摘要:

THE ANA4LYST. OCTOBER, 1896. WHITE-WINE VINEGAR.* BY ALFRED H. ALLEN. WHITE-WINE VINEGAR was originally understood to mean a vinegar made from wine derived from white grapes. Of late years the sale of the genuine article has greatly declined, and distilled malt vinegar or simple diluted acetic acid has been very commonly sold in its place. This practice, though very general, has not the sanction of universal custom, since some of the leading dealers always supply real white-wine vinegar when asked for it. The following are analyses of two samples of the real article purchased retail in a town in the Midland counties : Parts p e ~ 100 measures : A. B. Acetic acid ... ... ... ... ... ... 6.37 6.49 Extractive matters ... ... ... ... ... 1.43 1.55 ... ... Containing mineral matters ...0.28 0.30 With alkali (K,O) ... ... ... 0.046 0.046 ... Two other samples obtained direct from the importers, and which I believe to be specimens of genuine white-wine vinegar, showed on analysis : C. D. Specific gravity ... ... ... ... ... 1.0197 1.0211 Parts by zcieiglit pcr 100 measures : A. B. ,hetic acid ... ... ... .. 7.98 7-78 Albuminous matters . . . ... ..- 0.10 0.19 Extractive Carbohydrates, etc. ... ... ... 1-65 1-65 matters. Mineral matters ... ... ... 0.20 0-53 i Containing phosphoric acid ... trace 0-065 Genuine wine vinegar always contains a notable quantity of acid potassium tartrate, which is not present in vinegar from other sources, The following samples were procured by retail purchase from pharmacists in Midland towns, ‘‘ half a pint of white-wine vinegar ” being asked for in each case.The results showed that dilute acetic acid or distilled malt vinegar, sometimes coloured a pale yellow, was supplied in each case. The amount of extractive matter was insignificant. The price of the samples varied from 14-d. to 4d. per half-pint, * Abstract of a paper read before the British Pharmaceutical Conference.254 THE ANALYST. N iimbe r . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Label on Bottle. Pure white-wine vinegar White vinegar ... Acetic acid vinegar White-wine vinegar Distilled malt vinegar White- wine vinegar White-wine vinegar Distilled vinegar ... White-wine vinegar No label ... ... White-wine vinegar White-wine vinegar Vinegar ... ... Vinegar ... ... ... ... ... ... ... ... ... ... ... ...... ... ... ... Acetic Acid. Grammes per 100 C.C. 6-45 4.41 5.01 3-15 4.80 5.47 5.22 5.10 5-10 5-91 4.23 5-24 5.79 6.93 Colour. Water- whi t e Pale straw Nearly colourless Water - w hit e Water-white Nearly colourless TNa t er - w hi t e Water- white W at er-whi t e Water-whit e Pale straw Water-white Water-white W at er-white White-wine vinegar has the colour of sherry. I t has a, vinous aroma and peculiar flavour. However much it may be appreciated as a condiment by those who obtain the real article, it is clearly waste to employ it for pickling purposes, since its distinctive characters are thereby lost. It seems highly improbable that wine vinegar will ever again come into general use in this country, and it probably would completely disappear if distilled acetic acid were not supplied in its place, or if the label described correctly the nature of the article sold.Where distilled vinegar is substituted, according to the supposed requirement of the purchaser, it might with advantage be labelled, “ Distilled vinegar ; commonly called white-wine vinegar.” NOTE ON THE MICROSCOPIC DETECTION O F BXEF FAT I N LARD. BY THOMAS S. GLADDING. IN the preparation of crystals of lard and beef stearin for microscopic examination I find the following method gives excellent results, the crystals being of good size and of distinctive form. Dissolve 5 C.C. of melted lard in a mixture of 20 C.C. absolute alcohol and 10 C.C. ether in a small I+Grlenrneyer flask, heating gently if necessary. Place a plug of cotton in the mouth of the flask, and allow to stand in a cool place for about half an hour. The stearin crystallizes out, the olein remaining in solution. Filter rapidly through a paper wet with alcohol, using a filter-pump, and wash crystals and paper once with the above alcohol-ether mixture (10 : 5). Let the crystah dry in the air, and remove them from the paper to the flask. Dissolve in 25 C.C. of ether, replace the cotton plug, and place the flask in a slanting position in a large beaker (about 1 litre) nearly full of water. Theether evaporates very slowly, and the crystals of stearin are gradually formed in the solution, the large quantity of water surrounding the ether solution guarding against any sudden change of temperature. For valuable plates giving characteristic forms of lard stearin crystals and beef stearin crystals reference is made to Bulletin No. 13, Part IV., Division of Chemistry, United States Department of Agriculture. Keep this in a cool place over night.

ISSN:0003-2654    

DOI:10.1039/AN8962100253

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THE ANALYST, 255 ABSTRACTS OF PAPERS PUBLISHED FOOD ANALYSIS. The Microscopy of Honey. K. Dieterich. 47 ; through Chem. Zeit. Rep., 1896, 156.)-In spite IN OTHER JOURNALS. (He lfen berg er Annalen, 1895-9 6, of the statements that artificial honey can be distinguished irom the genuine product by the absence of pollen grains, the author finds that ordinary forms are present, and in addition to these, a special and characteristic form never met with in Dalmatian or American honey. This particular variety is in large excess of the normal forms, and fills the whole field of256 THE ANALYST. view, only isolated specimens of the others being observable. Artificial honey exhibits the same crystals of cane-sugar and glucose as the genuine substance, but the cane-sugar crystals are very few in number.F. H. L. Estimation of Sugar in Chocolate. X. Rocques. ( A m . d c Chiwzie AnaZpt. i. [XI, 288.)-In order that the proportions of ash, fatty matter, etc., found in chocolate may be referred to the original cacao, it is necessary to estimate the added sugar. This may be done by mixing 15 grammes of the grated chocolate in a flask with 90 C.C. of distilled water, raising the temperature to 40" C. to melt the fat and produce an emulsion. After agitating for a moment,.add 15 C.C. of a 10per cent. solution of subacetate of lead and filter, collecting 70 C.C. ( = 10 grammes of substance), and throwing down the lead therein by a mixture of 20 C.C. of a 20 per cent. solution of sodium sulphate apd 10 cIc. of glacial acetic acid (uuless the reagents be added together the precipitation is incomplete), leaving the glucose and sugar in solution.The glucose is estimated direct from a few c.c., and the saccharose by heating 50 C.C. for three hours on the water-bath, and treating with Fehling solution after making up the volume to 500 C.C. The acid in the liquid suffices to invert the saccharose. and, although requiring longer than inversion by hydrochloric acid, has the advantage of not acting on any dextrin that may have been added as an adulterant. By subtracting the weight of glucose from the total sugar, and multiplying the remainder by 0.95, the amount of crystallizable (added) sugar is obtained, which should average 55 per cent. of the chocolate. Ratios of 60 per cent. and thereabouts indicate additions of sugar to conceal inferiority of the cacao used and reduce the selling-price.C. S. On the Quantitative Estimation of Cellulose in Foods. G. Baumert. (Zeit. angezo. Chem., 1896, 408-411.)-The chief novelty in the author's process is the filtration of the cellulose through asbestos previously washed with acid and alkali, and arranged in a thin layer on a filter disc in a funnel. Two grammes of the finely- divided, air-dried substance (e.g., meal) are placed in a beaker of about 200 C.C. capacity, moistened with 90 per cent. alcohol, and, after the addition of some dry, pure asbestos, mixed with 100 C.C. of dilute sulphuric acid (12.5 grammes per litre). The mass is well stirred, covered with a glass, and placed in a water-bath, so that the beaker is only surrounded by steam.After an hour, with occasional stirring, the mass is filtered through asbestos, the filter washed with hot water, and the whole of the asbestos, with the residue, returned to the beaker. The contents of the beaker are next digested with dilute soda solution (12.5 gramines per litre) for an hour in the water-bath, and filtered through a new asbestos filter, which is then washed successively with hot water, alcohol, and ether. The asbestos is transferred to a platinum basin, dried at 100" C., and weighed. It is then ignited uctil all carbon has disappeared, and again weighed, the difference between the two weighings giving the amount of cellulose. When the material to be examined is very rich in fat, as in the case of cocoa, a preliminary extraction, with 30 C.C.of 96 per cent. alcohol, is made by placing the beaker containing the 2 grammes ofTHE ANALYST, 257 substance in the water-bath. The alcohol is filtered through asbestos, the extraction and filtration repeated once or twice with more alcohol, the asbestos filter and its contents placed in the beaker, and the extraction, with sulphuric acid and soda, carried out as before. The following table gives some of the results obtained in this way : Per Cent. Wheat meal, Russian ... 0.00 ,, ,, La Plata, 0.25 ,, ,, fine groats 0.15 ,, ,, coarse ,, 0.20 Rye meal, No. 0. ... 0.15 ,, ,, No. 11. ... 1.15 ,, ,, Fodder ... 1.80 Cellulose. 0.10 0.30 0:20 0.20 0.20 1.15 2-00 Per Cent. Cellulose. Rye bran ... ... 4-90 5 -05 Wheat bran ... ... 7.20 7-30 Wheat bread ...... 1-32 1.42 Malt coffee ... ... 10.60 10.80 Chicory coffee . . . ... 6.65 6.76 Coffee, roasted . . . ... 12-45 13-45 Cocoa husks . . . ... 16-30 16.35 Potatoes ... ... 0.44 0.46 If the time of digestion be lengthened the percentage of cellulose naturally falls; but the author considers the results obtained by digesting for one hour as the most correct. C. A. M. Examination of Peppers. F. Bauer and A. Hilger. (Forsclmzgsber. Lebeizs- mittel, etc., 1896, iii., 113; through Chcnz. h i t . Izcp., 1896, 15G.)-The best method for testing the purity of pepper depends on the estimation of the piperine, either in the form of piperic acid or by titration as piperidine. Genuine peppers contain between 5.55 and 7.77 per cent. of the alkaloid, while in the husks it only amounts to 0.2 per cent. ; therefore any sample containing less than 4 per cent. may be con- sidered adulterated. The author has also found that the amount of furfuralhydrazone yielded by 5 grammes of dry black pepper is 0.20 to 0-23 gramme, in white pepper 0.046 to 0.052, and in dust and husks 0-41 to 0.56 gramme, so that an addition of substances of a similar nature more than 15 per cent. in extent can be detected. The samples must always be examined microscopically also. ‘‘ Loug pepper ” contains 4.9 per cent. of piperine, and yields 0.185 to 0.197 gramme of furfuralhydrazone. Its ash is 6-02 to 6.80 per cent. in weight. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN896210255b

