摘要:

SEPTEMBER, 1008. Vol. XXXIII., No. 380. PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS. THE ESTIMATION OF FAT IN DRY MILKS. BY BASIL G. McLELLAN, F.I.C. SINCE the advent on the market of condensed milk in a dry form, as produced by the Just-Hatmaker and other procesBes, analysts have had to contend with the problem of analyging yet another form of milk. The difficulty of completely extracting the fat from the older varieties of condensed milk-especially in the case of sweetened milks-has been noted from time to time, and this difficulty still presents itself in the case of dry milks. The incompleteness of the extraction is due to the coating of the fat globules in the milk during the process of evaporation with an impermeable substance, which prevents tho solvent from penetrating.This investigation has been made with a view to test the extracting powers of354 THE ANALYST. various solvents which have been recommended for milk analysis, and also the accuracy of one or two rapid methods which have been recently suggested as applicable to this form of milk. The Werner-Schmidt method, which consists in the treatment of 2 grams of milk with warm water, boiling with hydrochloric acid and extracting with successive quantities of ether, gives good results, and is rapid in its application. Many analysts, however, prefer to extract the milk powder direct, using a Soxhlet extraction apparatus, and it is this method which I have specially investigated. As a result of my work I find that it is possible to completely extract the fat from dry milk in this way, but the extraction must be continued for a considerable time.This fact has been noted by many investigators, and is borne out by the accompanying figures : TARLE I. SHOWING LENGTH OF TIME REQUIRED FOR EXTRACTION OF FAT. Time of Extraction using Pure Ether (Sp. Gr., 0.720). Per Cent. Fat Extracted. 1. Four hours ... ... ... ... ... .., 2. Soaked in ether overnight and then for four hours 4. Soaked in ether overnight and then for eight hours 5. True result with longer extraction (see Table 11.) 3. Eight hours ... ... ... ... ... ... 24-84 25-51 25.70 26.14 26.64 The various solvents tried were : 1. Petrol: The petrol used was ordinary motor-car spirit, the fraction which boiled below 50' C. being collected for use.Usually about 70 per cent. of the spirit distils below 50" C. The price of this solvent rectified by the user is about 6d. per pound. 2. Methylated ether of 0.720 sp. gr. 3. Pure ethylic ether of 0.720 sp. gr. 4. Methylated ether of 0.730 sp. gr. 5. Pure ethylic ether, prepared by drying over calcium chloride and then over aodiurn, and finally distilled. This specially prepared ether is recommended in American text-books on milk analysis. I n applying the various tests, 5 grams of the milk preparation were used in each case. This was tLccurately weighed out and made up into a packet with three wrappings of filter-paper, and extracted for a long time with each of the solvents, in a Soxhlet apparatus. I t was customary to allow the packages to soak in the solvent overnight, to extract during the whole of the next day, to again soak in the solvent over the following night, and then, after extracting for an hour or two the following morning, to distil off m d weigh.Thus each solvent acts upon the milk for the same length of time and under the same conditions. Price about 1s. 2d. per pound. Price about 6s. per pound. Price about 10d. per pound.THE ANALYST+ 355 TABLE 11. SHOWINU PERCENTAUES OF FAT EXTRACTED BY THE VARIOUS SOLVENTS. Sample. A . . . . . . B . . . . . . c . . . . . . D . . . . . . E . . . . . . F . . . . . . .a . . . . . . Moisture. Por Cent. 5-70 3.88 5.82 3.90 0.7110 Ethylic Etlicr. - - - 25-00 26.34 25.90 26.64 Pcr Cent. Fat Estrtuted by- 0.720 Methy- lated Ether. - - - 25.12 26.78 25-84 26.62 O * i 3 0 Methy.lated Ether. 22-84 25.46 24.84 25.48 26.72 26.08 26-68 Pure Dry Ethylic Ether. - - - 23.98 24.59 24.64 24.90 Petrol. 20.86 23-92 23.28 23-84 24.39 24.48 24.60 I t will be noted from the table that neither the petrol nor the pure ethylic ether completely extracted the fat in the time mentioned. This fact was further proved by examining the extracted milk under the microscope for fat, which was still present in these two cases. In the case of methylated ether of sp. gr. 0.720 and 0.730 the extraction of fat was practically complete, as judged by microscopical examination, but in neither case was the fat which was extracted pure. These solvents extract more than the fat, this being evident from the fact that the fats, after having been dried in the oven, did not appear clear, but were niixed with a small amount of some semi-charred substance.That the fats extracted by the methylated ethers contained some substance other than pure milk-fat was determined by shaking the fats in the flasks (after weighing) with warm distilled water, cooling so as to solidify the fat, and evaporating the filtered aqueous solution to dryness. No residue was observed with the fats which had been extracted with petrol, 0.720 ethylic ether, and dry ether. A small amount of residue was left in the case of the fat extracted with 0.720 methylated ether and a somewhat larger amount with the fat extracted with 0.730 methylated ether. These residues were too small in quantity for any fuli examination, but were probably composed of lactose or an albuminoid constituent of the milk. In the case of 0.720 pure ether the extraction is complete, as is ascertained from the microscopical examination of the contents of the package ; and further, the fat is obtained clean.If, then, this is adopted as giving correct results, it will be seen that the results Gbtained with the two methylated ethers are too high. I t appears that the small amount of alcohol or moisture which is present in the 0.720 ethylic ether exerts a disintegrating action on the coatings which surround the fat globules, and so make the complete extraction of fat possible. I n the case of pure ether and petrol this disintegration does not go on, and consequently the extraction of fat is not complete. I t is clear, then, that when methylated ethera are used the impurities present This gives a very delicate indication of the presence of fat.356 THE ANALYST.dissolve substances other than fat, this being much more the case with methylated ether of higher specific gravity. The following two methods have been recommended for use in the analysis of dry milks, and although they did not appear to be of value, we have included results obtained by them, which are as follows : 1. One gram of the milk powder is dissolved in about 10 C.C. of warm water in a graduated cylinder. The solution is then mixed with 1 C.C. of ammonia water (of about 10 per cent.), and allowed to stand for about half an hour. Then 10 C.C. of alcohol (96 per cent.), 25 C.C. of dehydrated ether, and 25 C.C. of petroleum ether are successively added, and thoroughly mixed with the milk powder solution.After two or three hours the volume of the ether-petroleum ether-fat solution is read off and 40 C.C. of the solution drawn off into a weighed flask, the ether and petroleum-ether being then evaporated and the fat dried and weighed. 2. Five to 10 grams of the milk are placed in a long-necked flask with 20 C.C. of 50 per cent. alcohol, and boiled for a short time, cooled, and petrol (boiling-point, 40"-50") added, and the liquid again boiled whilst being well shaken. The contents of the flask are then transferred to a 250 C.C. cylinder, and the flask washed out into the cylinder with petrol. The contents of the cylinder are well shaken and allowed to stand till the petrol completely separates. Its volume is then read off, and an aliquot part of this is evaporated in the usual way and weighed. The unreliability of these two methods is shown by the figures given in Table 111. TABLE 111. New Methods tested on Sample G., Table 11. Fat, per Cent. No. 1, two estimations ... ... No. 2, four estimations .. . ... Actual per cent., see Table 11. ... 19.2 20.4 22.44 24-48 { 22.1 24.08 26.64 To summarise : 1. For an accurate estimation of fat in dry milk by direct extraction, ethylic ether (sp. gr. 0.720) must be used. 2. For an estimation accurate to about 0-3 per cent. it is possible to use methylated ether (sp. gr. 0.720). 3. Methylated ether (sp. gr. 0-730), petrol, and specially purified ether give incorrect results. 4. The Werner-Schmidt method gives satisfactory results, whereas the two methods (numbered 1 and 2) given above are useless.

