摘要:

Sept., 19501 DETERMINATION OF LE-ID IN BRONZES 473 Electrolytic Determination of Bismuth BY GEORGE NORWITZ SuNoPsIs-An accurate electrolytic method for the determination of bismuth is described. The bismuth is electrolysed from a perchloric acid solution containing hydrazine sulphate. X preliminary separation of bismuth prior to the electrolysis is usually necessary. THE methods previously proposed for the electrolytic determination of bismuth are not entirely adequate. Deposition at constant current has not proved satisfactory because of the difficulty of obtaining adherent deposits and complete deposition.* p9 Deposition of bismuth at controlled potentiall y 2 j 6 $ y 7 is an accurate method but requires apparatus that at present is available to few laboratories. An investigation by the author on the deposition of bismuth from various media resulted in the development of a constant-current method that has proved satisfactory. In this method the bismuth is electrolysed from a perchloric acid solution containing hydrazine sulphate.The latter reagent, which was found to ensure good electro-deposition of the bismuth and to prevent deposition of the bismuth on the474 NORWITZ : ELECTROLYTIC DETERMIN.4TION OF BISMUTH [Vol. 75 anode, has been recommended by Kny-Joness for the determination of bismuth at controlled potential using a sulphuric - nitric acid medium. With constant current, the use of hydrazine sulphate with a sulphuric - nitric acid medium, a sulphuric acid medium or a nitric acid medium was not successful. EXPERIMENTAL Various amounts of pure metallic bismuth were dissolved in 10 ml.of 70 per cent. nitric acid. Ten millilitres of 70 per cent. perchloric acid were added and the solutions evaporated until strong fumes of perchloric acid were evolved with the cover lids ajar. The solutions were diluted to 190 ml. with water, and 5 ml, of a saturated solution of hydrazine sulphate were added. The solutions were electrolysed at 1 ampere for 1 hour using tared platinum gauze cathodes, 60mm. in height and 50mm. in diameter, and platinum spiral anodes. During the electrolysis the solutions were stirred. The cathodes were immersed in water and then in alcohol, dried at 105” C. for 3 minutes, cooled and weighed. The results obtained for bismuth are shown in Table I. TABLE I RESULTS FOR BISMUTH IN BISMUTH METAL Bismuth present, g.0~0100* 0-0100* 0-0500* 0-0500* 0~1000 0~1000 0-2000 0.2000 1~0000 1~0000 Bismuth found, g. 0*0101 0.0103 0.0496 0,0502 0.0997 0,0996 0.2004 0.1999 1.0002 1.0006 * Aliquots of standard bismuth nitrate solution used. Various amounts of bismuth were dissolved in 10ml. of 70 per cent. nitric acid and an oxychloride precipitation made for the bismuth. The bismuth oxychloride precipitate was filtered, the paper and precipitate dissolved in 15ml. of 70 per cent. nitric acid and 10ml. of 70 per cent. perchloric acid and the solutions evaporated to strong fumes of perchloric acid. The solutions were diluted, hydrazine sulphate was added and the bismuth electrolysed as above. The results obtained are shown in Table 11. TABLE I1 RESULTS FOR BISMUTH AFTER PRELIMINARY SEPARATIOK OF THE BISMUTH AS THE OXYCHLORIDE Bismuth present, ,.5- 0~0100* 0.0 1 oo* 0-0500* 0*0500* 0~1000 0.1000 0.2000 0-2000 0-5000 0-5000 Bismuth found, g. 0.0103 0~0100 0.0497 0.0498 0*1001 0.0997 0.2006 0.2001 0.5003 0.4996 * Aliquots of standard bismuth nitrate solution used. DISCUSSION OF RESULTS In view of the scarcity of good methods for determining b i s m ~ t h , ~ the proposed electro- lytic method should have considerable application. Because of the variable composition of the precipitate the weighing of bismuth as bismuth oxychloride “is permissable only when a few milligrams of bismuth is involved.”3Sept., 19501 NORWITZ : ELECTROLYTIC DETERMINATION OF BISMUTH 475 A preliminary separation of the bismuth is normally necessary, as copper, silver, lead, mercury, cadmium, tin, antimony and arsenic will deposit with the bismuth. For this preliminary separation the oxybromide, sulphide, or carbonate methods may be used as well as the oxychloride method. Tin, antimony and arsenic may be volatilised with hydrobromic acid. 1. 2. 3. 4. 5. 6. 7. 8. 9. REFERENCES Collin, E. &I., Analyst, 1929, 54, 654. Diehl, H., “Electrochemical Analysis with Graded Cathode Potential Control,” G. Frederick Hillebrand, W. F., and Lundell, G. E. F., “Applied Inorganic Analysis,” John VT‘iley & Sons, Kny-Jones, F. C., AIzaZyst, 1939, 64, 172. - Ibid., 1939, 64, 575. - Ibid., 1041, 66, 101. Sand, H. J. S., J . Chem. SOL, 1907, 91, 373. Willard, H. H., and Diehl, H., “Advanced Quantitative Analysis,” D. Van Nostrand Co., New Smith Chemical Co., Columbus, Ohio, 1948, p. 42. New York, 1929, p. 189. - Ibid., p. 192. York, 1943, p. 356. 3363 RIDGE AVENUE PHILADELPHIA 32, PA. April, 1950

ISSN:0003-2654    

DOI:10.1039/AN9507500473

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

Sept., 19501 The NORWITZ : ELECTROLYTIC DETERMINATION OF BISMUTH Colorimetric Determination of Impurities 475 in Titanium Metal Iron and Manganese BY J. A. CORBETT SYNoPsIs-The colorinietrk methods for the determination of iron by- thiocyanate and for manganese by oxidation to permanganate are applied to the direct determination of these metals in metallic titanium, and the conditions for their adaptation to the photo-electric absorptiometer are specified. The procedures described are applicable to amounts below 2.0 per cent. for both metals, with a precision of f 2 per cent. for iron and & 1.0 per cent. for manganese. METHODS have been developed for the estimation of small amounts of iron and manganese in titanium metal. Iron is estimated by the coloured thiocyanate - iron complex, and manganese by oxidation to permanganate with potassium periodate, the intensity of the colours being measured in a photo-electric absorptiometer. The methods cover the range 0 to 2-0 per cent.of iron and manganese, with an accuracy of % 2 per cent. for the iron content and f 1 per cent. for the manganese content. IRON The estimation of iron in the presence of titanium usually involves the precipitation of the iron with hydrogen sulphide in an alkaline tartrate solution. Iron can then be estimated by several available procedures. This paper is concerned with the estimation of iron directly in the presence of large amounts of titanium. Haywood and Woodl have reported methods for the estimation of iron in copper alloys, aluminium and magnesium.The methods are based upon the coloured thiocyanate complex, but vary with respect to acid concentration, amount of oxidising agent and concentration of thiocyanate, which depend upon the particular metal present. Thornton2 has outlined a colour comparison method for iron in titanium pigments, using thiocyanate, but Snel13 reports the formation of yellow titanium compounds with thiocyanates such as K,TiO(CNS), and K,Ti( CNS),.GH,O.476 CORBETT THE COLORIMETRIC DETERMIN.4TION OF [Vol. 75 EXPERIMENTAL INVESTIGATION APPARATUS- The photo-electric instrument used in this work consisted of a single photo-cell connected to a galvanometer with variable shunt resistors, and the light source was a tungsten-filament lamp operated from an accum~ilator.~ ACID COXCEXTRATION- Titanium is most satisfactorily dissolved in dilute sulphuric acid and hydrogen peroxide, the excess of hydrogen peroxide being finally destroyed in the hot sulphuric acid solution.Table I shows the effect of sulphuric acid concentration on the thiocyanate reaction in the presence of titanium and iron. In a 9 N sulphuric acid solution, the yellow colour of the titanium masked the iron complex. In an acid concentration of 0.7 N , however, the red colour of the iron complex was obtained, the titanium having no apparent effect. TABLE I EFFECT OF SULPHURIC ACID COXCENTRATION 100 ml. of solution containing 100 mg. of titanium, 0.12 mg. of iron and 2 per cent. of ammonium t hiocyanate Sulphuric acid Condition after concentration Colour standing for 16 minutes 0.7 N red faded 3 N red-brown faded 6 N red-brown faded 9 N yellow white precipitate 12N yellow white precipitate STABILITY OF COLOUR- As shown in Table I, the colour faded rapidly; therefore ammonium persulphate was Table I1 shows the effect of adding various amounts of added to stabilise the colour.ammonium persulphate, a large excess of which was found necessary to prevent fading. TABLE I1 STABILITY OF IRON - THIOCYANATE COMPLEX 100 ml. of solution in Ar sulphuric acid, containing 2 per cent. of ammonium thiocyanate and 0.12 mg. of iron nil Time Visual 10 visible 16 fading 20 25 35 46 Ammonium persulphate added A -l 0.1 g. per 100 ml. 0.2 g. per 100 ml. Extinction Extinction coefficient * coefficient * 0-41 0.356 0-40 0.358 0.36 0.360 0.366 0.355 0.35 0.355 0.34 0.360 * The reading on absorptiometer with green filter FILTERS- Ilford “Wide Band” filters were used in this work and Table I11 gives results with two different filters, No.623 (blue-green) with maximum transmission at 4950 A., and No. 624 (green) with maximum transmission at 5 2 0 0 ~ . Filter No. 623 is the more sensitive, and covers a satisfactory range of concentrations. RESULTS- Typical results of analyses of titanium metal, prepared by the Kroll process, and titanium - iron alloys are shown in Table IV. The results are compared with those obtained by the normal volumetric method, in which iron was titrated with potassium dichromate after separation from titanium as sulphide. In the absorptioinetric method 0.5-g. portionsSept., 19501 IMPVRITIES I N TITANIUM MET.4L TABLE I11 COMPARISON OF FILTERS Titanium present = 100 mg.per 100 rnl.; 4-crn. cell 477 Iron content, mg. per 100 ml. 0.05 0.105 0-13 0.15 0.18 0-21 0.23 0-2s Extinction coefficient A f > With filter No. 623 With filter No. 624 0.21 0.15 0.435 0-3 1 0.54 0.39 0-62 0.445 0.78 0.535 0-865 0.616 0.97 0.70 1.30 0.74 were used, and the solution of titanium in sulphuric acid was diluted to 100ml. and the colour was produced in 20-ml. aliquots of solution, as described in the method below. The estimation was performed in 1 hour, against 6 hours required for the volumetric procedure. TABLE 117 COMPARISOX OF RESULTS ORTAIKED BY ABSORPTIOMETRIC AKD YOLUMETRIC METHODS Material ABP - 40 mesh . . .. .\BP 100-250 mesh . . ABP -250 mesh . . .. -4HS alloy . ... . . AHT alloy . . .. .. AML alloy . . .. .. AMN alloy . . . . .. Iron found h I \ By absorptiometric By volumetric method, method, . . 0.160 0-150 . . 0.130 0-130 . . 0.230 0-230 . . 0.96 0-95 .. 2-02 2.03 .. 1.06 1.07 .. 2-06 2.06 70 % 0.148 0.130 0.233 0.955 2-03 1-07 2.06 NETHOD RE-4GENTS- SuZphuric acid-A solution of 300 ml. of 36 A' sulphuric acid diluted with water to 1 litre Ammonium thiocyanate-A 20 per cent. solution. Ammonium pevsulphate-A 2 per cent. solution. Hydrogen peroxide-A 1 O-volume soh tion. PROCEDURE- Transfer 0.5 g. of titanium (containing not more than 10 mg. of iron) to a 250-ml. squat beaker, add 30ml. of 30 per cent. sulphuric acid, and warm until the reaction-has ceased. Add hydrogen peroxide (10-volume solution) dropwise until the red-brown colour of the titanium complex is evident, and then evaporate until the solution is colourless and all the titanium is in solution (see Note 1, below).Cool and dilute to 60 ml. with water, and then boil the solution to dissolve any titanium salts. Re-cool and transfer to a 100-ml. standard flask and dilute to the mark. Transfer a 20-ml. aliquot to a 100-ml. standard flask and add 40 ml. of water, 10 ml. of 2 per cent. ammonium persulphate solution and 10 ml. of 20 per cent. ammonium thiocyanate solution. Dilute to 100 rnl. with water, mix, and allow the solution to stand for 15 minutes. Measure the absorption, using a cell of the correct size (see Note 2, below) and a blue-green filter of maximum tralisinission at 4960 A. Perform a blank determination on the reagents under the same conditions.478 CORBETT : THE COLORIMETRIC DETERMINATIOS OF [Vol.75 CALIBRATION GRAPH- Standard iron soZzctio.n--Dissolve 0.5 g. of pure iron in the minimum amount of sulphuric acid, add 3 ml. of hydrogen peroxide (10-volume solution), and evaporate to remove excess of hydrogen peroxide. Dilute the solution with water, and boil to dissolve 'the iron salts. Dilute to 1 litre; take 50 ml. of this solution and dilute to 500 ml. 1 ml. of this solution = 0.05 mg. of iron. Transfer 0 6 g . of titanium (iron-free or of known iron content) into a 250-ml. squat Measure 20-ml. aliquots into 100-ml. standard flasks and add to each a suitable amount Add water and reagents Perform Plot the extinc- beaker. of iron solution, to give the range of iron concentrations required.in the same order as in the method, and measure the absorption of each solution. a blank determination on the reagents and adjust the readings accordingly. tion coefficient against iron concentration. KOTES- which will not dissolve. Treat as in the method until the 100ml. of solution is obtained. 1. Prolonged fuming of the sulphuric acid will cause precipitation of titanium dioxide 2. The range of the cells is as follows- Range, Cell length, Yo cm . 0 t o 0.25 4 0 to 0.60 2 0 to 1.00 1 0 to 2.00 0.5 Results obtained are within &2 per cent. of the iron content. 3. The presence of appreciable amounts of silica or any other insoluble material will require the introduction of a filtration treatment, and will necessitate the examination of this material for the possible presence of iron.Silica may be estimated in this fraction. 4. For calibration in the range of 0 to 2.0 per cent. of iron, prepare a standard solution of greater iron concentration by dissolving 1 g. of iron by the method given above. This solution contains 0.10mg. of iron per ml., anti this will help to preserve the correct con- centration of acid. MANGANESE The separation of large amounts of titanium from manganese is an unsatisfactory procedure, owing to adsorption. Because of the convenience and speed with which manganese can be estimated in the presence of many other metals, a study was made of the prospects of a direct estimation in the presence of large amounts of titanium. Methods for the absorptiometric estimation of manganese in ferrous alloys, etc., usually depend upon the oxidation of the manganese to permanganic acid either with persulphate and silver nitrate, or with potassium periodate.Hough5 has stated that in the presence of titanium, manganese is not completely oxidised with persulphate, but oxidations with potassium periodate and sodium bismuthate are satisfactory. No figures for the amounts of titanium involved are given, but as the work referred to the analysis of rocks it may be assumed that the amounts were not large. EXPERIMENTAL INVESTIGATIOS POTASSIUM PERSULPHATE- Experiments with potassium persulphate and silver nitrate with 200 mg. of titanium and from 0.10 to 4.0 mg. of manganese in sulphuric acid solutions verified Hough's finding6 (see above). SODIUM BISMUTHATE- Guerin6 and the author have both found that in the presence of large amounts of titanium, manganese is not completely oxidised.Tests with 10 mg. of manganese in the presence of 500 mg. titanium gave 88.0 per cent. recovery of the manganese by the sodium bismuthate - ferrous sulphate titration method. This is to be the subject of a separate investigation.Sept., 19501 IMPURITIES I N TITANIUM METAL 479 POTASSI u M PE RIODATE- Table V gives absorptiometric readings on manganese solutions in the presence of titanium, compared with results from similar solutions containing no titanium. Manganese was oxidised with potassium periodate in a boiling sulphuric acid solution to which nitric acid had been added. TABLE TT EFFECT OF TITANIUM ON THE OXIDATION OF MANGANESE WITH POTASSIUM PERIODATE Manganese in 100 ml.of solution Extinction coefficient* A I -l In presence of 200 mg. Manganese, Cell length, of titanium Titanium absent mg. cm. 0.10 4 0.135 0.130 0.50 4 0.77 0.77 1.00 2 0.76 0.76 4.00 0-5 0.83 0.83 * IVith green filter. RESULTS- In Table VI results obtained with the absorptiometric method outlined below are com- pared with those from a method in which the titanium was precipitated with zinc oxide. Manganese was then estimated in the filtrate by the sodium bismuthate - ferrous sulphate titration or by an absorptiometric method. The direct method was performed in 1 hour. Table VII shows the results obtained with synthetic mixtures of titanic sulphate and manganese sulphate. TABLE VI COMPARISON OF DIRECT ABSORPTIOMETRIC METHOD WITH A SEPARATION METHOD Manganese found A I -l By absorptiometric By separation Material method, method, Yo Yo Titanium ABP .. .. . . . . 0.04 0-03 0-04 0-032 1-26 3-23 Titanium - manganese allay . . .. 1-25 1-22 TABLE VII SYNTHETIC SOLUTIONS CONTAINING 200 MG. OF TITASIUM Manganese added, *g* 0.25 0.60 1.50 2.50 3.50 4.00 Manganese recovered, mg- 0.248 0.498 1-505 2-50 3.50 3.98 METHOU REAGENTS- Sulphuric acid--,4 solution of 300 ml. of 36 iV sulphuric acid diluted with water to 1 litre. Potassium periodate-A solution of 5 g. of potassium periodate in 100 ml. of diluted Hydrogen peroxide-A 10-volume solution. Sodium nitrite-A 1 per cent. solution. Nitric acid-A solution of sp.gr. 1.40. nitric acid (1 : 4).480 CORBETI’ [T’ol. 75 PROCEDURE- Transfer 0.2 g.of titanium (containing not more than 4 mg. of manganese) to a 260-ml. squat beaker, add 30 ml. of 30 per cent. sulphuric acid and warm until the reaction has ceased. Add hydrogen peroxide (10-volume solution) dropwise until the red-brown colour of the titanium complex is evident, and then evaporate until colourless and all the titanium is in solution. Cool, add 20 ml. of water and 10 ml. of nitric acid (sp.gr. 1.40) ; then heat to boiling, and add 10ml. of potassium periodate solution. Boil the solution for 5 minutes and then cool. Measure the absorption using a cell of correct size and a green filter of maximum trans- mission at 5200 A. Destroy the colour in the remainder of the solution in the flask by drop- wise addition of 1 per cent. sodium nitrite solution, and measure the absorption of this “blank.” CALIBRATIOX- Manganese soZutioit-A solution of potassium pernianganate containing 0.2877 g.per litre gives a solution of which 1 ml. contains 0.05 per cent. of manganese calculated on a sample weight of 0.200 g. This solution is prepared with the usual precautions and standardised against 0.01 N sodium oxalate solution. Weigh 0.2-g. portions of titanium (manganese-free or of known manganese content) and add to each portion a suitable amount of manganese solution, and treat as in the method. The range of the method is as follows- Transfer to a 100-ml. standard flask and dilute to volume. Range, 0 to 0.25 0 to 0.60 0 to 1.00 0 to 2.00 YJ Cell length, cm. 4 2 1 0.5 The results obtained are within 4 1 per cent. of the manganese content. REFERENCE s 1. 2. 3. 4. 5. 6. Guerin, B . , private communication. Haywood, F. W., and Wood, A. A. R . , “Metalhirgical Analysis by Means of the Spekker Absorptio- Thornton, W. M., jun., “Titanium,” Amer. Chem. SOC. Monograph series No. 33, N.Y. Chemical Snell, F. O., and Snell, C. T., “Colorimetric Methods of Analysis,” Chapman & Hall, Ltd., London, Williams, C. H., Australiam Chem. Inst. J . and PYOC., 1946, 13, 224. Hough, G. H., Ind. G. Eng. Chetn., Anal. Ed., 1936, 7, 408. meter,” Adam Hilger, Ltd., London, 1944. Catalogue Co., 1927. 1936, Vol. I, p. 286. COMhlONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION PHYSICAL METALLURGY SECTIOX BAILLIEU LABORATORY UNIVERSITY OF -MELBOURNE February, 1960