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THE ANALYST, 257 ORGANIC ANALYSIS. The Electrical Conductivity of Fats and Oils. L. Herlant. (BUZZ. de Z’Ass. belge, lS96, x., 48-54.)-Salt solutions offer different resistance to an electric current, the amount of which is constant under the same conditions for one and the same substance. The specific yesistame of a solution is the measurement for a cube with a 1 side of 1 cm., whilst the inverse function of this - gives the specijic conductivity. To simplify the process and to determine the eZectTolytic capacity of the troz~glz, a typical salt solution of known conductivity is employed, and the subsequent results based on this. For this purpose the author used a, -N solution of potassium chloride 1 500258 THE ANSLY ST. (1.49 gramme per litre), the conductivity of which salt was determined by Kohlen- rausch at 0.002244 for a cubic centimetre at 18" C.x k = 0.002244, k represents the capacity of the trough, and when the potassium chloride solution is replaced by the solution to be examined, the distance between the electrodes is modified, which gives the specific conductivity I of the solution, 1 I n the formula 1 I = ~~ x k. rc For the examination of fats and oils, 10 grammes, which must be dry and free from salts, casein, etc., are mixed in a flask with 45 C.C. of pure normal alcoholic potash, and saponified by heating for thirty minutes on the water-bath under a reflux condenser. When saponification is complete, the soap solution is made up to 250 C.C. with distilled water and electrolysed. The following table gives the results obtained in this way by the author : Butyro-refracto- Zeiss at 35" C.Substance. meter. Butter 1 ... 44.5 9 9 2 ... 45 7 , 3 ... 45 Y , 4 ... 48 Margarine 1 ... 52.5 ,, 2 ... 56.5 ,, 3 ... 54 4 ... 58 Cott& oil ... 63 Earthnut oil 1 ... 58-25 9 , ,, 2 ... 60.25 Sesame oil ... 63 Olive oil . . . ... 57-25 Reichert- Meissl 2 -J - -1 Critical Tempera- ture of dissolution. 98" to 103" 122" to 123" 115" to 116" 123" 120.5" 123" Specific Conductivity a t 18" C. 0.006457 0,00650 0.006507 0-008221 0.008459 0.008472 0.008489 (0.008629 -(0-00870 0-008741 0.008779 0 -009 92 7 These figures show that the conductivity stands in direct relation to the refractive index and critical temperature. After being left six weeks, soap solutions niade from butter and margarine showed a slight decrease in conductivity.The author believes that with more data the method will prove of use in detecting adulteration in butter, though in the case of oils the results are not so promising. C. A. M. A Colour Reaction for Earthnut Oil. A. Van Engelen. (Bzdz. de 1',4ss. belge, 1896, x., 161-162.)-The reagent is a solution of 0-25 gramme of sodium molybdate in 20 C.C. of concentrated sulphuric acid, and is called the molybdic reagent. Or Frohde's reagent recently prepared may be used. To about 5 C.C. of the oil, in a test tube, five or six drops of the niolybdic reagent are added and the tube shaken. Earth- nut-oil gives a violet-purple colour, fading after about a minute. With Frohde's re- agent the reaction is somewhat different. With the following oils the results were :THE ANALYST.259 Molybdic Reagent. Friihde’s Reagent. Without Shaking. With Shaking. Without Shaking. With Shaking. Olive ... Brown Mahogany brown Brown Mahogany browri Sesame.. . Dark brown Dark brown Dark brown Dark brown Cotton . . . Mahogany brown Black Black Black Poppy ... Greenish yellow Lilac Yellow Yellow w i t h Earthnut Greenish yellow Purple Greenish Violet A mixture of olive and earthnut oils did not give a satisfactory result. violet tint C. A. M. The Leffmann-Beam Process for the Estimation of Volatile Fatty Acids. W. Karsch. (Chenz. Z e d . , l896, sx., 607.)-This process was introduced by Dr. Vieth into the ‘‘ Milchwirthschaftliche Institut ” at Hameln. two years ago, and has been in constant use ever since.It is not only much quicker than the method of alcoholic saponification, but, as the figures in the annexed table show, it gives more uniform results, which, though always lower than those obtained by Wollny’s process, are evidently the more correct. It is carried out as follows : One hundred grammes of caustic soda are dissolved in an equal weight of water, and 20 C.C. of the solution mixed with 180 C.C. of pure concentrated glycerin. Five grammes of the filtered fat are weighed into a 300 C.C. Erlenmeyer flask, 20 C.C. of the alkali added, and the vessel held by rubber-covered tongs over a naked flame for three or four minutes, until the water is driven off and the liquid becomes clear. I t is next cautiously diluted with 135 C.C. of water free from carbon dioxide, and when the soap has dissolved, a fragment of pumice and 5 C.C.of 1 : 4 sulphnric acid are dropped in. The liquid is then ready for immediate distillation. The following samples of butter were saponified in this way, and also with alcoholic alkali according to Wollny’s directions ; but, owing to the difficulty of removing the last traces of alcohol in the time given (thirty to forty-five minutes), Samples 1 to 7 were allowed to remain for five minutes on the water-bath with the flasks open, while 8 and 9 were distilled without opening for one and a half to two hours. No. 10 was also tested by Sendtner’s process, and gave 28-85. Blank analyses showed the necessity for corrections corresponding to 0.2 to 0.3 C.C. of the decinormal soda; these have in all cases been made.Sample No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Glycerin Process. 28.18 ... 28.29 27.96 ... 28.07 27-96 ... 28.07 27-06 ... 2i.08 28.18 ... 28.29 28-13 ... 28-18 27-74 . . . 27.74 27.79 ... 27-85 28-18 ... 28-18 28-00 ... 28-07 Alcoh 29.18 28-63 28-86 27-97 29.29 28.41 28.08 27-86 28.30 28.41 ,olic Process. . . . 29.39 ... 29.07 ... 28-96 ... 28.08 ... 29.51 ... 29-18 ... 28.22 ... 28-02 ... 28.63 ... 28-68260 THE ANALYST, To investigate the influence of carbon dioxide, another solution containing the soap from Sample 10 was blown into three times, which caused the Reichert-Meissl number to rise from the values recorded to 29.17. The amount of water used for solution of the soap must also be adhered to, for experiments on Sample 9, when only 115 C.C.were employed, gave a mean result of 29-28. The author remarks that of all the samples of butter he has examined by the glycerin process since last October, the highest Reichert-Meissl number has been 30.82, and the lowest 26-53. F. H. L. The Analysis of Wool-Fat. F. Ulzer and H. Seidel. (Zeit. nngczo.. C h e w , 1896, 349-350.)--Not being able to obtain completely concordant results in the saponification of wool-fat, even when carried out under pressure, the authors propose t o determine the “ total acidity number’’ instead of the saponification number, as was recommended by Benedikt and Mangold in the case of beeswax. The “total acidity number” (Benedikt, Aizalyse der Fette, p. 441) is the amount of potash in tenths of a per cent. required to neutralize the mixture of fatty acids and fatty alcohols obtained by saponifying the wax (or wool-fat) and decomposing the soap with hydrochloric acid. To determine it, 20 grammes of potash are dissolved in 20 C.C.of water in a porcelain basin holding from 350 to 500 c.c., and the solution heated to boiling. Twenty grainmes of the melted wool-fat are then stirred in, and the whole heated to boiling for about a minute, the heating continued on a water-bath until a thick uniform soap is obtained, and the basin finally placed for two hours in the water-oven to complete the saponification. The soap is dissolved in about 250 C.C. of boiling water, and decomposed with 40 C.C. of hydrochloric acid previously diluted with water. The clear fatty layer is repeatedly washed with boiling water until the washings are free from acid, and then dried in the water-oven.From 5 to 6 grammes of the dry mixture of fatty acids and alcohols are warmed with acid-free alcohol on the water-bath and titrated with standard alkali, phenol-phthalein being used as indicator. The ‘‘ total acidity number” of a sample of Australian wool-fat determined by the authors was (1) 100.2, (2) 100.9, and (3) 101.9, whilst the results obtained with a South American wool-fat were 96.4, 96.7, and 96.9. The Reichert-Meissl numbers varied between 6.7 and 9.9. The authors conclude that for the technical analysis of wool-fat sufficient data are furnished by the determination of the acid value, the ‘‘ total acidity number,” the iodine number, and the Reichert-Neissl number. A gravimetric estimation of the unsaponifiable matter is also advisable.C. A. M. Estimation of Resin in Fatty Oils. P. Cornette. (Ann. Phnrnz., 1896, ii., 240; through Chcm. Zeit. Rep., 1896, 192.)-This process depends on the fact that the sodium salts of the higher fatty acids are insoluble in a saturated solution of common salt, while the corresponding resinates are perfectly soluble. Ten gramrnes of the oil are saponified, the soaps dissolved in warm water,. allowed to cool, and anTHE ANALYST. 261 -- 99.99 excess of a strong solution of sodium chloride added. The mixture is filtered cold, and the precipitate washed with salt solution. The filtrate, which should be clear, is acidified with sulphuric acid, and the resin acids collected and weighed. I n thecase of pure linseed-oil a slight turbidity is often observed, but it cannot be mistaken for the precipitate produced by resin acids.F. H. L. -- 99.99 On Resinated Metallic Oxides. H. Amsel. (xeit. angezo. Chent., 1896, 429- 433.)-These preparations, which now play such an important part in the manufacture of varnish, are made either by melting the resin and the oxides of lead or manganese together, or by saponifying the resin with potash, and precipitating the resinate from the aqueous soap solution by means of a lead or manganese salt. Colophony, which on account of its cheapness is the principal resin employed, is prepared from pine-tree resin by removing the turpentine-oil and water by heat, and then keeping the residue in a melted state until it becomes perfectly clear. According to Wiesner, this clarification is due to the change of crystalline abietic acid into its amorphous anhydride.The best varieties are quite free from crystals; in poorer qualities bow-shaped crystals can be observed under the microscope. The colour varies from yellow to dark-brown, according to the time of heating and degree of heat. In several concordant determinations with three differently coloured kinds of colophony the author obtained the following values : - k i d Value. Saponification XO. Ether No. Water reaction. Colophony, yellow, old ... 167 ... 175 ... 8 ... Clear 2 , ,, new ... 162 ... 169 ... 