ISSN:0003-2654    

DOI:10.1039/AN9083300353

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 357 ABSTRACTS OF PAPERS PUBLISHED IN OTHER JOURNALS. FOODS AND DRUGS ANALYSIS. The Unsaponifiable Constituents of Cocoanut Fat and its Detection in Admixture with Butter. H. Matthes and E. Ackermann. (Ber. Deut. Chem- Ges., 1908, 41,2000-2001.)-The authors have ascertained that cocoanut fat contains, in addition to the ordinary known phytosterol, a second phytosterol giving similar colour reactions, but combining by addition with two molecules of bromine, and yielding an acetate which forms a sparingly soluble tetrabromide which is charac- teristic. For instance, from 1 kilogram of cocoanut fat there were obtained 1-25 grams of crude phytosterol, and 0.25 gram of a liquid residue, as the result of a twice- repeated saponification, and shaking out with ether in a Hagemann's apparatus.The crude phytosterol melted at 135"-145" C.; after acetylation the product melted at 126"-128" C. The acetylated product was then brominated in presence of ether and glacial acetic acid, and the characteristic tetrabromide then separated out in the form of thin plates, melting with decomposition at 180"-183" C., and containing 39 per cent. of bromine. From the filtrate, after evaporation and recrystallisation from alcohol, crystalline aggregates of phytosteryl acetate dibromide, melting-point 132O-135" C., were obtained. Since butter contains only cholesterol, and as the latter does not form an acetate tetrabromide, it is suggested that this reaction may possibly be available for the identification of cocoanut fat, or at all events of vegetable fat, as am adulteration in butter, and the method would possess the advantage over the present indirect methods that an actual derivative of a constituent of the adulterating substance could be isolated.J. F. B. The Valuation of Indian Hemp. D. Hooper. (Plznrm Jozwn., 1908,81,80.)- The gradual deterioration of hemp drugs on keeping is to be attributed to the oxidation of the red-oil, cannabinol, and probably also of more volatile constituents. Hence a determination of the iodine value and percentage of unsaponifiable matter in an extract affords a criterion of the extent of deterioration. I n order to remove organic acids, resins, fixed oils, and lighter terpenes, 1 to 2 grams of the extract are saponified for two hours with 20 C.C. of alcoholic potassium hydroxide, the liquid then evaporated to dryness, the residue washed with water, the unsaponifiable matter containing the cannabinol dissolved in chloroform, the solution evaporated, the residue dried and weighed, and its iodine value determined. The following results were thus obtained with three samples of fresh charas and two samples several years old.1. 2. :3. 4. 3. (190s.) (1908.) (190s.) (1903.) (1893.) Unsaponifiable matter, per cent. 87% 84.4 83.5 66.4 54.8 Iodine value . . . ... ... 183 184 179 141 131358 Sucrose. THE ANALYST. Ash. Destrin. The iodine value of the dried extracts without previous purification also distin- guishes between old and fresh samples. From 0.1 to 0.2 gram of the extract is treated with 25 C.C. of freshly prepared Hiibl's solution, which is allowed to act for six hours.The following results were thus obtained : 1. 2. 3. Kashgar Charas, 1908 ... 234 231 233 Baluchistan Charas, 1905 , . . 202 205 183 (mouldy) ,, 1903 ... 196 202 Bhan; ... 1908 ... 173 (1905) 145 (1893) 112 Ganja ... 1908 ... 163 (1893) 130 C. A. 31. 'er Cent. 3.73 3.43 3.70 Composition of American Honeys. C. A. Browne and W. J. Young- (US. Dept. of Agric., Bull. 110, 1908, 1-94.)-The investigation recorded in this Bulletin was undertaken for the purpose of determining the general composition of American honey, and to establish a general range for the variation in the composition, which would be of use to the analyst in the examination of commercial samples. Analyses were made of about 100 samples, including 85 specimens from various States exhibited at the St.Louis Exhibition (1903), 11 samples from Hawaii, and 4 New England honeys. The average results obtained are given in the following table : Per Cent, 0.08 0.12 0.09 Ltevorotat ory honeys (92 samples) ... Dextrorotatory honeys (7:samples) All honeys (99 samples) ... ... 1.90 3.01 1.98 Lsvorotatory honeys Maximum ... Minimum ... Dextrorotat,ory honeys : Maximum ... Minimum ... 0.18 1.51 0.81 9.70 0.23 2.09 Water. 10.01 0.00 5.28 0.61 Per Cent. 17.70 16.09 17 -59 26.88 12.42 17-80 13-56 0.90 0.03 1.29 0.29 Invert Sugar. 'er Cent. 74.98 66.96 74-41 Per Cent, Per Cent. Per Cent. I EXTREME RESULTS. 83.36 62.23 71.69 64-84 7.58 0.04 12.95 6.02 I Qot-Esti- formic). 7.45 0-04 4-95 1-57 0-25 0.04 0.19 0.05 teciucing Sugars (as dex- trosih)..'er Ci,nt. 71.05 64.15 70.59 79.86 59.61 68.68 62-12 For detecting the presence of added invert sugar in honey, Ley's test (ANALYST, 1907, 32, 291) was found to be of some value, although it is not infallible. The greenish after-tone failed with many of the American honeys, but the brownish coloration of the reaction is useful as a confirmatory test. A positive reaction with aniline acetate may be regarded as an almost certain indication of adulteration withTHE ANALYST. 359 invert sugar. In this test a concentrated solution of the honey is placed in a test- tube and a solution of aniline acetate (prepared by mixing 5 C.C. each of aniline and water and adding sufficient acetic acid to clear the emulsion) is poured over its surface. If, when the tube is gently agitated, a red ring forms beneath the aniline acetate, this colour becoming gradually imparted to the whole layer, artificial invert sugar is present.The Bulletin also contains a description of the methods used in the microscopical examination of honey ; a number of photoinicrographs of different pollen grains are given, as well as a comprehensive list of the literature relating to honey. w. P. s. Calculation of Milk Adulteration. J. F. Liverseege. (Jozwn. SOC. Chem. I d . , 1908, 27, 604-605.)-1n calculating the composition of milk adulterated by the addition of both skimmed (or separated) milk and water, the usual method is by simultaneous equations, thus : 1. 0.085m + 0.09s = Non-fatty solids found in sample. 2. 0.035m + 0-002s =Fat found in sample.3. m+s+w==100, where m=percentage of average milk (taken as 3% per cent. fat and 8.5 per cent. non-fatty solids) ; s =percentage of Separated milk (containing 9.0 per cent. total solids and 0.2 per cent. fat) ; and w = percentage of added water. As the solution of such equations is tedious, the author has plotted out two curves, by means of which the composition of any sample may be readily calculated in terms of milk of average quality, separated or skimmed milk, and added water if any be present. The original paper should be consulted for reference to the curves and tables worked out by the author. A. R. T. Determination of Orcinol in “Orchella. Weed.” H. E. Watt. (Jozcrn. SOC. Chenz. Ind., 1908,27, 612.)-The author has modified Stenhouse’s original method (Jozcrn.p n k t . Chem., 1848, 45, lSOj, in which the colouring matter is extracted from the lichen by a solution of caustic alkali, and the liquid titrated with sodium hypochlorite solution which has been standardised against pure orcinol. Two grams of the powdered lichen are mixed in a mortar with an equal weight of sodium carbonate, and water gradually stirred in until the whole measures 100 C.C. The mixture is allowed to stand, with frequent stirring, for twenty minutes, when 50 C.C. ( = 1 gram lichen) is filtered off, excess of a standard solution of sodium hypochlorite added (which produces a fugitive blood-red colour), followed immediately by excess of a decinormal arsenious acid solution, The liquid is then titrated back with the sodium hypochlorite solution, using drops of acetic acid starch-iodide eolution on a porcelain tile as an indicator.It was found by experiment that, besides the instantaneous reaction which takes place between ( ( erythrin ” and the hypochlorite, a slow secondary action occurs. For this reason the excess of hypochlorite is immediately destroyed, and only that taken up instantaneously is measured. One decigram of orcinol was found to require360 THE ANALYST. 7.7 C.C. of a sodium hypochlorite solution, 4.55 C.C. of which were equivalent to 50 C.C. of decinormal arsenious acid solution. A. R. T. Estimation of Phosphoric Acid in Foods. E. Wormer. (&its. Unterszcch. Nahr. Genzmm., 1908, 15, 732-734.)-1n the method described the food material is oxidised by treatment with nitric and sulphuric acids, the phosphoric acid is precipi- tated with molybdate solution, and the precipitate is then heated with excess of standardised sodium hydroxide solution.The ammonia is thus expelled, and its quantity (as estimated by titrating back the excess of sodium hydroxide) is a measure of the amount of phosphoric acid present. I n the case of flour, from 1 to 5 grams of the sample are heated with 10 C.C. of a mixture of equal parts of concentrated sulphuric and nitric acids, a little more nitric acid being added from time to time until, when sulphuric acid fumes are given off, the solution does not darken in colour. The mixture is then diluted with water and filtered if necessary; to the filtrate, which should measure about 80 c.c., are added 30 C.C.of 50 per cent. ammonia; the mixture is heated to a temperature of 80" C., and the phosphoric acid is precipitated by the addition of 25 C.C. (or more, if necessary) of 10 per cent. ammonium molybdate solution. After fifteen minutes the supernatant liquid is poured through a small filter, the precipitate is washed by decantation with cold water until free from acid, using litmus-paper as indicator, and the filter is then placed in the vessel containing the precipitate. Water and a known volume of 2 sodium hydroxide solution are added, tbe mixture is boiled until all the ammonia has been expelled, and the excess of alkali is then titrated back, phenolphthalein being used as indicator. finder the above conditions the yellow phospho-molybdate precipitate has a constant composi- tion corresponding with the formula, 2(NH,),P0,.24M00,.4HN03.Each C.C. of c; alkali used corresponds with 0.00127 gram of phosphoric acid (P,O,), or 0*000556 gram of phosphorus. The process is applicable to the estimation of phosphoric acid in wine, beer, etc. w. P. s. Analysis of Turpentine Oil. F. W. Richardson and J. L. Bowen. (Journ. SOC. Clzern. Ind., 1908, 27, 613-616.)--Light hydrocarbons are almost the only adulterants of turpentine oil. Pine oils and pinolins, bye-products of the manu- facture of rosin oil, are powerful solvents of oils and resins, and as they are chiefly composed of volatile terpenes their use for ordinary purposes can scarcely be condemned, though they are objectionable for pharmaceutical use owing to their strong action on the skin.If the oil be shaken with half its volume of 6 per cent. iodine in carbon tetrachloride and heated for one minute at 100" C,, a dark green colour indicates the presence of pinolins (Valenta). Polarimetric methods are of little use as applied to turpentine oil, since varying amounts of lavo- and deztro-pinenes are present. Refractoinetric examination is useful, pure turpentine oil having a refractive index of 1.470 to 1473 at 15.5" C., while that of hydrocarbon adulterants varies from 1.410 to 1-460. The specijc refractivity (" 1, where n = refractive index and d = specific gravity is of little )THE ANALYST. 361 value in differentiating the pure oil from its adulterants. The speciific gravity of turpentine oil is a valuable guide as to its purity (average 0.864). Fractional distillation is one of the most useful methods o€ examination of turpentine oil, especially when combined with a refractometric determination of the fractions.The authors recommend, for general work, simple distillation of 100 C.C. of the oil in a, distilling-flask of 500 C.C. capacity, the thermometer-bulb being fixed just below the opening into the side-tube. Any residue over 200" C. should be transferred to a very small distilling-flask for final distillation. A sample of pure turpentine distilled as described gave 96.8 per cent. of distillate between 157" and 171' C. The method o j V&es (Journ. SOC. Chent. Inn., 1903, 22, 1106), which consists in determining the differences in refractivity of the fractions distilled in fifths (20 per cent.each fraction), was not found to yield any useful results. The acetic acid test of the British Pharmacopoeia was found to be unreliable, though if the test be applied in a manner similar to the well-known Valenta turbidity test, useful qualitative results can be obtained. In conjunction with the physical data described, the iodine absorption (Hiibl) is of great value. The bromine thermal value is not of much service in the examination of oil of turpentine, since the differences in rise of temperature with various mixtures of turpentine oil and petroleum products are too small. As petroleums give variable thermal values, the authors sought for some reagent which would be without action on the saturated hydrocarbons and upon such olefins as are usually present, while producing considerable heat constantly with terpenes.Antimony trichloride appeared to answer these requirements, and the test was carried out by immersing a thermometer with small spherical bulb in a platinum tube containing mercury, this apparatus being placed in a glass tube containing 1 gram of the finely powdered antimony trichloride. By means of a twisting action this substance was made to form a thin layer on the lower parts of the tube, and the whole apparatus was then introduced into a beaker packed with some non-conducting material (or a vacuum-tube may be employed). Two C.C. of the turpentine oil at the same temperature as the substances in this apparatus are added to the antimony chloride and the increase of temperature noted. This is the " antimony trichloride value." Petroleum gives no rise of temperature, while most genuine oils of turpentine give a value of about 47' G.One genuine oil examined, however, gave a rise of only 22.8" C,, in spite of the fact that it had an iodine absorption similar to another genuine sample that gave a rise of 47.2" C. The antimony trichloride value cannot, therefore, be implicitly relied on, and it is evident that a genuine turpentine may contain bodies reacting with iodine reagent and not to antimony trichloride. The authors do not reoommend any of the polymerisation methods, as they find that with nitric acid nitro-terpenes are formed which dissolve some of the petroleum, and, in addition, partial oxidation of the petroleum takes place ; while with sulphuric acid the polymerised bodies apparently dissolve some of the unpolymerised substances. A. R. T. Estimation of Water in Gluten. M. P. Neumann and P. Salecker. (Zeits. Unterszuh. Nuhr. Genussm., 1908, 16, 735-738.)-The cake of moist gluten obtained from flour in the usual way is pressed by means of the thumb over the bottom of a362 THE ANALYST. flat nickel basin, The basin and its contents are then placed in an air-oven at a temperature of 120" C. At this temperature the gluten becomes constant in weight in about three hours; some decomposition takes place, as is shown by the alteration in colour and in the decrease in solubility in 70 per cent. alcohol, but the alteration does not affect the weight of the gluten, as the results agree with those obtained by the method described by Bremer (ANALYST, 1908, 56), and with the percentages of moisture found when the gluten is dried under reduced pressure at a temperature of 95" C. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9083300357