ISSN:0003-2654    

DOI:10.1039/AN9507500475

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

Sept., 19501 JENKINS AND WEBB 481 The Use of Gelatin in the Determination of Silicon in Ferrous Alloys, Especially S ilicon-Rich Ferro-Alloys BY M. H. JENKINS AND J. A. V. WEBB SYNoPsIs-The precipitation of silica by means of gelatin and its application to silicon determinations on high-silicon alloys is discussed. Two methods have been devised. One involves the boiling of a sulphuric-acid extract of the melt; it gives results that are low, though possibly suitable for plant- operating requirements. The other involves a dehydration procedure prior to the precipitation o f silica by gelatin; it is as rapid as the first method and capable of giving a high degree of accuracy. IX order to overcome the drawbacks of the conventional dehydration methods for the deter- mination of silicon in steels, alloys and other materials, numerous workers1 929394+5$ have introduced modifications utilising the fact that colloidal solutions of glue, isinglass, gelatin and related substances cause silica to be precipitated from colloidal solutions of silicic acid.Attempts to apply this principle to silicon-rich ferro-alloys do not appear to be successful to date, and the purpose of this study was to apply it to this type of alloy. The most thorough investigations to date appear to be those of L. Weiss and H. SiegeP and K. L. we is^.^ Their papers cover not only the underlying principles, but also optimum experimental conditions, sources of error and application to a variety of materials, chiefly steels of different types. These two papers served as a basis for the work outlined below.EXPERIMENTAL The experimental work was divided into three parts, the application of the Weiss method for steels, carbonate fusions of pure silica, and sodium peroxide fusions of ferro-alloys. METHOD FOR STEELS Procedure-Dissolve 5 g . of steel in hydrochloric acid and add nitric acid dropwise until the ferrous chloride is oxidised. Adjust the acidity to 20 per cent. or more (by weight) of hydrochloric acid, and adjust the final volume to 100 to 150 ml. Boil for 10 minutes, add 10 ml. of concentrated hydrochloric acid, and adjust the temperature to 60" to 70" C. ; add 5 ml. of 2 per cent. gelatin solution dropwise, stirring vigorously all the time and for at least 1 minute after the addition, drawing as much air as possible into the solution. Allow the solution to stand for 5 minutes, dilute to double the volume, and filter.Proceed as in the usual gravimetric method. Rest&-The method was tested and the following conclusions were drawn- (a) For silica (SO2) concentrations below about 40 mg. per 100 ml., results tended to be low. Above this concentration, satisfactory results were obtained. With straight carbon steels containing 0.20, 0-29, 0.41, 1-59 and 1-91 per cent. of silicon, values of 0.14, 0.26, 0.41, 1.59 and 1.91 respectively were obtained, while with stainless steels, containing about 12 per cent. of chromium, and 0.12, 0.19, 0.38, 0.39, 0.48 and 0.72 per cent. of silicon, values of 0.07, 0.12, 0-38, 0-33, 060 and 0.75 per cent. of silicon were obtained. (b) For a concentration of 20 per cent. w/w of hydrochloric acid, all results tend to be low and an appreciably higher concentration is advisable.The above results were obtained by using a concentration of 26.5 g. of hydrochloric acid per 100 ml. of solution before boiling. ( c ) Other conditions prescribed by Weiss, namely replenishment of boiled-off acid, temperature adjustment and the standing period after gelatin addition were found to be essential. Increasing the standing period did not increase the accuracy of the results. USE OF SULPHURIC ACID- Further investigation showed that replacement of part of the hydrochloric acid by sulphuric acid had the advantages that a higher boiling temperature could be obtained, and sulphuric acid is non-volatile and cheap. With a slightly longer standing period, more accurate results for small amounts of silicon were obtained.With 5 g. of sample dissolved in 50 ml. of hydrochloric acid (2 + l), 50 ml. of sulphuric acid (1 + 1) added before boiling, and 15 ml. of hydrochloric acid after boiling and standing for 10 minutes before dilution, the482 following results were obtained: 0.18 per cent. of silicon on a mild steel of 0.20 per cent., and on stainless steels containing 0.12, 0.20, 0.39 per cent. of silicon, values obtained were 0.06, 0.22, 0-41 per cent. of silicon respectively. ACID-SOLUBLE FERRO-ALLOYS- The foregoing work provided the basis of a method for determining the silicon in acid-soluble ferro-alloys. Increasing the sulphuric acid concentration further gave better results and the following procedure was therefore adopted.Oxidise dropwise with a minimum of nitric acid. Cool and add 50 ml. of sulphuric acid (5 + 1). Boil for 15 minutes, add 20 ml. of water, and cool to 70” C. Add 15 ml. of a 2 per cent. solution of gelatin dropwise, stirring vigorously all the while and for 1 minute after the addition, allow the solution to stand for 15 minutes, dilute to double the volume, and allow to stand for 10 minutes to permit the precipitate to settle. Results obtained by this method (shown in Table 11) are slightly low, but are within the limits of accuracy usually required for routine determinations. The amount of silica found in the filtrate is approximately constant, and this may make it possible to use a correction factor. CARBONATE FUSIONS OF PURE SILICA Investigation of the carbonate fusions of pure silica, though not exhaustive, gave values for the silica recovery which were very low, when the conditions prescribed by the Weisses and Sieger were adhered to.It was difficult to maintain a sufficiently high acid concentration for gelatin precipitation and at the same time to dissolve the melt. Evaporation of the hydrochloric-acid extract gave rise to a hard crust of silica, which could not be removed by a rubber-tipped rod, on the sides of the beaker; this difficulty was also encountered by the Weisses and Sieger. This crust formed when the solution was boiled with high concentrations of hydrochloric acid; the results obtained were low. This difficulty did not arise in solutions in sulphuric acid, but the results by adding sulphuric acid to the slightly acid extract of the melt and boiling were still low.Increasing the standing time to as much as 2 hours did not increase the recovery of the silica. PEROXIDE FUSIONS OF FERROSILICONS AND SILICON-RICH ALLOYS The same difficulties encountered in the carbonate fusions of pure silica were found when peroxide fusions of ferrosilicons and silicon-rich alloys were investigated, and numerous modifications were applied. Finally, the procedure described below was tested and adopted. Fusions of the samples in the manner described below and treatment of the acidic extract of the melt by the method as described for acid-soluble alloys, but with doubling of the standing time, gave results which, although low, might be acceptable for rapid industrial analyses.The results obtained by this method are given in Table 11; the samples used in testing this and the following method are given in Table I. TABLE I DESCRIPTION OF SAMPLES USED JENKINS AND WEBB: THE USE OF GELATIN I N THE [Vol. 75 Procedztre-Dissolve 5 g. of alloy in 50 ml. of hydrochloric acid (sp.gr. 1.16). Filter and proceed as usual. Sample No. Description 1 2 3 4 5 U.S.A. National Bureau of Standards, Ferrosilicon 58 U.S.A. National Bureau of Standards, Ferrosilicon 59 U.S.A. National Bureau of Standards, Ferrochromium 64 British Chemical Standard, Ferrochromium 204 British Chemical Standard, Steel “J,” No. 160 Others Carefully prepared samples, analysed in replicate by Standard methods of analysis Better results than those in Table I1 were, however, obtained by a method which involves a single dehydration with sulphuric acid.A technique of dehydration was evolved which is comparatively rapid, and hardly lengthens the time taken for a determination. Con- sequently the idea of developing a precipitation method dispensing altogether with dehydration was abandoned. PROCEDURE- Mix a convenient weight of finely ground sample with ‘7 g. of flux in an ingot iron crucible, cover with 2 g. of flux and fuse over a suitable gas flame, observing the usual precautions.Sept., 19501 DETERMINATION CfF SILICON 483 For material containing less than 40 per cent. of silicon, fuse 1 g. of sample with sodium peroxide, and for material containing over 40 per cent. of silicon fuse 0.5 g. of sample with a mixture of equal parts of sodium peroxide and sodium carbonate. TABLE I1 PRECIPITATION OF SILICON WITHOUT PREVIOUS DEHYDRATION Sample No. 1 6 8 9 10 11 12 3 4 14-l 15t 5.t Material Ferrosilicon Ferrosilicon Ferrosilicon Ferrosilicon Weight of sample taken, €5 0-25 0.25 0-35 0.25 Ferrosilicon 1.0 Ferrosilicon 1.0 Silicomanganese 1.0 Silicomanganese 1.0 Silicochromium 1.0 Ferrochromium 1.5 Ferrochromium 1-5 Ferromanganese 5.0 Low carbon Ferrochromium Low carbon 5.0 Pig iron 5.0 Carbon steel 5.0 Silicon present, 75.6 % 72.59 72.47 50.00 16-10 12.87 17-48 16.39 20.76 2.05 1.01 3.09 2.36 2-69 0.09 Silicon found, % 76.77 75-41 75.60 75.48 72.54 72.63 72-44 72.54 72.26 71.92 49.83 49.98 50.0 49.61 49.98 15.98 12.80 17-51 17.30 17.23 16-35 20.84 2.09 1.10 3.06 3.06 2-33 2.33 2-66 2.66 0.08 Error + 0.17 - 0.19 0.00 - 0.12 - 0.05 - 0.14 - 0.05 - 0.21 - 0.58 - 0.17 - 0-02 0.00 - 0.39 - 0.02 - 0.12 - 0.07 + 0.04 + 0.03 - 0.18 - 0.15 - 0.04 - 0-12 + 0-04 + 0.09 - 0.03 - 0.03 - 0.03 - 0.03 - 0.03 - 0.03 - 0.01 Silica (SiO,) found in filtrate, mg.* * 1.0 2-4 * * 0.8 0.4 0.2 5.0 * * nil 2.2 0.2 2-6 1.2 0-8 1.4 2.6 2.0 3.4 * * 3.2 2.4 * * 3.6 3.2 * * Not determined. t Samples 14, 15, 16 and 5 are acid-soluble materials. Carefully cool the covered crucible in water and then tap it on a firm, clean, metal surface to loosen the cake. Transfer the melt to a clean nickel or steel plate and remove the adhering melt from the crucible and lid by means of a minimum of hydrochloric acid (1 + 1) and by rubbing with a rubber-tipped rod. Wash the cleanings into a 500-ml.Pyrex Griffin beaker with the minimum of water. Add 30 ml. of concentrated hydrochloric acid to the beaker, and place in a bath of cold water, preferably cooled with ice; move the cover glass to one side and add the melt from the plate, covering the beaker immediately. When the reaction has subsided, wash the traces of melt still on the plate into the beaker with a few drops of hydrochloric acid and a small quantity of water.484 Heat the solution for about 10 minutes on a water-bath, partly cool the solution and ac 7.5 ml. of sulphuric acid (3 + 1). Evaporate until fumes of sulphur trioxide just appe: which occurs readily owing to the continuous evolution of hydrogen chloride from the solutic Cool the solution, and add 75 ml.of water, followed by 10 ml. of concentrated hydrochloi acid. Cool to 70" C. and add 15 ml. of 2 per cent. gelatin solution dropwise, stirring vigorous for at least 2 minutes. Allow the solution to stand for 30 minutes, dilute with 100rni. water, and allow the precipitate to settle for a further 15 minutes. Filter through a Whatm No. 540 filter-paper, applying light suction towards the end of the filtration. Wash t precipitate with dilute (1 per cent.) hydrochloric acid, ignite cautiously at first and finally 1200" C.; then treat with hydrofluoric acid as usual. JENKINS AND WEBB: THE USE OF GELATIN I N THE [Vol. Heat until all the salts have dissolved. Results obtained by this method are given in Table 111. TABLE I11 PRECIPITATION Saniple s o . Material 1 Ferrosilicon ti Ferrosilicon .- Ferrosilicon > - Ferrosilicon 17 Ferrosilicon 8 Ferrosilicon 9 Ferrosilicon OF SILICA AFTER PRELIMINARY SIXGLE Weight of Silicon Silicon sample, present, found, 0.5 75.60 75-48 75.54 g.Yo % 0.5 72.59 72-61 72.52 72.43 0.25 72-59 72.61 72.58 0.5 73.47 72.43 72.61 73-44 0.5 50.00 50.10 49.83 0.6 47-95 47-96 47-92 0.25 48.01 47.86 1.0 18-10 16-05 16-16 1.0 12-87 12.93 12.91 DEHYDRATIOK Silica (SiO Error in filtrate mg. - 0.12 nil - 0.06 ni 1 + 0.02 nil - 0.07 0.3 - 0.16 i- 0.02 - - 0.01 - - - 0.04 - + 0.14 0.2 - 0.03 0.4 + 0.10 nil - 0.17 nil + 0.01 0-4 - 0.03 0.4 + 0.06 - - 0.09 - - 0.05 0.6 + 0.06 nil + 0.06 0.2 + 0.04 nil 10 Silicomanganese 1.0 X7-48 17.46 - 0-02 0.4 17-41 - 0.07 nil 11 Silicomanganese 1.0 16.39 16-44 + 0.05 0.2 16-36 - 0.03 nil 18 Ferrosilicon 1.0 15-63 15.62 - 0.01 0-4 15.55 - 0.08 1.6 DISCUSSION OF RESULTS Bearing in mind that (i) Pyrex ware was used for the investigation and (ii) the valc for silicon listed on the certificate accompanying U.S.A.National Bureau of Standar ferrosilicon sample No. 58 range from 75.53 to 75.90 and for sample No. 59 from 49.92 to 50 the results shown in Table III may be regarded as highIy satisfactory. The precision of t method is of practically the same order as the A.S.T.M. method. According to the U.S.A. National Bureau of Standards (see analysis certificate for Sam] No. 58), 1.0 to 1.5 mg. of silica are left in the filtrate of a peroxide fusion after two dehydratic with sulphuric acid, and 0.6 to 1.0 mg. after two dehydrations with hydrochloric acid. T figures in. the last column of Table I11 show that the proposed method leaves much less sili unprecipit at ed.Sept., 19501 DETERMINATION OF SILICON 485 In spite of contrary claims by previous workers, the precipitation of silica by gelatin does not appear to be quantitative within a reasonable period of time, though complete precipitation may be attained for small amounts of silicon. For larger amounts the error is considerably higher and therefore the dehydration method must be used. Thanks are due to the management of African Metals Corporation, Ferro-Alloys Works, Vereeniging, for permission to publish this paper. REFEKENCES 1. 2. 3. 4. 5. 6. Tananaev, N. A., and Bichkov, JI. K . , Zed. Anal. Ciaem., 1936, 103, 349-53; also Zacod. Lab., Tananaev, N. V., Zavod. Lab., 1946, 12, 248-49. Weiss, L., and Sieger, H., Zed. Anal. Chem., 1940, 119, 245-80. Weiss, K . L., A,rch. Eisenhiittenw., 1941, 15, 13-18. Spronk, S . J . H . , Chem. Weekblad, 1947, 43, 259-64. Lundgren, P., and Thorn, N., Svensk. Farm. Tzd., 1948, 52, 1-4. 1935, 648-50. AFRICAN METALS CORPORATION VEREENIGING SOUTH AFRICA Februavy, 1969

