter would not necessarily be lzvo-rotatory.It would appear, there- fore, that unless the United States Department of Agriculture modify their existing regulation, considerable injustice may be done, not only to the home producer, but also to vinegar manufacturers in other countries, whose inalt vinegar may be optically inactive or slightly lzvo-rotatory, and who may wish to introduce it into the United States. Whilst many samples of malt vinegar are undoubtedly dextro- rotatory, to insist upon this analytical requirement would be tantamount to exclud- ing from the United States the vinegar of every manufacturer who is successful inCHAPMAN : STANDARDS FOR MALT VINEGAR 127 very thoroughly fermenting away the carbohydrate constituents of his worts, and would practically amount to putting a premium on bad working, to say nothing of tempting dishonest manufacturers to make their vinegar comply with the require- ments by the appropriate additions.Perhaps the simplest way of manufacturing a malt vinegar to insure its satisfying the United States authorities in respect of its rotation would be to eniploy in its manufacture a proportion of coinmercial glucose. The requirements of the United States Department of Agriculture in respect of the proportion of soluble phosphoric acid in the ash of malt vinegar affords a further example of the inadvisability of putting forward standards for manufactured products, the composition of which must in the nature of things depend somewhat considerably on the precise methods adopted in their manufacture.The amount of phosphoric acid passing from the grain into the wort, as also that left in the soluble conditioii when the resulting vinegar is incinerated, must depend very largely on the mineral composition of the water used for mashing. Although this is sufficiently obvious, it may perhaps be of interest to record the following experiments which illustrate this point. Two different malts were taken, and were mashed (a) with distilled water, (b) with water containing about 20 grains per gallon of total dissolved solid matter, and (c) with a very hard water cortaining more than 100 grains per gallon of calcium sulphate. The mashes were made under precisely the same conditions of time and temperature, and were, in fact, treated in the same way throughout.At the end of the mashing period of one and aquarter hours the mashes were filtered, and the total phosphoric acid determined in the worts in the usual way. MALT A. Phosphoric Acid (P,O,). Distilled water ... . . . 46.56 grains per gallon. Water containing 20 grains of total dissolved solid matter ... 42.44 ,, ,* Very hard water ... ... 30.44 ,, 1 , Distilled water ... . . . 44.77 grains per gallon. Water containing 20 grains of total dissolved solid matter ... 37.61 ,, 9 , Very hard water ... ... 26.88 ,, 9 , MAL'r B. Phosphoric Acid (P,O,). I may add that in the preparation of the above worts the same proportions of malt and water were used in all cases. I have at different times examined several samples of genuine malt vinegar made with very hard water, and have found that when ignited they yielded ashes which contained almost the whole of the phosphoric acid in the insoluble condition-that is to say, as tribasic calcium phosphate. On extracting these ashes with water, the resulting solutions were practically free from phosphoric acid, and were almost neutral. I think I have shown that the United States definittion of malt vinegar requires amendment in at least two respects, and have incidentally provided yet another example of the dangers of setting up official standardi for the composition of manufactured foodstuffs. My best thanks are due to my assistant, Mr. R. L. Collctt, for help in connection with this investigation.

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DOI:10.1039/AN9123700123

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年代:1912

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128 SHREWSBURY: A METHOD OF ESTIMATING A METHOD OF ESTIMATING CALCIUM CARBONATE IN SOILS. BY HERBERT S. SHREWSBURY, F.I.C. (Read nt the LWeeting, March 6, 1912.) METHODS of estimating calcium carbonate in soils depending on the measurement of carbon dioxide evolved from the carbonates by absorption or otherwise have not been found very satisfactory ; the modified method proposed by F. S. Marr ( J . Agricul- tural Science, 1909, 3, 155) appears to give good results, but is somewhat lengthy, and entails rather special apparatus and skilful manipulation for its successful application. An alternative method which I have devised depends upon the extraction of the calcium carbonate from the soil in F acetic acid, the conversion of the calcium acetate so formed into calcium oxide and its solution in & acetic acid, and the titration of the excess of acid required by the lime with +& potash or soda, using phenolphthalein as an indicator.Ten grms. of finely divided air-dried soil are placed in a, dry wide-mouthed flask or bottle, and 100 C.C. of approximately For a period of ten minutes the flask is shaken with a rotary movement every time the bulk of the soil settles, which occurs about every thirty seconds. The soil is then allowed to settle for the last time, and the liquid contents of the flask decanted through a dry filter. A control experiment is made with another 10 grms. of soil, using distilled water as the extracting solvent. Twenty-five C.C. of each filtrate are evaporated to dryness in a platinum dish, and ignited at a bright red heat for thirty minutes, the residues when cool being treated with 10 C.C.OE & acetic acid (or more if necessary). Solution is effected in a, few minutes, particularly if the residues are gently rubbed with a glass rod tipped with a small rubber bung. The excess of acid is then titrated with & soda or potash, using phenolphthalein as indicator. The volume obtained from the control is now subtracted from that obtained from the acid extraction of the soil, and the result multiplied by 0.2. The product gives the percentage of calcium carbonate in the soil. Notes on the Process.-The quantities given will answer for soils containing up to 5 per cent. of calcium carbonate, which covers the usual range. For larger percentages proportionate amounts of soil are taken.The time and method of extraction were based on experiments made with pure calcium carbonate and Some soils appear to retain a portion of the calcium acetate, presumably by reason of a greater concentration of tho solution occurring in immediate contact with the soil particles. The occasional error due to a soil of this type does not appear to be large enough to warrant a complete washing of the soil, an operation which is lengthy and tedious. The purpose of the control is to measure alkaline carbonates and alkaline organic salts, soluble organic calcium salts, calcium nitrate, or any bodies which are acetic acid are added. Schleicher and Schiill’s filter cones answer the purpose admirably. acetic acid.CALCIUM CARBONATE IN SOILS 129 solubIe in water, and which on ignition leave an alkaline residue soluble in TT acetic acid.One-tenth C.C. of ?G acid was the maximum obtained in this titration for three soils that were examined. & acetic acid is chosen for the solution of the residues because it does not dissolve ignited iron oxide, whilst easily attacking calcium oxide, I t is preferable to measure the calcium oxide by titration rather than to weigh it or estimate it by conversion into oxalates and comparison of the turbid liquid with standards, since the first mothod excludes other salts of calcium than the carbonate, with the possible exception of organic calcium salts insoluble in water but soluble in 2 acetic acid. I t is desirable to make qualitative tests on the same volumes of the acetic acid extract of the soil for the presence of calcium and magnesium chlorides and sulphates.Frequently the last three are only present in traces. If the amount of magnesium is comparatively large, it may be quickly estimated by the method given by Thresh (“Examination of Water and Water-Supplies,” p. 238), depending on the comparison of the precipitate obtained with sodium hydrogen phosphate (after removal of calcium with ammonium hydrate and ammonium oxalate), when shaken up in a certain volume of water, with standards prepared in the’same way. The magnesium estimated would of course include any salt of magnesium soluble in acetic acid, but in most soils the error introduced would be insignificant. The following table sets out the results of test experiments, made with the process on soils prepared with known percentages of calcium carbonate. The sample of precipitated chalk used for this purpose was analysed, and found to confain prac- tically 100 per cent. of cdciuni carbonate : Sample of Soil. A. Surface soil from soft ferruginous shale . . . B. Heavy clay subsoil previ- ously treated with hot concentrated hydro- chloric acid for twelve hours, washed, and dried in steam-oven C. Clay subsoil ... ... D. Clay subsoil ... ... Per Cent. Calcium Carbonate in Soil, Originally Present. 0.07 Nil 0.29 0.23 Added. 0-05 0.50 0.50 4.76 Total. 0.12 0.50 0.79 4.99 Found by Process. 0.13 0.50 0.61 4.86 GOVEKNMENT LABORATOICY, TRINIDAD, 5. W. I.