7 ... Maly (-41m. cxxix., 121 and 389) showed that colophony consisted of 80 per cent. of abietic anhydride, to which he assigned the formula C44H,j204.Therefore the author considers that metallic resinates must consist principally of the metallic derivatives of abietic acid, which is dibasic. The lead compound (PbC,,H,,O,) contains 23.6 per cent. of lead, whilst the manganese compound (MnC,,H,.O,) has 7.58 per cent. of manganese. The 80 per cent. of other colophony acids, sylvic acid (C20H.Jo02), and its isomer, pimaric acid, also combine with lead and manganese to form monobasic salts : > 9 ,, white ... ... 172 ... 179 ... 7 ... 9 , cent. of manganese). Therefore a theoretical lead resinate should consist of 77.1 per cent. of the lead salt of abietic acid, and 22.9 per cent. of the lead salts of sylvic and pimaric acid, whilst the proportions of the manganese compounds should be 80.3 and 19.7 per cent.respectively. Calculated on this basis the resinates have the following coniposi t ion : Pb ... ... 24-96 C ... ... 59-09 H ... ... 7.10 0 ... ... 8-84 Mn ... , .. 7-74 C ... ... 72.87 H ... . . . 8.60 0 ... ... 10.78262 THE ANALYST. More recent research (Mona Chem., 1893, 186) has ascribed to abietic acid the formula C1uHz80y, which would give to the lead and manganese salts the formuh c19Hz702\Pb, and C1')H2702\Mn (containing 26.5 and 8.74 per cent. of their respective metals). Since, however, the question does not appear to the author to be definitely settled, and the difference would not be very great, he has preferred the older formulz, In the chemical examination of resinates the mineral matter (ie., the metals) and the combined acids should be determined.The author considers that this is most simply accomplished by incinerating a weighed quantity, weighing the oxides, and taking the resin acids by difference ; or the resinate may be treated with fuming nitric and concentrated sulphuric acids, and the metals determined in the usual manner. Comparative experiments described show that both methods furnish fairly concordant results. By direct incineration in a porcelain crucible the subjoined results were obtained : CiJLOZ/ C,J&Oy/ Mineral Matter. Organic Matter. Per cent. ' Per cent. 1. Resinated Manganese Extract ... 8.9 ... 91.1 3. Manganese Resinate (melted) ... 4.19 ... 95.81 3. $ 9 ,, (precipitated) 10.91 ... 89.09 4. Lead and Manganese Resinate (I.) ... 10-4 ... 89% 5. ,, (11.) 12.09 ... 87.91 7. ,, ,, (precipitated) .. . 25-3 ... 74.7 8. 7 , (I.) ... ... ... 28-47 ... 71.53 9. ,, ) I (11.) * * ..- ... 11-7 ... 883 10. 9 ) ,, (111.) ... ... ... 29.39 ... 70.61 ... ... ... 6. LeLi Resinate '{melted) ... ... 20.76 _.. 79.24 ... 9 , I n many of these samples the proportion of the metal is not what is required' by theory. No. 8 contains 4.5 per cent. too much, whilst No. 9 contains 11.3 per cent. too little, or, in other words, 50 per cent. of lead resinate and 50 per cent. of uncombined resin. Nos. 2 and 4 do not contain the right proportions, but Nos. 1, 5, and 7 may be considered pure resinates. No. 4 was found to contain 8.1 per cent. of lead and 2-3 per cent. of manganese, corresponding to 33.6 per cent;. of lead resinate and 30 per cent. of manganese resinate, which leaves 36.4 per cent.of uncombined resin. I n No. (3 the amounts were i per cent. of lead and 5.23 per cent. of man- ganese, corresponding to 39 per cent. and 67.5 per cent. of the respective resinates- a difference of only 3.5 per cent. from the theoretical requirement. As a further test, the acid and saponification values may be determined. For the acid value, about 2 grammes of the resinate are dissolved in 25 C.C. of a mixture in equal parts of alcohol and ether, and titrated with semi-normal alcoholic potash, phenolphthalein being used as indicator. The saponification number is determined by heating on the water-bath about 2 gramines of resinate with 10 C.C. of alcohol and 25 C.C. of semi-normal potash for half an hour, and titrating back with semi- normal hydrochloric acid.The results obtained with the same samples of resinates were :THE ANALYST. 263 Acid Value. Saponification Xo. 1. Manganese Extract ... ... ... 116 ... 195 3. Manganese Resinate (melted) ... 75 ... 171 3. 9 , ,, (precipitated). .. 118 ... 185 4. Lead and Manganese Resinate (I.) 75 ... 151 5. $ 8 (11.) 46 ... 134 8. $ 9 (1.1 9. 9 , ) I (11.) 6. Lead'Resinate :melted) ... ... 47 ... 130 7. l j ,, (precipitated) ... 37 ... 128 ... ... 45 ... 126 ... ... 103 ... 165 10. 9 , I 1 (111.) ... ... 40 ... 128 Although of some value as confirmatory tests, no certain conclusions can be drawn from these results except in the case of No. 9, where the high values show the presence of free resin. This is owing to the resinates being decomposed by the alkali.What is required is a solvent which will dissolve colophony readily and leave the resinates. The author believes that cold petroleum spirit will do this, agd promises a further communication on the subject. 1 , C. A. M. Estimation of Ethylene in Mixed Gases. P. Fritzsche. ( Z e d nngezu. ClLem., 1896, 456-459.)-1n order to estimate ethylene apart from other unsaturated hydro- carbons, the author has made use of the reaction C,H,+H2S0,==C,HGS0,, subse- quently distilling the ethyl sulphuric acid with water, and determining the amount of alcohol produced. The gas to be examined, after removal of any ammonia or sulphuretted hydrogen, is shaken in the reagent tube with concentrated sulphuric acid, the shaking being continued until, on cautiously opening the tap, no more air enters the tube.The acid is then washed into the distillation flask, distilled, and two-thirds of the distillate distilled after the addition of a little soda. The alcohol in the distillate is determined by taking the specific gravity. The most accurate results are obtained by bringing the alcohol in the fluid to about 1 or 2 per cent. The process is more tedious where only traces of ethylene are present, and to obtain accurate results with a gas containing only 0-5 per cent. at least 5 litres of gas must be used for the determination, and repeated distillation employed. The author's experiments prove that the alcohol produced corresponds quantitatively with the amount of ethylene present. The absorption-tube employed was 200 millimetres in length and 60 millimetres in diameter, but for use with coal gas its dimensions were 500 by 120 millimetres.It had a capillary tube fitted with a tap at each end. Butylene may be removed from a gas by passing through a wash-bottle containing 70 per cent. sulphuric acid, while any propylene is determined as ethylene. C. A, M. Warming the tube in a water-bath accelerates the reaction. The Separation of Trimethglamine from Ammonia. H. Fleck. (Jozw. Anzer. Chem. SOL, 1896, xviii., 670-672. )-Several chemists have based methods for the detection of trimethylamine in the presence of ammonia on the different solu- bilities of their hydrochlorides in absolute alcohol. The author shows that when only a low percentage of trimethylamine is present these methods are not evenTEE ANALYST.reliable as qualitative separations. He has found the following quantitative process satisfactory. The mixed hydrochlorides are repeatedly extracted with boiling abso- lute alcohol, and the solvent distilled off. An excess of sodium hydrate is added to the residue, and the gases formed on boiling driven over into a large quantity of water. This is exactly neutralized with sulphuric acid, litmus being used as indicator. The liquid is evaporated to dryness, and extracted with one litre of cold absolute alcohol, which dissolves trimethylamine sulphate and leaves ammonium sulphate undissolved. After distillation of the alcohol the residue is transferred to a weighed dish, dried, and weighed. In this way 32.910 grammes of the dried mixed chlorides gave 2.5 grammes of trimethylarnine sulphate, corresponding to 2-21 grammes of hydrochloride, or 6-71 per cent.The completeness of the extraction was proved by the total absence of fishy odour on treating the ammonium residue with alkali. The purity of the trimethyl- amine extract was shown by the analysis of the platinum double salt prepared from the trimethylamine sulphate . Required for [N(CH,),HCI],PtC14. Per Cent. 1%. Per Cent. Pt. 1. 0-0983 gramme gave . . . ... 36.92 ... 2, 0.3017 9 , ... ... 37-13 36-93 C. A. M. Examination of Commercial Saccharin by means of the Calorimeter. I€. Langbein. (Zeit. aizgezu. Chem., 1896,486-494.)-Saccharin, the anhydride of ortho- sulphamine-benzoic acid, often contains small quantities of para-sulphamine-benzoic acid, which detract from its sweetness.The determination of the melting-point is quite inconclusive, and the author points out that no reliance can be placed on Hefel- mann’s method, since an error of 0.1 per cent. in the imide nitrogen makes an error of 1.3 per cent. in the amount of saccbarin. For determining the calorimetrical value, a modification of Mahler’s bomb calorimeter was employed, and the usual corrections made. With pure saccharin a mean result of 4753.1 calories was obtained, whilst para-sulphamine-benzoic acid gave 4307.3 calories. A mixture of 60 per cent. of saccharin and 40 per cent. of the para- acid gave as the heat of combustion 4574-3 calories, the calculated value being 4574.78 calories. With a mixture containing 2 per cent. of para-acid, the result was 4743.9 calories, corresponding to a calculated quantity of 2.06 per cent.Owing to the greater solubility of saccharin in various solvents, the para-acid could be concentrated by crystallization and a greater difference obtained. Thus, 11.451 grammes of the above 2 per cent, mixture were dissolved in acetone, and petroleum spirit added until precipitation commenced. There separated 6.1090 grammes, which on combustion gave 4736.1 calories. This corrasponded to a calculated percentage of 3-81 per cent. of para-acid in the precipitate, or 2-03 per cent. on the original mixture. With pure saccharin no difference was observed in the heat of combustion of separate portions obtained by fractional crystallization. Specimens of commercial saccharin examined in this way gave the results here tabulated :THE ANALYST, 265 Mois- Saccharin.Calories. Calories. Ash and moisture- Crystallized frac- Sulphinide . . . Crystallose , . . Refined Sac- charin ... Sucrin ... Saccharin . . . Maker. Heyden Heyden Fahlberg and Co. Bayer and Co. Monnet Bweet- ness com- pared with Sugar. 550 400 500 550 - 0.08 0.098 4754.4 4753.7 4756.2 4754.7 None - I -- 14753.6 4755.6 4755.7 - Kone C. A. M. Analysis of the Kola Nut. P. Carles. (Jow. de Pliarm. et Clzim., 1896, xvi., 104-108.)