ISSN:0003-2654    

DOI:10.1039/AN9507500481

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

Sept., 19501 DETERMINATION OF SILICON 485 Sodium Peroxide Decomposition of Minerals in Platinum Vessels BY T. A. RAFTER SYNOPSIS-It is shown that niinerals resistant to decomposition by the usual methods can be decomposed easily and completely at comparatively low temperatures by means of sodium peroxide without the slightest attack on platinum vessels and with insignificant attack on iron or nickel vessels. Thermal analyses and gas-evolution experiments were made with several minerals as a preliminary to more detailed study of the mechanism of peroxide decomposition. THAT sodium peroxide is one of the most powerful decomposing agents for minerals is well known. What does not appear to be so we31 known is the very low temperature required for the decomposition. In the past, iron or nickel crucibles have been used for peroxide fusions, and platinum avoided on account of severe attack.Work carried out in conjunction with Seelyel established the fact that sodium-peroxide decompositions of the most resistant minerals could be made in platinum vessels without the slightest attack on the vessels. The experiments described in this paper were devised to determine the temperature of decomposition and to study the gases evolved during the reaction. EXPERIMENTAL Ii mixed with sodium peroxide in a platinum crucible and heated for 7 minutes in an electric muflle maintained at 480" i 20" C., zircon, one of the most resistant minerals, was rendered completely soluble in nitric acid. Many decompositions have been made in platinum crucibles and basins, without loss in weight of the reaction vessels, provided that the temperature was kept below 540" C., and such easily oxidisable materials as sulphides were avoided.At these low temperatures the attack of peroxide on iron or nickel vessels is also insignificant. A nickel basin weighing 51 g., after seven decompositions of 10 g. of zircon with 25 to $0 g . of sodium peroxide, lost 0-1 g. Many minerals can be decomposed at a temperature 200" C. lower than that required for zircon-with consequently even less attack on the vessel. This peroxide decomposition has enabled every mineral that has been examined to be brought quickly and cleanly into solution. With osmiridium, however, four successive decompositions were required. The experimental details for the peroxide-frit decomposition taken from a paper written by the author and Seelye2 are given below.486 RAFTER SODIUM PEROXIDE DECOMPOSITION OF [Vol.75 PROCEDURE- Fine grinding is essential for a 99 to 100 per cent. decomposition at the first attempt. If coarse material is used, a second frit may be necessary. Take a convenient amount of material (0.2 to 1 g.) in a weighed 30-ml. platinum crucible and mix with 1.2 to 3.0 g. of sodium peroxide. Place the crucible (covered if necessary) on a vitreosil plate well inside an electric muffle next to the pyrometer, the point of which rests on the plate, and leave for exactly 7 minutes. A number of decompositions can be done at the same time. Whether after disintegration of the cake in water the solution is filtered or immediately taken up in nitric acid depends upon the nature of the mineral and the sequence of chemical operations to be followed.If the digested cake is to be acidified, it is advisable to add the acid rapidly to the cold alkaline solution; this avoids the precipitation of insoluble acids, which occurs if the neutral point is approached slowly. After acidification and filtration, any unattacked mineral can be recovered and re-treated. If the aqueous extract of the melt is filtered to remove soluble sodium salts and the residue treated with diluted nitric acid (1 + 3), any undecomposed mineral remains on the filter-paper. Particle size-Grind all samples to pass a KO. 240 B.S.S. sieve. Keep the temperature a t 480” i 10” C. for the final 5 minutes. TEMPERATURE, “C.Fig. 1. Temperature - gas evolution curves for the decomposition of minerals by sodium peroxide. Fig. 2. Thermal analysis curves for the decomposition of minerals by sodium peroxide. QUALITY OF SODIUM PEROXIDE USED This paper describes an examination of the use of sodium peroxide as a reagent for decomposing resistant minerals. The sodium peroxide used was taken from one tin of AnalaR brand. It was found that various methods of analysis of the peroxide gave different results. The iodimetric method described in “AnalaR Standards for Laboratory Chemicals”3 was found to be very slow even when catalysed by sodium tungstate, and gave a yield of 82 per cent. of peroxide. The method given by T h ~ r p e , ~ in which loss of oxygen is avoided by mixing the powder witK boric acid, acidifying with sulphuric acid and titrating with potassium permanganate, gave a yield of 92 per cent.of peroxide. A gas-evolution method is also described by Thorpe.* The gas evolved on acidifying with sulphuric acid containing 2 drops of a saturated solution of cobalt nitrate is collected over caustic potash. This method gave a yield of 98-3 per cent. of peroxide. On analysis of the gas, it was found that 2 ml. of nitrogen was mixed with the oxygen liberated from 1 g. of peroxide. The peroxide content after correction for nitrogen was 95.6 per cent. The content of peroxide in the sample was probably 92 to 96 per cent.Sept., 19501 NIXERALS IN PLATINUM VESSELS 487 As work is described below on the evolution of oxygen when various minerals were heated with peroxide, it was necessary to find the amount of gas evolved when the sample of sodium peroxide is heated alone, in order to apply a correction for it.The peroxide was heated in a platinum Lawrence Smith alkali tube as described later, and the amounts of gases evolved are shown in Table I. TABLE I GAS EVOLVED FROM SAMPLES OF SODIUM PEROXIDE Weight of Xa,O;taken, Temperature, g. " C . ' 1 280 2 200 1 300 2 300 1 400 2 400 Total volume of gas evolved per g. of Na,O,, ml. at N.T.P. 4-48 4-28 4.24 3-22 2.75 2-68 Volume of oxygen per g. of Na,O,, ml. at N.T.P. 2.36 2-93 3-36 3-14 2.16 2.65 Volume of nitrogen per g. of Na,O,, ml. at N.T.P. 2.12 1.34 0.88 0.15 0-69 0-05 From these results it appears that some of the nitrogen evolved at lower temperatures is reabsorbed at higher temperatures.GAS-EVOLUTION ANALYSIS To study the temperature of decomposition of minerals by sodium peroxide and the volume of gas evolved, the Gooch platinum apparatus for the determination of moisture in rocks was first used, but was later replaced by a Lawrence Smith alkali tube and rubber stopper. The rubber stopper was kept cool by cold water run through a few turns of copper tubing. A short glass tube connected the platinum tube to a gas-collecting burette filled with 10 per cent. caustic potash solution. The platinum tube was heated in a copper block by a small vertical electric furnace. The temperature of the block was recorded. The copper block was heated at a uniform rate of 5" C. per minute and the volume of gas recorded. About 0.2g.of mineral was used, mixed with about 0.6 g. of sodium peroxide, great care being taken to avoid access of moisture. The curves of Fig. 1 indicate that quartz and talc decompose very easily at a temperature between 260" and 270°C. with evolution of a considerable amount of oxygen; from the chromite curve it appears that in spite of complete decomposition little or no oxygen is evolved; rutile decomposes at the same temperature as talc; zircon is attacked much more slowly over a considerable range of temperature. The curve for sodium peroxide indicates that com- paratively little decomposition takes place when sodium peroxide alone is heated. Table I1 indicates the volume of gas evolved, corrected to N.T.P., for the weights of the various minerals shown.The gas is mainly oxygen, but a correction has to be applied for a small volume of inert gas (presumably nitrogen) liberated on the decomposition of sodium peroxide, and not reabsorbed as it is when peroxide is heated alone. The following equations have been used to calculate the theoretical amounts of oxygen evolved- Typical gas-evolution curves are shown in Fig. 1. Mineral Equation 1. Quartz . . SiO, + 2N%O, = Na,SiO, + 0, 2. Talc . . 3MgSi0,.HzSi03 + 8Na,02 = 3Mg0 + 4Na,Si04 + H,O + 40, 3. Rhodonite . . 2MnSi0, + 6Na,0, = ZNa,SiO, + 2Na2Mn04 + 0, 4. Beryl . . 3BeO.AlZ0,.6Si0, + 16Na,02 = GNa,SiO, + 3N+BeO, + 2NaA10, + 80, 5. Rutile . . TiO, + 2Na,0, = Na,TiO, + 0, 6. Garnierite Sample of indefinite composition 7. Chromite . . 2(Fe0.Cr203) + 7Na,02 = 2Na3Fe0, + 4Na,CrO, X-ray studies or optical examinations would be necessary to verify the equations for the reactions given above.X-ray powder photographs were taken of the frit remaining when the calculated amounts of quartz and peroxide in accordance with equation 1 were used. The product was devoid of quartz and peroxide, and was not metasilicate, but as no A.S.T.M. diffraction-data card for the orthosilicate was available its presence could not be checked.488 Mineral 1. Quartz.. 2. Talc . . 3. Rhodonite 4. Beryl . . 5. Rutile . . 6. Garnierite 7. Chromite RAFTER SODIUM PEROXIDE DECOMPOSITION OF TABLE rr VOLUMES OF GAS EVOLVED Weight taken, €5 . . 0.183 . . 0.193 . . 0.197 . . 0.198 . . 0.144 . . 0.191 . . 0.199 Weight of taken, g. 0.63 0-69 0.60 0.64 0.61 0.60 0.61 N%O* Tempera- ture of decom- position, O c.260 270 270 270 270 270 370 Gas evolved, ml. at N.T.P. 72-1 51.7 24.5 70-5 46.0 48.9 2.7 Theoretical volume, ml. at N.T.P. 68.2 45.5 16.9 65.9 40.4 nil - [Vol. 75 Difference, ml. 3.9 6.8 7.6 4.6 5-6 2.7 - The volume of nitrogen evolved during the decompositions summarised in Table 11 was found by analysis to average 2*9ml. From the data given in the table and from the relevant equations it was calculated that the volume of oxygen produced by the action of heat on the sodium peroxide in excess of that required to react with the mineral would average about 1.0 ml. On average, a total correction of 3.9 ml. should, therefore, be deducted from the volume of gas evolved as shown in Table 11. This cori-ection considerably reduces the difference between the experimental and the theoretical volume of gas evolved.With some of the minerals, e.g., rhodonite, the difference is partly due to the presence of impurities. The table shows a fairly good correspondence between actual and theoretical evolutions of oxygen, and in conjunction with the gas-evolution curves indicates that the reactions are not necessarily dependent on oxidation-indeed the most vigorous, that with quartz, is due to combination only. DIFFERENTIAL THERMAL ANALYSIS The encouraging results obtained by the gas-evolution experiments led to an attempt to study the nature of the reaction by differential thermal analysis. An apparatus for differential thermal analysis with automatic photographic recording was used. As the chrome1 - alumel thermocouple used for the thermal analysis of clays was found to be too sensitive for the decomposition experiments, it was replaced by one of platinum and platinum - rhodium.The copper block used for holding the platinum crucibles during the decomposition was 2.5 cm. thick. It had two holes to receive the platinum micro-crucibles, a third hole to receive a thermocouple, and a fourth tapped hole to facilitate removal of the block from the furnace by means of a threaded rod. One crucible held the mixture of mineral and peroxide, while the other held the alumina used as the reference material. The mineral was ground to pass a No. 320 B.S.S. sieve, and 0-2 g. was intimately mixed with 0.45 to 0.6g. of sodium peroxide. After each experiment the completeness of the decomposition was checked by weighing any residue after solution of the reaction products in dilute acid.The curves obtained for the less resistant minerals (quartz, talc, rhodonite) are shown in Fig. 2, and those for the more resistant minerals (chromite, rutile, zircon) in Fig. 3. These curves show that the decomposition of most silicates and other minerals by sodium peroxide takes place at a temperature between 250" and 300" C. The reaction for the less resistant minerals is strongly exothermic, and only with the more resistant minerals (e.g., zircon) are temperatures higher than 300" C. necessary for complete decomposition. Before the exothermic peak for the minerals chromite, rutjle and zircon, an endothermic peak appears, more developed in some instances than in others. The significance of this peak can be understood by consideration of the thermal analysis curve for sodium peroxide reproduced in Fig.4. The curve has been redrawn from that experimentally obtained, in order to have the cooling curve on the same temperature scale as the heating curve, and to show a uniform rate of cooling, which could not be obtained in practice. At the temperature required for the decomposition of most minerals, sodium peroxide undergoes an endothermic change. Another endothermic peak occurs between 400" and 500" C. in the region of the reported meltingpoint of peroxide. The cooling curve shows that the changes are reversible, exothermic pea.ks appearing at temperatures approximately the same as those of the endothermic peaks of the heating curve.Sept., 1950j MINERALS IN PLATINUM VESSELS 489 Characteristic colour changes and other alterations were noted during the heating of the peroxide, and these changes were reversed on cooling.At about 260" C., fresh AnalaR sodium peroxide undergoes an endothermic change accompanied by incipient fusing or fritting of the particles. Whether this incipient fusion is characteristic of pure sodium peroxide has not been determined. It is probable (see later) that traces of sodium hydroxide present or formed by absorption of moisture during the handling and heating of the powder result in the formation of a low melting point mixture, as the reported melting-point of sodium hydroxide is 318" C. The thermal analysis curves suggest that when peroxide reaches a temperature of 260" I f r 10" C.it becomes reactive with most minerals with which it is in intimate contact. With chromite and rutile, reaction takes place only after a portion of the endothermic peak TEMPERATURE. "C. Fig. 3. Thermal analysis curves for the Fig. 4. Thermal analysis curve of sodium decomposition of minerals by sodium peroxide, peroxide. associated with peroxide appears, the depth of this peak being an approximate index of the resistance of the mineral. With zircon there appears to be a slight break between the endothermic peak and the exothermic peak accompanying the decomposition. The curve for tantalum oxide has been included, as this decomposition may in the future play an important part in the analytical chemistry of the earth-acid elements.CALCULATION OF THE TEMPERATURE RISE DURING DECOMPOSITION- A galvanometer connected to the thermocouples in the heating block was calibrated in millivolts per cm. and from specially constructed tables the approximate temperature rise during the reaction was obtained (see Table 111). Table 111 shows that peroxide attacks easily-decomposable minerals with the evolution of a considerable amount of heat. If an unknown substance is to be decomposed by peroxide in platinum, the safest procedure is to commence heating at 200" C. and slowly increase the temperature. The heat evolved at the moment of decomposition will then be unable to raise the temperature of the platinum to that at which it is attacked by peroxide. From the figures for the percentage decomposed, it can be seen that complete decomposition has not been obtained for rutile, chromite or zircon.Two results have been included for chromite. In each case the temperature rise at the peak temperature was the same, although in the first experiment 69 per cent. was decomposed and in the second, 98 per cent. The difference between these results was due to the temperature at which the thermal analysis was stopped. In (a) the reaction stopped at 350" C., in (b) at 450" C. Up to 360" C., the thermal analysis curves were almost identical, but for (b) further exothermic peaks appeared at temperatures above 350" C., indicating additional attack.490 RAFTER : SODIUM PEROXI1)E DECOMPOSITION OF [Vol. 75 To study the effect of longer times and higher temperatures on the decomposition, rutile and peroxide were heated to 300" and 350" C.and held at these temperatures for a definite time. The results are given in Table IV. Mineral Quartz . . Talc Rhodonit; Beryl .. Garnierite Rutile . . Chromite (a) Monazite Ilmenite Zircon . . (b) .. .. .. .. .. .. .. .. .. . . . . SODIUM PEROXIDE Heating A B Cooling B' A' .. . . . . .. . . . . .. . . .. . . .. .. .. . . .. TABLE I11 TEMPERATURE DURING REACTION Peak temperature, O c. .. 263 .. 266 .. 250 .. 283 . . 284 ,. 286 .. 297 .. 294 . . 271 . . 279 . . 385 .. 279 .. 492 * . 498 . . 254 Temperature rise, O c. 191 65 165 62 56 7 24 24 15 25 10 -11 -8 +g +I1 Mineral decomposed, LOO 100 LOO 98 100 68 69 98 94 65 % - Table IV shows that to decompose rutile completely it would be necessary to heat at 350" C.for 40 to 45 minutes. The shape of the thermal analysis curves for these decompositions has not been reproduced for this paper. The curves for heating to 350" C . were very similar, but during the time that the temperature was held constant, indefinite exothermic peaks occurred at nearly regular Intervals. The table shows that the peak TABLE IV EFFECT OF TIME AND TEMPERATURE ON DECOMPOSITION Peak Temperature Percentage Run No. temperature, rise, decomposed, Remarks O c. O c. 28 286 7 68 Heated to 350' C. in 30 minutes 30 291 7.5 74 Heated to 300" C. in 30 minutes and 31 285 11 93 Heated to 350" C. in 36 minutes and 32 283 7 98 Heated to 350' C. in 40 minutes and held for 30 minutes held for 30 minutes held for 40 minutes temperatures and the temperature rises are reproducible with reasonable accuracy.The temperature rise in run 31 appears to be high, but this was because of the difficulty in deter- mination of the base of the exothermic peak. At the peak temperature, 70 per cent. of the mineral is decomposed. The remaining 30 per cent. can be attacked at a higher temperature or in longer time at peak temperature. Similar experiments were carried out with zircon, and, as expected, even higher temperatures or longer times are required for a 70 per cent. decomposition. X-RAY EXAMINATION- In an endeavour to correlate any change in crystal structure with the initiation of decomposition by peroxide, powder X-ray photographs were taken of peroxide powder and of the fritted cake obtained after heating the .powder to 500°C.and cooling. No change in crystal structure could be detected. The thermal analysis curve for sodium peroxide indicates that no permanent change in crystal structure could be expected, since any change that takes place during heating is completely reversed on cooling.Sept., 19501 MINERALS IN PLATINUM VESSELS 491 MICROSCOPIC EXAMINATION- Minute amounts of peroxide were heated in a platinum dish inserted in a copper block and covered with a glass slide. Any changes that occurred were observed through a micro- scope. The minute specks liquefied at about 260°C. If larger amounts of peroxide are taken, fritting can be observed, but no visible melting occurs. THE NATURE OF THE PEROXIDE DECOMPOSITION The lower temperature peak, A, in the thermal analysis curve for sodium peroxide (Fig.4) can be attributed to the melting of a small amount of sodium hydroxide present as impurity in the peroxide. The melting point of sodium hydroxide is 318" C., but the fact that the heat change occurs at 280" C. is accounted for by the lowering of the melting point because of the solubility in the melt of a small amount of sodium peroxide or of impurities that may be present. The upper temperature peak, B, on the thermal analysis curve is apparently due to the heat change at the melting point of sodium peroxide. According to Centnerszwer and Blumentha16 the melting point of sodium peroxide is 460" C. The present work gives the melting point as 495" C., and this should be accurate to within 5" C. It is, of course, the, value for the particular sample, containing at least 5 per cent.of impurities; but impurities should make the melting point lower than that of pure material. From the fact that there are indications of smaller intermediate peaks as well as the two major peaks at 280" and 495" C., it appears that further work is desirable on the phase diagram for mixtures of sodium peroxide with impurities occurring in the commercial product. It is probably the presence of the liquid phase in the mixture, as shown both by micro- scopic examination and by the lower temperature peak, A, of the curve, which enables the reaction to proceed rapidly. This does not explain why the peroxide is so much more reactive than the hydroxide at low temperatures, although it suggests that the cause may be the solution of some of the peroxide in fused hydroxide.APPLICATION OF THE PEROXIDE DECOMPOSITION AT LOW TEMPERATURES It has been shown that the most resistant minerals can be readily brought into solution by a peroxide frit in platinum vessels without any attack on the reaction vessel. This method of decomposition should prove of great help to the analytical chemist, especially in the analysis of the earth-acid and rare-earth minerals. Schoeller, in his treatise on the earth-acids, does not favour the use of alkali fusions owing to platinum contamination. We have found at the Dominion Laboratory that the peroxide frit brings completely into solution tantalum oxide and the few tantalum minerals that are available in New Zealand. The fritted cake dissolves completely in cold water. If the solution is acidified with tartaric acid it remains clear indefinitely, and can be used as the starting-point for the separation of the earth-acid elements.Preliminary experiments indicate that, by taking advantage of the differences in stability of the persalts of the earth-acids, it is possible to reduce the amount of niobium in reagent samples of tantalum pentoxide, or of titanium in supposedly chemically pure niobium metal. In the industrial field, if peroxide could be reduced in price, its ease in handling, its lack of corrosiveness, and the ready solubility of the reaction products after the peroxide frit could greatly simplify many existing metallurgical processes, especially for the more valuable elements. The writer wishes to express his appreciation to Mr. F. J. T. Grigg, Director of the Dominion Laboratory, Wellington, New Zealand, for permission to publish this paper; to Mr. F. T. Seelye for his active interest and advice; to Mr. W. Vose, Director of the New Zealand Pottery and Ceramic Research Association, for advice on the practical application of the peroxide decomposition, and for the use of the Research Association's facilities; to Mr. I. McDowall under whose directions the thermal analyses were made; to Mr. J. D. Butler, who performed most of the gas evolution experiments and analyses of the sodium peroxide; and to Mr. R. J. Munster, who carried out the X-ray work.492 MILLER AND PEARMAN : TITRIMETRIC REFERENCES [Vol. 75 1. 2. 3. 4. 5. Seelye, F. T., and Rafter, T. A,, Nature. 1950, 165, 317. -,- , Report of Dominion Laboratory, Rock and Mineral Section (unpublished), 1948. “AnalaR Standards for Laboratory Chemicals,” British Drug Houses Ltd., and Hopkin & Williams Thorpe, E., “Dictionary of Applied Chemistry,” Vol. 6, Longmans, Green & Co., Ltd., London, Centnerszwer, M., and Blumenthal, M., Bull. Acad. Polon. Sc. Letter, 1933, (.4), 502; “Landolt - Ltd., London, 1944, p. 190. 1926, p. 242. Bornstein Phys. Chem. Tabellen,” Ed. 111, 325, Berlin, 1935. DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESEARCH DOMINION LABORATORY SYDNEY STREET WEST WELLINGTON, NEW ZEALAND April, 1950