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DOI:10.1039/AN9123700128

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年代:1912

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I30 AULD : THE PHOSPHOMOLYBDATE ESTIMATION THE PHOSPHOMOLYBDATE ESTIMATION OF PHOSPHORIC ACID IN SOILS. BY S. J. M. AULD, D.Sc. (LoND.), PH.D., F.I.C. (Read at the Meeting, Nuarch 6 , 1912.) THE necessity of estimating very small quantities of phosphoric acid during the chemical analysis of soils has lead to the suggestion of many methods for the direct utilisation of the bulky phosphomolybdate precipitate, instead of finally precipitating its ammoniacal solution with magnesia mixture. The difficulties attending these methods are concerned chiefly with the varia- tion in composition of the yellow ammonium phosphomolybdate precipitate, the constitution of which has been the subject of much investigation. Under standard methods of precipitation, however, any variation in composition is practically confined to the amount of ammonia in combination and to the quantity of water of crystallisation ; this, of course, apart from the possible co-precipitation of molybdic acid, admixture with other ammonium salts or incomplete separation (in soil analysis) from silica, etc.The ratio of P,O, : MOO, was originally stated'by Debray and others to be 1 : 20, but was definitely shown by Finkener (Ber., 1878, 11, 1638) and Gibbs (Amer. Chem. J., 1882, 3, 317) to be P,O, : MOO, = 1 : 24. This has been con- firmed more recently by Levi and Spelta (Gazz. Chim. Ital., 1903, 33, 207). Gibbs gives the formula of the yellow precipitate as (NH4),PO;12Mo0, + (NH4),HPO;12Mo0, + 8H,O ; whilst Finkener describes the precipitate, washed with ammonium nitrate solution and carefully heated in a crucible until the ammonium nitrate is volatilised, as (9 - z)( NH4),0~zH,0*3P,0,~72M00,, where x generally equals 1.reprecipitated compound as Carnot (Bull. Soc. Chim. 1893, 9, 343) regards the 3(NH,),O~P,O5~24Mo0;3H,O, and Hundeshagen (Zeit. f. Anal. Chem., 1889, 28, 141) states that the precipitate dried at 130" C. is always (N H4),P0,-12M00,, independent of the content of mineral acids, phosphoric and molybdic acids, or ammonium salts. The ratio NH, : P,O, is thus variously given as 5 : 1, 16 : 3, and 6 : 1. This may possibly be due to the fact, shown by Levi and Spelta (Zoc. cit.) that phosphomolybdic acid contains twenty-seven replaceable hydrogen atoms, five o€ which behave differently from the remaining twenty-two. The estimation of phosphoric acid by Carnot's method (Zoc.cit.), by weighing the reprecipitated compound after drying at 100' C., which is still extensively used and recommended in certain textbooks, should therefore be rejected on the grounds of insufficient evidence or' composition ; besides which, the coefficient recommended by him-viz.,OF PHOSPHORIC ACID 1N SOILS 131 Precipitate dried a t 100" c. Weight of 0*0373-is calculated on the f u l l y hydrated precipitate of the formula given above. On the other hand, the factor 0.043 recommended by the Committee of the Association of Official Agricultural Chemists of the United States has been recognised as inaccurate (cj. Wiley's "Agricultural Analysis, i. 423). To test the possible removal of water of hydration during drying, and the composition of the residual precipitate, an extended series of analyses by the Carnot method were carried out, using standard solutions of purified sodium phosphate to check the results, which were also controlled by dissolving the precipitates in ammonia, solution and precipitating with magnesia mixture. Previous to drying, the precipitates were thoroughly washed with a 1 per cent solution of nitric acid.Precipitate dried a t 105" to 110" C. TABLE I. Grms. 0.0946 0.0710 0.0473 0.0236 Series. Grms. Grins. 2.5165 0.0376 2.5045 0.0378 1.8761 0.0378 1.8732 0.0381 1,2671 0,0375 1,2443 0.0381 0.6300 0.0376 0.6185 0.0383 1 ... ... 2 . . I ... 3 ... ... 4 ... ... Volume of Na,HP04 Solution. c. c. 20 15 10 5 Although carried out with care, a number of the estimations gave only approxi- mate results, and these were not included in the above table. The method was certainly not completely satisfactory, and if used should probably be calculated from the' coefficient 0-0378, the theoretical value for the anhydrous salt.This, however, probably does not represent the true state of affairs, and it will be noticed that heating for some time at 105' to 110'C. gives a residue containing a percentage of phosphoric acid incompatible with Hundeshagen's asserted stability of the ammonium salt, assuming that his simple formula correctly represents its compos- ition. This tends to confirm the statement of Dehbrain (" Chim. Agricole," p. 449) that decomposition may ensue if the yellow precipitate is heated above 90' C.He recommends the factor 0 0376. I t was chiefly, however, for the purpose of examining the more generally adopted procedure of gravimetlrically estimating the P,O, in soils that this work was started. The operation, first suggested by Hehner (ANALYST, 1879, 4, 23), consists of dissolving the ammonium phosphomolybdate precipitate in dilute ammonia, evaporating the ammoniacal solution, and weighing the residue after drying or gentle ignition. The factors employed for calculating the percentage of phosphoric acid vary somewhat according to different authors and works of reference, but, from their order of magnitude, apparently frequently depend on an assumed stability of the combined ammonia on herttiag at moderate temperatures :132 AULD : THE PHOSPHOMOLYBDATE ESTIMATION Mode of Treatment.Heat gently to volatilise the am- monium nitrate ... ... ... Ignite gently over an Argand burner Repeated evaporation to dryness with small quantities of water . . . Heat to dark blue colour ... ... Factor. 0-0374 0.0379 0.0350 0.0396 Reference. Finkener (Zoc. cit.). Hall (‘‘ The Soil,” p. 146). Hehner (Zoc. cit., p. 27). Wood (“ Pract. Agric. Chem.,” p. 17). The difference in the factors becomes of importance when one is forced to estimate very small quantities of P,05, as, for example, in the estimation of avail- able or ‘‘ citric soluble ” phosphoric acid in soil. In this case there is difficulty in increasing the amount of material used, and the weight of the final residue may not amount to more than 0-3 to 0.4 grm. During the heating, the residues generally take on a more or less blue colour-sometimes to a very considerable extent-and this cannot be controlled to any particular stage coincident with the complete removal of the extraneous ammonium salts.Hehner avoided this by washing the precipitate with dilute alcohol, dissolving in ztmmonia, and weighing the residue after repeated evaporation to dryness with small quantities of water. The formation of the blue colour generally obtained would also indicate a partial decomposition of the phosphomolybdate, and suggest prima facie that the residue should be obtained either wholly yellow or wholly blue. That one is not so likely to obtain a uniform product at all by dissolution of the yellow precipitate in ammonia may be gathered from 8 consideration of the reactions involved.According to Levi and Spelta (Zoc. cit.), ammonia resolves ammonium phospho- molybdate into ammonium phosphate and ammonium molybdate. Certainly, repeated evaporation of the ammoniacal solution with water gives acid molybdate and ammonium phosphate. But the reaction is probably not quite so simple as might be expressed by the equation z(NH4)2O*Pz05*24MoO3 + 2(27 - 3)NHdOH = 24(NHJgO.MoO, + 2(NH,),PO4 + (27 - ~ ) H 2 0 , and may, at any rate partially, involve the formation of ammonium phospho- pentamolybdate : x(NH4)20.P,0,*24M~03 + 2(22 - z)NH,OH = 19(NH,),0*MoO3 + S(NH4),0*P,0,*5Mo03 + (22 - x)H~O. This would serve as an explanation of the separation from the ammonia solution by Gibbs (Zoc. cit.), under certain conditions, of Debray’s duodecaphosphomolybdate, since the pentaphosphomolybdate salts in certain circumstances split off phosphoric acid : 4(5Mo03*P,0,) + 9H,O = 20Mo03*P205 + 6R3P04.I t is difficult to see, therefore, how a satisfactory product for weighing can be obtained by heating the residue at 100’ C. or by partial ignition, since ammonium05' PHOSPHORIC ACID IN SOILS 133 Partially Blue Residue, ~ phosphate readily loses ammonia, on heating, and the molybdate is partially reduced with the formation of blue rnolybdic oxide (Mo,O,). There would also appear a possible danger, by overheating, of loss of phosphoric acid. By the ordinary method used in the analytical laboratories of the South-Eastern Agricultural College, the residue is heated over an Argand burner for some time, .and weighed in a partially blue state., Taking at random the residue in five phosphoric aoid estimations in soils, and further heating, till uniformly blue, over a medium-sized Bunsen flame, different percentage losses were obtained, although the blue residues after moderately strong heating for another half-hour in no case lost any further weight.Blue Residue. Loss 011 TABLE 11. Soil. 1 ... ... 2 ... ... 3 ... 4 ... ... 5 ... ... Weight of Residue ; partially Blue. Weight of Residue ; wholly Blue. Grms. 0.0770 0.1595 0.0981 0.1452 0,0679 Grms. 0.0710 0,1535 0.0909 0.1390 0.0650 Loss on Heating. Per Cent. 7.5 3.7 7.1 4.1 4.4 The effect of heating until uniformly blue and of constant weight was conse- quently tried with precipitates dissolved in ammonia obtained from standard phosphate solutions, and also with soil extracts, in order to determine the constancy of the P,O, content.The results are given in Tables 111. and IT7. Weight of P20, taken. Grnis. 