-For estimation of the alkaloids the author mixes 10 grammes of the finely powdered and sifted nut with 1 gramme of calcium hydrate, adds 20 granimes of 80 per cent. alcohol, and dries until the weight is about 13.5 to 14 grammes. The pulverized mixture is then extracted four times with successive portions (35 c.c.) of a mixture of 100 grainmes of chloroform and 20 granimes of alcohol, and the extract dried on the water-bath and weighed.Kola nut, even in extremely fine powder, will not yield all its caffeine to pure chloroform. Kolanin, the kola red of Heckel, is in the main an insoluble compound of tannic acid with the kola alkaloids. It appears hardly to exist in fresh nuts, since when placed in alcohol they yield little or no coloration. I t is produced by the action of a laccase, assisted by atmospheric oxygen, and is not a definite chemical compound, but contains resinous matter, etc. The kolanin from dried Congo nuts contained 10 per cent. of caffeine, that from Indian nuts 16 per cent., and that from Dahomey nuts 20 per cent.It is insoluble in chloroform, and nearly so in water, but dissolves readily in alkaline solutions, which decompose it. To estimate it, the nut is first extracted with water, and then with 70 per cent. alcohol. The alcoholic extract, washed with cold water and dried at 100" C., gives the amount of crude kolanin. The alkaloids in this are estimated by mixing 1 gramme with 1 gramme of calcium hydrate, 3 granimes of chalk, and 6 grammes of 70 per cent. alcohol, drying the mixture, and extracting with chloro- form. On treating the dried and sifted nuts (200 grammes) with 1 litre of 60 per cent. alcohol for ten days, 1 litre of extract contained in grammes : Its best solvent is 70 per cent. alcohol. Congo. Dahomey Nuts Dahomey ATuts Indian. dry. roasted.Dry Extract ... 26-00 18.00 30-00 32-00 Crude Kolanin ... 9-10 4-00 9.50 10.20 Alkaloids . . . . . . 3-00 3-00 2-65 2-50 C. A. M. The Examination of Sumbul Root. J. H. Hahn. (Anzer. Jour. Pharm., 1896, lxviii., 395, 396.)-By exhausting the powdered root with petroleum benzine, the author obtained 17.25 per cent. of a fixed oil of a yellowish colour, which became266 THE ANALYST. blackishGbrown on keeping. I t was thick and viscid, had at first a bland but subse- quently a bitter taste, and when rubbed between the fingers gave off a disagreeable odour. It was soluble in alcohol, ether, and carbon bisulphide, and was readily saponified by potash. When a drop of sulphuric acid was added to 3 or 4 drops of oil, acrimson-brown colour was produced, which changed in a short time to dark purple, and after twenty-four hours to brownish-black.On mixing with petroleum benzine and pouring upon a filter, crystals were deposited which could be recrystallized from carbon bisulphide. The sample, which was purchased in the open market, contained 4 per cent. of moisture and 8 per cent. of ash. It has been asserted that much of the sumbul root of commerce is fictitious, but the author was unable to obtain any evidence supporting this statement. The analyses of four samples purchased from diEerent firms all gave the same results. C. A. IT. These were not further examined. The Examination of Powdered Gamboge. E. G. Eberhardt. (Anzer. Jozmz. Pham., 1896, lxviii., 371-374.)-The test for starch given by the American Pharma- copeia is to boil the sample with water, cool, and test with iodine, when there should be no green colour.This test detects less than 1 per cent. of starch, but in the author’s experience it is not easy to find a powdered gum answering to this require- ment, although a good pipe gamboge generally does so. I t is difficult to account for the presence of the starch, which, being 1 per cent. and less, can hardly be an adulterant. To obtain an idea as to the quantity present, the following test is pro- posed : One gramme of the powdered gamboge is dissolved in 5 C.C. of caustic potash solution, 45 C.C. of distilled water added, and an excess of hydrochloric acid, the whole being stirred until of a uniform yellow colour. The liquid is then strained through a plug of cotton-wool, placed in the neck of a funnel, and the almost color- less liquid tested with iodine solution.If more than 2 per cent. of starch be present, a dark colour or precipitate is immediately produced. Commercial gamboge gives a greenish tint, gradually developing into faint blue. Pure gamboge, with 1 per cent. of starch or flour, gives a faint blue, darkening on standing, and depositing a slight precipitate, Two per cent. of starch gives an immediate decided blue, while 5 per cent. gives a precipitate almost immediately. Five per cent. and less of curcurna gives a clear starch reaction. But freedom from starch does not necessarily show purity, and the author considers the estimation of the resin, which is the active part of the gamboge, as the only proper criterion. I n the following table are given the amounts of resin extracted from different varieties of air-dried gamboge by alcohol : This should not be less than from 75 to 80 per cent.Pipe. Pipe. Pipe. Powdered. Resin ... ... ... ... 78-9 76.54 75.9 81.4 Starch ... ... ... ... none none none trace C. A. I f .THE ANALYST. Substance. lIorn ... Flesh Hood (driedj' 267 Addition of Sodium Pyropho .phate. Addition of Potassium Sulphate. 7.- -- Soda lime Kjeldahl A- coinbus- Wit11 \ ~ i t t ; ~ o \Vith j 2 \vith 1 With 2 With 1 gramme* "on. mercury. gmnlmcs. gnimnies. gr:rmnies. gramme. gramnics. 1 to 3 hoiirs. 2 to 3 hours. 24 to3&hours. 3 t o 44 hours. 1 t o 2 hours. ~~ ~ 13-00 13-00 1:3.15 13-15 15-20 13.20 13 -20 13-20 10.34 10.35 10'41 10.45 10.45 10.45 10*4@ 10.45 10.45 10.45 13.55 10.55 10.60 10.65 10.65 10-60 On Kjeldahl's Method and its Modifications.G. Rivihre and G. Bailhache. (Bull. Soc. Chim., xvi., 806-811.)--This paper contains an account of experiments made by the authors with the object of shortening the time required for decolorization with sulphuric acid. Their chief objection to mercury is the necessity of subsequent precipitation, and the inaccuracy introduced if too much be used. With phosphoric acid in place of sulphuric acid the results were not satisfactory, even after the addition of manganese dioxide and phosphate of manganese. By adding ferric oxide to the phosphoric acid correct results were obtained, but the process was slower and more unpleasant than Kjeldahl's method. Various substances were tried as means of raising the temperature of the sulphuric acid, such as iron sulphate, vanadic acid, molybdic acid, boric acid, and arsenic acid; but in each case where the results were correct the process was too slow.The only objection the authors have to the use of potassium bisulphate is that with certain substances, such as horn, a relatively long time is required to complete the conversion. The modification found to give the most speedy results was the addition of sodium pyrophosphate, obtained by calcining the ordinary phosphate. At the same time a smaller amount (1 to 2 grammes) was required than in the case of potassium bisulphate. The following comparative results of the time required for decolorization and the percentage of nitrogen obtained are taken from the long table given in the original paper : Prior knowledge of Dr.Dyer's work on this subject is disclaimed. C. A. M. The Chemical Nature of Diastase 11. T. B. Osborne and G. F. Campbell. (JOZLT. rimer. C'hena Soc., 1896, xviii., 536-542.)-The results of the former investiga- tion (ANALYST, xx. 232) have been confirmed, but no diastase with greater activity has been obtained. The method employed was the same as before, the malt (15 kilos.) being extracted with sodium chloride brine, the filtrate saturated with aninionium sulphate, the precipitate dialyzed in water to remove globulin, and the solution dialyzed into alcohol of varying strengths, commencing with alcohol of 0-86 specific gravity, and ending with absolute alcohol, the various precipitates being filtered off, The six fractional precipitates thus obtained were treated with water, in which the two last were completely soluble, the others partially so.The filtered aqueous solutions were dialyzed first into water and then into alcohol, and absolute268 THE ANALYST. alcohol finally added until the proteids were coinpletely precipitated. The six pre- parations, which weighed (a) 1-37, ( b ) 1.47, ( c ) 4.05, (d) 4.82, ( e ) 2.17, and (f) 0.63 grammes respectively, were dehydrated with alcohol, and dried over sulphuric acid. Their diastatic capacity, determined in the same way as before, was (a) = 0, ( b ) = 60: ( c ) = 300, ( d ) = 300, (8) =slight, (f) = 0. Fractions c and d , which contained nearly all the enzyme, were united, dissolved in water, and filtered from insoluble matter, which, when washed with water and absolute alcohol and dried over sulphuric acid, weighed 0.23 gramme.The filtrate and washings were treated with alcohol, which made a solution containing 36.5 per cent. of alcohol. The precipitate (0.25 gramme) had a diastatic power of 15. The filtrate from this was treated with more alcohol, raising the percentage to 50.7. The precipitate weighed 2.35 grammes, and had a diastatic capacity of 86. The alcohol in the filtrate was brought to 61.6 per cent., and the resulting precipitate weighed 3-87 grammes, and had a diastatic power of 600. Absolute alcohol was added to the filtrate, and gave a precipitate (1.00 gramme) with a diastatic value of 100. When more absolute alcohol was added to the filtrate from this, a precipitate was produced which weighed 0.4 gramme, and had only a trace of diastatic power. More absolute alcohol added to the resulting filtrate gave 0.17 gramme of substance which was totally inactive ; and, finally, the filtrate from this, when evaporated to dryness, left, a residue weighing 0-65 gramme. These results show that nearly all the diastase was thrown down when the pro- portion of alcohol in the solution was brought to about 60 per cent. The diastatic power of 600, which was also the highest obtained in the former investigation, could not be exceeded. An attempt was made to further purify the most active preparation by treatment with water and absolute alcohol, but the resulting substance lost one- third of its diastatic activity in the process. A similar series of experiments were made with a diastatic malt extract, but no diastase could be obtained with greater power than 300. The authors consider that diastatic activity is largely dependent on the presence of other substances, and that the purer the diastase becomes the more sensitive it is to external conditions, and hence the determination of its maltose-producing power may not necessarily be the most certain test for its purity. I n support of this view it is pointed out that the addition of sodium chloride often promotes diastatic activity, whilst it is probable that albumen is an essential factor, since in this investigation those preparations which contained the most albumen were always found to be the most active, and in no case was diastatic activity exhibited in the absence of albumen. W. J. S. and C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN8962100257