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

362 THE ANALYST. BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. A New Method for Estimating Diastatic Ferments. J. Wohlgemuth. (Biochem. Zeits. 1908, 9, 1-9.)-In each of a series of test-tubes are placed 5 C.C. of a 1 per cent. starch solution and successively increasing quantities of the ferment under examination. The tubes are placed in ice-water until the last one has been prepared, and all are then inserted in a water-bath heated to a temperature of 40' C., allowed to remain there for from thirty to sixty minutes, and next transferred to the ice-water bath in order to stop further action. One drop of & iodine solution is now added to each test-tube, the contents are shaken, and the tube is selected which shows no trace of blue colour, but is next in the series to the tube exhibiting a purple or blue colour.Suppose the selected tube contained 0.02 C.C. of saliva, then 1 C.C. of saliva would have converted the starch in 250 C.C. of the solution in the flame time. The starch solution used should be prepared by rubbing down the required weight of soluble starch with a little water, adding more water to the paste, and heating the whole on a water-bath for about ten minutes. The solution is then diluted to the correct volume. w. P. s. Method for the Estimation of Fat and Unsaponifiable Substances in Animal Tissues, and a Critical Examination of the Methods now in Use. M. Kumagawa and K. Suto. (Biochem. Zeits., 1908, 8, 312-347.)-The methods at present employed for the estimation of fat in animal matters, such as dried meat powder, etc., give very varying results, much depending on the solvent used for extracting the fat.The authors, therefore, propose a method in which the substance is hydrolysed, the fatty acids formed being then extracted by means of petroleum spirit, and the true fat calculated from the weight of fatty acids found. From 2 to 5 grams of the dry tissue are heated on the water-bath for two hours with 25 C.C. of 20 per cent. sodium hydroxide solution. The mixture is then transferred t o 8 separating funnel, acidified with 30 C.C. of 20 per cent. hydrochloric acid, and the fatty acids shaken out with 100 C.C. of ether. The ethereal extract is filtered through asbestos, and the ether is evaporated at a temperature of 50" C. The residue obtained contains, besides fatty acids, colouring matters, lactic acid, and other substances, After being dried at the above-mentioned temperature for several hours, the residue is treated with about 30 C.C.of pbtroleum spirit; the impurities remain insoluble, and the petroleum spirit solution of the fatty acids is filteredTHE ANALYST. 363 through asbestos, the solvent is distilled 08 at a temperature of 50' C., and the residue is dried until constant in weight. The fatty acids thus obtained are practically free from phosphorus and nitrogen. The unsaponifiable matters present can be estimated by treating the fatty =ids in petroleum-spirit solution with alcoholic sodium hydroxide solution, adding water, and separating the substances remaining dissolved in the petroleum spirit. R. Inaba (ibid., pp.348-355), as the results of his experiments, considers that $he method proposed by Kumagawa and Suto is trustworthy for the estimation of fat in faeces and vegetable materials. w. P. s. Estimations of Fermentations with Yeast. A. Slator. (Journ. SOC. Chem. Ind., 1908, 27, 653-654.)-An apparatus is described for measuring the rate of alcohol fermentation by yeast. A given quantity of the yeast and sugar solution is introduced into a glms bottle of about 150 C.C. capacity, fitted with a rubber bung and connected by pressure tubing to a mercury manometer, which can register pressures from a vacuum to about 30 cm. of mercury. The bottle contains some glass beads, to assist in the thorough shaking of the solution; it rests in a thermo- stat, and is taken out at intervals and shaken to overcome supersaturation of gas i n the liquid.The apparatus can be exhausted and kept air-tight by means of a side tube provided with a stopcock. The change in pressure registered on the manometer is a measure of the amount of fermentation in a given time. Experiments made with the apparatus show that the rate of fermentation of dextrose is exactly pro- portional to the amount of yeast present in the solution. The rate in the case of .dextrose, liEvulose, galactose, and mannose is approximately independent of the concentration of the sugar solution when the concentrations vary from 1 to 10 grams per 100 C.C. The fermentative activity of yeasts can also be measured by means of the apparatus. Fifteen grams of the yeast are mixed with water, and diluted to a volume of 250 C.C.; 10 C.C. of this mixture are placed in the bottle, together with $0 C.C. of 5 per cent. sucrose solution, and the bottle is connected with the mano- nieter and placed in the thermostat heated to a temperature of 30" C. The apparatus is exhausted, and readings of the manometer are taken every five minutes. Some specimens of yeast show a constant activity for several hours after mixing; the activity of others changes gradually. Where yeast is used in such a manner that the initial activity is of importance, such estimations are evidently of value. Small quantities of fermentable sugar can also be estimated by the use of the apparatus, as it is possible to ferment completely 0.1 gram of dextrose in twenty minutes, and to measure the fall in pressure due to this fermentation. The meaeure- ment, after correction for the autofermentation of the yeast, is proportional to the amount of sugar introduced into the bottle of the apparatus. By carrying out two experiments, one with a sugar solution of known concentration, and the other with a solution of unknown strength, the amount of sugar in the latter can be ascertained.w. P. s.36,4 THE ANALYST. Estimation of the Total Sulphur in Urine. E. Osterberg and C. G. L, Wolf. (Biochem. Zeds., 1908, 9, 307-309.)-As the result of a number of experi- ments, the authors conclude that the total sulphur in urine cannot be accurately estimated by oxidising the latter with fuming nitric acid, and precipitating the sulphuric acid formed with barium chloride.The results obtained did not agree amongst themselves, and were always lower than those obtained by oxidation with sodium peroxide or by combustion in a calorimeter bomb. Other observers have also found too low results when using the nitric acid method. (See ANALYST, 1903, 28, 45.) w. P. s. Estimation of Creatinine in Urine by Means of Picric Acid. M. Barberio. (SOC. Chim. d i Roma, May 24, 1908 ; Chem. Zeit., 1908, 32, 722.)-In Jaffe's method (Zeit. physiol. Clzem., 1886, 10, 391) of precipitating creatinine from urine by means of potassium picrate, the double salt - C,H7N,0.C,H,(N0,),.0H -t C,H,(NO,),OK -is accompanied by appreciable quantities of uric acid and of a substance of a mercaptan nature. Since repeated crystallisation is required to eliminate these completely, it has not hitherto been found possible to make the method quantitative. For this purpose the following modification is recommended : The urine is de- colorised by treatment with blood charcoal in the proportion of 2 grams per 100 c.c., and an aliquot portion (20 c.c.) of the 6ltrate treated with an equal volume of 1 per cent. solution of potassium picrate. The precipitate is then collected, washed with alco.ho1 and ether, dried at l l O o C., and weighed. As a check, the author advocates the subsequent conversion of the precipitate into potassium sulphate. C. ,4. M.