0.0946 0.0473 0.0460 0.0236 0.071 0 0.0710 0.0946 000946 Weight. Grms. 1.2800 1.2153 0.6650 1.9271 1.9280 9.5002 2,5256 - Ignition. Weight. - 0-0372 0.0379 0.0356 0.0368 0.0368 0.0378 0.0375 Per Cent. 496 3.7 4-2 5.5 4.1 4.8 - - Grms. 2.3995 1,2215 0.6111 1.8450 1.8221 2.3969 2.4050 - 0.0394 0.0388 0.0387 0.0385 0.0389 0.0394 0.0393 -4134 AULD : THE PHOSPHOMOLYBDATE ESTIMATION 0.0393 0.0989 0.0392 0.0389 TABLE IV. Soil Extracts. 1.4 0.1620 0.0399 2.4 0.1600 0.0399 3.0 0.1601 0.0401 8.3 0.1781 0.0398 Soil. Q.C. ... P; I ... I?. 2 ... Q.B. ... H. ...P,05 Content of Extract. Grnis. 0.0057 0.0064 ObO063 0.0064 0.0071 Partially BIue Residue. I I I3lrie Residue. Weight. (hYlS* 0.1501 0.1626 0.1640 0.1651 0-1823 Loss 011 Ignition. Weight . Factor. This series of soils was simply one of many tested during the ordinary routine analytical work, and the residues in Column 3 give the actual weights taken for calculation. The difficulty of testing the soil content sufficiently accurately by estimation as magnesium pyrophosphate may be responsible for the high factor obtained, but the experience gained in these numerous analyses rather points to a difficulty of preventing the decomposition of the yellow compound where the amount is small, and the gradual attainment of a more uniform weight and factor on heating. From this point of view the figures in Tables 111.and IV. are very suggestive, the rather bluer yellow ” residues from the smaller phosphoric acid content of the soils giving higher, but more concordant, factors than those from the yellower residues of Table 111. It must be remembered, also, that the residues in Column 3 of Table IV. were obtained by Mr. R. H. Carter, the College analyst, in the ordinary course of practice, and in the case of the Higher factors for P. 1 and Q.B. the residues were much more blue than the others. The experiments would therefore seem to show that residues containing, on the average, 3.891 per cent. of phosphoric acid are generally obtained by the method described by Hall, as against the 3.794 actually laid down. The factors obtained by heating the ammoniacal solution residues to complete blueness are more concordant than those obtained in practice from the yellow residues, and average 0.0393; bur, in harmony with the non-uniformity of the residue, as shown above, the results vary somewhat. Much better results were obtained by heating the yellow ammonium phospho- molybdate precipitate direct until it is of a blue colour.This method is described by Wood (Zoc. cit.). He gives the blue residue the same formula-vie., P205024M003- as that obtained by heating the residue after dissolution in ammonia, and uses the same coefficient for calculating the results-viz,, 0-0396. Owing to the necessity of freeing the yellow precipitate from silica or other con- tamination, the procedure described below was eventually adopted.Hethod Reconznzended.-The yellow precipitate obtained in the ordinary way is dissolved in dilute ammonia, and the filtered solution reprecipitated by the addition ofOF PHOSPHORIC ACID IN SOILS 135 excese of nitric acid (I part of acid to 2 parts of water). A further 5 C.C. of ammonium molybdate solution are also added, and the mixture is allowed to stand in a warm place for some time, as in the first precipitation. The precipitate thus obtained is of a, fine consistency, and may be completely filtered with ease and rapidity through a, Gooch crucible. I t is then washed thoroughly with 1 per cent. nitric acid, dried in the oven, and ignited until of a uniform dark blue colour and of constant weight. During ignition the base of the Gooch should be protected by a cap or by placing if inside anof her crucible.A quicker method, useful for students, and nearly as accurate, consists of reprecipitating the ammonia solution wit-h nitric acid in a porcelain dish, washing out most of the ammonium nitrate by decantation, and, after drying on the water- bath, igniting untiI uniformly blue. Very little phosphoric acid remains in solution after addition of the nitric acid. The resuIts obtained by the method are given below : TABLE IT. Experiment. 1 ... ... 2 ... ... 3 ... ... 4 ... ... 5 ... ... 6 ... ... 7 ... ... 8 ... ... Weight of P,O, taken. Grnis. 0.0473 0.0473 0,0236 0.0236 0-0710 0.0946 0.0236 0.0236 “ Yellow ” Residue. Reiglit. Grms. 1.2391 - - 0.6250 2 * 4 705 0.6255 006230 - Factor. 0.0382 - - 0.0379 0.0383 0.0380 0,0379 - Blue Residue.Weight. Grms. 1.2015 1°2010 0.5970 0.5975 1-7925 2.3800 0.5961 0.6011 Factor. 0,0395 0.0395 0.0396 0.0396 0.0396 0.0397 0,0396 0.0394 The factors from the yellow resides vary much as before, but by careful manipulation very constant results were obtained with the blue residues, the average being 0*0396. It is interesting to find that the coefficient obtained doee not correspond to the phosphomolybdic acid (P20;24Mo0,), which contains 3.94 per cent. of P,O,, but to a, partial reduction corresponding to the formula P20;110,0,*21M00,. SUMMARY OF RESULTS. 1. Owing to the difficulty of controlling the amount of ammonium salts present, and the possible variation of the amount of combined ammonia, methods of weighing the phosphomolybdate precipitate direct should be avoided.If used, Carnot’s method should be employed, using the factor 0*0378. 2. If the precipitate is dissolved in ammonia, the difficulty of removing ammonium salts without, in practice, decomposing the residue to an indefinite extent renders it desirable to weigh the residue in the uniformly blue condition. In136 PHOSPHOMOLYBDATE ESTIMATION OF PHOSPHORIC ACIDS IN SOILS the ordinary method of heating till partially blue, the factor used should be 0.0389 ; if heated until quite blue, 0.0393. 3. Since ammonia splits a p the ordinary phosphomolybdate precipitate on solution, and the P,O, content of the residue may be subject to variation, it is best to reprecipitate the ammoniacal solution with nitric acid, filter through a Gooch crucible, wash, and ignite the residue until dark blue in colour and of constant weight.Factor = 0,0396. 4. As a quicker method of carrying out the operation, the reprecipitated phos- phomolybdate may be washed by decantation, evaporated to dryness on the water- bath, and the residue ignited direct, using the same coefficient for calculating the result. The author wishes to thank Mr. F. Knowles for carrying out some of the analyses qgoted above. CHEMICAL DEPARTMENT, SOUTH-EASTERN AGRICULTURAL COLLEGE, WYK. DISCUSSION. Dr. DYER said that ever since Hehner read his paper in 1879, he had adopted Hehner's modification of the molybdic acid process for the determination of such small quantities of phosphoric acid as were contained in soil. If, after the ammo- niacal solution was evaporated down, the residue was again evaporated two or three times with water, as Hehner had suggested, a precipitate was obtained which could be rapidly dried in the water-oven to a constant weight, If the evapora- tion with water were omitted, the residue had to be kept in the water-oven for a much longer time.The PRESIDENT said that he used the molybdic acid method for the determination of phosphorus, chiefly in the case of steel and iron. The composition of the compound was perfectly definite, provided it was precipitated under definite conditions, which conditions, of course, must be duly learnt. Having obtained the precipitate under those definite conditions, he thought it immaterial by what method it was weighed. He had never found any difficultyin obtaining correct results by drying the precipitate in a porce- lain crucible at 100" C.in the water-oven, the precipitate being rinsed from the filter- paper into the crucible and dried and weighed. Latterly, however, he had adopted the more rapid method of Handy-namely, dissolving the precipitate from the filter with a standard solution of caustic soda and titrating back the excess of soda with standard nitric acid solution. When it was desired to check the results, a larger quantity of steel was taken, and the larger molybdate precipitate was redissolved, and the phos- phorus precipitated with magnesia mixture and weighed as magnesium pyrophosphate. The results commonly agreed within a point or two in the third decimal place, which showed that the composition of the molybdate precipitate was quite definite, and also that its reaction with caustic soda was definite, so that probably its reaction with ammonia would be equally definite.Dr. AULD, in reply, said that the estimation of phosphoric acid in soil called for a nearer approach to absolute accuracy than many other chemical estimations,FOOD AND DRUGS ANALYSIS 137 because in the conversion of the results, say, into pounds per acre, any error that might exist was very largely multiplied. He therefore could not agree that it was not desirable to get as near to scientific exactitude as possible. I t was only recently that his attention had been directed to Hehner's method, and he had never seen it used-perhaps because the washing of the precipitahe with alcohol and its repeated evaporation with water were regarded as troublesome-and from that point of view it was an advantage to be able to weigh the precipitate at once without further manipulation. He agreed that the composition of the precipitate was, practically speaking, constant, but with very small quantities': the error due to the use of an inexact factor became relatively large. He had found titration to give good results, but in order to keep the experimental error of reading within proper limits about 12 C.C. of liquid must be used in an ordinary burette, and with soils the precipitate was usually too small to allow of this unless the quantity worked upon was incon- veniently large. * Such as were obtained in estimating the " citric soluble " phosphoric acid in soil, and in which the weight of residue might not he more than 0'03 gmi.