ISSN:0003-2654    

DOI:10.1039/AN9507500485

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

492 MILLER AND PEARMAN : TITRIMETRIC [Vol. 75 Titrimetric Determination of Ethylene BY S. A. MILLER AND F. H. PEARMAN SYNoPsrs-The determination of ethylene in gas mixtures that contain no other unsaturated compounds, by shaking with excess of bromine in acetic acid, and titrating the unreacted bromine, is described. The method is simple and reliable, and gives results accurate to f 0.02 per cent. A METHOD is described for determining the amount of ethylene in gas mixtures containing up to about 7 per cent. of ethylene with an accuracy of & 0.02 per cent. The usual gasometric methods, such as those employing the Bone and Wheeler apparatus, can be relied upon a t best to & 0.1 per cent., and the Orsat apparatus only to & 0.2 per cent. A method was devised which was found to be simple and reliable in operation, capable of being used by the average laboratory assistant, and which gave the desired accuracy.Of the usual gases met with in normal gas analyses, only other unsaturated compounds can interfere. The method depends on the determination of the unreacted bromine remaining after a known volume of gas mixture has been shaken with an excess of bromine solution, under specified conditions. METHOD REAGENTS- Sodium thiosulphate-0.1 N , standardised in the usual way. Potassium iodide--lO per cent. solution, Starch solution-1 per cent. solution. Saturated brine-A solution of commercial salt, boiled and Bromine in acetic acid-5 g. of potassium bromide, 1 ml. of filtered. bromine, 300 ml. of acetic acid. All the reagents (except the brine) were prepared from A.R.grade chemicals. APPARATUS- It consists of two bulbs separated by a tap, with a further tap at each of the other ends of the two bulbs, and a funnel attached to the tap of the small bulb. The volume of the smaller bulb is about 100 ml. and that of the larger bulb 1 litre. The two taps connected to the smaller bulb are of 8 mm. bore. The apparatus is shown in Fig. 1. Fig. I . PROCEDURE- bulb. The larger bulb is filled with saturated salt solution through the funnel and the small The middle tap is then closed, and the apparatus inverted, and used in the normalSept., 19501 DETERMINATIOS OF ETHYLENE 493 manner of collecting a gas sample. After the sample is taken the tube is returned to the original position, and the temperature in the smaller bulb is measured; the barometric pressure is also read.By using a wide bore tap, it is possible to insert the thermometer through the bore of the tap. It is assumed that the temperature is the same in the two bulbs. The smaller bulb is then thoroughly rinsed out three or four times with distilled water to wash away all trace of brine. The bromine in acetic acid reagent is then pipetted into the small bulb, the tip of the pipette being made to pass through the bore of the tap. The quantity of reagent taken is 15 ml. per 1 per cent. of ethylene present in the gas; thus for a gas believed to contain some- thing of the order of 5 per cent. of ethylene, 75 ml. of reagent solution is used. The reagent is conveniently blown into the pipette by means of a blow-ball. No reagent should remain adhering to the funnel or the tap of the bulb, but if any does so, it should be washed in with not more than 1 ml.of distilled water. The middle tap is then opened and the apparatus shaken vigorously for 20 minutes. The middle tap is then closed, the upper tap opened and 20ml. of 10 per cent. potassium iodide added, and washed in with 1 to 2 ml. of water. The upper tap is then closed and the middle tap opened to allow the iodide to run into the larger bulb. The tap is then closed and the apparatus vigorously shaken for a short time and allowed to stand for 5 minutes. The liquor is then run into a 500-ml. iodine flask, together with five rinsings of distilled water, each of 10 to 20 ml. The iodine solution is then titrated with thiosulphate in the usual way.A blank determination is carried out in exactly the same way, using 25 ml. of bromine reagent. CALCULATION OF RESULTS- The tap is then closed. Straightforward calculation shows that if V = Volume of the larger bulb, in litres, P = Barometric pressure in millimetres of mercury, T = Temperature of the gas in degrees C., F = Factor of the thiosulphate ( x 0.1 K ) , a = Titration starting with 75 ml. of bromine solution, b = Blank titration starting with 25 ml. of bromine solution, 273 + T 760 x - per cent. P x (3b -- n ) F x ____ 0.1121 the ethylene present = ~ V 273 REACTION CONDITIONS BROMINE SOLVENT- The use of carbon tetrachloride as a solvent for bromine was not found to be satisfactory. Owing to the immiscibility of the carbon tetrachloride with water, it would be necessary to add water as well as the 10 per cent.potassium iodide solution, with a greater risk of loss of bromine by vapourisation at this stage. Both gave similar results with the same reproducibility, but the stability of the stock methanol solution was inferior, which made it necessary to carry out blank determinations with each analvsis. In the case of the glacial acetic acid solution, one or a t most two blanks were sufficient for a day's work. Methanol and glacial acetic acid both appear to be suitable so1vents.l TIME OF REACTION- In the first study of the conditions, a temperature of 0" to 5" C. was thought to be desirable in order to reduce possible substitution, either of the ethylene itself or of the accompanying saturated hydrocarbons, and the amount of bromine used was 125 per cent.of that equivalent to the ethylene present. Mixtures of known constitution were prepared volumetrically, using pure ethylene obtained by fractionation on the Podbielniak apparatus. The mixtures contained 4 to 5 per cent. of ethylene, about 5 per cent. of oxygen and 10 per cent. of carbon dioxide, the rest being nitrogen. The results obtained in a number of preliminary experiments are shown in Table I.494 Time TEMPERATURE MILLER AND PEARMAN TITRIMETRIC TABLE I EFFECT OF TIME ON THE REACTION Excess reagent . . . . 25 per cent. Temperature . . .. 0" to 5°C. of shaking, Ethylene present, Ethylene found, Error, min. /'0 % 0' ,'O 01 5 4-49 3 8 i - 0.62 5 4.76 3.64 - 1.12 7 4.01 3-35 - 0.66 15 4.65 4.5 1 - 0.14 20 4.67 4.56 - 0.11 OF REACTION- [VO~.75 As the reaction was incomplete even in 20 minutes at 0" to 5', the cooling was omitted, and the reaction studied at room temperature. The results obtained are shown in Table 11. TABLE I1 REACTION AT ROOM TEMPERATURE Temperature . . . . 15" to 20" C. Excess reagent . . . . 25 per cent. Time of shaking . . . . 20 minutes Ethylene present, Ethylene found, Error, 0' % / O O / 10 4-06 3.51 4.12 4.83 3.97 3-51 4-03 4.82 7- 0.08 0.00 - 0.09 - 0.01 AMOUNT OF REAGENT- The excess of reagent taken had first been tried at 25 per cent., which seems to have been used in other connections in determinations with bromine and acetic acid.l Experiments were carried out using both 25 and 50 per cent. excess of bromine (calculated for a gas containing 5 per cent.of ethylene). The results obtained are shown in Table 111. TABLE I11 EFFECT OF AMOUNT OF REAGEKT USED Temperature . . * . 20" c. Time .. .. ,, . 20 minutes I > r \ Ethylene Ethylene Ethylene Ethylene present, found, Error, present, found, Error, 25 per cent. excess bromine 50 per cent. excess bromine JL 0' /O 0) 46 4.05 3.9i 5.25 523 - 0.04 - 0.08 % 0' / O % 3.5 1 4.83 5.51 4.84 4.13 3.51 0.00 4-94 4-95 + 0.01 4-82 - 0.01 2.97 3.00 + 0.03 5.29 - 0.22 4.54 4.54 0.00 4.73 - 0.11 4.83 4.82 - 0.01 4.03 - 0.10 Mean error . . .. . . - 0.09 Mean error . . . . . . 0.00 The second group of five results in Table I11 shows the desired level of accuracy in the determination. Attempts were then made to reduce the shaking time to 5 minutes, using the preferred level of 50 per cent. of excess reagent, and a reaction temperature of 20" C.Under these conditions, however, the reaction was incomplete and deficiencies of up to 0.46 per cent. were recorded. Similarly, a determination which was carried out by shaking for 5 minutes and then allowing to stand for 15 minutes also led to a seriously low result.Sept., 19501 DETERMINATION OF ETHYLENE 496; COMPARISON WITH GASOMETRIC DETERMINATIONS- Samples of gas containing ethylene in admixture with (mainly) nitrogen, oxygen and carbon dioxide were analysed titrimetrically and gasometrically with the following results- TABLE IV COMPARISON OF ETHYLENE DETERMINATIONS BY THREE METHODS Ethylene found, per cent. A r -I Bromine method A r \ Orsat, Bone and Wheel,er, Mixture Individuals Mean mean value mean value I 3.95 3-93 3-94 3.6 4.1 I1 3-69 3.63 3-61 316 3-8 I11 5.66 5-72 5.69 5.9 8-8 IV 5.01 4.97 4.99 5.0 5.2 v 4.53 4-57 4.55 4.4 4.9 FURTHER TEST- * Further studies of the reproducibility of the method, and comparison of the results with those obtained gasometrically, were carried out on a gas containing about 90 per cent. of methane, and on another gas conSisting in the main of methqne, hydrogen, carbon molaoxide and nitrogen in roughly equal proportions. The results are shown in Table V, the above mixtures being I and I1 respectively. TABLE V FURTHER COMPARISONS WITH GASOMETRIC METHODS Ethylene found, per cent. A r -I Bromine method Orsat r \ CT~-, Boneand Mixture Individuals Mean Individuals Mean Wheeler I 3.8 1 3.82 3.84 3.82 3.8 3.7 3-75 4.0 I1 0.73 0.74 0.74 0.74 0.6 0.5 0.55 - A The authors wish to thank the Directors of the British Oxygen Co., Ltd. for permission to publish this paper. REFERENCE 1. Morgan, P. W., Ind. Eng. Chm., AnaE. Ed., 1946, 18, 500. THE BRITISH OXYGEN COMPANY LIMITED MORDEN ROAD, LONDON, S.W.19 A V U Y , 1950