ISSN:0003-2654    

DOI:10.1039/AN9083300362

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

36,4 THE ANALYST. ORGANIC ANALYSIS. Titration of Amino-Acids in Presence of Formaldehyde ; Decolorisation of the Solutions. S. P. L. Ssrensen and H. Jessen-Hansen. (Conzptes Rend. Tmv. Lab. de Carlsberg, 1908, 7, 58-71.)-The titration of rtmino-acids in presence of formaldehyde by the method previously described (,~NALYST, 1908, 20) becomes praotically impossible when the solution to be tested is strongly coloured, as is generally the case with the products of the hydrolysis of proteins by acids. The authors have found, however, that very dark-coloured solutions may be sufliciently decolorised by the precipitation therein of silver chloride, by the addition of silver nitrate, and slightly more than the equivalent quantity of barium chloride. The coloured bodies are carried down by the precipitate without appreciable precipita- tion of nitrogen, and the titration may be carried out on the filtered solution.The procedure is as follows : If the liquid to be titrated be of suitable acidity (about $*), 25 C.C. are placed in a marked 50-C.C. flask; if the acidity requires correction, only 20 C.C. of the liquid are taken and treated with 5 C.C. of $ hydrochloric acid or sodium hydroxide, as the case may be. In the case of a solid substance, 1 to 3 grams are dissolved in the flask in 25 C.C. of Fa hydrochloric acid. There are then added to the liquid in the flask about 4 C.C. of a 2N solution of barium chloride, after which about 20 C.C. of a solution of silver nitrate are added, little by little,THE ANALYST 365 with frequent agitation. Finally, the contents of the flask are diluted to 50 C.C.with water free from carbonic acid; 4 drops of water may be allowed for the valume of the precipitate. The liquid is poured, together with as much of the precipitate as possible, on to a dry filter, and the filtrate is returned until it runs through clear. A suitable quantity (15 to 30 c.c.) is then taken for the titration in presence of formaldehyde, as previously directed, phenolphthalein being used as the indicator, and the blank being tinted with orange and brown dyestuffs, to match the shade of the solution under titration. If it be desired to ascertain the quantity of nitrogen present in the precipitate (generally negligible), the latter is washed on the filter with a dilute solution of barium chloride (about ;), and subjected to the Kjeldahl process.When large quantities of acid liquid have to be decolorised, silver nitrate is scarcely suitable, on account of the large quantity of nitric acid (or njtrates) left in the liquid., In such cases silver sulphate may be used, accompanied by the addition of an equivalent quantity of baryta, water, to precipitate the sulphuric acid, if necessary. Silver sulphate, however, must be employed in the form of a solution, since the solid salt causes the precipitation of nitrogenous matters in considerable quantities. J. F. B. A New Method of Estimating Casein. Determination of its Equivalent Weight. G. T. Matthaiopoulos. (Zed. anal. Chem., 1908, 47, 492-501.)-The method is based upon the fact that, if a definite quantity of very dilute acid be added to milk, and the liquid then titrated with standard sodium hydroxide solution, with phenolphthalein as indicator, the whole of the substances acid to the indicator, including the casein, are neutralised.But if the precipitated casein be filtered off before the titration, it smaller quantity of alkali will be required, the difference corresponding to the amount of casein. Various values have been given as the equivalent weight of casein, ranging from 5000 to 6000 [Salkowski (Zeits. fiir Biolog., 1899, 37, 401), Hammarsten (Konig. Gesell. der Wissenschaft zu Upsala, 1877)] to 1135 [Laqueur and Sackur (Hofmeister’s Beitrage, 1903, 3, 193)]. In the author’s experiments, the amount of sodium hydroxide solution, corresponding to the casein in a definite quantity of milk, was found as described below, and the quantity of the casein in the same milk subsequently estimated by Hoppe-Seyler’s gravimetric method.From the mean results of many estimations, it was found that 1 C.C. of ;k sodium hydroxide solution corresponded to 0.11315 gram of casein, and the equivalent weight of casein in its sa1t.s with bases was therefore taken as 1131-5. In the author’s opinion, the higher values of 5000 to 6000 are incorrect, and were possibly obtained with hydrolysed or acid salts of casein. In making estimations by this method, 20 C.C. of milk are diluted with 80 C.C. of water in a 200-C.C. flask, and & sulphuric acid added drop by drop from a burette with continual shaking, until the casein separates in large flakes.From 23.1 to 23.5 C.C. of the acid are usually aufficient to enable a clear filtrate to be obtained, though any excess must be avoided. One hundred C.C. of the clear filtrate are then titrated with TG sodium hydroxide solution, with 1 C.C. of a 1 per cent. alcoholic solution of phenol phthalein as indicator, and the number of C.C. required calculated for the total quantity of water, milk, and added acid. A second portion of 20 C.C. of the milk is treated in the same366 THE ANALYST. way as the first portion, except that it is titrated without previously filtering off the casein, and the difference between the number of C.C. of alkali consumed in the two titrations, multiplied by the factor 0.11315, gives the amount of casein in the 20 C.C.of milk. Experimental estimations are described to show that the method gives very accurate results; and it is suggested that, since the quantity of casein in milk varies within smaller limits (1.91 to 4.65 per cent.) than that of the fat, it might be advisable to base conclusions as to the purity of a milk on the proportion of the former rather than upon the amount of fat. Moreover, in the case of milk which has become sour, it is, as a rule, neceesary to filter off the casein before the free acid can be titrated, although, if the original acidity of the milk be known, that which has been formed may be estimated by the method of Soxhlet and Henkel, since the casein is precipitated by the equivalent amount of acid which has been produced. C. A. &I. Quantitative Estimation of Active Hydrogen in Organic Compounds. T.Zerewitinoff. (Ber. deut. Chenz. Ges., 1908, 41, 2233-2243.)-1n a previous paper (ANALYST, 1907, 32, 299) the author described 8r method for the quantitative estiniation of hydroxyl groups in organic compounds, based on the measurement of the volume of methane given off when the substance is treated with magnesium- methyl iodide in presence of a suitable solvent (amylic ether or pyridine). This method has been employed by the author for the solution of a number of constitutional questions in connection with complex substances, chiefly colouring matters of the flavone group. A few notes are added dealing with details of manipulation necessary to ensure good results. The method tends to give numbers which are higher than the theoretical numbers, chiefly owing to the dificulty, previously mentioned, caused by the secondary action of the pyridine on the magnesium-methyl iodide.This secondary action tends to be increased by the heat, which is developed in the reaction with the hydroxyl compound, The improved procedure is as follows : A s soon ae the solution of magnesium-methyl iodide is brought into contact with the pyridine solution of the hydroxylated substance, the contents of the reaction flask must be shaken vigorously so long as the mercury in the measuring-tube falls rapidly, but when it begins to fall more slowly, the reaction flask must be at once cooled in a vessel of water in order to restrict the secondary reaction with the pyridine. The stock of pyridine employed must be kept in closely-stoppered vessels over lumps of barium oxide, but the greatest care must be taken to prevent particles of the barium hydroxide from entering the reaction flask.For this reason the pyridine is best stored in tall, stoppered cylinders. The method described for the estimation of hydroxyl groups may be employed for tbat of other active groups which yield methane with magnesium-methyl iodide--for instance, the SH group of mercaptans, for which either amylic ether or pyridine may be used as the solvent. The imines and acid imides evolve only one molecule of methane for each imino group, but the amines and acid amides may evolve two molecules, according to the tempera- ture. In the cold, only one hydrogen atom of the amino group reacts, and the restriction to this stage may be made quantitative by preventing the riss of tempera- Imino and amino groups also react quantitatively.THE ANALYST.367 ture which tends to take place, by keeping the flask immersed in a vessel of cold water and shaking well during the reaction. I n order to obtain a full reaction of both hydrogen atoms of the amino group heat must be employed, and the results must be corrected by performing a blank experiment under identical conditions in the following manner : 5 C.C. of the magnesium-methyl iodide solution and 15 C.C. of pyridine are heated in the reaction flask in a water-bath at a temperature of 85" C. for exactly five minutes. During this time the flask is shaken two or three times, and then rapidly cooled to the original temperature before reading the volume.The author has observed the following peculiarity with this class of compound: Compounds which contain two amino groups, or one amino and one imino group attached to a single carbon atom, always show a deficiency of one active hydrogen atom, which escapes reaction with the magnesium-methyl iodide, Thus, urea gives three molecules of methane instead of four, and phenylurea gives two instead of three. The enolic forms of tautomeric ketones behave as mono-hydroxylated bodies, but only yield the full theoretical results when the reaction is carried out at 100" C. The enolic forms of diketones only show the presence of one hydroxyl group. J. F. B. Analysis of Inks [Estimation of Gallo-tannic Acid]. E. Kedesdy. (Papier Zeit., 1908, 33, 2297-2298, 2383.)-The German specification for normal ink states that it should contain at least 30 grams of tannic and gallic acids derived from oak galls and 4 grams of iron per litre ; it fails to state whether the presence of other tannins in excess of the above gallo-tannic acid is permissible. The estimations of the total dry substance and the iron are perfectly simple, but that of the gallo-tannic acid is less straightforward.The most convenient method is that of Finkener : The ink is acidified with hydrochloric acid, and the organic acids are extracted by shaking repeatedly with ethyl acetate, in which they are freely soluble. The extract con- taining the tannic and gallic acids is then evaporated to dryness and weighed. In order to identify these acids as the product of oak galls, certain '' constants " must be determined. One of these is the copper equivalent, but unfortunately gallic acid has a distinctly higher copper equivalent than tannic acid, and both these acids may be present.If the method be permissible, it is carried out by adding a known exce~s of copper sulphate to the aqueous solution of the tannin in presence of chalk, and titrating the excess of copper with a standard solution of gallo-tannic acid until a filtered drop of the liquid no longer reacts with potassium ferrocyanide. A better method is the iodine method, because both gallic and tannic acids combine with practically the same quantityof iodine. The aqueous solution of the acids is treated in closed vessel with an excess of standard iodine solution in presence of sodium bicarbonate.After standing for some time the excess of iodine is titrated back with thiosulphate. Tannins from other sources than galls, which are soluble in ethyl acetate, possess different iodine values from that of gallo-tannic acid. By comparing the gravimetric result with the iodine value, a very fair idea may be gained as to whether the whole of the tannin has been derived from galls, but the method does not identify mixtures of tannins. The colour of the reaction of the tannin extract with very dilute ferric chloride should be noted, since a green coloration indicates the absence of gallo-tannic acid. The last important constituent of ink is the free368 THE ANALYST. mineral acid, but no satisfactory method for its estimation is available on account of the presence of the iron salt and the organic matters. Some test-paper of standard sensitiveness might possibly be devised.The formation of sediments and crusts is generally due to a deficiency of free acid; the iron contents of the deposits are generally very small, and they probably consist chiefly of polymerised oxidation products of the tannin. The ink, when kept in an open vessel protected from dust, should gradually dry to a homogeneous mass without the preliminary formation of crusts. J. F. I3. On the Fractional Distillation of Commercial Petroleum Spirit. R. Kissling. (Chem. Zed., 1908, 32,695-697.)-The following method of examining petroleum Rpirit by fractional distillation is recommended : The apparatus of Holde and Ubbelohde (Chem. Zed.[Rep.], 1908, 32, 620) is used in conjunction with an Engler's distillation flask, and a thermometer graduated in tenths of a degree. The upper part of the thermometer-bulb should be in the same plane as the lower edge of the outlet-tube of the flask, and the rate of distillation should be regulated so that in the first ten minutes, 2 c.c.; in the next twenty minutes, 3 C.C. ; and in the last ten Ininutes, 2 C.C. distil over, the distillation being complete in forty minutes. The temperature at which the first drops fall from the condenser is taken as the lower boiling-point, and the volumes of distillate are measured every 10" C., beginning with the first completed 10" C. The temperature at which the bottom of the flask is free from liquid, or at which white vapours appear, is taken as the upper boiling-point, and the weight of the residue in the distillation flask is subsequently determined.In case of a deviation of +_ 5 mm. from the normal barometrical pressure, a correction must be applied for the influence of atmospheric pressure. This is found by adding to or subtracting from the temperature of each of the fractions the difference between 100" C. and the temperature of boiling water under the pressure in question. In testing a petroleum spirit for small quantities of constituents of high boiling-point, it is best to stop the distillation when 95 per cent. by volume has passed over, to transfer the residue to a clock-glass, and to allow it to evaporate at the ordinary temperature, which takes from five to ten hours.C. A. 1\12. . Detection and Identiflcation of the Divalent Phenols. A Delicate Reaction for Resorcinol. T. Silbermann and N. Ozorovitz. (Bull. SOC. Sci. de Bucharest, 1908, 17, 41-42.)-When the divalent phenols are heated with formaldehyde in acid solution, characteristic resinous condensation products are formed, which are insoluble in all ordinary solvents, but which undergo changes when further treated under certain conditions. The reaction with resorcinoE is extremely delicate, and is distinct with a solution containing only 1 part of the phenol per 100,000. When a solution of resorcinol is heated with formaldehyde, with the addition of a, few drops of hydrochloric or sulphuric acid, a white flocculent pre- cipitate is formed.When the product of the reaction is mixed with strong sulphuric acid or heated with strong hydrochloric acid, the mass is coloured a brilliant carmine red, which changes to orange on dilution or neutralisation. Both the carmine and the orange products are changed to a Bordeaux red colour by alkalis. If the con-THE ANALYST. 369 densation be originally effected in presence of concentrated acid, a, red product is formed directly. Pyrocatechol, when heated with formaldehyde in acid solution, yields a white resinous precipitate, which is coloured a deep brown-violet by con- centrated acids, the colour changing to fleeh-colour on dilution or neutralisation ; an excess of alkali turns it greenish-brown. In the case of qzbinol it is neoessary to use more acid to effect the condensation (10 C.C. of strong hydrochloric acid per 100 c.c.). A similar white resin, insoluble in all media, is precipitated. Concentrated acids turn it yellowish-brown, and the colour becomes paler on dilution or neutralisation ; excess of alkali turns it olive-green. The reactions with pyrocatechol and quinol are not SO delicate as in the case of resorcinol. J. F. B. A Test to Distinguish a- and B-Naphthol. Volcy-Boucher. (Repertoire 1908, 20, 289 ; Pharm. Journ., 1908,81,82.)-A solution of 0-5 gram of the naphthol in the smallest possible amount of alcohol is treated with 2 C.C. of a 10 per cent. solution of copper sulphate end 4 C.C. of a freshly-propared 10 per cent. solution of potassium cyanide, the liquid being shaken after eaoh addition. I n the case of a-naphthol a, violet-red precipitate is obtained, whilst P-naphthol gives a yellow precipitate. On treatment with just sufficient 95 per cent. alcohol, the red precipitate gives a solution which is rose-coloured by transmitted light and violet by reflected light, whilst the @naphthol precipitate forms an orange-yellow solution. The test is capable of detecting 1 part of a-naphthol in the presence of 2,000 parts of /3-naphthol, of distinguishing between the camphorated naphthols, and of detecting either naphthol in the free state in benzo-naphthol, which gives no coloration in the test. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN9083300364