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

268 THE ANALYST. INORGANIC ANALYSIS. Electrolytic Determination of Lead, and the Influence of Arsenic, Selenium, and Manganese thereon. B. Neumann. (Chenz. Zeit., xx., 1896, 38l.)-Although lead can be deposited from a large number of solutions by electrical agency either as metal or peroxide, it is only in the latter form that it is available for quantitativeTHE ANALYST. analysis. I n nitric acid solution, provided the liquid contains at least 10 per cent. of free acid, the lead is completely thrown down as peroxide, the current being pre- ferably 1 to 2 amperes per 100 square centimetres of anode surface at a tension of 2.3 to 2.7 volts. The operation may be conducted either at ordinary temperatures or at 60" to 70" C., and the anode should be a platinum basin with a matt surface.As the oxide contains water, it must be dried at 180". I n the presence of other metals Zn, Fe, Co, Ni, Al, and Mn remain in solution; while Cu, Sb, Au, and Hg are deposited with the lead. Ag and Bi may be thrown down partly as metal and partly as oxide; but if they are present only in comparatively small amount, and the free acid be increased to 20 per cent., the error becomes too small to be appreciable. For the analysis of lead and copper ores, brass, bronze, etc., the electrolytic process is very exact and convenient,, and even extremely small quantities of lead can be determined by its help. The author has carried out a large number of experiments on the influence of arsenic, seleuium, and manganese on the electrolysis of lead salts, using solutions prepared so as to imitate the conditions obtaining when 1 gramme of an ore with 22.38 per cent.of lead and the impurities in question should be under analysis, and his conclusions may be briefly summarized as follows : Although it is possible to recover the whole of the lead by the use of a large excess of acid, and by allowing the current (0.5 to 0.6 amp&re per square centimetre) to pass for EL long time, arsenic or selenium in any quantity above 0.5 per cent. on the ore practically prohibits the use of the method. Providing manganese is not present in excess of 3 per cent., that the electrolysis is conducted at 70" with a fairly strong current (1 to 1-3 ampBre per 100 square centimetres at 2-5 to 2-7 volts) passing for not over thirty minutes, anlY that sufficient acid (30 C.C.of 1 : 4 nitric per gramme of ore) is employed, the results may be considered reliable. An experiment where 0-5 per cent. each of As and Se and 1 per cent. of Mn were present at the same time was fairly successful, but would probably not have been so had the amounts of the impurities been higher. F. H. L. Volumetric Estimation of Lead. F. J. Pope. (Jozw. AWZCY. Clzcnz. soc., 1896, xviii., 737-740.)-The chief objection to the various processes which have been proposed is the use of an outside indicator. To obviate this, the author describes a method in which the lead is first converted into sulphate, and then into acetate. An excess of standard potassium bichroinate is added, which precipitates the lead as chromate ; the unused bichromate is reduced by excess of standard arsenious acid, and this titrated with iodine solution. The solutions required are : Iodine.-12-7 grammes dissolved in concentrated potassium iodide solution and made up to a, litre.Arsc?zio?u Acid.-4.95 grammes dissolved in 20 to 30 C.C. of saturated filtered solution of sodium carbonate with gentle warming, and made up to a litre. This is standardized by slightly acidifying 10 to 15 C.C. with sulphuric acid, adding 50 C.C. of saturated solution of pure sodium bicarbonate, and titrating with iodine, starch270 THE ANALYST. paste being used as indicator. The iodine value of the bicarbonate used should be determined, and a correction made. Potnssimn Biclzro~natc.--Five gramines per litre, standardized on the arsenious acid solution.From 3 to 7 granimes of the ore are moistened with water in a porcelain dish, treated with 4 or 5 C.C. of a mixture of two volumes of sulphuric acid, three volumes of nitric acid, and one of water, and evaporated as nearly as possible to dryness without spurting. After cooling, water is added, the precipitate filtered off, and washed until nearly free from acid. The filter-paper and precipitate are placed in EL 300 to 400 C.C. beaker, any remaining acid neutralized with dilute ammonia, and the whole boiled for about ten minutes, with constant stirring, with 10 to 15 C.C. of strong ammonium acetate solution acidified with acetic acid. After cooling, the liquid is neutralized with ammonia, and 100 C.C. of standard bichrornate solution added. The precipitate is removed by filtration, washed with dilute animonia or ammonium acetate, and the filtrate made up to 500 C.C.To 100 C.C. of this solution in a 1,500 C.C. basin from 10 to 20 C.C. of standard arsenious acid solution are added, followed by sulphuric acid (40 per cent.) until decidedly acid, a large excess being avoided. The liquid is stirred until it assumes a greenish tint, or until the yellow colour disappears. It is then neutralized with a saturated solution of sodium bicar- bonate, and an excess of 50 C.C. added, the solution being diluted with water if it has a greenish tint. Finally, starch paste is added, and the liquid titrated with standard iodine solution. With a specimen of galena, containing quartz and calcium carbonate, the per- centage of lead found by the author in four determinations varied from 81.89 to 81-96.With another ore containing 5 per cent. of copper, 26 per cent. of iron, quartz, and gypsum, another operator found (1) 15.89, (2) 16.01, and (3) 15-97 per cent. of lead. With pure lead sulphate the following results were obtained : Grammes taken. Grammes found. 1.0 ... ... ... ... ... ... 1.000568 1.1 ... ... ... ... ... _.. 1.099375 1.3 ... ... ... ... ... ... 1-200467 1.3 ... ... ... ... ... ... 1.300673 1.4 ... ... ... ... ... ... 1.399571 C. A. M. Analysis of Aluminium and its Alloys. H. Gouthihe. ( A m . de Chinzie. Aiinlyt., i. [14], 265-270.)-Copper, Nickel, Lead, nizd Iron.-From 5 to 10 grammes of aluminium turnings are attacked in successive portions by sodium hydroxide solution (1 to 3) in EL conical 300 C.C.flask. Heat is evolved, brisk effervescence occurs, and the operation is complete in about twenty minutes, care being taken to prevent the liquid cooling, or a gray deposit, difficult to dissolve, will be formed. The hot, clear liquid is decanted on to a small filter, and the black deposit very quickly washed five or six times with boiling water, after which it is dissolved in luke-warm dilute nitric acid, evaporated to a syrup, mixed with 2 C.C.THE ANALYST. 271 of pure nitric acid, and electrolysed by the current from three or four Leclanchb cells at a temperature of 50" to 60" C. Both electrodes are of platinum, the negative being a crucible or cylinder, and the positive preferably gauze. I n two or three hours all the copper will be deposited as metal on the negative electrode and the lead on the positive as PbO,, the weight of which, multiplied by 0.8661, will give the metallic lead.The liquid separated from the copper and lead is united with the washings, and heated with excess of ammonia to throw down the iron and dissolve the nickel pre- cipitate first formed. When the proportion of the latter metal is large, the iron precipitate should be redissolved in dilute nitric acid and reprecipitated as before. After filtering and washing with boiling water, the iron oxide is dried, calcined, and weighed. The ammoniacsl filtrate is heated to drive off the excess of ammonia, then mixed with a few drops of sulphuric acid, concentrated, nearly neutralized by ammonia, and then electrolyzed at about 60" C., the nickel depositing in the metallic state on the negative electrode.Alzcminizm is generally estimated by difference, on account of the time and trouble required by the washings and incineration. If determined direct, one of the usual methods, or that described by Moissan (Ann. de Chinlie Aizcilyt., 1896, p. lo), may be followed, Tiy~, A.rttimony.