ISSN:0003-2654    

DOI:10.1039/AN9507500492

出版商:RSC    

年代:1950

数据来源: RSC

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496 HARRIS: DETERMINATION OF FERROUS IRON [Vol. 75 Determination of Ferrous Iron in Certain Silicates BY F. R. HARRIS SYNoPsIs-Errors caused by atmospheric Oxidation in the determination of ferrous oxide by Densem’s method have been reduced to a negligible quantity by (a) modification of the decomposition chamber and (b) by replacing the direct permanganate titration of ferrous iron by an indirect residual titration in which the ferrous iron in the assay solution is oxidised by means of an excess of standard permanganate solution and the excess determined by adding an excess of standard ferrous iron solution, the excess of which is found by titration to a pink end-point by means of standard permanganate solution. THE major difficulty in determining ferrous oxide in glasses or other silicates is aerial oxidation during decomposition of the glass and in the subsequent titration.Back-titration methods were suggested by Hackl,l though he does not appear to have adopted the idea. Hillebrand2 showed that in the rapid grinding of small samples aerial oxidation was negligible. Densem3 used Pratt’s method for the determination, in which silicates are decomposed in a gently boiling mixture of sulphuric and hydrochloric acids in an atmosphere of carbon dioxide, and found errors due to dissolved oxygen in the reagents, which were minimised by “boiling- out” all the reagents used. He decomposed the silicates by means of a mixture of sulphuric and hydrofluoric acids in a platinum crucible heated on a sand-bath and enclosed in a cylinder of tinned iron covered by a glass funnel to prevent entry of dust.The author repeated Densem’s work, and while confirming his findings, made modifications in his apparatus and technique which constituted improvements (see Fig. 1). These altera- tions may be summarised as follows- (i) Contamination by sand was avoided by replacing the sand-bath by a layer of asbestos fibre, previously extracted with nitric acid and ignited. (ii) The tinned-iron vessel was replaced by one of sheet copper. (iii) The crucible was covered by a copper lid, suspended by a copper wire passing through the tubular of the funnel, to prevent condensate falling into it. (iv) The decomposition mixture was poured into a boiled-out mixture of boric acid and a measured volume of standard permanganate solution, and air expelled by the addition of a small amount of sodium bicarbonate.(v) Densem’s titration box was improved by adding a sloping base on which to stand the flask. This prevented reflections in the flask. These modifications, although of a minor nature, reduced the chances of atr,ospheric In the direct titration method careful work is necessary with samples of low This oxidation. iron content, and the longer the time taken for this, the greater the risk of oxidation. risk is obviated by back-titration. METHOD Boric acid of good quality is dissolved in hot water, filtered to remove ferruginous impurities, which cause erratic blanks, and recrystallised. Two hundred millilitres of distilled water and 10 g. of the purified boric acid are boiled, filtered under vacuum, and then boiled for 10 minutes with 10 ml.of concentrated sulphuric acid. The boiling mixture is poured into a 400-ml. round-bottomed flask, a pinch of sodium bicarbonate added and the flask stoppered, cooled and set aside until required. One to two grams of the glass sample are rapidly and finely ground in an agate mortar, weighed (by difference) and added to a cooled decomposition mixture consisting of 10 ml. of 40 per cent. hydrofluoric acid, 30 ml. of water and 5 drops of concentrated sulphuric acid, which has been previously boiled for 5 minutes and cooled in a platinum crucible under carbon dioxide in the decomposition chamber. After adding the sample, the mixture is again boiled in the decomposition chamber, through which passes a rapid stream of washed carbon dioxide from a cylinder.When the decom- position of the sample is complete, the flask containing the boric acid mixture is opened, a pinch of sodium bicarbonate added, and a measured excess of 0.02 or 0-01 h7 permanganateSept., 19501 I N CERTAIN SILICATES 497 solution added from a pipette. The contents of the crucible are then rapidly washed into the flask and shaken. A measured excess of 0-1 N ferrous ammonium sulphate solution is then added and the mixture titrated back with 0-02 or 0.01 N permanganate solution to the usual pink end-point. This is best seen by means of the light-box described by Densem. A k Glass Filter-Funnel Copper Wire Sheet-Coppur ---- Vessel Copper Lid Platinum Crucible .Asbestos Fibre F!g. 1. Potassium dichromate and ceric sulphate were found to be useless as the oxidant, and internal indicators, such as the diphenylamine derivatives, ferroin, etc., were unsatisfactory.The permanganate end-point was entirely satisfactory. A blank determination is necessary, but with A.R. quality reagents it is small, usually of the order of 0.2 ml. of 0.02 N permanganate, equivalent to about 0.0003 g. of ferrous oxide. The boric acid appeared to be the one suspect material. RESULTS The above procedure was tested with known amounts of ferrous salts in place of glass. A comp8rison of the results by direct titration and by back titration is made in Table I, which shows that there is greater concordance in the replicate results by the recommended procedure than by direct titration, and that the effect of atmospheric oxidation has been reduced .When the back titration method was applied to a series of simple soda - silica compositions of low iron content there was again concordance in the replicates. This is shown in Table 11, which gives the results for a number of glasses containing about 0.1 per cent. of ferrous oxide. Check analyses on some of Densem’s glasses are shown in Table 111.498 HARRIS : DETERMINATION OF FERROUS IRON [Vol. 75 TABLE I COMPARISON OF RESULTS BY DIRECT AND BACK TITRATIONS ON FERROUS OXIDE Direct titration Back titration L I 7 f 7 A Average Average FeO added, FeO found, oxidation, FeO found, oxidation, mg. mg. 94 mg. % 0.1 0.05, 0.04, 0.06 50 0.09, 0.11, 0.09 3.0 0.5 0.44, 0-38, 0-41 18 0.48, 0-49, 0.48 2-4 1.0 0.94, 0.93, 0.90 7.7 0.97.0.99, 0.98 2.0 2-5 2.08, 2.29, 2.27 11.0 2.48, 2-51, 2.50 1.2 5.0 4.94, 4.73, 4.7H 4.0 4.98, 4.97, 5.00 0.3 10.0 9.74, 9.48, 9-55 4.0 9.94, 9-97, 10-04 0.2 25.0 24.30, 23.8, 34-15 3.7 24-95, 24.87, 24.90 0.4 50.0 44.9, 48.2, 47.7 5.4 19.7, 49.7, 50.05 0-4 100.0 96.8, 95.2, 95.0 4.7 99.7, 99.3, 99.8 0 4 TABLE I1 RESULTS OF BACK TITRATION METHOD APPLIED TO GLASSES GIass A B C D E Maximum FeO found, per cent. 0.112 0.119 0-150 0.155 0.182 Minimum FeO found, per cent. 0.099 0.1 13 0.145 0.151 0.178 TABLE I11 COMPARISON OF DIRECT AND BACK TITRATIONS ON GLASSES Glass FeO, (i) (ii) (iii) (iv) (v) (vi) (vii) 0.14 0.23 0.28 0.38 0.43 0.84 1.23 Densem F. R. H. 0.14 0-23 0.29 0.38 0.43 0.84 1.39 In general, agreement is good, and where discrepancies arise it is the new technique which gives the higher (and probably more accurate) figure.Accuracy of the method for glasses of low iron content having been shown to be satis- factory, the ferrous iron was determined in a series of glasses of high iron content melted by the writer. No comparisons were available for these, but the proximity of the totals to 100 per cent. is a sufficient test of accuracy in glasses of this kind. The results are shown in Table IV. % TABLE IV DETERMINATIONS OF FERROUS IRON IN GLASSES OF HIGH IRON CONTENT Glass SiO,, N%O, as Fe,O,, FeO, 3 FeO, Fe,O,, &03, (a, 13, c, d, e ) , Total Fe Fe,O, True Total 0 % Yo '3.0 % % 5% % / o (a) (b) (8) - 99.69 1 73.37 24-95 2 72-39 25.17 2.36 1.26 1.40 0.96 - 99.78 3 71-68 25.05 3.14 1.29 1-43 1.71 - 99.73 4 71.67 24.37 3.94 1.94 2.16 1.78 0.02 99.78 3 72-37 23-38 4.44 2.32 2.58 1.86 0.01 99.84 6 68-76 23-68 7-98 ,4.98 5.53 "45 0.02 99-89 7 71.61 21.75 7.10 5.09 6.56 1.45 0.02 99-92 8 67.28 20.80 16-28 4-95 5.50 6.78 0.02 99.84 (4 (4 1.44 0.63 0.70 0.74 In these glasses about one half of the iron is in the ferrous state, and under ordinary, direct titration, conditions the time taken for titration would be long and the risk of atmos- pheric oxidation great.This source of error has been obviated by the method of back titration. The samples used in this work were prepared. for research purposes and their composition differs from that of commercial glasses. It is hoped later to investigate the back-titration method as applied to more complex glasses, including commercial compositions, especially those containing arsenic and manganese. REFERENCES 1. Hackl, O., 2. anal. Chew., 1928, 67, 197. 2. 3. Hillebrand, W. F., J . Amer. Chem. SOC., 1908, 30, 1120. Densem, N., Glass Review, 1936, 12, 64; J. SOC. Glass Tech., 1936, 20, 3 0 3 ~ . WOLVERHAMPTON AND STAFFORDSHIRE TECHNICAL COLLEGE WOLVERHAMPTON, STAFFS. First submitted, July, 1949 ,lmended, May, 1950