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 369 INORGANIC ANALYSIS. The Iodometric Estimation of Arsenic and Antimony in the Presence of Copper. F. H. Heath. (Zeits. Anorg. Chenz., 1908, 59, 87-93.)-A solution con- taining copper, antimony and arsenic in their higher states of oxidation is acidified with 1 to 2 grams of citric acid. For quantities of copper up to 0.3 gram, dissolved in 50 to 100 C.C. of liquid, 3 to 5 grams of potassium iodide are added, and the liberated iodine is at once titrated with sodium thiosulphate solution. The cuprous iodide is filtered off on asbestos, and the filtrate heated to boiling after adding 1 C.C. of bromine to destroy tetrathionates. If the liquid does not become clear after some time, it is cooled, 0.5 C.C. of bromine added, and again boiled for some time until its volume is reduced to 60 C.C.About 40 C.C. of water and 2 grams of potassium iodide are then added, and the liquid is boiled down to 50 C.C. to reduce the arsenic and antimony. The cooled liquid is exactly decolourised by means of a solution of sulphur dioxide, after adding starch solution. Sodium bicarbonate is then added in excess, and arsenic and antimony are titrated together with iodine solution. The results obtained are fairly satisfactory, both for copper and for the sum of arsenic and antimony present. A. G. L. Estimation of Sulphur and Arsmic. W. C. Ebaugh and C. B. Sprague. (Eng. and Min. Joum., 1908, 85, 1048; Chem. Zeit. Rep., 1908, 32, 349.)-The370 THE ANALYST. following modification of the methods of Eschka and of Pearce is recommended for the estimation of arsenic and sulphur in ores, rocks, foods, etc.: 0.5 gram of the substance is mixed with a sufficient quantity of a mixture of soda and zinc oxide (1 : 4) in a porcelain crucible, which is then heated for fifteen to twenty minutes in a muffle.The mass is taken up with water, filtered, the filtrate acidified, and the sulphate precipitated with barium chloride. The filtrate is acidified with acetic acid, treated with silver nitrate, and boiled, the precipitated silver arsenate filtered off, washed, and dissolved in nitric acid, and the silver titrated with ammonium t hiocyanate. C. A. M. Note on the Electrolytic Estimation of Bismuth. J. Peset. (Zeit.9. Anal. Chew%., 1908, 47, 401.)-About 0.04 to 0.08 gram of a bismuth salt is dissolved by warming with 3 C.C. of concentrated sulphuric acid and 4 to 5 C.C.of water. The liquid is then diluted to 140 C.C. with water, any cloudiness being neglected, and electrolysed for eighteen to twenty-four hours at a temperature of 50' C., using a current of N.D,,, = 0.002 to 0.1 ampihe at 2 volts. The anode is rotated to prevent the formation of bismuth peroxide. As soon as a test with ammonium sulphide shows the whole of the bismuth to be deposited, a known weight (0.08 to 0.15 gram dissolved in 10 C.C. of water) of cadmium sulphate is added, and the electrolysis con- tinued for another eight hours with a current of 0.2 to 0.3 amperes at 2.5 to 3.5 volts. The cadmium is deposited over the bismuth, and protects it from oxidation during the subsequent washing and drying.A. G. L. Estimation of Cerium in Presence of Other Rare Earths by Means of Potassium Ferricyanide. P. E. Browning and H. E. Palmer. (Zeits. Anorg. Chem., 1908, 59, 71-73.)-An excess of a standard solution of potassium ferricyanide is added to the solution of a ceric salt. Potassium hydroxide is then added, the precipitated ceric dioxide is filtered off, and the potassium ferrocyanide formed is titrated in the filtrate, after acidifying with dilute sulphuric acid. A blank deter- mination should always be carried out on the ferricyanide solution, which keeps uncbanged for a week or even longer. Results obtained by this method on solutions of cerium containing other rare earths show errors of up to about +I per cent. A. G. L. Detection and Quantitative Estimation of Chlorites and Hypochlorites in Commercial Chlorate.B. Carlson and J. Gelhaar. (Chem Zeit., 1908, 32, 604-605, 633-634.)-To detect hypochlorites and chlorites in commercial chlorate, 5 grams of the sample are dissolved in 100 C.C. of cold water. HFpochlorite is present if a blue colour is produced on adding a few drops of a solution of iodide of potassium and starch, as little as 0.000002 per cent. of hypochlorite (on the solution) producing a faint blue colour after a few minutes; if a few drops of a weak solution of sodium thiosulphate are added, the instantaneous disappearance of the colour is especially marked. If hypochlorite is absent, 2 C.C. of sulphuric acid are added. The appearance of a blue colour now indicates the presence of chlorite, 0.0001 per cent.of chlorite producing a blue colour after a few seconde, whilst, with the quantity ofTHE ANALYST. 371 acid used, chlorate only produces a colour after sixty minutes. Samples of chlorate which are odourless are also free from chlorite or hypochlorite. Hypochlorite is estimated quantitatively by adding an excess of a standard solution of arsenious acid, and titrating back with iodine solution, as usual. To estimate chlorite, the calculated quantity of arsenious acid necessary to reduce the hypochlorite is added to another portion of the sample. The solution is then diluted to 250 c.c., heated to 95" C., and acidulated with sulphuric acid. The chlorite is then titrated with a solution of sodium indigo-sulphonate (containing 6 grams of the salt per litre) which has been standardised on a pure solution of chlorite, the strength of the latter being determined iodometrically. The authors state that commercial samples of chlorate are almost invariably free from both chlorite and hypochlorite, but may contain chloride, chromate, iroq and calcium.A. G. L. Estimation of Chromium as Silver Chromate. F. A. Gooch and L. H. Weed. (Zeits. Anorq. Chem., 1908, 59, 94-96.)-A solution containing chromium as potassium dichromate is heated to boiling, and a considerable excess of silver nitrate solution is added. The whole is again boiled, rendered slightly alkaline with am- monia, and then slightly acid with acetic acid, and allowed to stand for thirty minutes. The silver chromate is then filtered off on asbestos, washed first with dilute silver- nitrate solution, and finally with 20 to 30 C.C.of water, and dried at 135' C., or gently ignited. The presence of sodium or animonium The results obtained are good. nitrate is without influence. A. G. rJ. Separation and Estimation of Cobalt and Nickel. E. Pozzi-Escot. (Bull. SOC. Chim., 1908 [4.], 3, 776-777.)-The double molybdate of nickel and ammonium, the formation of which affords a means of detecting nickel in the presence of cobalt (ANALYST, 1908, 33), is completely insoluble in a saturated solution of ammonium molybdate, whereas the corresponding double salt of cobalt and ammonium is soluble. On this fact is based the following rapid method of estimating cobalt and nickel in the presence of each other : The solution containing the two metals is divided into two parts, in one of which the cobalt and nickel are estimated together by one of the known electrolytic methods. The other portion is concentrated, nearly neutralised (though still left slightly acid), treated with a very large excess of a saturated solution of ammonium molybdate, and with about 10 grams of ammonium chloride, and heated to about 60" to 70" C.with continual stirring. The liquid is then cooled, and the precipitated nickel filtered off, washed with a cold saturated solution of ammonium chloride containing Bome ammonium molybdate, and dissolved in hot water. From this solution the nickel is precipitated by means of potassium hydroxide and bromine, the nickel oxide washed and dissolved in an acid, and the nickel estimated electrolytically.The difference between the result and that obtained in the previous electrolytic estimation gives the amount of cobalt. C. A. M.372 THE ANALYST. Estimation of Graphite. F. Browne. (Chem. N~ZOS, 1908, 98, 51.)-The author has observed that when ferric oxide is heated in an open dish with graphite at a bright red heat, all the carbon is burnt off, and the oxide of iron is partially converted into magnetic iron oxide. The error due to this loss of oxygen can be avoided by regulating the temperature as roughly measured by the eye, and the author has based on these observations the following method for the determination of graphite : Five grams of magnetic iron oxide, prepared by heating ferric oxide in a covered crucible at a pale red heat for two to three hours, are heated in an open dish, with occasional stirring, at a temperature not exceeding a pale redness for one hour, and then weighed. Half a gram of the (i graphite " is then stirred in, the mixture heated as before for one to two hours, stirring once or twice meanwhile, and then cooled and weighed.The oxide remains unaltered, and the loss of weight after the addition of the graphite represents the carbon. Another determination can then be made on the same used sample of oxide. The mineral matter in coal may be similarly estimated, though the results are somewhat higher than the '( ash '' of coal determined by simple ignition of the sample. A. R. T. Estimation of Iron and Vanadium in Presence of each Other. G. Edgar. (zeits. Anorg. Chem, 1908,69,74-78.)-The solution of vanadic acid and ferric sulphate is rendered slightly acid with sulphuric acid and reduced as usual with sulphur dioxide, the vanadium being reduced to V,O, and the iron to FeO.The liquid is then titrated with potassium permanganate, a t first in the cold and, finally, at 70" to 80" C. The same solution is then run over a long column of amalgamated zinc in a Jones reductor, the reduced solution being caught in a flask containing ferric sulphate solution. After adding phosphoric acid, to lessen the colour of the iron salt, the contents of the flask are again titrated with potassium permanganate solution. From the two results obtained, tho quantities of iron andvanadium present are calculated. The test results quoted aru good for both elements.The zinc reduces vanadium to V,O, and the iron to FeO. A. G. L. Volumetric Estimation of Iron and Chromium by means of Titanous Chloride. S. B. Jatar. (Journ. SOC. Chem. Ind., 1908, 27, 673-674.)-The titration of chromium alone (in the form of bichromate) by means of titanous chloride can be best accomplished by the use of an indicator prepared by adding a few drops of thio- cyanate solution to B dilute ferrous sulphate solution. If a drop of this indicator be mixed on a white plate with a drop of the titration mixture, a red coloration is produced as long as any bichromate is present. For the estimation of iron and chromium in ferro-chrome and chrome iron ores, the following process may be used. The principles involved are : (1) Hydrogen peroxide oxidises chromic salts in alkaline solutions to chromates, these becoming bichromates on acidifying the solutions ; (2) Hydrogen peroxide in acid solutions reduces bichromates to chromates, ferric salts being unchanged; (3) When titrating a mixture of bichromate and a ferric salt, for all practical purposes the bichromate ie reduced first, the colour change marking the reduction, the ferric salt being left in solution. The first of these considerations is involved in bringing the iron and chromium in an ore into solution, whilst theTHE ANALYST.373 process depends on the second and third. About 0.5 gram of the finely-ground ore is fused with sodium hydroxide, with subsequent addition of sodium peroxide ; the fused mass is extracted with water, the solution is boiled to remove all traces of hydrogen peroxide, carefully acidified with dilute sulphuric acid, again boiled, and diluted to a volume of 500 C.C.Fifty C.C. of this solution are transferred to a small flask and titrated with standardised titanous chloride solution until the solution assumes a clear violet colour, showing that all the bichromate is reduced; a, few more drops of titanous chloride are added to make sure, then a few drops of thiocyanate solution, and the solution is further titrated until the coloration disappears. The volume of titanous chloride used represents- the bichromate and iron combined. A second 50 C.C. of the original solution are treated with hydrogen peroxide ; after a short time the mixture is boiled for about fifteen minutes to expel the excess of peroxide, and the solution, now violet in colour, is cooled.A few drops of thiocyanate solution are added, and the solution is titrated with titanous chloride solution until it becomes quite clear and violet in colour. The volume of titanous chloride used represents the amount of iron only; this volume, subtracted from that required for the first titration, gives a measure of the bichromate. w. P. s. Estimation of Nickel and Chromium in Steel. E. D. Campbell and W. Arthur. (Joum. dmer. Chem SOC., 1908, 30, 1116-1120.)-0ne gram of the steel is dissolved in 10 to 15 C.C. of nitric acid (specific gravity 1*2), with the addition of a, little hydrochlorio acid if necessary. The solution is evaporated to the point of fuming with 6 to 8 C.C. of sulphuric acid (1 : 1).The residue is heated with 30 t o 40 C.C. of water until dissolved, and filtered if necessary; 13 grams of sodium pyrophosphate, dissolved in 60 to 70 C.C. of water heated to 60" to 70' C., are then added, the whole is cooled to room temperature, and dilute ammonia, added gradually with vigorous stirring, until the greater part of the ferric pyrophcsphate is dissolved and the solution has assumed a greenish tinge. At this stage the liquid should be alkaline to litmus, but should not smell of ammonia. The solution is then warmed and stirred until the pyrophosphate is completely dissolved, any brownish colour being destroyed by carefully adding dilute sulphuric acid. The solution is then cooled, and the nickel titrated as usual with silver nitrate and potassium cyanide.If copper is present, it will be estimated together with the nickel; but steels oontaining copper can generally be dissolved in dilute sulphuric acid, leaving the copper in the residue, which is filtered off. The iron in the filtrate is oxidised with hydrogen peroxide before proceeding as above. If chromium is present as well as nickel, the sulphuric acid solution of the steel obtained as above is boiled and treated with potassium permanganate solution until a, permanent precipitate of manganese dioxide is obtained. The liquid is cooled and filtered, and chromium estimated by adding a known weight of ferrous ammonium sulphate in excess of that required to reduce the chromium, and titrating back with potassium permanganate solution. The chromium is then again oxidised to chromic acid by boiling with potassium permanganate, and the filtered liquid is titrated for nickel as before, after adding sodium pyrophosphate and ammonia.374 THE ANALYST.The advantage of using sodium pyrophosphate instead of citric acid to keep the iron in solution is stated to lie in the fact that the end-point is more easily seen. A. G. L. The Estimation of Tungsten and Chromium in Steel. F. W. Hinrichsen and L. Wolter. (Zeits. Anorg. Chem., 1908, 59, 183-197.)-The authors show that, in the absence of chromium, Von Knorre’s benzidine method (ANALYST, 1(307,32, 131) gives good results for tungsten in steel. If chromium also is present, however, the results obtained for tungsten are low if the chromium, which invariably contaminates the precipitate, is estimated and deducted.The presence of tungsten also interferes with the estimation of chromium by precipitation with ammonia, high results being obtained. For such steels a modification of the Berzelius method gives good results, the procedure being as follows : Two grams of the sample are oxidised by repeated evaporation with nitric acid. The residue is ignited and fused with 16 grams of sodium peroxide. The melt is dissolved in water, the solution filtered through asbestos, and the filtrate evaporated to about 150 C.C. The separated silica is filtered off on aRbestos, and the filtrate made up to 250 C.C. ; 50 C.C. of the filtrate are then acidified with nitric acid, made alkaline with ammonia, heated to boiling, and precipitated with mercurous nitrate.The washed precipitate is ignited, treated with hydrofluoric and sulphuric acids to remove silica, and weighed as WO, + Cr,O,,. The mixed oxides are then fused with sodium carbonate and a little potassiuni carbonate, the aqueous solution of the melt is evaporated with sulphuric acid to remove nitrous acid, and in the solution obtained the chromium is estimated iodometrically, tungstic acid being kept in solution by the addition of sodiuni phosphate, so as not to obscure the end-point. A. G. L. Separation of Tungsten from Chromium and Estimation of Tungsten in Steel containing Chromium. G. v. Knorre. (Zeits. anal. Chem., 1908, 47, 337-366.)-The author agrees with Hinrichsen’s conclusion (Stnhl. u. Eisen, 1907, No. 40) that his own benzidine method for estimating tungsten in steel (ANALYST, 1907, 32, 131) gives unsatisfactory results in the presence of chromium.He also shows that Rose’s method, in which chromic hydroxide is separated from tungstic acid by means of ammonia, is useless, and that the modification oi Berzelius’s mercurous nitrate method proposed by Hinrichsen is too tedious. He has now worked out the following modification of the benzidine method for the case of steels containing chromium and tungsten, the results obtained being very exact : From 1.5 to G grams of the steel are heated in a flask with dilute hydrochloric acid until the action ceases. The liquid is nearly neutralised with a solution of sodium hydroxide, about 10 C.C. of -& sulphuric acid and 30 to GO C.C. of benzidine solution (containing 20 grams of benzidine and 25 C.C.of fuming hydrochloric acid per litre) are added, and the liquid is well cooled. After standing for twenty minutes, the mixture of undissolved metal, benzidine tungstate, and benzidine sulphate (which last renders filtration easy) is filtered off, washed with dilute benzidine solutiori, and ignited. The oxides obtained are fused with sodium carbonate, the melt extracted with water, and the insoluble iron oxide washed with dilute sodiumTHE ANALYST. 375 carbonate solution. The alkaline filtrate ie then rendered just acid with hydro- chloric acid, using methyl-orange as indicator. If much chromium is present, the liquid is boiled for some time, to convert the tungstic acid into metatungstic acid, after which it is cooled, treated with sulphur dioxide, to reduce the chromic acid, and precipitated with an excess of benzidine solution.The tungstic oxide obtained after filtration and ignition of the benzidine metatungstate is quite free from chromium. If only a little chromium is present, the neutralised solution of the melt may be treated with 10 C.C. of & sulphuric acid and about 0.4 gram of hydroxylamine hydrochloride ; the whole is mixed and at once precipitated with an excess of benzidine solution, the benzidine tungstate being filtered off, washed, and ignited as above. The presence of hydroxylamine prevents the oxidising action of the chromate on the bemidine, but the latter must be added to the liquid before the chromate has been reduced by the hydroxylamine. The second procedure is quicker than the first, but the precipitate may be contaminated with traces of chromium.9. G. L. The Influence of Fine Grinding on the Water and Ferrous-Iron Content of Minerals and Rocks. W. F. Hillebrand. (Jozm. Anzer. Chem SOC., 1908, 30, 1120-1131.)-Confirrning the work of Nauzelius (Soeriges Geol. Undcrs. Arsbok, 1907, 1, No. 3) and others, the author shows that many minerals take up hygroscopic water and undergo extensive oxidation when subjected to prolonged fine grinding before analysis, The oxidation appears to be due chiefly to local heating of the particles in presence of air, and is greatest when mechanical grinders are employed. The author recommends that the portions of minerals used for fusions should simply be crushed, without grinding, so as to pass a sieve with 80 meshes to the inch, and that, if a finer powder is used for separate estimations, a moisture estimation should be carried out on it, and a correction applied.For alkalis, the portion may generally be ground after weighing. For ferrous iron, the portion may be ground under alcohol before weighing, or, preferably, the coarse powder may be decomposed as far as possible by a short boiling, in an atmosphere of carbon dioxide, with hydro- fluoric and sulphuric acids, and any undecomposed residue left after the titration ground under water and again treated. Pratt’s method appears to give more exact results than Cooke’s (United States Geological Swuey, Bull. 305, p. 138). A. G. L. Colorimetric Estimation of Phosphorus in Steel. G.Misson. (Chew,. ZeLt., 1908, 32, 633.)-Results accurate to about 0-005 per cent. of phosphorus are obtained in ten minutes by the following method : One gram of the steel is dissolved in 20 C.C. of nitric acid (specific gravity 1.2) in a 100 C.C. flask, provided with a mark at 80 C.C. The solution is boiled, 10 C.C. of a 0.8 per cent. solution of potassium permanganate are added, and the solution is again boiled for a few seconds. Ten C.C. of a hydrogen peroxide solution, prepared by gradually adding 40 grams of sodium peroxide to a well-cooled mixture of 100 C.C. of nitric acid and 900 C.C. of water, are then added, followed by 10 C.C. of a solution of ammoniuin vanadate, containing 2.345 grams of the salt and 20 C.C. of nitric acid per litre, and the liquid376 THE ANALYST.again boiled until the hydrogen peroxide is completely decomposed. The liquid is diluted to 60 or 65 c.c., cooled, 10 C.C. of a 10 per cent. ammonium molybdate solution are added, and the solution is diluted to the 80 C.C. mark. The colour is then compared with that of a standard steel, preferably in Eggertz tubes. The colour obtained is due to a compound of the probable formula : (NH,),PO,,(NH,)VO,, 16Mo0,. The standards keep well for about fourteen days. A. G. L. Volumetric Estimation of Phosphoric Acid in Superphosphate. S. Kohn. (ChenL. Zeit., 1908, 32, 475-476.)-Twenty grams of the superphosphate are extracted with 1,000 C.C. of water; 50 C.C. of the solution are filtered, diluted with water to 350 c.c., and titrated with standard sodium hydroxide solution free from carbonate, methyl orange being used as indicator.The quantity of alkali used corresponds to the free phosphoric acid. A considerable excess of a neutral solution of calcium chloride and a little phenolphthalein are then added, and the titration continued until a distinct red colour is obtained. The quantity of alkali so used corresponds to the combined phosphoric acid, according to the equation : CaH,P,O,+ 2CaC,I, + 4NaOH = Ca,P,Os + 4NaCl+ 4H,O. The results obtained by the new method agree within about 0.3 per cent. with those given by the citrate method. The method cannot be applied to mixed fertilisers containipg ammonium salts. A. G. L. Examination and Valuation of Red Lead. P. Beck. (Zeit. anal. Chem., 1908, 47, 465-492.)-Many reducing-agents may be used to render red lead com- pletely soluble in, e.y., dilute nitric acid, such as sugar, oxalic acid, lactic acid (cf.ANALYST, 1907, 32, 395), methyl alcohol, formaldehyde, glycerim, phenylhydrazine, hydroxylamine salts, etc., and especially hydrogen peroxide. Thus, for 100 grams of red lead, from 80 to 100 C.C. of nitric acid (specific gravity P4j with 15 to 20 C.C. of hydrogen peroxide (90 per cent.) are required, whilst the dissolved lead may be separated by the addition of 35 C.C. of strong sulphuric acid previously diluted to 100 C.C. When the decom- position of the red lead is complete, the liquid is diluted to 500 c.c., and kept boiling for an hour, to destroy the excess of hydrogeD peroxide and facilitate the separation of iinsoluble constituents.After standing for some hours in a moderately warm place, the insoluble matter may be filtered off, and the filtrate tested for impurities after separation of the lead as sulphate. In estimating the barium sulphate it is sufficient for technical purposes to dry and weigh the insoluble matter. The results are only approximate, however, since the37 7 THE ANALYST. barium sulphate is never pure, and also dissolves to a considerable extent in the nitric acid. For the estimation of the lead peroxide Topf's method (Zeit. a d . Chenz., 1887, 26, 296) gives the most reliable results, since, owing to the large quantities of the sample that may be used, the chance of error is reduced. When only a small quantity is available, however, distillation with hydrochloric acid in a current of carbon dioxide is preferable, especially for works' laboratories.From 0.3 to 0-4 gram of red lead is placed in a distillation flask, c, d, provided with a tubulure, a, closed by means of a rubber stopper, b, through which passes a glass tube, c, reaching nearly to the bottom, and having at cl a disc-like projection to protect the lower part of the stopper. The open end of the flask is connected by means of rubber tubing with two absorption tubes (not shown), each of which contains 35 C.C. of a 5 per cent. solution of potassium iodide (free from iodate). The flask, e , contains sufficient (100 c.c.) hydrochloric acid of specific gravity 1.14 to 1-15 to decompose the whole of the red lead, and is connected by indiarubber tubing at f with the distillation flask.The hydrochloric acid is forced into the latter by the pressure of the purified carbon dioxide entering the upper flask, the distillation flask being then cautiously heated, a slow current of the gas passed through the apparatus during the distillation, and a more rapid current for ten minutes after all the chlorine has been driven over. The contents of the absorption tubes are then washed into a beaker, solid sodium bicarbonate added to neutralise the free acid, and the liquid diluted to about 750 C.C. and titrated with i>G sodium arsenite solution, with starch solution (or preferably zinc-iodide starch solution) as indicator. The advantages of this method over the original Bunsen-Yresenius method are that there is no loss of chlorine, that the latter is completely expelled by the carbon dioxide, and that there is no frothing.The results are closely concordant, and the chlorine does not act upon the rubber to any appreciable extent in the presence of the carbon dioxide. C. A. 11. Estimation of Lead in Alloys. W. Elborne and C. M. Warren. (CheViL. Nezus, 1908, 98, 1.)-The following simple method is applicable to all lead alloys soluble in the solvent used, and is based on the insolubility of lead chloride in absolute alcohol, the chlorides of antimony, tin, arsenic, bismuth, iron, nickel, cobalt, manganese, zinc, copper, cadmium, aluminium, and magnesium being soluble. One gram of the alloy in fine shavings is treated with 50 C.C. of concentrated hydrochloric acid, and a slow current of chlorine gas, obtained by the interaction of manganese peroxide and strong hydrochloric acid in the cold, passed through the cold liquid for twenty-four hours, the liquid being occasionally agitated.This treatment readily dissolves type- and stereo-metals. More refractory alloys will dissolve on boiling the solution and repeating the treatment with chlorine. When solution is complete, the liquid is evaporated to dryness on a water-bath, and the cold residue extracted with absolute alcohol by stirring the mixture and immediately pouring off the supernatant liquid through a dry weighed filter-paper. This extraction is repeated three or four times, allowing five minutes for the final extraction with alcohol. The residue and filter-paper containing the lead chloride are then dried at 100" C.for three hours and weighed. A. 1%. T.378 THE ANALYST. New Method of Separating Lithium Chloride from the Chlorides of the other Alkalis, and from the Chloride of Barium. L. Kahlenberg and F. C. Krauskopf. (Journ. Amw. Chem. SOC., 1908, 30, 1104-1115.)-The authors show that the chlorides of sodium, potassium, rubidium, caesium, and barium are practically insoluble in pyridine containing less than 5 per cent. of water, while lithium chloride is quite soluble even in pure pyridine. The chlorides of strontium, calcium, and magnesium occupy an intermediate position. In order to separate lithium chloride from the first-named chlorides, the aqueous solution is evaporated just to dryness, and the residue, which should not weigh more than 2 grams, is treated with 25 C.C.of boiling pyridine for a few minutes, any large crystals being broken up with a glass rod. The liquid is then decanted through a small filter, the residue washed twice with a little hot pyridine, dissolved in hot water, the solution again evaporated, and the extraction repeated a second, and, if necessary, a third time. From the filtrates the pyridine is removed by distillation, the lithium converted into anhydrous sulphate, and weighed. The method gives good results. A. G. L. The Use of Organic Acids and Anhydrides as Standards in Alkalimetry, and a Comparison between Swecinic Acid, Arsenious Oxide, and Silver Chloride as Standards in Iodometry and Alkalimetry. J. K. Phelps and L. H. Weed. (Zeits. Anoiy. Chem., 1908, 59, 114-119, 120-12G.)-Continuing their previous work on the use of succinic acid as a standard for volumetric work (ANALYST, 1907, 32, 230), the authors now show that, in titrating sodium hydroxide solutions with phenolphthalein as indicator, succinic acid and anhydride, malonic acid, benzoic acid, and phthalic acid and anhydride all give results as accurate a s those obtained by the use of hydrochloric acid standardised by means of silver nitrate, or arsenious acid (by the potassium iodide and iodate method).On account of their easy solubility in water, succinic acid and malonic acid are the most convenient to use of the organic standards. They are readily obtained by hydrolysis of their esters with water acidulated with nitric acid, and crystallisation of the solution obtained.Crystals of succinic acid can be kept for a year over sulphuric acid or calcium chloride without any succinic anhydride being formed. A. G. L. The Application of the Cobaltic Nitrite Method to the Estimation of Potassium in Soils. W. A. Drushel. (Zcits. Anory. Chem., 1908, 59,97-101.)-The dried soil is treated on the water-bath with an excess of hydrochloric acid. The solution is filtered and evaporated to dryness. Bases are then removed wit;h sodium carbonate, or arnmonia, and ammonium oxalate. Tlie filtrate is again evaporated to dryness, and the residue gently ignited. The alkalis left are dissolved in a little water, acidified with a few drops of acetic acid, and evaporated to pastiness with excess of a solution of sodium cobaltic nitrite. The mass is stirred with cold water, and filtered through asbestos ; the precipitate is washed with sodium chloride solution, and then treated with an excess of hot dilute standard potassium perrnanganate solution.The excess of the latter is destroyed by standard oxalic acid solution, the excess of which is exactly titrated with potassium permanganate solution. (Clf. ANALYST, 1908, 35,) A. G. L.THE ANALYST. 379 A Short Volumetric Method for the Estimation of Sulphuric Acid. T. Cooksey. (Proc. Boy. SOC., New South Wales, 1908.)-The method proposed depends on the volumetric estimation of the excess of barium ohloride left in the solution after precipitation of the sulphuric acid as barium sulphate. The solution containing the sulphuric acid to be estimated should be free from bases or metals other than the fixed alkalis, and must not contain carbonates, phosphates, silicates, or borates. Any free acidity is neutralised by the addition of sodium hydroxide solution, using phenolphthalein as indicator, and the solution is then treated with an excess of neutral stsndardised barium chloride solution, a quantity of alcohol equal to one-half the volume of the final total solution being also added. After the addition of a little more phenolphthalein, the excess of the barium chloride is titrated back with standardised sodium carbonate solution ; the solution is stirred constantly during the titration, and the end-point is taken when the pink coloration obtained is permanent.The addition of the alcohol causes the precipitated barium carbonate to settle rapidly, and enables the end-point of the titration to be observed sharply and distinctly. The difference between the quantity of barium chloride added and that found by the titration is a measnre of the sulphuric acid present. I n the estimation of sulphuric acid (sulphates) in a solution containing magnesium or other metals, it is advisable to precipitate these by the addition of a mixture of potassium hydroxide and potassium carbonate, filter off the precipitate, and carry out the estimation of the sulphate on the filtrate. Calcium, and possibly strontium, can also be estimated by titration with sodium carbonate solution, if alcohol be added to the solution. The solution containing the calcium salt, and free from carbonates, borates, phosphates, and silicates, is rendered neutral to phenolphthalein, and is then titrated with standardised sodium carbonate solution, small quantities of alcohol being added from time to time with constant stirring, until the proportion of spirit in the mixture at the end of the titration is about one-half of the whole. If sulphates are not present, the whole of the alcohol may be added at the beginning of the estimation ; otherwise, it must be added gradually so as not to precipitate calcium sulphate. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9083300369