-Five or ten grammes of aluminium are attacked by hydrochloric acid, and, after nearly neutralizing the solution by ammonium carbonate, a current of hydrogen sulphide is passed, the resulting precipitate being collected, washed with hydrogen sulphide water, and digested for some time with dilute ammonium sulphide at a moderate heat. Then, after filt'ering and washing with ammonium sulphide water, the soluble sulphides are thrown down by a slight excess of dilute hydrochloric acid, or, better, by the aid of heat.Sulphur is removed by carbon bisulphide ; antimony (which is rarely present) is recognised by the colour of the sulphide ; arsenic sulphide volatilizes during calcination, and stannic oxide remains for weighing. Zinc is precipitated from the hydrochloric acid solution (after removal of the tin, antimony, etc.) by hydrogen sulphide following an addition of sodium acetate. The precipitate-sometimes containing sulphur-is washed, calcined, and weighed as ZnO. Ai.scizic.-The sulphides precipitated from 5 grammes of the substance are washed and dissolved in dilute nitric acid. The solution is filtered, evaporated with sulphuric acid until white fumes appear, and then placed in a Marsh apparatus.The gas evolved is passed through a solution of silver nitrate, and the precipitated silver converted into, and weighed as, silver chloride. This, multiplied by 0.0871, gives the arsenic. Silica.-The solution resulting from the action of hydrxhloric acid and 3 or 4c.c. of nitric acid on 5 grarnnies of aluminium is evaporated to dryness until the acid is driven off; the mass is then heated to 110"-120" C., taken up with hot dilute hydrochloric acid, digested for awhile, and, after adding boiling water and pouring off the liquid, washed with boiling water, dried and calcined in EL muffle.272 THE ANALYST. The dry chlorine method may be also employed, but necessitates a special and complex apparatus. Total Carbon. - Boussingault's method is used - chlorination by mercuric chloride, digestion in dilute hydrochloric acid, and heating in a current of hydrogen.Creak and Ulgreen's method is also applicable-solution of the aluminium in cupro- ammonium chloride, removal of the precipitated copper by hydrochloric acid, and combustion of the carbon by a mixture of chromic and sulphuric acids in a special apparatus provided with potash absorption-tubes. SZLZ~~LUV is estimated by the Rollet method-2 grarnmes of aluminium being heated to redness, in a current of two-thirds hydrogen and one-third carbon dioxide, and the hydrogen sulphide passed into silver nitrate solution. The silver sulphide is washed and calcined, the silver inultiplied by 0.1481 giving the weight of sulphur. A fairly accurate estimate of the sulphur may be rapidly made by the Eggertz colorimetric method, noting the effect of the hydrogen sulphide on a silver plate.The results of ten analyses of aluminium are given, the chief impurities being lead, iron, and copper ; tin, arsenic, and nickel were only found in two samples. c. s. Determination of Iron Oxide and Alumina in Phosphate Rock by the Ammonium Acetate Method. T. S. Gladding. (Jow. Arner. Chenz. SOC., 1896, sviii., 717-721.)-1n spite of the adverse criticisms which have been passed upon this method, the author describes experiments to prove that, when carried out under the right conditions, it gives an accurate separation of iron and alumina from calcium phosphate, and yields a neutral phosphate, in which the two constituents may be accurately determined.He shows that when iron and aluminium are repeatedly precipitated as phosphates, there is no appreciable loss, provided a large excess of phosphoric acid be present. Moreover, in the presence oE a large amount of calcium phosphate, three successive precipitations leave the iron and aluminium phosphates sufhiently pure to be estimated as such. The process recommended is as follows: Four grammes of the finely-ground sample are digested for 30 minutes at a temperature just below boiling with about 30 C.C. of dilute hydrochloric acid (1 : l), which prevents the solution of any pyrites present. The solution is filtered and washed into a 200 C.C. flask, oxidized with nitric acid and made up to the mark. Two portions are taken-50 C.C.= 1 gramme, and 25 C.C. = 3 gramme. These are nearly neutralized with strong ammonium hydrate, thoroughly cooled, and the neutralization completed with dilute ammonium hydrate until the precipitate just remains permanent ; dilute hydrochloric is then added until the precipitate just dissolves. A mixture of 15 C.C. of strong ammoniuin acetate solution (made by neutralizing 30 per cent. acetic acid with strong ammonia) and 5 C.C. of acetic acid is poured into the beaker in a thin stream, the liquid being mean- while stirred. A€ter digesting for 30 niinutes to an hour at 60" C., the precipitate is filtered off and the beaker washed with ammonium acetate solution (10 per cent.). The precipitate is dissolved from the paper with a few C.C. of hot dilute hydrochloric acid (1 : 4).One gramme of ammonium phosphate is added, and the liquid neutralized with ammonium hydrate until the precipitate just dissolves as before, and pouredTHE ANALYST. 273 into a mixture of 15 C.C. of ammonium acetate solution and 5 C.C. of acetic acid. The digestion, filtration, etc., are again repeated to this point, and the precipitate washed three times with dilute ammonium acetate solution. The filter while wet is ignited in a platinum crucible, finishing with a blast, and the combined phosphates of iron and aluminium weighed together. The iron is determined volumetrically in the solution of the weighed precipitates. The iron oxide in the rock is also estimated volumetrically, preferably by the bichromate method. C. A. M. A New Method of Estimating Iroa Oxide and Alumina in Phosphate Rock.T. S. Gladding. (Jozir. Anzer. Chenz. SOC., 1896, xviii., 721-724).-To obviate the necessity of the repeated precipitations in the ammonium acetate method (see preceding abstract) the following modification is described. It consists in the separation of alumina from calcium phosphate and iron oxide by means of its solubility in caustic potash. Four grammes of the finely pulverized rock are dissolved in dilute hydrochloric acid (I : l), heated for 30 minutes just below the boiling-point. The solution is filtered into a 200 C.C. flask, oxidized with nitric acid, cooled and diluted to the mark. To 50 C.C. of the solution, 25 C.C. of pure caustic potash solution (500 grammes per litre) are added, the whole digested for an hour at 70" C., and the precipitate filtered off and washed with hot water.One gramme of ammonium phosphate is added to the filtrate, then hydrochloric acid to acid reaction, and ammonia until a permanent precipitate is formed. This is just dissolved in hydrochloric acid, ammonium acetate solution and acetic acid added as described in the preceding abstract, and the contents of the beaker digested at 70" C. for an hour. The precipitate is filtered off, washed five or six times with 10 per cent. ammonium acetate solution, ignited, and weighed as normal aluminium phosphate. The iron oxide is determined volumetrically in a solution of the precipitate of iron oxide and calcium phosphate, thrown down by the caustic potash. The results obtained by this method are in close agreement with those given by the ammonium acetate process.C. A. 11. Reactions of Vanadic and Molybdic Acids with Thiocyanates. W. Ellram. (Proceedings of the University of Dorpnt, 1895, xi., 28; through Chern. Zeit. Rep., 1896, 153.)-If powdered ammonium vanadate and one drop of sulphuric acid are added to the solution of a thiocyanate, the liquid turns yellow ; but if the acid is increased to 5 or 15 drops it alters to sky-blue, and is unchanged by further additions or by boiling. If some of the vanadate still remains undissolved, the colour returns to yellow in the presence of more acid. The reaction will detect 1 part of a thio- cyanate in 12,000. I t is available in the case of saliva, but here the colour has a somewhat greenish cast, and it is rendered cloudy by albumen.In serum the latter substance must first be removed with zinc sulphate. In milk the test also succeeds, but all animal liquids need to be purified as much as possible. Conversely, vanadic acid or its salts may be detected by nieans of a thiocyanate, even in dilutions of274 THE ANALYST. 1 part per 5000: a few crystals of the reagent being added to the liquid and then sulphuric acid till the yellow colour changes to blue. Molybdic acid and its salts give with potassium thiocyanate a yellow, orange, or blood-red colour, visible after a minute in dilutions of 1 per million. With zinc and sulphuric or hydrochloric acid molybdates yield an indigo-blue colour, or a greens either olive, grass, or pale in shade. The intensity depends on the concentration, and with excess of metal the colour is usually blue, changing into the greens on further additions of acid.The reaction is available up to 1 part per 35,000. F. H. L. Estimation of Dissolved Oxygen in Water. Romija. (Rec. trav. chink. dcs Pays-Bas, 1896, xv., 76; through Chem Xeit. IZep., 1896, 191.)