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DOI:10.1039/AN9123700130

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年代:1912

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FOOD AND DRUGS ANALYSIS 137 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Micro-Chemical Detection of Certain Alkaloids. A. Grutterink. (Zeitsch. anal. Chem., 1912, 51, 175-234.)-The reactions between alkaloids and many other substances are described, and particular information is recorded as to the crystalline compounds which are formed as the result of these reactions. In many cases the crystals are characteristic, and may be obtained from very small quantities of the alkaloids, In the original paper the reactions are recorded in tabular form, and tbose relating to the alkaloids of the strychnine, cocaine, quinine, and calumba groups receive special attention. Many of the natural and synthetic bases may be identified microscopically, the following organic acids yielding characteristic com- pounds or crystals : m-nitrobenzoic acid (with strychnine) ; p-nitrobenzoic acid (with strychnine and tropacocaine) ; dinitrobenzoic acid (with hydrastine, novocaine, brucine, and strychnine) ; trinitrobenzoic acid (with novocaine, tropacocaine, strych- nine, brucine, and conine) ; dinitro-anisic acid (with hydrastamide) ; dihydroxy- benzoic acid (with cinchonine) ; trihydroxybenzoic acid (with quinidine) ; opianic acid (with brucine) ; meconic acid (with quinidine) ; mellitic acid (with quinidine and cinchonidine) ; naphthalenesulphonic acid (with cocaine and strychnine) ; p-nitrophenylpropiolic acid (with hydrastinine, hydrsstine, strychnine, tropacocaine, cinchonidine, nicotine, and hydrastamide).Potassium permanganate is also a very useful reagent for the micro-chemical detection of hydrastinine, hydrastine, tropa- cocaine, and cotarnine.w. P. s.138 AIJSTRACTS OF CHEMICAL PAPERS Process of Extracting Alkaloids from Syrups. E. Kohn-Abrest. (Bull. SOC. Chim., 1912, 11, 73-75.)-When a syrup containing alkaloids is treated with alcohol and solid potassium carbonate, the alcohol, in causing the dehydration of the potassium salt, simultaneously precipitates the sugar, whilst the alcohol forms a supernatant layer containing the whole of the alkaloids present. Syrups of sp. gr. 1.15 to 1-90 should be shaken with about four times their volume of absolute alcohol and about their own weight of potassium carbonate, the shaking being repeated several times, and the mixture then left for twelve hours.I n the case of more con- centrated syrups it is preferable to use 95 per cent. alcohol to insure complete elimination of sugar from the alcoholic layer. After standing for it sufficient time, the alcoholic extract is decanted, filtered, and distilled, and the residue taken up with a little absolute alcohol and again filtered. The fresh residue is dissolved in 10 to 15 C.C. of boiling chloroform, the filtered solution evaporated, the residue dissolved in hydrochloric acid, the solution evaporated to dryness, and the hydro- chloride of the alkaloid crystallised. The method has given excellent results with syrups containing morphine, codeine, quinine, strychnine, and atropine. Thus, 20 grms. of a syrup containing 0-040 grm. of morphine hydrochloride gave a residue of 0-15 grm., which, after purification as described, yielded 0.040 grm.of crystals consisting entirely of morphine hydrochloride. C. A. M. Estimation of Glycyrrhizic Acid in Liquorice Juice. H. Cormimboeuf. (Ann. Chim. anal., 1912, 17, 47-50.)-1n the following method the errors caused by the solubility of glycyrrhizic acid in water (about 0.5 per cent.) are eliminated : Two grms. of the sample are treated with 50 C.C. of hot water, the solution filtered through a tared filter, and the insoluble organic matter washed with 50 C.C. of hot water, dried, and weighed. The filtrate is treated with 5 C.C. of N-sulphuric acid and allowed to stand for about twelve hours, after which the supernatant liquid is decanted, and the precipitated glycyrrhizic acid washed with as little water as possible until the washings are no longer acid.The precipitate is now dissolved in ammonia solution, and the resulting solution will contain the bulk of the glycyrrhizic acid. The filtrate and the washings are then evaporated nearly to dryness, the black viscous residue is mixed with successive portions of 10, 10, and 5 C.C. of water, and the liquids filtered after each treatment. The fresh quantity of glycyrrhizic acid thus separated is dissolv6d in ammonia solution and added to the main solution, the whole being then evaporated to dryness, and the residue of ammonium glycyr- ahizate dried at 100" C. until constant in weight. The gummy substances may be estimated by evaporating the last filtrate to dryness, drying the residue at 100" C.until constant in weight, and deducting 0.330 grm. for the ammonium sulphate corresponding to the 5 C.C. of N-sulphuric acid originally added. As thus separated the gummy substances should be a transparent yellow mass, which, when dissolved and treated with an acid, should not yield more than a trace of glycyrrhizic acid. In various estimations the amount of glycyrrhizic acid retained by the gums did not exceed 0-010 grrn., corresponding to a negligible error of not more than 0.5 per cent. in the amount of ammonium glycyrrhizate in the sample. (Cf. ANALYST, 1911, 36, 409, 410, 497.) C. A. M.FOOD AND DRUGS ANALYSIS 139 Bitter Resins of Hops in Worts and Beers and their Volumetric Estimation. D. Neumann. (Wochensch. Brau., 1912, 29, 97-99.)-h a previous note (ANALYST, 1912,92) the author described how the resins could be extracted from wort or beer by means of ether without the production of troublesome ernulsions.The beer is shaken, in small portions at a time, with five times its volume of ether, the same ether being used for each successive portion of wort or beer until the entire sample has been treated. Each extraction should be performed in a shaking machine for at least fifteen minutes. The ethereal extract is concentrated to a, volume of 15 to 20 c.c.; it is treated with 40 to 50 C.C. of benzene, and transferred to a separating funnel, in which it is washed with water until the washings are neutral. Too vigorous shaking at this stage is to be avoided. Finally, the ethereal benzene solution of the resins is titrated with & alcoholic potassium hydroxide according to the usual method of hop analysis.The error, due to the carbon dioxide of the air, using phenolphthaleln, amounts to about 0.1 C.C. of & potash, or 0,004 grm. of bitter resin. Performed in conjunction with a blank test, this method appears to give very satisfactory results when applied to unhopped worts, to which known quantities of standardised hop-extract were added. Bnt when the worts were boiled for two hours under a reflux condenser with the hop resins, a considerable deficiency, corresponding to about 35 per cent, of the original resin, was found on analysis. This deficiency is not due bo loss of resin by volatilisation or precipitation, but evidently corresponds to a constitutional change in the resin itself.Experiments with the purified crystalline a-resin of hops showed that this substance, after boiling with wort, undergoes a change, whereby a portion of it becomes soluble in water without losing its bitter properties, and is removed in the washing process. The author has applied his method to the analysis of ordinary beers (1 litre taken For extraction), aud found that it gave concordant results with beers of the same manufacture, and that it showed clearly the effect of variations in the proportions of hops used in brewing. J. F. B. Examination of Meal. E. Kohn. (Chem. Zeit., 1912, 36, 121-123.)-1n the microscopical examination of meals for the detection of foreign seeds, the author prepares the sample in the following manner: 0.5 grm.of the meal is shaken in a test-tube with 10 C.C. of ether, and the mixture is poured out into a wide, shallow porcelain dish. The characteristic seed-hairs for the identification of the meal constituents can easily be floated off from the surface of the ether in the test-tube, whilst yellow-coloured bran particles and foreign impurities can be separated by tilting the dish so as to spread the liquid in a thin layer as the ether evaporates. Alternatively, the ethereal-meal suspension may be poured on to filter-paper and allowed to spread out. A method for the differentiation of various meals may be based on the variable rates of the attack on the starch granules by diastase. Two grms. of starch or meal are weighed out into a 300 C.C. Erlenmeyer flask, mixed with 100 C.C.of water, 0.4 grm. of Msrck's diastase, and 1 C.C. of Fa hydrochloric acid. The mixture is digested at the optimum temperature (50' to 52" C.) for a given time-e.g., four hours. The liquid is filtered, aud the amount of dissolved solids or sugar is deter-140 ABSTRACTS OF CHEMICAL PAPERS mined with the pyknometer, or preferably by Fehling’s solution. The figures so obtained are compared with those established with standard meals. Rye starch or meal gives the highest values, bean flour the lowest ; wheat flour shows higher values than barley. The values vary slightly for different grades of the same flour ; mixtures show intermediate values. J. F. B. Estimation of Potassium Nitrate in Meats. J. Tillmans and A. Splitt- gerber. (Zeitsch. Untersuch.Nahr. Genussm., 1912, 23, 49-56.)-When the quantity of potassium nitrate in 8 sample of meat does not exceed 1.5 per cent., it may be accurately estimated by Noll’s brucine-sulphuric acid method, or by the diphenylamine-sulphuric acid method. I n order to obtain a solution to which the reagents may be applied, the following procedure is recommended : Fifty grms. of the finely-divided meat axe immersed in about 500 C.C. of water for three hours, with occasional shaking ; the aqueous portion is then decanted through a filter and diluted to a volume of 1 litre. Fifty C.C. of this solution are now treated with 50 C.C. of a mixture consisting of equal volumes of 5 per cent. mercuric chloride solution and 2 per cent. hydrochloric acid, and, after filtration, the nitrate is estimated in a definite volume of the filtrate by means of the methods mentioned ; the comparison solutions employed should contain definite quantities of potassium nitrate, and, in the case of the diphenylamine method, sodium chloride must be added to these solutions as well as to the meat solution (cf. ANALYST, 1911, 36, 67). The brucine- sulphuric acid method will be found to be the more convenient for single estimations, and the diphenylamine method preferable when a series have to be made. In cases where the amount of potassium nitrate present in the meat exceeds 1.5 per cent., Schloesing’s method should be employed. The results of a considerable number of analyses are given, which show that the methods are trustworthy. The preparation of the diphenylamine reagent has been described previously (Zoc. cit.), and the brucine reagent is made by moiRtening 0.25 grm. of brucine with water, and then dissolving it in 100 C.C. of concentrated sulphuric acid. w. P. s.

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DOI:10.1039/AN9123700137

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年代:1912

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140 ABSTRACTS OF CHEMICAL PAPERS BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. Estimation of Dextrose in Urine and Blood. B. Oppler. (Zeitsch. physiol. Chem., 1911, 75, 71-134 ; through Chem. Zentralbl., 1912, I., 380-381.)-For the estimation of dextrose at concentrations below the limits at which the qualitative tests are sensitive, the urine is decolorised by the addition of crystallised phospho- tungstic acid, protected from the light. After standing for twelve hours, the liquid is filtered, and the filtrate treated with neutral lead acetate ; after a further twelve hours in the dark it is again filtered, and the lead is removed by hydrogen sulphide. Urines thus treated in most cases no longer contain any perceptible quantity of laevo-rotatory substances ; at the same time, substances which interfere with the cupric reducing reaction are removed.The dextrose can then be estimated by polarisation, or cupric reduction, before and after fermentation by yeast. Healthy urine contains, however, cupric reducing, optically inactive substances, which are removable by yeast, to an amount equivalent to 0.04 per cent. of dextrose. In the urine ofBACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 141 mental patients dextrose was found in the majority of cases, but mostly in small amounts. Such urine frequently shows an abnormally high Imo-rotation, equivalent to as much as 0.97 per cent. of glucose. The application of the above method of purification to blood showed t hst the colouring, Imo-rotatory, and interfering matters of the serum behaved very much in the same way as those present in urine, and the methods applicable for the estimation of sugar in urine are likewise suitable in the case of blood.J. F. B. Estimation of Sugar in Blood. D. Takahashi. (Biochem. Zeitsch., 1911, 37, 30-33.)-Results of estimations of sugar in dogs’ blood by various methods are recorded ; the methods described by Bertrand and by Kumagawa and Suto yielded results which agreed with one another and with those obtained by the polarimetric method. The total amount of sugar found to be present varied from 0.12 to 0.18 per cent. when these methods were employed, whilst Bang’s method gave results which were about 0.03 per cent. higher. No sugar was found after fermentation. w. P. s. Are the Alkalinity and Peroxydase of Milk Identical? W.D. Kooper. (Zeitsch. Untersuclz. Nahr. Geizussm. , 1912, 23, l-l3.)-The alkalinity value of milk (as measured by the quantity of acid required to change the violet coloration to green when 100 C.C. of milk are treated with a mixture containing p-phenylenediamine hydrochloride, guaiacum , and hydrogen peroxide, the alkalinity value being expressed in C.C. of Tc acid) is not a constant quantity, varying from 106 to 112, with an average of 110. The value is higher for colostrum, but decreases as the lactation period proceeds ; for fresh goats’ milk it generally lies above 120. The addition of water to milk raises the value, whilst the acidity of the milk is diminished, and the decrease in the acidity is greater in the case of old milk than with fresh milk; on the contrary, the increase in the alkalinity is smaller.These and other results of an investigation carried out by the author led him to the opinion that the property possessed by milk of being capable of producing a coloration with the above-mentioned reagent is due to the action of inorganic compounds contained in the milk. These compounds appear to be various phosphates of the alkalis and alkali-earths. w. P. s. Separation of Rennin and Pepsin by Means of the Electric Current. W. E. Burge. (Amer. J. Physiol., 1912, 29, 330-334; through Chcm. Zerztralbl., 1912, I., 697.)-When an electric current of 10 milliamp4res was passed through a solution containing rennin and pepsin for twenty-four hours, the liquid completely lost its property of digesting fibrin, whereas the activity of the rennin, as displayed by its power of coagulating fresh milk, remained unchanged.J. F. B. Estimation of the Acidity of Urine. L. Grimbert and J. Morel. (Comptes rend., 1912, 154, 378-380.)-1n titrating the acidity of urine, with phenolphthalein as indicator, apparent neutrality is obtained when the monosodium phosphate has been converted into disodium phosphate, but the absolute acidity would correspond to the formation of trisodium phosphate. If the conversion of the monosodium salt into142 ABSTRACTS 0 F CH EMICA L PAPERS the disodium salt be regarded as indicating the real acidity, account must still be taken of the influence of ammonium and calcium salts upon the results of the titration. The first source of error may be obviated by titrating the ammonia by RonchBse’s formaldehyde method, and making a correction from the result obtained; and the second by adding to the urine a small quantity of powdered potassium oxalate to remove the calcium salts.If, then, the proportion of phosphoric acid in the urine ( =’@) be calculated into that of the Lorresponding monosodium salt, the acidity of the latter towards phenolphthalein will represent the phosphatic acidity, p , of the urine. On the other hand, if R represent the real acidity as estimated by direct titration, it is possible to calculate : (1) the organic acidity, a ; (2) the absolute acidity, A , and the amounts of monosodium and disodium phosphate in the urine. If the phosphatic acidity is inferior to the real acidity, disodium phosphate cannot be present, but there will be organic acidity. Since a=R - p , and A=2p+a, the pro- portion of monosodium phosphate will be equivalent to pxa-680. Again, if the phosphatic acidity is superior to the real acidity, there can be no organic acidity, but the total phosphatic acidity must be distributed between the acidity due to the mono- sodium phosphate (=m), and that due to the disodium phosphate, d. The calcula- tions would then be as follows : m= R, d = p - R, A = 2B+ d, whence- NaH,PO,= R x 3.680, and Na,HPO, = d x 4.356. C. A. M.