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 379 APPARATUS, ETC. The Autolysator : Apparatus Tor the Automatic Estimation of Carbon Dioxide. C. A. Keane and H. Burrows. (Joa~m. SOC. Chenz. Ind., 1908, 27, 608-611.)-The economic importance of the fullest possible control of the combustion of fuel has led to the construction of a number of forms of automatic apparatus for the estimation of carbon dioxide in furnace gases, and it is now recognised that the best plan is to obtain frequent analyses at short intervals. The apparatus giving the most accurate results are those in which the carbon dioxide is determined by an absorption method. In the ‘‘ Autolysator,” the gas to be analysed is drawn by water suction of constant pressure through two similar capillary tubes, each of which is connected with a manometer. A constant flow of gas, carefully regulated, is obtained through the two tubes, and the manometer readings are in each case the same in the absence of any absorbable constituent.Between the two capillary tubes absorption-vessels containing soda-lime are interposed, and the removal in these380 THE ANALYST. vessels of the carbon dioxide causes a difference in the respective pressures, as recorded on the manometers, and thus a means is obtained of determining the presence and amount of carbon dioxide in the furnace gases. Dust and aqueous vapour are removed from the gas before it passes on to the manometer and absorbing- vessels. A recorder is attached to the apparatus, on which the readings of the manometer, showing the amount of absorbed gas, are automatically traced out.The " Autolysator '' gives accurate results when tested against actual volumetric methods in the laboratory, and in works' tests the results obtained by it agree closely with those given by the '' Ados " automatic recorder, A. R. T. New Apparatus for the Determination of the Specific Gravity of Portland Cement. P. Philosophoff. ( C h e m Zeit., 1908, 32, 685.)-The apparatus consists of a conical glass vessel provided with a ground-in neck graduated in & C.C. (from 0 to 2 c.c.), and closed by a stopper carrying a narrow glass tube. This tube is connected by means of a long rubber tube with a second narrow glass tube inserted in the stopper of a burette 0, the jet of which is connected by a short rubber joint with a capillary tube B, which terminates about 0.5 cm.above the bottom of the conical glass vessel. The cement is weighed out in the vessel itself, which for this purpose is provided with a glass stopper (not shown) t o replace the neck A. The apparatus then being connected as above, light petroleum is run into the conical vessel from the burette to any point in the neck between the 0 and 2 C.C. graduations. The volume of the empty vessel having been ascertained in a preliminary experiment, the specific gravity is calculated as usual. L A. G. L. b c Water-Pump with Automatic Non-Return Valve. d (Cham. Zeit., 1908, 32, 542.)--A ground-glass plate, cl, is fitted below the end of the tube c , and is supported by the con- striction on the outer tube, b. The water enters at the top of the apparatus, 20, and passes downwards between the walls n and b ; should the water-supply be interrupted, the air-pressure causes the glass plate to be pressed against the bottom of the tube c, closing the hole 0, so that water cannot be drawn over into the vessel from which the air is being exhausted. w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9083300379