-A gas pipette fitted with stop-cocks at either end, and provided with a funnel holding about 1 C.C. on the top, is filled with the sample of water. One C.C. each of solutions containing respec- tively (1) 1.12 grainme of manganese chloride and 0.085 gramme of potassium iodide, (2) 10 grammes of Rochelle salt, and (3) 0.1 gramme of caustic soda per 12 c.c., are introduced successively by opening the taps, and the tube is well shaken and allowed to stand for ten minutes.One C.C. of 25 per cent. hydrochloric acid is then added, and the whole rinsed out into a flask, and the liberated iodine titrated with thiosulphate, An allowance for the 4 C.C. of water displaced by the reagents must be made. F. H. L. Analysis of Crude Monazite, and the Estimation of Thorium, etc. C. Glaser. (Chem. Zeit., 1896, xx., 612.)-Since the advent of the ‘‘ incandescent ” system of gas-lighting, monazite has become an article of commerce; and the older methods for the valuation of the native mineral, which consisted in determining the ferric oxide, silica, and titanic acid, and returning the residue as a pure phosphate of cerium, etc., are no longer sufliciently exact. The author has checked the statements ma&de by digerent investigators respecting the behaviour of the rare earths with various reagents, and his observations are shown in the accompanying table.He has also conducted a large number of experiments on the separation of these sub- stances one from another (for full details of which the original paper must be con- sulted), and has embodied his results in the following scheme for the analysis of monazite. After being finely powdered, the sample is dissolved by boiling for some time in strong sulphuric acid, any insoluble residue being attacked by fusion with potassium bisulphate; if it be desired to estimate the silica, however, it is better to avoid the latter process, and to break up the mineral simply by repeated digestion in acid. The mixture is then poured into ice-cold water; everything, except the silica, tantalic acid, and possibly some titanium and thorium, is in the solution.The residue is heated twice with hydrofluoric acid, moistened with sulphuric acid, dried, and ignited, the silica being found from the loss in weight. If anything remains after this treatment, it is boiled with sulphuric acid or melted with bisulphate, the undissolved matter being returned as tantalic acid, and the solution mixed with the original one. Sulphuretted hydrogen is then passed through the hot liquid until it becomes cold, causing the precipitation of titanic acid and the metals of the fifthTHE ANALYST. 275 group. When these have settled, they are filtered off and washed, the filtrate boiled till free from H2S, the greater part of the free acid neutralized by ammonia, 100 C.C.of a cold-saturated boiling solution of ammonium oxalate for every 2 gramines of the sample added, and the whole allowed to stand over night. The precipitate contains the oxalates of the cerium earths and t,horium, and the solution H,PO,, Fe, A l , Mn, Be, Y, Zr, and Ca. To separate the latter, they are thrown down by ammonia, washed, ignited, and fused with sodium potassium carbonate. The melt is extracted with water, the liquid mixed with the previous filtrate, and the phosphoric acid and the alumina estimated in aliquot portions. The insoluble part of the melt is dissolved in H,SO,, precipitated with NH,, and the lime determined in the filtrate. The paper containing the residue is burnt, the ash dissolved in warm EC1, and almost neutralized with Excess of a solution of ammonium carbonate with sufficient sulphide to throw down the metals of the fourth group is then placed in a beaker, and the last- mentioned solution poured in.The iron and manganese are precipitated, and estimated as usual ; the filtrate containing Zr, Yb, and Be, is boiled for an hour, when these bodies are completely precipitated. This precipitate is dissolved in HCl, boiled, cooled, and an excess of NaHO added. The two former earths fall; the Be remains in solution, and can be recovered by boiling the liquid. To separate the Zr and Yb, the hydrates are dissolved again in HCl, the solution warmed and saturated with potassium sulphate, allowed to cool, and the insoluble double salt of Zr filtered off. The Yb may be precipitated from the filtrate by ammonia.The oxalates of the Ce metals are ignited, the resulting oxides dissolved in H,SO,, the liquid nearly neutralized with NH,, heated to the boil, and an excess of a boiling solution of ammonium oxalate added. After a few minutes, when the oxalates of the Ce group have fornied again, a few C.C. of ammonium acetate are intro- duced, and the whole allowed to cool. Next day the liquid is filtered, and the Th precipitated from the filtrate by NH,. The Ce niay be separated from the La and Di by leading chlorine through the freshly-precipitated hydrates in the usual manner. Treated in this way, three samples of monazite from North Carolina gave : NH,. SiO, ... ... TiO, ... ... Ta,O, ... ... p205 A l p , ... ... ... ... ... ... ...P b CaO ... ... CeO ... ... La,O, and Di,O, ... Tho, ... ... Fe,O. ... ... MnP, ... Be,O, ... ... ZrO, and YbO (?) ... ... ... ... ... ... ... ... ... ... ... ... ... ... I. 6-40 4-67 0.66 18-38 trace 1.62 1.20 32-93 1 1.43 7-83 13.98 1-25) 7.93) - ... ... ... ... ... ... ... ... ... ... ... ... 11. 3-20 ... 0.61 ... 28-16 ... absent ... 63.80 ... 2-32 ... absent 1 trace J ... 1.52 ... - ... - ... , I ... 111. 1 a45 1.40 6.39 26.05 0.15 59.09 1.19 0-65 2.68 - - 98.28 99.61 99-05BEHAVIOUR OF THE EARTHS WITH DIFFERENT REAGENTS. A1,0, .., Be,Os or Be0 .., ZrO, .., G adolini te earths .. Tho, .. CeO .. Ce,O, .. .. K or NaI-IO. ppt. sol. in excess ppt. sol. in excess,re- pptd. on boiling or dilution ppt. insol. in excess ppt. insol. in excess ppt. insol. in excess ppt.insol. in excess ppt. flesh- coloured by excess PPt. ppt. sol. in large es- cess, or by addition of co, ppt. slightly sol. in ex- cess,pptd. by NH3 ppt,. sol. in excess, in- sol. double salt (Y), pptd. after a, t h e NH,givee p p t . o n h e a t ing, sol. agiin in the cold ppt. slightly sol. p p t , s o l . ppt. aliiiost insol. i, or Na,SO,. f o r m . of alum no ppt., or d o u b l e salt double salt i f h o t , pptcl. on cooling,in- sol. in HC1. ppt. in strong sols., sol. in H,O k K,SO,. Y not pptd. insol. double salt wit 11 K. Na salt more sol. double salt insol. in K2SO.i - h 2 S , ( l i . ppt. i n neutral sols. on boiling. 110 ppt. PPt. hyd- rate and sulphidr imperfect even oil boiling s t r o n g sols. no ppt. 1Y PPtd. no ppt. NH,,. PPt. ppt. insol.in es- cess ppt. insol. in ex- cess ppt. insol. in ex- cess ppt. insol. in ex- c e s s , falls be- f o r e cerite ppt. insol., falls after Tho, as KHO PPt. ppt. sol. ill excess, rc- b o i l i n g , A1,0, in- terferes ppt. sol. in large es- cess, re- pptd. on boiling ppt. sol. in- sol. double ppt!. 011 salt pptci. (Y) as with KHy as with NH, ppt. sol. in large es- cess, pptil. 011 boiling (NIT,) ,S. 3Pt. hx- dmte ept. hy- drate PPt. hY - drstc ppt. hy- drate as with N H:* as with NH3 as with NH, NTI4C1. ;ol. in NaHO PPtd. iydrate sol. on long boiling, NH, given Off 10 ppt. (2 no ppt. 110 ppt. no ppt. (NH,),C,O,. no ppt. n o P P t . , d o u b l e salt formed. ppt. sol. in ~xcess. E pptd. from hot acid sols. as red powder. ppt. sol. in excess hot, cooling ppt. even in acid sols., s o l . i n s t r o n g acid PPt. o n ditto ?pt. on boiling sol. of basic salt (?> no ppt., hinders the pptn. with (NH& C,O,; from this sol. partly pptd. by HC1, or as hydrate does not hinder bYNH, PPtn. does not hinder Pptn.THE ANALYST. 277 The samples were cleaned from rutile, granite, and other impurities before analysis. F. H. L. Nom.-This paper contains a good many statements of doubtful accuracy, and the method in its general course is far from the simplest that can be adopted for the separation of the rare earths into fairly well-defined groups. 0. H. APPARATUS, Litmus Pencil.-This useful little appliance, which has recently been intro- duced by Messrs. Christy and Co., of London, has the form of an ordinary lead- pencil, one half of its core being filled with blue, the other half with red litmus. I n 1lsing it, the ends are sharpened and lines drawn on a strip of white neutral paper with one of the slightly-moistened points. The lines thus produced are said to be much more sensitive than ordinary litmus-paper. w. 3. s.