ISSN:0003-2654    

DOI:10.1039/AN9507500496

出版商:RSC    

年代:1950

数据来源: RSC

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Sept., 1950) NOTES 499 THE ESTIMATION OF VITAMIN B, USING THE FLUORIMETER: THE PREPARATION OF THE STANDARD CURVE THE method used for the estimation was that recommended in the Medical Research Report published in the Biochemisal Journal and abstracted in The Analyst.’ It is recommended that the standard curve be obtained by calibrating a series of aneurine standards (oxidised by the same technique as employed for the flour extracts) against the quinine standard. There is a rather serious error in The Analyst abstract, where reference is made to a standard quinine solution of 0.01 g. per 100 ml. of 0.1 N sulphuric acid. In the original paper this is the strength of the standard stock solution, and the actual solution used in the fluonmeter cell is a 1 in 100 dilution of this.In the preparation of the graph, it was found that over the approximate range 1.0 to 4.0 pg. of vitamin B,, the density drum could be accurately read and the points on the curve easily reproduced. In an actual determination it is this part of the curve that is used, but for the “blank” determination an extension of the curve over the range 1-0 to 0.1 pg. is important. It was decided to prepare from the experimental curve another curve plotting the reciprocal of the antilog of the density as given by the drum reading, against pg. of vitamin B,. A straight line was obtained passing through the origin. If this straight line is extended to the point l/antilog {density) = 1.000 and the equivalent pg. of vitamin B, read off at this point, then there is no further need for the curve.Any drum reading can be readily converted to pg. of vitamin B, by the following formula- 1 antilog (density) p g . of vitamin B, = x constant, C, where the constant, C = pg. of vitamin B, at the point l/antilog (density) = 1.000. This constant is actually the number of pg. of vitamin €3, which exhibit a fluorescence equal to the standard quinine fluorescence. Theoretically, using vitamin B, itself as the standard fluorescence, if, in an experiment, 5 p g . (say) of vitamin B, constituted the standard fluorescence, then without the aid of a curve 1 antilog (density) pg. of vitamin B, in the solution under test = x 5 I t is not recommended that vitamin & itself be used as the standard fluorescence in place of quinine. It should be borne in mind that the accuracy of the standard graph or of the constant, C, depends upon a reproducible quinine standard.Care should be taken when using quinine sulphate B.P. as this substance is very liable to lose its water of crystallisation, and this may lead to errors. In our own experiments the sample of quinine sulphate used contained 3.7 per cent. of water (i.e., not B.P.) and a constant of 8.0 was obtained from the straight line as deduced from the experimental curve. pg. of vitamin B, = antilog [log (constant, C) minus (drum reading)] This method of approach does give a check on the shape of the experimental standard curve and also, if developed as outlined, it simplifies calculation. REFERENCE The formula may be further simplified to 1. “The Vitamin B, Content of National Flour and Bread-the Results of Comparative Tests by Various Methods,” Biochem.J . , 1943, 37, 433; Analyst, 1943, 68, 379. BIRMINGHAM March, 1950 CITY ANALYST’S LABORATORY F. G. STOCK DEVICE FOR USE WITH WATER-DRIVEN VACUUM PUMPS TO PREVENT WATER SUCKING BACK INTO APPARATUS SPORADIC fluctuations in water pressure can cause much annoyance and loss of time when water- driven vacuum pumps are thereby caused to suck back into the apparatus being evacuated. The conventional water-trap is not always an adequate protection, particularly where the apparatus concerned is of any considerable size. For this reason, the pumps in these laboratories have been fitted with the device described below and illustrated in Fig. 1, and have since given entirely satisfactory service.500 NOTES [Vol.75 The apparatus, A, to be evacuated is connected to the capillary system by a length of rubber pressure tubing, B, and the drying tube, C,, which can be omitted if desired. We use calcium oxide in C, as the drying agent. The tap T, serves to release the vacuum in A and the capillary system, water vapour being excluded from the latter by the similar drying tube, C,. The mano- meter, M, gives a continuous indication of the pressure, the lower ends of both M and the tube D being drawn out to an external diameter of approximately 1 mm. The tube D passes through a three-hole rubber bung into the jar E, where it dips into about 1 cm. of mercury. Also passing through the bung are the tap T, (which is optional) and the t ~ b e P, which is connected to the pump, and whose lower end is protected by the tube H.The latter gives a running fit on P, and is closed at the lower end. It is buoyed up by the mercury and presses on the lower surface of the bung. To prevent this from giving a gas-tight seal, it is necessary to cut a very small notch in the rim with a triangular file. The apparatus, A, having been evacuated with both taps closed, the vacuum is releasedas follows- (i) Either the pump is turned off or T, is opened. (ii) TI is opened. The object of this routine is to avoid the violent agitation of the mercury in the jar E which results when T, alone is opened, and may cause mercury to be drawn into the pump despite the protection To f- - f , I All tubing I mm. bore M NOT TO SCALE 6 5 ems.-+ Fig.1Seyt., 19501 NOTES afforded by H, especially if the mercury is too deep. The same trouble at thecommencement of the evacuation of a large vessel can be controlled by the use of a screw clip on the tube B. A simplified form of the device may be made in which the manometer M is omitted, when a reading of the pressure at any time may be had by opening T,. The mercury at once rises in D and may be measured, whilst the vacuum in the rest of the system is unaffected in the absence of leaks such as dry ground-glass joints in A. The device described, apart from preventing the entry of liquid water from the pump, offers the additional advantages that water vapour from the pump is excluded from access to the drying agents, and, further, TI provides a convenient point at which to inject an inert atmosphere when A has no such point.Excess pressure from a cylinder attached at TI is allowed free egress through the pump, in case of accident. Again, the additional volume to be evacuated is minimised, especially when E has filled with water, whereas the usual water-trap is often larger than the apparatus in use. VIROL LTD. HhNGER LANE EALING, LONDON, w.5 P. R. BOOTH April, 1950 A DELICATE TEST FOR CUPRIC AKD FERRIC IONS IN AQUEOUS SOLUTIOK ~C-HEN potassium hydrogen phthalate and hydrogen peroxide are boiled together in aqueous solution, in the presence of traces of copper or iron salts, the phthalate ion undergoes degradation with the evolution of carbon dioxide and the formation of a strongly brown-coloured colloidal solution.This reaction can be used as the basis of a sensitive test for the two metals. No other metal has been found to give the same series of changes. PROCEDURE- Take 100 ml. of the solution under test, add 10 nil. of 0.2 N potassium hydrogen phthalate and 10 ml. of 20-volume hydrogen peroxide, boil, and maintain a t 97" to 99" C. The formation of the brown colour is progressive, and both the time which elapses before the colour is noticeable and the intensity after any given time depend upon the concentration of catalyst. With metal concentrations of 10-5 M , 2 minutes at 98" C . are sufficient to develop a distinct colour, after which the intensity continues to build up with time. Ten minutes will give a coloration with 10-6 M solutions, and about an hour gives a detectable colour at lo-' M.At concentrations lower than lo-' M , some additional reaction between the brown coloration and the excess peroxide interferes with the progressive formation of the colour. A distinction between copper and iron can be drawn from the fact that fluoride ions completely inhibit the development of the colour with iron catalysis but have no influence on the copper- catalysed reaction. Any reagent that removes the free metal ions from solution is similarly effective, e.g., phosphate ions with iron catalysis. It is always advisable to carry out blank experiments to check that the reagents are free of catalysts to the desired degree. The water used in these experiments had been distilled twice, the second time from an all-Pyrex glass still. The phthalate had been recrystallised twice from the distilled water and the peroxide was made up by dilution from a stock solution of 100-volume material. With these precautions, the phthalate and peroxide could be boiled together for 6 hours without the slightest formation of the brown colour.A preliminary study of the reaction has been made, and there is strong evidence to support the view that the metal catalyst is cyclically oxidised and reduced with the liberation of hydro- peroxide radical (HO,) , which is then responsible for the degradation of the phthalate and the formation of the brown colour. Other, but not all, benzene carboxylic acid salts give analogous reactions and a great many benzene derivatives undergo severe degradation when in reaction with peroxide and catalyst.Experiments are proceeding on the detailed mechanism of the reaction and it is hoped to publish a full account elsewhere in the near future. DEPARTMENT OF INORGANIC AND PHYSICAL CHEMISTRY UNIVERSITY OF LIVERPOOL G. A. BOTTOMLEY Aeril, 1950502 NOTES [Vol. 75 A TEST FOR VOLATILE SUBSTANCES PRESENT I N TRACES APPLICATION TO CYANIDE BY using an inert gas, generated along with the sample in a simple form of Gutzeit apparatus, as a stripping agent and carrier, and a suitable test paper, traces of many volatile substances can be easily and quickly detected and, under appropriate conditions, approximately estimated. A small flask is fitted with a stopper carrying it short glass tube that has a constriction near the top on which the test paper rests. To prevent spray from reaching the paper the lower end of the tube is loosely plugged with cotton wool, which is changed for each test.The most suitable paper for the test strips seems to be Whatman No. 54 filter-paper; it is semi- transparent when wet, so that stains show up very clearly, and it can also be dipped into moderately strong acid or alkali, when required, without becoming distorted. It is cut into 4 to 5-mm. wide strips trimmed to a point with an angle of about 60” to enhance sensitiveness. For the detection of traces, this is more sensitive than the modified disc form, because, with a suitable rate of gas production, the stain forms on a much smaller area. For the detection of traces of cyanide by the method of Gettler and Goldbaum,l about 1 inch of the end of the strip is dipped in slightly acidulated 10 per cent.ferrous sulphate solution and dried. Before use, the end is dipped in 10 to 20 per cent. caustic soda solution and the excess removed by momentarily resting it on filter-paper. The sample and a few grams of zinc of suitable quality are placed in the flask, about 25 ml. of 10 per cent. sulphuric acid solution are added and the stopper with the test paper in place in the tube is inserted. Hydrogen should be evolved freely but not vigorously, the solution being opaque from the presence of innumerable minute bubbles, biit not forming a froth; the rate can be regulated by adding copper sulphate solution. The zinc for this test should be pi-actically free from sulphide, since hydrogen sulphide stains the paper black and, if present in any quantity, discharges the cyanide. The paper is removed and “developed” in 50 per cent. hydrochloric acid to which a little ferric chloride has been added. If cyanide is present the tip of the paper will show a blue stain. A microgram of hydrocyanic acid is clearly detected in 15 minutes and, with appropriate conditions so that hydrogen is evolved steadily for 45 to 60 minutes, even 0.2 microgram will give a minute stain on the extreme tip of the paper; it is distinctly visible when an unexposed strip is placed in the acid beside it for comparison. REFERENCE 1. Gettler, D. A., and Goldbaum, L., AnaZ. Chew., 1947, 19, 270; Abst., Analyst, 1949, 74, 473. DEPARTMENT OF CHEMISTRY ADELAIDE, SOUTH AUSTRALIA A. R. HICKINBOTHAM February, 1950

ISSN:0003-2654    

DOI:10.1039/AN9507500499

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

Sept., 19501 503 MINISTRY OF FOOD Ministry of Food STATUTORY INSTRUMENTS* The Food Standards (Preserves) (Amendment) Order, 1950. 1950.-No. 1056. Price 2d. This amending Ordev, which comes into force (a) in respect of sales by the manufacturer of the article, on the 25th day of September, 1950; (b) in respect of sales by wholesale and sales by retail, on such dates as the Minister of Food may by Order appoint, raises the minimum f r u i t contepit of cevtain jams by aniertding the Food Standards (Preserves) Order, 1944, as amended by S . R. & O., 1944 (No. 842), II, p . 513, S.R. d+ O., 1946 (Nos. 157 and 1221), 11, p p . 26 arid 25, and S.I., 1949 (No. 1893), I I , p . 9, by substituting the following f o r Part 11 of the Schedule- THE SCHEDULE PART I1 Minimum Fruit Contewf Column 1 Description of Jam or Marmalade (Fresh Fruit Standard or Full Fruit Standard) -I,-- JAM -%pple and Blackberry .. . . . . . . . . . . Apple and Blackcurrant . . . . . . . . . . . . Apple and Damson . . . . * . . . .. .. . . Apple and Plum . . . . . . . . . . . . . . ,%pple and Raspberry and,t'or Loganberry . . . . . . . . ,4pple and Strawberry . . . . . . . . . . . . Apple Jelly . . . . . . . . . . . . . . . . ,4pricot . . . . . . . . . . . . . . . . . . Apricot and Peach . . . . * . . . . . . . . . Bilberry. . . . . . . . . . * . . . . . . . Blackberry (or Bramble) and Blackberry (or Rramblc) Seedless or Jelly . . . . . . . . . . . . Blackcurrant and Blackcurrant Jelly . . . . Cherry . . . . . . . . . . . . . . Damson and Dainsoii Jelly . . .. . . . . EIderberry Jelly and Elderberry Seedless . . . . Gooseberry . . . . . . .. . . . . Greengage . . .. . . . . . . . . Loganberry . . . . . . . . . . . . Peach and Mixtures of Peach with Citrus Fruit . . Pineapple . . . . . . . . . . Plum and Plum Jelly . . . . . . . . Plum and Blackcurrant . . . . . . Plum and Raspberry . . . . . . . . Plum and Strawberry . . . . . . Raspberry and Gooseberry . . .. . . Raspberry and Loganberry . . .. . . Raspberry and Redcurrant . . . . . . Redcurrant Jelly . . . . . . . . Rhubarb and Blackberry . . . . . . Rhubarb and Raspberry . . . . . . Strawberry . . .. . . . . . . Strawberry and Gooseberry . . . . . . All other Jams .. . . .. . . Quince 'Jelly . . . . . . . . . . Raspberry and Raspberry Seedless or Jelly Rhubarb . .. . .. . . . . B.-MARMALADE~ . . . . .. . . . . . . .. .. .. .. . . . . . . . . .. . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. . . . . . . . . . . . . . . .. .. .. .. .. .. . . . . . . .. .. .. . . .. .. . . . . .. . . Column 2 Percentage of Fruit or Vegetables 40 (30/10) 40 (30/10) 40 (30/10) 40 (30/10) 40 (30/10) 40 (30,/10) 40 4 0 40 40 (20/20) 38 22 40 38 40 30 38 25 40 40 40 40 (30/10) 40 (30/10) 40 (30/10) 40 25 30 (15/15) 25 (15/10) 30 (15/15) 35 40 40 (30/10) 40 (30/10) 371; 35 (179/173) 40 20 No~~-M'here figures in brackets are specified in the second column above in respect of a description of jam containing more than one variety of fruit or vegetables, the first figure denotes the content of the variety of fruit or vegetables first mentioned in such description, and the second figure denotes the total content of the other varieties of fruit or vegetables mentioned in such description.t For special standard marmalade, see paragraph 5 of Part I of this Schedule. * Obtainable from H.M. Stationery Office. Italics indicates changed wording.584 MINISTRY OF FOOD [Vol. ‘i5 1950.-No. 1061. The Labelling of Food Order, 1950. Price 6d. This Order substantially re-enacts in a consolidated form the Labelling of Food Order, 1946 (,41talyst, Certain 1947, 72, 65) and its amending Orders. new provisions have been introduced, the principal ones being- Weights and Measures provisions are omitted. to Provide for the use of the description ginger wine or orange wine f o r products wholly or partly derived from f r u i t other than grapes; to permit the sale of Black Beer aizd Rum containing not less than 20 per cent.proof spirit; to permit the sale of alcoholic cordial containing ?tot less than 5 per cent. proof spirit subject to special labelling requirements ; to permit the sale of bitters containing not less than 15 per cent. proof spirit; to permit the sale of non-alcoholic f r u i t (or vegetable) juice cocktail containing not less than 80 per cent. undiluted f r u i t or vegetable juice; to provide that all liquors for which tonic, i*estorative OY niedicinal properties are claimed or which are held out to be benejicial for invalids shall be labelled with a statement indicating the quantity of the ingredients on which the claim i s based; to impose requirements as to the labelling of pvepacked concentrated acetic acid; to prohibit the claiming of tonic properties f o r any food by reason only that the food contains (a) alcohol, (b) sugars OY other carbohydrates, (c) protein or substances prepared by the hydrolysis of protein, or (d) caffeine or other purine derivatives; to require that pre-packed cheese be labelled in compliance with the provisioits of the Order, except as regards declaration of ingredients ; to require that the ingredients of Christmas puddings be specified after the 31st iIarcli, 1951; to permit nuts and synthetic cveain to be designated cs such when forming a n itig~edieiit of some other food; fish to be designated (IS such when forming a n ingredient o j fish products, and vine fruits to be designated as szrch when forming a n ingredient of some other food other than a beverage; to require tomato ketchup, catsup, sauce a d velish prepacked for sale as such to be Iabelled with a declaration of ingredients.The provisions of this Order come into force on the 1st of Norember, 1960, on which date the Labelling of Food Order, 1946, i s revoked. 1950.-No. 1239. The Mineral Oil in Food (Amendment) Order, 1950. Price Id. This Order, which comes into operation on August l s t , 1950, amends the Mineral Oil in Food Order, 1949 (S.I., 1949, No. 614), so that the prohibition in the principal Order relating to mineral oil in food shall not apply in relation to dried fruit containing not more than 1 part by weight of mineral oil per 100 parts bv weight of dried fruit; and makes provision as respects articles of food containing mineval oil by reason of the inclusion therein of dried f r u i t containing mineral oil.Dried fruit i s defined as primes, citrrants, sultanas and raisins. CIRCULAR MF11/50 This circular, dated 27th June, 1950, gives a list of products that have been approved by the Ministry of Agriculture and Fisheries and the Ministry of Food, under Regulations 26 (6) (a), which provides for the zrse of oxidising or preservative agents as alternative to scalding &th boiling water or steam, in the cleansing of w i l k fankers, vessels or appliances. A l l the products so f a r approved are solutions of sodium Jaypochlorite, having a total available chlorine content of between 9 and 12 per cent. w/w, and containing not less than 0-7 per cent. w/w of sodium chlorate, .to act as a detector should any sodium hypochlorite solution get into the milk through vessels not being properly rinsed’or otherwise, and not more than 2 per cent. w/w of free caustic alkali. Regulation 26 (6) (c) requires that all traces of sodium hypochlorite solution (or of any other oxidking or preservative agent that may in future be approved) used for cleansing purposes, shall be removed from milk tankers, vessels or appliances before they are again brought into contact with milk. Samples of milk should accordingly be taken occasionally for testing for the presence of chlorate where approved sodium hypochlorite solutions are used by the dairy, as a check on compliance with this regulation. 6. The list of products i s as follows- DEOSAN, CHLOROS, DAIROZON, HYPOSAN, DELSANEX.