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST- 381 PARLIAMENTARY REPORT. ROYAL COMMISSION ON WHISKY AND OTHER POTABLE SPIRITS, INTERIM REPOHT (CD. 4180). THE Commissioners are : Lord James of Hereford ; L. N. Guillemard, Esq., C.B. ; Dr. W. E. Adeney ; Dr. T. R. Bradford, F.R.S. ; Dr. H. T. Brown, F.R.S. ; Dr. G. S. Bucbanan, Inspector of Foods to the Local Government Board; Dr. J. Y. Buchanan, F.R.S. ; and Dr. A. B. Cushny, F.R.S. (Secretary, A. V. Symonds, Esq.). The scope of the inquiry was whether, in the general interest of the consumer, or in the interest of the public health, or otherwise, it is desirable- (a) To place restrictions upon the materials or the processes which may be used in the manufacture or preparation in the United Kingdom of Scotch whisky, Irish whisky, or any spirit to which the term ( b ) To require declarations to be made as to the materials, processes of manufacture or preparation, or age of any such spirit ; (c) To require a minimum period during which any such spirit should be matured in bond ; and ( d ) To extend any requirements of the kind mentioned in the two sub- divisions immediately preceding to any such spirit imported into the United Kingdom.whisky ” may be applied as a trade description ; The following conclusions have been arrived at : 1. That no restrictions should be placed upon the processes of, or apparatus used in, the distillation of any spirit to which the term “ whisky ” may be applied as a trade description. 2. That the term ‘‘ whisky” having been recognised in the past as applicable to a potable spirit manufactured from (1) malt, or (2) malt and unmalted barley or other cereals, the application of the term ‘( whisky ” should not be denied to the product manufactured from such materials. The questions of the advisability or otherwise of attaching special significance to particular designations, such as ‘‘ Scotch whisky,” “ Irish whisky,” ‘‘ grain whisky,” and malt whisky,” of placing restrictions upon the use of such designations as trade descriptions, or of requiring such designations to be used in connection with the sale of whisky, are reserved for further consideration.