ISSN:0003-2654    

DOI:10.1039/AN8962100268

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THE ANALYST. 277 REV1 E WS. NITRO-EXPLOSIVES. By P. GERALD SAXFORD, F.I.C., F.C.S. London : Lockwood THIS small volume gives much useful and interesting information, and, with a little more care on the part of the author, niight have been a valuable addition to our libraries. As it is, the book suffers somewhat from imperfect arrangement, leading, among other drawbacks, to unnecessary repetitions. I n parts either too much or too little detail is given, and there are various inaccuracies and omissions of what, to English chemists at least, would be important imformation. Thus the author deals with blasting gelatine, gelatine dynamite, cordite, etc., before describing the manufacture and preparation of the various nitro-celluloses. The proper arrangement would have been to give the manufacture and properties of all the various nitro-compounds used in the preparation of explosives before treating these explosives thernselves. In the next place, it: appears to us that the part dealing with the manufacture of nitro-glycerine, nitro-cellulose, etc., while giving details not necessary to the general chemist, is yet not detailed enough to serve as a really useful guide to the manu- fitcturer.Further, the author does not bring out sufficiently clearly the very marked differences existing between the bwo chief classes of so-called nitro-explosives, viz., the nitric ethers, like nitro-glycerine and nitro-cellulose and similar compounds, on the one hand, and true nitro substitution compounds, like tri-nitro-phenol, mono- and di-nitro-benzole, etc., on the other.He thus misses the chance of bringing home to manufacturers and inventors some valuable lessons based on this difference. Nitric ethers, although stable at ordinary temperatures when perfectly pure, are far more prone to decomposition at slightly elevated temperatures than the true nitro coin- pounds. This difference is still more strikingly manifested in the presence of free acids. Hence the absolute necessity, not only of freeing the nitric ethers from all and Co. Price 9s.THE ANALYST, acids, but also of not bringing them into contact with substances liable to become acid. Nitrate of ammonium, for example, is liable to lose ammonia and beoonie acid. This change is of little or no importance when the nitrate is mixed with a true nitro- compound, but its presence is fatal to the stability of any nitric ether.Hence explosives like bellite, roburite, etc., are unobjectionable as regards their stability, whereas the admixture of this salt with gun-cotton, nitro-glycerine, etc., is inad- missible, and no explosive of the latter class is licensed in this country. I t is also a pity that the author has not extended his study of official documents a little more widely than he seems to have done, as he would then have been saved from several errors. Thus, had he examined the list of explosives authorized to be manufactured in, or imported into, this country, he would have learned that roburite is not a mixture of nitrate of ammonium, and chloro-di-nitrobenzole, but a mixture of the former salt with chlorinated di-nitrobenzole, containing, at most, 4 per cent.of chlorine, corresponding, roughly, with a mixture of 1 part of chloro-di-nitrobenzole and 3 parts of di-nitrobenzole. He would also have seen that there is no such explosive as his so-called Rhenish dynaniite legally in use in this country; can the author have mistaken dynamite nianufactured by the Rhenish Dynamite Company for his Rhenish dynamite ? -4s a matter of fact, out of the thirty-four explosives given at the end of the work as being in common use, sixteen only are authorized in this country. Surely in a work intended primarily, we suppose, for use in England, such an important fact should have been mentioned. Most explosives given in this table not only are not authorized in this country, but the composition of several, as given, is incompatible with their stability ; as, for example, ammonia nitrate powder, which is stated to contain nitrate of ammonium and chlorate of potassium, two salts incom- patible with each other ; or his ammonium dynamite, containing nitro-glycerine and nitrate of ammonium, which, as before stated, are also incompatible with each other.Again, blasting gelatine with only 3 per cent. of nitro-cotton would never be allowed to be issued by itself; carbonite, as authorized, has not the composition given. Ordinary dynamite does not usually consist of 25 parts of kieselguhr and 75 parts of nitro-glycerine ; usually it contains only from 73 to 74 per cent. of nitro-glycerine, and the above-given proportion is simply the maximum proportion of nitro-glycerine per- mitted by law ; it is, so to speak, the ideal, but not the actual, composition. We also cannot help thinking that the author should have raised some note of warning against the use of chlorate of potassium.Chlorate of potassium offers great temptations to the inventor of explosives. There are, however, many drawbacks connected with its use, such as great sensitiveness of the resulting explosive to per- cussion and friction, and great liability to spontaneous decomposition. These diffi- culties have, up to the present, proved practically insurmountable, and no chlorate- explosive, in which this salt forms an essential constituent, is licensed in this country. The chapter on the estimation of nitrogen is well done and fairly complete; many of the other parts on the analysis of explosives, however, require revision.Has the author never tried to dissolve the nitro-glycerine from dynamite by means of rnethylic alcohol ? This alcohol, although by far the best solvent for nitro-glycerine, is, strangely enough, not even mentioned among the solvents @en on page 19. We certainly know of no chemist accustomed to the analysis of blasting gelatine, cordite,THE ANALYST. 279 etc., who estimates the nitro-cotton contained in these explosives by iiieans of the method given by the author, viz., precipitation with chloroform. We should also like to ask the author whether he has ever tried to estimate the moisture in a sample of wet gun-cotton by drying the same in a water oven at 100" C.? We can only warn our readers against making the attempt if they wish to obtain accurate results.We hope that, in a second edition, the author will deal with some, at least, of the points raised above, and supply us with a much-wanted manual at once complete and accurate. Such a book, of moderate size, would be a most valuable addition to the library of every practical chemist. A HANDBOOK OF INDUSTRIAL ORGANIC CHEMISTRY. A. D. By SAMUEL P. SADTLER, Ph.D., F.C.S., Professor of Chemistry in the Philadelphia College of Pharmacy, and in the Franklin Institute of the State of Pennsylvania. Second enlarged and revised edition. WE are glad to see that the excellent f f Handbook of Industrial Organic Chemistry " published by Dr. Sadtler in 1891 has already reached a second edition.The work compares very favourably with some so-called technical manuals published in this country, and shows that the author is fully alive to the requirements of the day. The present edition extends to 537 pages, including the index, against 519 pages in the case of the first edition. I n his preface Dr. Sadtler points out that the bibliography has in all cases been rewritten and brought carefully to date, and the statistics have also been brought down to 1895 whenever new figures were obtainable. While the body of the text has not been materially altered, numerous corrections have been made and new sections inserted in many cases. In the appendix two new tables have been added, giving the physical and chemical constants of the oils, fats, and waxes, classified for correction and comparison.The arrangement of the work appears to be well adapted for the convenience of the user of the book. Referring to particular sections, we are sorry to see that in that on vinegar no addition has been made to the somewhat bald article of the first edition; and no reference is made to the inforniation on the subject of vinegar published within the last few years in the pages of the BNBLYST. The section on flour-testing might also be revised with advantage. These are minor defects; and Dr. Sadtler is to be congratulated on the ability and thoroughness with which he has treated such varied and numerous subjects within a reasonable space. The work is eminently one for reference, and should find a place in the laboratory of every analyst and manufacturing chemist.The type is everything that can be desired, and the illustrations are satisfactory. A. H. A. COMMEHCIAL ORGANIC ANALYSIS, By ALFRED H. ALLEN. Second edition. VOL. III., Part 111. of ur. Allen's ~ C L ~ Z Z L ? ~ Z opus fully maintains the high-water mark of the preceding volumes ; and perhaps no higher praise than this could be awarded to it. The Part 111. now before us is indeed in reality Vol. V. of the greatest treatise on Commercial Organic Analysis that has ever appeared in this country. Why a, work which is of the utmost value to every scientific analyst should be Philadelphia and London : J. B. Lippincott and Co., 1895. Vol. III., Part 111. London : J. and A. Churchill. Price 16s.280 THE ANALYST. dubbed with the term “Commercial” we hardly know; but we are sure that an analyst can venture on no better commercial speculation than to purchase this book, which for fulness of detail, accuracy, and scientific breadth of treatment leaves little to be desired. In Part 111.the analysis of vegetable alkaloids is concluded, the account of their reactions, etc., extending over 89 pages. As samples of the care with which Mr. Allen has dealt with this branch of the subject, we may refer our readers to the section dealing with the alkaloids of laburnum and furze, and to that on the alke- loids of ipecacuanha, as examples. These sections are thoroughlyup to date in their treatment, and in them will be found the newest researches of Pantheil, Gerrard, and Paul and Cownley. The Non-Basic Vegetable Bitter Principles are next dealt with, and all that is known with certainty about the chief of these somewhat obscure bodies will be found recorded.We may instance the articles on the glucosides of digitalis and of strophantus as admirable specimens of 141r. Allen’s treatment of his subject. I t seems a little odd, however, to meet with the adulterations of mustard under the head of the glucosides of mustard, for we opine that these glucosides are not the bodies which the analyst usually estimates when he has to report on the adultera- tion of the condiment in question. But with respect to such a good memoir on iiiustard generally, it is hypercriticism to carp at the place assigned to mustard adulteration in the book under review. hima1 Bases occupy 160 pages of the book, and of these some 30 pages are devoted to ptomaines.Either the heading or the arrangement of this section is perhaps not happy, since it is difficult to understand why such bodies as asparagine and glutamine are placed among animal bases, until we see that they are conveniently treated of as amides, together with glycocine and leucine. The apparent anomaly then disappears. I n treating of ptomaines Brieger’s work is closely followed, and making every allowance for the non-confirmation of some portions of his work by others, Brieger’s classical memoirs on the Ptomaines stand unequalled for completeness. c n - happily, the discredited work of some other experimenters finds more than its due recognition by Mr. Allen. The practical analytical points are, however. duly noted by the author, and especially the behaviour of ptomaines towards alkaline bicar- bonates, and the precautions to be adopted in their separation. The toxicological analyst will find in this section invaluable help. After a concise review of the animal acids, the volume under review concludes with a section on cyanogen and its derivatives, in which the author is very much a t home. I n one point only, from the ‘‘ commercial” point of view, do we find this section defective. The author does not give us any warning of the not infrequent presence of sulphocyanides in sewage, and its detection and estimation therein. On several occasions where it was noticed that sewage, when applied to land, proved inimical to vegetation, we have found sulphocyanides-no doubt derived from gas liquors-in the harmful sewage. Chemists will hail with gratitude the promised coacluding volume of Mr. Allen’s monumental work. T. S.

ISSN:0003-2654    

DOI:10.1039/AN8962100277

出版商:RSC    

年代:1896

数据来源: RSC