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DOI:10.1039/AN9123700140

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年代:1912

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142 ABSTRACTS 0 F CH EMICA L PAPERS ORGANIC ANALYSIS. Alkaloidal Assay of Calabar Beans. A. H. Salway. (Amer. J. Pharm., 1912, 84, 49-51.)-The United States Pharmacopceia method for this assay was found by the author to give very low results, and the following modification is sug- gested: Twenty grms. of powdered beans (No. 60 powder) are well shaken with 200 C.C. of ether, 10 C.C. of an aqueous solution of sodium carbonate (10 per cent.) are added, and the mixture shaken vigorously at intervals for four hours. The powder is allowed to settle, after which 100 C.C. of the ethereal liquid are trans- ferred to a separator and sufficient & sulphuric acid added to make it distinctly acid. After thorough shaking, the acid layer is drawn off, and the operation repeated twice, using 10 C.C.of TG sulphuric acid each time. The combined acid extracts are made alkaline with sodium carbonate solution (10 per cent.), and the liquid extracted successively with 10 quantities of 20 C.C. each of ether. After washing the whole ethereal extract with 5 C.C. of water, the ether is distilled, the alkaloidal residue dissolved in 5 C.C. of & sulphuric acid, and the excess of the latter titrated with TC alkali, using iodeosin as indicator. A. R. T. Application of Methyl-Red to the Colorimetric Estimation of Hydrogen Ion Concentrations. S. Palitzsch. (Biochem. Zeitsch., 1911, 37, 131438.)- Methyl-red (p-dimethylaminoaeobenzene-o-carboxylic acid) is particularly suitable for use as an indicator in the measurement of hydrogen ion concentrations between the zones p , = 4-2 and pH = 6-3, the change of colour being from violet-red to yellow.ORGANIC ANALYSIS 143 A table of corrections is given, these corrections (which are only small) being applied in case proteins and salts are present. w.P. s. Detection of Pine Oil in Turpentine Oil. C. Piest. (Chem. Zeit., 1912, 36, 198.)-A mixture of 5 C.C. of the turpentine oil and 5 C.C. of acetic anhydride is shaken with 10 drops of concentrated hydrochloric acid, and allowed to cool, after which an additional 10 drops of hydrochloric acid are added, and the mixture again shaken. Under these conditions pure turpentine oil remains transparent and light yellow, whilst pine oil becomes black. This test will give a distinct coloration in the presence of 10 per cent.of pine oil, whilst even 5 per cent. causes a slight darkening of the liquid. In the case of old turpentine oil the sample should be distilled, and the test applied to the distillate. Purified pine oil also gives a dark coloration, though not to so marked an extent as ordinary pine oil. C. A. M. Viscosity of Fish Oils. G. F. White. (J. I d . Eug. Chem., 1912, 4, 106- 1lO.)--For determining the viscosity of moderately viscous liquids such as fish oils, the author has devised a viscosimeter very similar to that previously described by him for less viscous liquids (Biochem. Zeitsch., 1911, 37, 482), but w th a shorter capillary and wit the volumes of the limbs considerably less. The method of standardising the instru- ment was similar to that described in detail in the earlier paper, but water could not be used as the time of flow would have been too short.Therefore, the viscosity of a sample of Menhaden oil was determined in the earlier form of apparatus which had been stan- dardised with water, the temperature being 50" C. to reduce the time necessary for measurement. The viscosity was found to be 0.1518 in the left limb and 0.1514 in the right limb. The new viscosimeter was next calibrated with this oil and the following constants obtained for the instrument : Length of capillary (approximate) ... 1.7 cm. Volume of left limb ... ... ... 2.1310 C.C. Volume of right limb . . . ... ... 2.0748 C.C. Pressure correction, left limb . . . ... 1.23 cm. Pressure correction, right limb . . . ... 1-20 cm. Ratio of r4 to Z ... .... . . 0.00004577. 0*00004582. In use the liquid is forced through the capillary under a pressure Vd - in the 87rtL of 100 to 180 cm. The kinetic energy correction +pt va formula q = -- - ~- is low, this being necessary if the work is to be of a high order of accuracy, This correction was always less than 0-5 per cent. of the total viscosity. I n the above equation 7 is the viscosity, r and I are the radius and length 8vL 87rtl144 ABSTRACTS OF CHEMICAL PAPERS of the capillary, z1 is the volume of the liquid of density d, p is the pressure, and t is the time of flow. With this instrument the viscosity of the following oils in absolute measure (c.g.s. units) was determined at 30°, 50", 70", and 90" C. : Menhaden I. (Brevoortia tyrannus) ,, II., dark ... ,, III., light ...Whale (Bnlana mysticeius) .. . Cod liver (Gadus callarias), white 9 , 7 , brown Sperm (Physeter macrocephalus) Dogfish (Mustelus canis) . . . ,, liver, I. ... ... ,, 11. ... ... TTT 2, ... ... ... .,. ... ... ... ... ... ... ) ? ... ... ,, 111. ... Spiny dogfish liver (Squalus acanthias) Sand shark liver (Cacharias littoralis) Hammer-head shark liver (Sphyrna x y p n a ... ... ... Torpedo liver I. (Tetranarce occidental is> 9 9 11. ... ... ... Squeteague (Cynoscion regalis) ... Sarp (Stenotomus chrysops) . . . Eel (Anguilla rostrata) . . . ... ... Butter-fish (Poronotus tricanthus) . . . 30'. 0.2961 0.6019 0.3238 0.3485 0.3884 0.3924 0.3333 0.4319 0.4096 0.3762 0.3776 0.3993 0.3678 0.5470 0.4263 0.4774 0.4980 0.4195 0-4266 0.4015 50". 0.1516 0-2935 0.1 7 2.7 0.1822 0.2003 0.2079 0.1720 0.2135 0.2072 0.1977 0.1943 0.2049 0.1943 0.2681 0.2133 0.2356 0.2402 0.2141 0.2092 0.2026 70".0.09555 0.1683 0.1049 0*1101 0.1 188 0-1195 0.1038 0.1261 0.1212 0.1161 0.1154 0.121 4 0.1177 0.1537 0.1257 0.1379 0,1384 0.1239 0.1194 0-1187 goo. 0.06350 0.10970 0.07097 0.07241 0.07872 0.07855 0.06655 0.08283 0.07972 0-07740 0.07638 0.07957 0.07916 0.09794 0.08073 0.08 75 1 0.08099 0.08124 0.07613 0,07803 When, after heating to 90" C., these oils were cooled to 30" C. and their viscosity redetermined a t that temperature, this was found to have been unaffected by the heating. The fluidities of the oils are not linear functions of the temperature, indicating that there is some association at the lower temperature (cf. Bingham, Zeitsch.Phys. Chem., 1909, 66, 1). G. C . J. " Pergamyn " and Imitation Parchment Papers. W. Herzberg. (Mitt. K. Materialprufungsamt, 1911, 29, 464-467 ; through Chem. Zentralbl., 1912, I . 688.) -'I Pergamyn," '6 greaseproof," or imitation parchment papers owe their special qualities to the mechanical treatment followed in their manufacture and not to any addition of an external substance, such as paraffin wax. Genuine parchment papers possess somewhat similar characters owing to a chemical treatment, a modification of the fibres by the action of sulphuric acid. Customs officials are not always in a position to recognise these distinctions, and pergamyn papers and the like are some- times charged as impregnated or waxed papers, sometimes as genuine parchment papers.Test for Parafin W7az.-The paper is extracted witb ether, the ethereal extract is saponified with alcoholic potash, the dried residue after saponification is extracted with ether, and the ethereal extract is dissolved in hot acetic anhydride. If paraffin wax is present, it separates out on cooling. I t is generally sufficient to observe whether the paper loses its lustre and transparency after extraction with ether; pergamyn papers remain unaltered.ORGANIC ANALYSIS 145 Test for Genuine Parchment Papers.-A portion of the paper is boiled with a 2 or 3 per cent. solution of sodium hydroxide whilst stirring. Imitation parchment papers fall to pieces under this treatment, whilst genuine, chemically modified parch- ment papers retain their form. J. F. B. Unification of Reducing Sugar Methods (A Correction for Lactose). P.H. Walker. (J. Amer. Chem. SOL, 1912, 34, 202-209.)-Attention has been called to arithmetical errors in the tables originally published for lactose (J. Amer. Chem. Soc., 1907, 29,541). Table IV. giving the amount of sugar for each mgrrn. of cuprous oxide has been wrongly calculated and does not agree with the experimental results of Table III., which is correct. The same error has been reproduced in the U. S, Bulletin, No. 107, Bureau of Chemistry, Official and Provisional Methods of Analysis, pp. 243-251, which has been in use for several years. I n the formula- y = a + bx+cxz, where y = cuprous oxide and x = reducing sugar, the true values in the case of lactose are a = 4.1759, b = 1.48697, c = - 0,00009.The lactose used was the crystallised hydrate C,,H220,, + +H,O. J. F. B. Estimation of Sugars in Natural Products. C. Neuberg and M. Ishida. (Biochem. Zeitsck., 1912, 37, 141-169.)-1t is shown that by treating sugar solutions with 50 per cent. mercuric acetate solution followed by precipitation with 25 per cent. phosphotungstic acid solution, all optically active proteins, their derivatives (amino- acids, etc.), and other substances are removed, whilst the sugars remain in solution and can be estimated polarimetrically. The process is particularly applicable to the analysis of mixtures of sugar with amino-acids, molasses, etc., and results of experiments are. recorded showing that the method is trustworthy. The amino-sugar, d-glycosamine, may be estimated in the presence of amino-acids by means of this method, as it is not precipitated by the reagents mentioned. A method is described for preparing the phosphotungstic acid reagent ; 200 grms. of crystallised sodium tungstate are dissolved in hot water, 5 grms. of solid phosphoric acid are added, and the clear solution is mixed first with 60 C.C. of dilute sulphuric acid, and then with 58 grms. of concentrated sulphuric acid, the solution being cooled during the addition of the acid. The solution is next evaporated on a water-bath to a volume of 290 c.c., cooled in an ice-chest, the crystals of sodium sulphate are separated, and the- residual solution is diluted with an equal volume of water. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9123700142