ISSN:0003-2654    

DOI:10.1039/AN9083300381

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

382 THE ANALYST. LOCAL GOVERNMENT BOARD REPORT. On Preservatives in Meat Foods packed in Cans or Glass. A. W. J. MacFadden. (Reports of Inspector of Foods, No. 6, 1908, 1-37.)-During the year 1906 samples of canned and glass-packed meats were examined by a large number of Public Analysts throughout the country, and their reports were submitted to the Local Government Board. From these reports it is seen that over 19 per cent. of the samples contained chemical preservatives other than salt and saltpetre, and 14 per cent. contained boron compounds. As, with certain possible exceptions, there should be no need for the addition of preservatives to this class of goods, nor should the meat used have been preserved before canning, the Board decided to make some inquiries into the oircumstances which lead to the presence of preservatives in canned meats, etc.As regards the presence of boron compounds in American canned meats, it is considered that the finding of boron compounds in a food which can be satisfactorily sterilised by the use of heat, and sealed up hermetically, indicates that the materials were in such a state, or were kept under such conditions, as to lead the canner to believe that the addition of a preservative was necessary to prevent decomposition until the meat could be safely canned. Suggestions of this kind were not admitted by any of the American representatives who were interviewed ; they offered explana- fions for the occurrence of small quantities of boric acid in canned meats, such as accidental contamination of the cauldrons by some of the pickling liquids, feeding the cattle on pastures containing boron deposits, etc.The United States Meac Inspection Act of 1906 prohibits the use of artificial preservatives in meat-food products. Boric acid has been found in large amounts in canned meats of British manufacture, as the result of eniployiug meats imported from abroad in this preservative. Since the passing of the Ynited States Meat Inspection Act, the use of boron compounds in hams and bacon sent to this country is said to have been confined to eyternal application as a packing material. I t is said that this use of boric acid is not objectionable, provided that the amount of preservative absorbed by the meat is not excessive; but it is pointed out that some manufacturers dispense with its use.Imported hams and bacon can be obtained in British markets which are free from preservative. The amount of boric acid in some samples of potted meats, which were mixtures of meat and farinaceous matter, was larger than is ever likely to be found in raw material of the kind above mentioned, and could only have been deliberately added in the course of manufacture. The use of chemicai preserva- tives is considered to be especially undesirable in meat foods packed in glass. There appears to be no difficulty in sterilising such articles of food, or in hermetically closing them. Grgater care in their preparation and greater cleanliness are required than in the case of canned goods, which, added to the fact that the contents are more or less capable of inspection, renders them unlikely to contain any gross contamination.It is considered desirable that steps should be taken that specified chemical preservatives (boron compounds, sulphites and preparations of sulphurous acid, benzoic acid, and formalin) should not be used in the preparation of canned meats intended for consumption i n this country. All cans, etc., should bear a, label giving the name of the manufacturer. I n many cases the origin of tins of meat cannot be traced further than the middleman or importer. and it would be worth attention to arrive at a reasonable maximum limit of permissible starchy matter in specified canned foods. In the case of sausages, it is considered that a limit of 0.25 per cent. of boric acid would probably be ample to meet legitimate trade requirements, and it The results of the inquiries are embodied in this report.THE ANALYST. 383 is a, matter for consideration whether such addition should not be notified on a label attached to the sausages. Much of what has been said respecting the presence of boric acid in canned meats applies to the use of sulphites. The practice of using solutions of sulphurous acid or sulphites as a spray or wash, or for mixing with the meat, appears to be open to many abuses, and is generally undesirable. * a + * * * w. P. s.

ISSN:0003-2654    

DOI:10.1039/AN9083300382

出版商:RSC    

年代:1908

数据来源: RSC

摘要:

THE ANALYST. 383 REVIEWS. THE DETERMINATION OF RADICLES IN CAHBON COMPOUNDS. By DR. H. MEYER and Price 5s. 6d. net. The appearance of a third edition of this well-known little book will be welcomed by all those interested in the quantitative side of organic chemistry, a subject which, in spite of its importance, is frequently neglected in college courses of organic work. While the original form of the book has been retained, a considerable aniount of new material has been added in the form of an appendix. This consists mainly of notes and descriptions of new or improved methods of estimating hydroxyl, methoxyl, amino, azo, etc., groups, to which is added a selection of miscellaneous methods for the determinatjon of various individual substances. I t would perhaps have been better had the new material been placed under the original headings, instead of being formed into an appendix, which necessitates a number of cross references, and somewhat detracts from the compactness and utility of the book.Moreover, the selection of the “ IIiscellaneous Methods ” at the end of the volume leaves much to be desired on the score of completeness. There seems to be no real necessityfor the inclusion of these iniscellaneous methods, which have little in common with the main subject-matter of the book ; while, on the other hand, a more detailed account of several of the methods for the determination of radicles, such as the titration of azo groups by titanium trichloride, would have been welcome. The rather obscure equation on p. 79 for the conversion of the volume of nitrogen found by Benedikt and Strache’s method, into percentage of carbonyl oxygen, might with advantage have been replaced by a, simpler and more obvious calculation.With the exception of a few printer’s errors, more especially in the new portion, the book is commendably free from inaccuracies. There seems to be no reason, however, why the spellings ‘‘ glycerin ” and “ glycerol ” should both be adopted, or a certain method described as ‘‘ ingenuous.” The book presents in a small compass a clsmprehensive and up-to-date survey of the methods at present available for the determination of organic radicles, and should prove useful both to advanced students and to those engaged in research work, as the information it contains is of a kind that is not readily accessible.THE AXALYSIS OF ASHES AND ALLOYS. By L. PARRY. Price 5s. net. London : The The appearance of a, work on alloys and metal waste by the author, whose experience has been so largely associated with tin, antimony, lead, copper, zinc, and other metals in alloy, will be welcomed by all who have to deal with the somewhat complicated methods of analysis which have to be adopted. A considerable amount of technical experience and of knowledge as to the uses to which the material will be put, is necessary in deciding upon the method of analysis and in interpreting the result. Much information of great value for this purpose is included in the work, and the comparison of diflerent methods and the reasons for selecting 8 special method are fully set out.J. BISHOP TINGLE, Ph.D., F.C.S. New York : John Wiley and Sons. Third Edition, revised. London : Chapman and Hall. G. W. M.-W. Mining Joamtnl384 THE ANALYST, The work is divided into three sections: The first deals with the individual elements and the estimation of each in various classes of material; the second refers to the analysis of metal ashes, drosses, and general metallic waste ; while the third contains a useful summary relating to general matters, including the prepara- tion of standard solutions, etc. The work, which covers 143 pages, is thoroughly practical, and contains much new matter and many suggestions of value to the specialist. I t is, of course, only written for those whose work relates to metals and alloys, but it includes both the rough commercial and the more elaborate methods which are in use, and may be welcomed as an important addition to a special branch of metal analysis.I t is to be hoped that the next edition will be provided with a proper index, instead of the extremely brief table of contents which appears at the end of the book. G. T. H. -4 SYSTEMATIC INTRODUCTION TO ANALYTICAL CHEMISTRY : AN ELEMENTARY CLASS- BOOK. By A. F. Walden, M.A., and 13. Lambert, M.A. v+176 pp. J. Thornton and Son, Oxford; and Simpkin, Marshall, Hamilton, Kent and Co., London. 1908. 3s. 6d. This work is intended to furnish an elementary and a systematic introduction to the study of chemical analysie; but as the authors assume that the student is concerned only with single substances or simple salts, this limitation materially restricts the usefulness of the treatise as a text-book of analytical che’mistry. Tabular schemes of separation are omitted, and the student is left to construct his own (‘ tables,” because the authors consider that ‘‘ the blind, unintelligent use of tables is responsible for much, if not all, of the bad results commonly and rightly attributed to mere test-tubing.” But surely it is possible for the teacher and students of analytical chemistry to make a clear-sighted and intelligent use of the systematic schemes for analysis ; and when this is done the analytical group separations acquire a considerable educational value, and constitute an important branch of the study of general chemistry.Moreover, from the practical standpoint the elementary student should be encouraged to carry out analyses of easy mixtures long before he is in a position to compile his own methods of analysis.Such exercises, successfully effected, give the student confidence in his analytical powers, and furnish a welcome relief from the monotony of plodding through the reactions of individual acids and bases. The Introduction, which contains a clear exposition of the fundamental concep- tions of acids, bases, salts, equivalents, and valency, is followed by a chapter on the reactions of the common metallic radicals. The behaviour of the metal itself towards air, water, and acids is fully given, except in the case of magnesium ; and in this instance a reference to the action of nitric acid might have served to qualify the state- ment, on p.3, that “ i t is not possible to obtain hydrogen from it [nitric acid] by the action of any metal at all.” Probably owing to the circumstance that the separation of the metals is not dis- cussed, no mention is made of the interactions of potassium cyanide, and the salts of copper, cadmium, cobalt,, and nickel. Yet these important reactions should be known to students who are suiliciently advanced to deal with the tests for double cyanides, acetates, tartrates, etc. The acidic radicals are treated more fully, a series of the less commonly occurring acids being included. The instructions for dealing with an unknown substance and with insoluble substances are admirable, and the practical hints in connection with the blowpipe and dry tests merit careful attention, and would be very valuable not only in the examination of simple substances, but in qualitative work generally.G. T. M.384 THE ANALYST, The work is divided into three sections: The first deals with the individual elements and the estimation of each in various classes of material; the second refers to the analysis of metal ashes, drosses, and general metallic waste ; while the third contains a useful summary relating to general matters, including the prepara- tion of standard solutions, etc. The work, which covers 143 pages, is thoroughly practical, and contains much new matter and many suggestions of value to the specialist. I t is, of course, only written for those whose work relates to metals and alloys, but it includes both the rough commercial and the more elaborate methods which are in use, and may be welcomed as an important addition to a special branch of metal analysis. I t is to be hoped that the next edition will be provided with a proper index, instead of the extremely brief table of contents which appears at the end of the book.G. T. H. -4 SYSTEMATIC INTRODUCTION TO ANALYTICAL CHEMISTRY : AN ELEMENTARY CLASS- BOOK. By A. F. Walden, M.A., and 13. Lambert, M.A. v+176 pp. J. Thornton and Son, Oxford; and Simpkin, Marshall, Hamilton, Kent and Co., London. 1908. 3s. 6d. This work is intended to furnish an elementary and a systematic introduction to the study of chemical analysie; but as the authors assume that the student is concerned only with single substances or simple salts, this limitation materially restricts the usefulness of the treatise as a text-book of analytical che’mistry.Tabular schemes of separation are omitted, and the student is left to construct his own (‘ tables,” because the authors consider that ‘‘ the blind, unintelligent use of tables is responsible for much, if not all, of the bad results commonly and rightly attributed to mere test-tubing.” But surely it is possible for the teacher and students of analytical chemistry to make a clear-sighted and intelligent use of the systematic schemes for analysis ; and when this is done the analytical group separations acquire a considerable educational value, and constitute an important branch of the study of general chemistry. Moreover, from the practical standpoint the elementary student should be encouraged to carry out analyses of easy mixtures long before he is in a position to compile his own methods of analysis.Such exercises, successfully effected, give the student confidence in his analytical powers, and furnish a welcome relief from the monotony of plodding through the reactions of individual acids and bases. The Introduction, which contains a clear exposition of the fundamental concep- tions of acids, bases, salts, equivalents, and valency, is followed by a chapter on the reactions of the common metallic radicals. The behaviour of the metal itself towards air, water, and acids is fully given, except in the case of magnesium ; and in this instance a reference to the action of nitric acid might have served to qualify the state- ment, on p. 3, that “ i t is not possible to obtain hydrogen from it [nitric acid] by the action of any metal at all.” Probably owing to the circumstance that the separation of the metals is not dis- cussed, no mention is made of the interactions of potassium cyanide, and the salts of copper, cadmium, cobalt,, and nickel. Yet these important reactions should be known to students who are suiliciently advanced to deal with the tests for double cyanides, acetates, tartrates, etc. The acidic radicals are treated more fully, a series of the less commonly occurring acids being included. The instructions for dealing with an unknown substance and with insoluble substances are admirable, and the practical hints in connection with the blowpipe and dry tests merit careful attention, and would be very valuable not only in the examination of simple substances, but in qualitative work generally. G. T. M.

ISSN:0003-2654    

DOI:10.1039/AN9083300383

出版商:RSC    

年代:1908

数据来源: RSC