出版商:RSC    

年代:1912

数据来源: RSC

摘要:

ORGANIC ANALYSIS 145 INORGANIC ANALYSIS. Detection of Bromine by Fluoresceln. H. Baubigny. (Bull. Soc. Chim., 1912, 11, 13.)-The author’s test (Comptes rend., 1897, 125, 654) has been stated by Pribram, and later by Labat, to be inconclusive as applied to the detection of bromine in animal organs, on the ground that chlorine or iodine would give the- same reaction. This is denied: the chlorine compound of fluorescein is almost colourless, and iodine should be converted into iodate by oxidation with permanganate, as indicated in the original paper. 0. E. M.146 ABSTRACTS OF CHEMICAL PAPERS Estimation of Alkalis in Silicates by Fusion with Calcium Chloride. E. Makinen. (Zeitsch. anorg. Chem, 1912, 74, 74-78.)-Instead of the calcium carbonate and ammonium chloride of the Lawrence Smith method (Ann.Chern. u. Pharrn., 1871, 159, 82), anhydrous calcium chloride is recommended. The calcium chloride should be prepared in the laboratory, as the purest commercial salt may contain as much as 0.02 grm. of alkali chloride in 7 grms., the amount of flux recommended for use with 0.5 grm. of the silicate. Intimate admixture of the silicate with the flux is unnecessary, as the latter, unlike the mixture of Lawrence Smith, really melts. The crucible is supported on asbestos millboard, so that its upper portion and the cover may remain relatively cool and so serve to prevent volatilisation of alkali chloride, The crucible is heated gently at first until the calciuw chloride is fused, but is then raised to a full red heat by means of a Teclu burner. After twenty-five to thirty minutes fusion the flame is withdrawn, the crucible cooled suddenly, and the analysis completed in the usual manner, except that the use of ammonium carbonate in-place of ammonium oxalate is recommended for removing the last traces of calcium.Ammonium carbonate is said to separate the last traces of calcium as well as oxalate, and is preferred because of the high temperature which is necessary to expel oxalic acid from the residue of alkali chlorides. When the results obtained diEer from those yielded by the Lawrence Smith method, they are higher, and the author thinks they should be preferred. G. C. J. The me of a blowpipe-flame leads to volatilisation of alkali. Estimation of Ferrous Iron in Silicate Bocks. M. Dittrich and A.Leon- hard. (Zeitsch. anorg. Chem., 1912, 74, 21-32.)-The paper contains a detailed description of the experiments which led Dittrich to publish the statement (ANALYST, 1911, 36, 602) that the uncertain end-point in the titration of ferrous iron in certain rocks, after decomposition by means of hydrofluoric acid, was due to the presence in those rocks of Ti,O,, and not to the presence of manganese. The following method of conducting the estimation of ferrous iron avoids any difficulty due to the presence of Ti,O,. From 0.8 to 1 grm. of the not too finely powdered sample is mixed with 0.5 grm. quartz sand (ANALYST, 1911, 36, 372) and 2 C.C. sulphuric acid, and decom- posed by means of 8 C.C. of hydrofluoric acid. The crucible is placed on a boiling water-bath and covered with an inverted fmnel, which is sufficient to prevent any appreciable oxidation during the few minutes required for decomposition of the rock.The contents of the crucible are poured, without previous cooling, into a mixture of 100 C.C. water, 10 grms. precipitated silica, 20 grms. potassium sulphate, and 2 C.C. sulphuric acid, and the mixture is titrated at once with permaaganate. G. C. J. Estimation of Chromium and its Separation from Vanadium Steels. J. R. Cain. ( J . Ind. Eng. Chem., 1912, 4, 17-19.)-After drawing attention to the difficulties which attend the estimation of chromium in chrome-vanadium steels, the author recommends the following method, which depends on the fact established by him (ANALYST, 1911, 36, 475) that chromium can be precipitated completely by boiling the nearly neutralised (ferrous) solution with barium carbonate, and on the observation of Noyes and Bray (Technology Quarterly, 1908, 21, 14), thatINORGANIC ANALYSIS I47 chromate may be separated from vanadate by precipitation as lead chromate if certain precautions are observed.The drillings, which should preferably contain not more than 0.06 or 0.07 grm. of chromium, are placed in a 300 C.C. Erlenmeyer flask and dissolved in fuming hydrochloric acid of which about 10 C.C. is taken for each grm. of steel. The solution is diluted to 100 or 150 C.C. with hot water and nearly neutralised with saturated sodium carbonate solution. A slight excess of an emulsion of barium carbonate is added and the mixture boiled vigorously for ten or fifteen minutes with small additions of barium carbonate every two or three minutes, the flask being kept covered to exclude air as completely as possible.The excess of barium carbonate used should not be more than 2 grms. or there may be dificulty in extracting the chromium by a single fusion. The precipitateis allowed to settleand is then filtered off and washed twice with hot water, these operations being conducted as quickly as possible. The filter and precipitate are transferred to a platinum crucible, the paper is burned away, 2 grms. sodium carbonate and about 0.25 grm. potassium nitrate are mixed in, and the mixture is maintained in a state of fusion for twenty minutes. The product of the fusion is digested with boiling water and the solution filtered.Hydrogen peroxide (1 or 2 C.C. of a 3 per cent. solution) is added to destroy any nitrite, and the solution is boiled for five minutes to decompose the excess of peroxide. The solution is cooled and transferred to a separator, rendered slightly acid with nitric acid and vigorously shaken to expel carbon dioxide. It is then transferred to a beaker, just neutralised with sodium hydroxide, and then made acid by addition of 2 C.C. nitric acid (1 : 1) for each 100 C.C. of solution. Lead nitrate (20 C.C. of a 20 per cent. solution) is added to the cold solution with vigorous stirring, and the lead chromate is filtered off on asbestos and washed three or four times with cold water. The asbestos mat is transferred to a beaker or flask and the lead chromate decomposed with hot hydrochloric acid (1 : 4).The solution iscooled, madeup to 150 or 200 c.c., and titrated against -& ferrous sulphate with ferricyanide as an outside indicator. The amount of sodium carbonate permissible in the fusion is limited by the fact that for a successful separation of chromium from vanadium not too much sodium nitrate should be present (Noyes and Bray, Zoc. cit.), and it is this necessity for restricting the amount of sodium carbonate which makes it advisable to take for analysis not more of the sample than corresponds to 6 or 7 cgrms. of chromium. Larger amounts are not readily extracted by 2 grm3. of sodium carbonate, especially if too great an excess of barium is present. The shaking of the solution to eliminate carbon dioxide deter- mines the subsequent formation of a precipitate which settles and filters well, and equally cogent grounds underlie other directions as to manipulative detail.Test numbers, obtained with solutions of a vanadium and chromium free steel to which known amounts of bichromate and vanadate were added, show maximum errors of +_ 0*0004 grm. with from 0.02 to 0.3 grm. chromium present. The filtrates from the barium carbonate precipitation were tested for chromium with negative results in every case, and in only a few cases was any trace of vanadium found in the chromium solution after titration, and in those cases the amount was negligibly small. On the other hand, it is well to examine the insoluble matter from the fusion by fusing it again with sodium carbonate and potassium nitrate.With much chromium in the original148 ABSTRACTS OF CHEMICAL PAPERS weight of drillings, a yellow-coloured solution may result. it may be estimated with sufficient exactness colorimetrically. If so, the chromium in G. C. J. Analysis of Higher Oxides of Lead. A. Chwala and E. Colle. (Gazz. Chim. Ital., 1911, 41, 551-579.)-From the results of an experimental study of the different methods proposed for the analysis of lead peroxide the author recommends the following modification of Lux’s method (Zeit. anal. Chem., 19, 153) as the most convenient and reliable : From 1 to 2 grms. of the sample are treated with 100 C.C. of oxalic acid solution, and the liquid boiled for ten to fifteen minutes, until solution is complete. The excess of oxalic acid is then titrated with standard permanganate solution, and the amount of lead peroxide calculated from the result- nitric acid and 25 C.C.of YbO, + C2H20, = PbO + H2O + 2C02 The duration of the boiling with nitric acid and the concentration of that acid have considerable influence upon the results. The results of experiments have shown that the differences between the results given by the oxalic acid method and the iodometric methods are entirely due to the occurrence of secondary reactions in the latter, leading to the formation of lead iodide and methyl acetate, so that part of the iodine escapes titration- In some instances the error thus produced may be considerable, and, in any case, should always be taken into account in iodometric estimations of oxidising substances in the presence of weak acids and heavy metals.Various samples of commercial lead peroxide analysed by the foregoing method contained from 43.5 to 95-56 per cent. of lead peroxide. Pb(CH,COO), + 21 = CH3COOCH3+ PbI2+ GO2 C. A. M. Bismuthate Method for Manganese. D. J. Demorest. ( J . Ind. Eng. Chem., 1912, 4, 19.)-The following modification of the bismuthate method is recommended for use with chrome and chrome-vanadium steels. The drillings are dissolved in nitric acid (sp. gr. l a l ) , boiled to expel nitrous fumes, and potassium bismuthate is added until permanganic acid or manganese dioxide persists on boiling. Potassium nitrite is added to dissolve the manganese dioxide, and the solution is boiled to expel nitrous fumes, after which it is cooled and the manganese oxidised by bismuthate in the cold as usual.The solution is then filtered rapidly through asbestos on glass wool and titrated with a standard solution of sodium arsenite, made by dissolving 2.25 grms. of arsenious acid in a hot solution of sodium carbonate and diluting to 2.5 litres. The test numbers, obtained in presence of three or four times as much chromium or vanadium as manganese, are good, the worst being 0.671 per cent. found with 0,666 present. G. C. J. Determination of the Density of Minerals by Means of Rohrbaoh Solution of Standard Refractive Index. H. E. Merwin. (Amer. J. Science, Silliman, 1911 [43, 32, 425 ; through Chem. Zentralbl., 1912, I., 524.)-The density of a solution contained in the cell of a refractometer is adjusted until a fragment of theINORGANIC AJSALYSIS 149 mineral under examination is just suspended in it ; its refractive index is determined, and from this its density, and hence the density of the sample, is found.For Rohrbach (barium mercury iodide) solution, the relation between D (density) and n (refractive index), at 20" C., is as follows : D = 3.449 3.396 3.246 3.180 3.046 2.980 n = 1.7686 117960 1.7312 1.7195 1.6944 1.6823 D = 2.748 2.649 2.648 2.367 2.163 2.067 For densities between 2-25 and 3.40 it may be expressed, with a maximum error of f 0-002, by the empirical formula : D20= 5.39 (n - 1.5467) + 2-25 =5*39n - 6.0865. For variations from 20" exceeding 3" a correction of +_ 0*001 per L- 2" is necessary. For densities between 2.0 and 2.25, D=5.7n-6.567; and between 3.4 and 3.5, D = 552n - 6.313.For approximations, the mineral is brought to suspension, and n then determined on a drop of the liquid. 12 = 1.6391 1.6207 1.6205 1.5685 1.5320 1.5148 0, E. M. Estimation of Nitrates in Sewage Effluents. H. Silvester. (J. Sot. Chem. Ind., 1912, 31, 95-96.)-Effluents derived from sewage containing wasto gas liquor may contain thiocyanates, and in presence of thiocyanates the phenol- sulphonic acid method for the estimation of nitrates is not trustworthy. The zinc- copper couple method is recommended as the best for sewage effluents. I n using this method it is convenient to have an approximate idea of the amount of nitrate present, and for this purpose the diphenylamine test serves well. To 2 C.C. of the effluent a few drops of the diphenylamine reagent and 10 C.C.of sulphuric acid (free from nitrate) are added. The intensity of the blue coloration which results enables the analyst to form a rough estimate of the amount of nitrate present. G. C. J. Detection of Nitrates in Presence of Nitrites. H. K. Sen and B. B. Dey. (Zeitsch. anorg. Chem., 1912, 74, 52-54.)-When nitrites are destroyed by means of urea, as in Piccini's method for the detection of nitrate in presence of nitrite, small quantities of nitrate are invariably formed by the decomposition of nitrous acid into water, nitric oxide, and nitric acid. I t is shown that the reaction of hydrazine sulphate with nitrites (ANALYST, 1911, 36, 468) is unattended by the formation of even such traces of nitrate as may be detected by the diphenylamine reaction, and hydrazine sulphate is therefore recommended for the preliminary destruction of nitrite when it is wished to test for nitrate in a liquid containing nitrites.G. C. J. Note by Abstractor.-Stutzer and Goy (ANALYST, 1911, 36, 524) have stated that the decomposition of nitrite by hydrazine sulphate is never complete. Estimation of Phosphoric Acid by von Lorenz's Method. H. Neubauer and F. Lucker. (Zeitsch. anal. Chem., 1912, 5lY161-175.)-The following procedure is recommended in estimating phosphoric acid by this method, the principal modi-150 ABSTRACTS OF CHEMICAI, PAPEE28 iication introduced being that acetone is employed instead of alcohol and ether for washing the phosphomolybdate precipitate. The reagents required are : (1) Xolybdic acid reagent.One hundred and fifty grms. of ammonium molybdate are dissolved in 400 C.C. of boiling water, and the solution, when cold, is added gradually to a solution of 50 grins. of ammonium sulphate in 450 C.C. of nitric acid of sp. gr. 1.4 ; the whole is then diluted to a volume of 1 litre, filtered, and stored in a dark place. (2) Nitric acid containing sulphuric acid. Thirty C.C. of sulphuric acid of sp. gr. 1-84 are added to 1 litre of nitric acid of sp. gr. 1.20. (4) A 2 per cent ammonium nitrate solution. A quantity of from 10 to 15 C.C. of the phosphoric acid solution under examination (for instance, the solutions obtained in the analysis of fertilisers for total and citric acid soluble phosphoric acid) is diluted to a volume of 50 c.c.; should sulphates not be present, the dilution is made with the nitric acid containing sulphuric acid, otherwise with the dilute nitric acid.The mixture is then heated nearly to boiling, and 50 C.C. of the molybdate reagent are added, the whole being stirred for five minutes. After the lapse of from two to eighteen hours (the longer period is necessary if less than 3 mgrms. of phosphoric be present), the precipitate is collected in a Gooch crucible, washed with the 2 per cent. ammonium nitrate solution about four times, and then twice with acetone. The crucible is now placed for at least thirty minutes in a vessel in which the pressure has been reduced below 150 mm., and then weighed. The precipitate thus obtained contains 3.295 per cent. of phosphoric anhydride (P,O,).I t is shown that the acetone removes the ammonium nitrate completely from the precipitate and filter, and results of estimations are recorded which show that the method is accurate . w. P. s. (3) Nitric acid of sp. gr. 1.20. (5) Neutral acetone. Determination of the Penetration of Salts in Treated Wood. (Forest Service CiwuLa?; 190, U.S. Dept. of Agriculture ; through Chem Tyade JozLrizal, 1912, 50, 12.)-If zinc chloride is the preservative, a representative disk of the wood is dipped first, for not more than ten seconds, into 1 per cent. potassium ferrocyanide, and then, after removal of the excess with filter paper, into 10 per cent. uraniuiii acetate; it is then allowed to dry. The untreated portion will now be dark red, the treated portion somewhat lighter than the natural wood.The method allows 0.2 pound per cubic foot to be detected, Copper and iron sa1t.s are determined by the dark-red and deep blue coloration, respectively, of the treated zone on immersion in potassium ferrocyanide solution ; mercuric chloride by the blackening in hydrogen sulp hide sola t ion. 0. E. M. Rapid Method for Determination of Sulphur in Roasted Blende. C. C. Nitchie. ( J , Ind. Eng. Chern. 1912, 4, 30-32.)-For determining whether a particular car-load of roasted blende is sufficiently roasted to be suitable for use in the spelter furnaces, or whether it should be returned to the kiln for additional roasting, a rapid inethod is essential. The following method is recommended as rapid, and sufficiently exact for the purpose. The sample is ground no niore finely than is necessary to get a 1-grm.sample which shall be fairly representative; finer grinding prolongs the time necessary for the subsequent roasting of the ore. OneINORGANIC ANALYSIS 151 grm. of the sample is weighed out into a boat, which is placed in a silica combustion- tube previously heated to 1000" C., and a current of air, freed from carbon dioxide, is led through the tube and through an absorption apparatus containing standard caustic alkali. X fume of zinc oxide, formed by reduction of zinc oxids by zinc sulphide, volatilisation of the zinc, and its subsequent oxidation in the air-current, passes through the absorption apparatus, only negligible traces being dissolved by the alkali solution. Experiment has shown that the roasting may be discontinued when this fume is no longer seen in the absorption apparatus.The only sulphur then remaining with the roasted ore is that combined as calcium sulphate. The whole of the "false " sulphur-sulphur which should have been eliminated in the kiln, but which remained as sulphide or sulphate of zinc or lead in the sample- will have passed into the absorption apparatus, mostly as sulphur dioxide with some trioxide. The excess of alkali hydroxide is titrated with standard acid, using phenol- phthalein as indicator, and the sulphur in 1 grin. of the sample is calculated from the alkali neutralised by the gases resulting from roasting the ore. The roasting process usually occupies only about six minutes. The maximum error of the method is -0.1 per cent.on the ore, which is quite near enough for the purpose, the percentage of '' false " sulphur in roasted blende being of the order of 1 per cent. Without; modification the method is not sufficiently exact for application to unroasted blende. G.. C. J. Rapid Volumetric Method for Estimation of Free Sulphur. C. Davis and J. L. Foucar. (J. SOC. Chem. Ind., 1912, 31, 100.)-The method depends on the quantitative conversion of the sulphur into thiocyanate by digestion with an alcoholic solution of sodium cyanide, and the subsequent titration of the thiocyanate. One grm. of the finely ground (60 mesh) spent oxide or other material is dried for an hour in the steam oven and then transferred, with 1.5 grm. sodium cyanide and 50 C.C. absolute alcohol, to a 250 C.C. flask.The contents of the flask are boiled under a reflux condenser for two hours, and the alcohol is then completely removed by distillation. The residue is dissolved in 100 C.C. of hot water, and the solution, when cool, made up to 250 C.C. To 25 C.C. of this solution, 75 C.C. of water and 5 C.C. of a saturated solution of iron alum are added and the mixture heated, with constant stirring, to 95" C., filtered, and the filter washed until free from thiocyanate. To the cool filtrate, 5 C.C. of nitric acid and enough water to bring the bulk up to aboutl 500 C.C. are added, and the mixture is titrated with silver nitrate until the red colour of ferric thiocyanate disappears, or excess of silver nitrate may be added, and the solution titrated back with TG thiocyanate.Should the sample contain thiocyanate, as is most likely in the case of spent oxide, a blank test must be con- ducted, the thiocyanate being extracted with water. Test numbers obtained on applying the method to sulphur crystals agree well with those obtained by oxidising the sulphur and weighing as barium sulphate. The test numbers for spent oxides are from 0.3 to 04 per cent. lower than those obtained by oxidation of the carbon bisulphide extract, but the latter method includes as free sulphur the sulphur of any compound soluble in carbon bisulphide. G. C. J.152 ABSTRACTS OF CHEMICAL PAPERS Estimation of Sulphur in Illuminating Gas. J. Niermeyer. ( J . f. Gas- beleuchtwq, 1911, 54, 1078-1079 ; through Chem. Zentralbl., 1912, I., 375-376.)- According to Dennstedt and Ahrens, the ratio between sulphur dioxide and sulphur trioxide in the products of combustion of illuminating gas shows only small varia- tions: 92 to 94 per cent.of the total sulphur exists as the dioxide and 6 to 8 per cent. as the trioxide. On this observation the author has based a simple method for the estimation of sulphur. A known volume of gas is burnt, the sulphur dioxide is estimated in the products, the quantity of sulphur found is increased by 6 to 8 per cent. and calculated per cub. m. of gas. The sulphur dioxide is absorbed in g8 iodine solution, to which an excess of potassium iodide has been added to reduce the volatility of the iodine. The glass tube of a Drehschmidt sulphur-estimation apparatus is used, and the thin, downwardly inclined portion of the tube is utilised as a cooler for the products of combustion, which are then aspirated through the washing vessel containing the iodine.The gas-consumption is adjusted at 70 to 80 litres per hour ; 10 C.C. of & iodine solution, 10 C.C. of 10 per cent. potassium iodide solution, a few drops of starch solution, and 50 C.C. of water are placed in the washing vessel, and a current of air is aspirated. The burner is then placed under the glass tube, and, when the iodine solution is decolorised, the volume of gas burnt is read off on the meter. The quantity of iodine used represents 1.6 mgrm. of sulphur ; this is divided by the number of litres of gas burnt, and the result is increased by 6 per cent., giving mgrms. of total sulphur per litre. J.F. B. Estimation of Sulphur in Nitrocellulose. C. Kullgren. (Zeitsch. ges. Schiess- und Sprengstofwese?~, 1912, 7, 89.)-About 0.75 grm. of the substance, denitrated by heating for thirty minutes on the water-bath with 10 C.C. hydrochloric acid, is dried in a large porcelain boat. It is then burnt i n a stream of oxygen by the method of Bnrlow (J. Amer. Chenz. SOC., 1904, 26,341), the sulphur being absorbed as sulphuric acid in water or alkali. Hydrogen peroxide is added to the solution to ensure conversion of any sulphur dioxide to sulphuric acid, which is then precipitated with barium chloride solution. The results showed satisfactory agreement. 0. E. M. Estimation of Sulphuric Acid. K. K. Jarvinen. ( A m . acad. scient. Fennica, 1911, Serie A.2. Nr. 16; through Chem.Zentralbl., 1912, I., 526.)-By the method given, about -0025 grin.-molecule of sulphuric acid is titrated with a maximum accuracy of 0.2 per cent. The following ions may be present : sodium, potassium (magnesium j, ammonium, in almost unlimited quantity ; calcium, alu- minium, manganese, zinc, iron, to the extent of 4 equivalents ; copper, 1 ; chloride, 8 ; nitrate and borate, 4 ; phosphate, 2 ; oxalate, 1. Strontium, lead, chromium, and chromate ions must be absent. The solution, containing -002 to -003 grm.-molecule sulphate in 40 to 50 c.c., is neutralised if necessary until about 1 to 3 equivalents ( = 2.5 to 7.5 C.C. 2 N) hydrochloric acid are left free; 3 equivalents are only required if 2 of phosphoric acid or 1 of oxalic acid are present. Ferric salts, 1 to 4 equivalents, are reduced by boiling with 9 to 2 equivalents of hydroxylamine. The solution is boiled up and slowly precipitated with about 40 C.C. (1 to 5 equiv-INORGANIC ANALYSIS 153 slents) of hot benzidine hydrochloride solution ($+Fc HCI). The liquid is now evaporated to one-half, cooled, filtered, the precipitate washed with water contain- ing benzidine sulpbate, transferred to the original flask, and titrated hot with ; sodium hydroxide free from carbon dioxide, and phenolphthalein. The result is usually not more than 0.1 to 0-2 per cent. high. 0. E. M. Rapid Method of Estimating Zinc. K. Voigt. (Zeitsch. angew. Chem., 1912, 25, 205-206.)-V. Hassreidter has stated (Zeitsch. angew. Chew,., 1911, 24, 2471) that the author’s method (ANALYST, 1912,35) is open to objection on the ground that zinc may be underestimated owing to the re-formation of zinc silicate in presence of hydrated silioa. The author points to the test numbers in his earlier paper for proof of the accuracy of the method, and adds that many of those test numbers were obtained in presence of 30 to 40 times as much (‘ soluble I’ silica as zinc. He also points out that Hassreidter’s experiments were not conducted in accordance with his directions, since Hassreidter used the smallest possible excess of ammonia, as he wished finally to complete the analysis by titration with sodium sulphide, which is rendered difficult or impossible by excess of ammonia. The large excess of ammonia directed to be used by the author prevents the zinc passing into the precipitate as silicate. A still larger excess is without influence on the results, but serves no useful purpose (cf. ANALYST, 1912, 35). G. C. J.

ISSN:0003-2654    

DOI:10.1039/AN9123700145

出版商:RSC    

年代:1912

数据来源: RSC

摘要:

INORGANIC ANALYSIS 153 APPARATUS, ETC. Automatic Pressure Pipette. W, Skinder. (Chenz. Zeit., 1912, 30, 166).-The apparatus shown in the illustration is useful in cases where it is desired to bring two solutions to the same temperature before they are allowed to react with one another. It consists of a hollow rod, D, and a mantle, C, which are joined together by means of two ground-in joints. A small opening is provided at a, and another at b, which passes through both the hollow rod and the mantle. The apparatus is filled by raising the rod and immersing the mantle in the fluid ; on withdrawing the apparatus from the fluid, it closes automatically. The hollow rod is then rinsed out with water, and the apparatus is placed in a vessel con- taining another fluid, and when the desired temperature is attained the contents of the apparatus are discharged by means of a pressure-bulb fitted to the upper end of D, the pressure produced raising the mantle, and allowing its contents to mix with the other fluid. w.P. s. Device for Preventing the Bumping of Boiling Liquids. E. Pieszcgek. (Chem. Zeit., 1912, 36, 198.)-A glass tube, 6 to 8 cm. long and 3 to 5 mm. in diameter, is drawn to a point at one end, into which is then fused a length of platinum wire to serve as a handle. The tube is immersed with its open end downwards, in a nearly vertical D a c b position, in the liquid. On heating the latter, bubbles of enclosed air escape from the tube, and all bumping is prevented, even in the case of liquids containing barium154 ABSTRACTS OF CHEMICAL PAPERS sulphate, or those covered with a layer of fatty acids.expelled from the small tube. The air is never completely C. A. M. Method of Measuring Absolute Viscosity. H. P. Gurney. ( J . 8.mer. Chcm. Soc., 1912, 34, 24-28.)--The desirability of expressing the viscosity of liquids t where y = the density of the in absolute units is urged, and the apparatus figured is suggested for the purpose, for which the author claims extreme accuracy, simple and rapid manipulation, ease of working, shortness of time required for calibration, and the capacity for being used with opaque liquids and very small volumes. F, H is a capillary tube of suitable dimensions, graduated at F, G, and H, fixed vertically, and jacketed if necessary. The liquid to be tested is poured into I until it rise8 in the capillary to H, B being open to the atmosphere.B being then closed, A is opened, and the liquid drawn up above 3’. Atmospheric pressure is then restored, and the time required by the liquid to fall from F to G is taken by means of a stop-watch. In- creased accuracy is attainable by repeating and averaging results. The density of the liquid may be obtained by any suitable method, and the radius of the capillary from the length and weight of a thread of mercury. A mathematical discussion of the results obtainable follows, from which the author deduces a very simple expression for the calculation of the viscosity. Thus, for a capillary tube of 1 metre in lengtb, and bore of radius 0.03475 cm., of which the distance from F to G is 57.08 cm., and from G to I21.37 em., p = 0*00247yT, liquid, and T=the time of flow from F to G in seconds, the radius of- the dish I being 4.4 em.H. F. E. H. “Luminator” Treatment of Water. H. B. Lake. ( J . SOC. Chem. Ind., 1912, 31, 57.)--It has been claimed (J. SOC. Chenz. Ind., 1910, 30, 933) that the passage of a hard water over aluminium plates reduces its temporary hardness, and causes the deposit of its mineral matter, on boiling, as a sludge and not as a scale ; the apparatus should be arranged north and south, exposed to direct light, and be given a weekly rest. The author has submitted water passed through either an aluminium chute or an aluminium tube, under the conditions stated, to soap-tests for total andGOVERNMENT REPORT I55 permanent hardness, and to mineral analysis, comparing the residues obtained by evaporation of treated and untreated water. The differences were small. With one of the two waters treated there appeared to be a tendency towards the conversion of calcium salts from permanent to temporary hardness; with the other this was reversed. The treatment was without effect on the conversion of carbonates of lime and magnesia to sulphates, in hard water, by aluminium sulphate. 0. E. M.

ISSN:0003-2654    

DOI:10.1039/AN9123700153

出版商:RSC    

年代:1912

数据来源: RSC