ISSN:0003-2654    

DOI:10.1039/AN9507500503

出版商:RSC    

年代:1950

数据来源: RSC

摘要:

Sept., 19501 REVIEWS 805 Reviews OILS, FATS AXD FATTY FOODS-THEIR PRACTICAL EXAMINATION. By K. A. WILLIAMS, B.Sc., Ph.D., F.R.I.C. Third Edition. Pp. ix + 500. London: J. & A. Churchill, Ltd. 1950. Price 63s. The first edition of this work by Bolton and Revis was published in 1913 under the title, “Fatty Foods-Their Practical Examination.” It is not now possible to say whether it satisfied a growing demand or whether by the presentation of a carefully considered selection of methods at a time when-as pointed out by the authors in their preface-“the analysis of oils and fats was both prolific of method and uncertain in result” it focussed attention on an unsatisfactory situation and thereby created the demand, but in any case it was immediately accepted as an invaluable reference book and attained a very wide circulation.A second edition by Bolton, with the indicative name now altered slightly to “Oils, Fats and Fatty Foods,” was published in 1928. This covered much the same ground as its predecessor. A third edition has long since been called for but, as pointed out by Dr. Williams, the second world war effectively interfered and it was not until hostilities ceased that he could turn his attention to this task. The general method of presentation remains unaltered, although particulars of more recent and proved methods have been added to the older fundamental methods that have stood the test of time; and a number of oils are now described which do not appear in the earlier editions. The section on milk products and vitamins has been extended; and a new feature is that not only are the usual ranges of analytical data and figures for typical specimens given but, in the case of the more important oils and fats, the standard figures of the British Standard Institution, the British Pharmacopoeia and the American Oil Chemists Society (U.S.A.) are also given.Following on a general introduction covering 11 pages, the next 55 pages are devoted to consideration of methods of sampling and preliminary examination, this being the author’s some- what modest way of referring to descriptions of suitable techniques for the preparation of samples for analysis, the determination of moisture and residual solvents, impurities, metallic contamination, glycerine and glycols, refining tests, rancidity, keeping quality and susceptibility to oxidation, and preservatives.It covers the range of such examination, analytical and physical, as may be necessary for commercial purposes. It is to be noted that it does not start from a sample in a bottle, but rather from a wharf with a barge loaded with oil alongside or from a store where the raw material is stacked in barrels or stored in tanks: it thus surveys the problems so often presented in actual practice. In many ways this chapter on sampling and preliminary examination determines the outstanding character of the book.506 REVIEWS [Vol. 75 The next chapter deals with analytical methods, with full working details, and includes methods officially accepted as standard. Here it is to be noted that Dr. Williams points out in his introduc- tion that he has not covered the whole range of analytical methods used in the investigations of oils and fats, and that many methods not commonly used by him have been excluded.It might possibly have been useful to have added a warning that what is accepted to-day may be abandoned to-morrow and that acceptance of a standard method should not mean the abandonment of critical examination and of personal initiative. The extent of the new matter in this chapter can be assessed from the fact that the 55 pages in the previous edition have now been extended to 86 pages : inter alia, melting-point methods and colour assessment, particularly with the aid of modern physical instruments, require six or seven times the earlier space; and new additions include bromine, thiocyanogen, and hydroxyl values, determinations of oxidised acids, linoleic, linolenic and elaeostearic acids, ester fractionation, and estimation of monoglycerides and glyceryl esters.As an example of the critical way in which methods are considered in this chapter the section on specific gravity and apparent density may be quoted, where, after the usual details of apparatus and correction for temperature, further information on the effect of and correction for stearine deposition are given, followed by a brief but fully detailed account of the method for calculating the weight of oil in bulk when tanks scales are not available. Short chapters follow on interpretation of analytical methods with analyses of typical samples, industrial production of vegetable oils and fats, and the manufacture, characteristics and analysis of hydrogenated or hardened oils.About two-fifths of the book is required for what may be regarded as the analytical section indicated above; the next section of about the same length deals first with butter and margarine, then with animal fats, next with marine animal and fish oils, and finally with over one hundred vegetable oils and fats. As with the earlier editions, the sources, characteristics and analytical data of the various oils and fats are given, and as these include many new additions the unique value of this section as a reference book has been very substantially increased. The final section deals with cooking fats and lard substitutes; cocoa, chocolate and milk chocolate; animal feeding stuffs; milk and milk products; and a dissertation of 8 pages on the nutritive value of edible oils and fats.Dr. Williams is to be heartily congratulated. not only on his comprehensive and thorough revision of the original work, and on the additional data that bring the book up to date, but also on the inclusion of so much new and valuable information based on his own extensive commercial experience. One effect of this is that the sub-title reference to the practical examination of fatty foods takes on a new meaning. The methods as set out are, of course, practical as any other analytical methods are practical, but the issue of this book is rather in effect the practical examina- tion of the results of analysis, a somewhat different matter.GEORGE TAYLOR ,4N ADVANCED TREATISE ON PHYSICAL CHEMIE~TRY. By J. R. PARTINGTON, M.B.E., D.Sc. Volume I: Fundamental Principles. The Properties of Gases. Pp. xlii + 943. London: Longmans, Green & Co. 1949. Price 88s. It was to the courageous enterprise of the House of Longmans that we owed the publication in English of the first “Comprehensive Treatise on Inorganic and Theoretical Chemistry” by J. W, Mellor, perhaps the only person in Great Britain endowed with the qualities necessary for the successful composition of such a work. Now we can welcome, again owing to the enterprise of the same publishing firm, the first of three 017 four volumes of a comprehensive treatise on Physical Chemistry, and again we can recognise in the author. perhaps the only one in Great Britain who has the knowledge, teaching experience, literary ability and physical energy required for the task.Since an undue extension of the period of publication is one of the dangers to which all comprehensive treatises must be subject, it is gratifying to learn that the second volume of this work is already in the press. The author adopts the van’t Hoff definition of physical chemistry as “the science devoted to the introduction of physical knowledge into chemistry, with the aim of being useful to the latter,’’ and the present work is intended to present this field of science as a whole, The term “advanced” occurring in the title refers to the size and scope of the work rather than to its difficulty. Its principal aim is to give information to those in search of it and not to train students or even to “make readers think”; and the author believes in encouraging an open and receptive attitude towards original thought rather than in producing an attitude of scepticism and unreceptiveness.\J7hile dealing fully with the relevant theory, due regard will be given to descriptions of experimental Congratulations may be offered tmo both publisher and author.Sept., 1950J REVIEWS 507 methods: and it is intended to assemble “empirical or semi-empirical formulae which are likely t o be of interest to laboratory workers or to chemists or engineers engaged in large-scale work, who often require quantitative data not available which can be calculated with sufficient approxima- tion for their needs by means of such formulae.” In view of the author’s well-known interest in the history of science, i t is not surprising to learn that the treatment of a section often begins with a short historical survey.Such a survey, even if it may not be, as the author thinks, to the taste of all readers, isAessentia1 in a comprehensive treatise and will, the reviewer believes, be welcomed by most readers. Practically half of the present volume is taken up with a mathematical introduction, dealing with the elements of the calculus and passing on to differential equations and Fourier’s series, and with an account of the principles of thermodynamics, the kinetic theory of gases, statistical mechanics and wave mechanics. There then follow sections on thermometry, high and low temperatures, and a long section on the properties of gases.Whether in a treatise such as that under review, which will presumably be used not by the undergraduate but by the graduate student and specialist worker in physical chemistry, the space of 114 pages should be allotted to a mathematical introduction is no doubt a matter of opinion; but the thought occurs that either the reader will have already passed beyond the need for such a condensed treatment of mathematics, or such a condensed treatment will fail to meet his needs. The author, however, is a teacher of long experience and respect must be paid to his judgment. I n any case, one can recognise the excellence of the author’s treatment of the subject. A special word of praise must be given to the clearness of the type in which the mathematical formulae are printed.Even the smallest symbols are readily legible without eye-strain. The book is eminently readable and the author writes with the knowledge and lucidity of style with which his previous works have made us familiar. Xo doubt a few minor errors or misprints occur-a few such have been noticed-but it is obvious that the author has taken great pains to secure the maximum degree of accuracy. Although one hesitates to question the author’s accuracy in matters of historical detail, one statement has caught the reviewer’s eye which seems to call for comment. On p. 510 the author states that “the first to obtain liquid hydrogen in bulk was Dewar in 1895.” In 1895, Dewar, by the expansion of hydrogen at -ZOOo obtained a jet of gas along with a liquid; but he himself describes the production andcoEZection of liquid hydrogen as being carried out for the first time on May loth, 1898.All students and workers in the field of physical chemistry, and all teachers of physical chemistry, will be grateful to Professor Partington for his Advanced Treatise, and one can only express the hope that the author will be able t o bring this truly monumental work to a conclusion at not too distant a date. ALEX. FINDLAY Of the work as a whole, one can speak only in terms of the highest praise. Is this really correct ? OUTLINES OF PHYSICAL CHEMISTRY. By F. DANIELS, Ph.D., B.Sc. Pp. viii + 713. New York: Appearing first in 1913, Dr. F. H. Getman’s “Outlines of Physical Chemistry” has passed through seven editions, the last four of which have been Dr.Daniels’ complete responsibility. His revisions have been so extensive that nothing remains of Dr. Getman’s original work, so the present edition has been issued under Dr. Daniels’ name as the first edition of a new book. How- ever, it is still recognisable to the reviewer who learned his physical chemistry with the aid of the last edition of “Getman and Daniels.” Much has been revised and recent work has been added, including data (e.g., on p. 646) from journals published in 1948, the year of publication of the book, a creditable achievement in a textbook for degree students. A table of stable and unstable isotopes (pp. 647-654) gives data on all 96 elements to curium, including the artificial products of the atomic pile.Turning the pages, the reviewer noticed the heading “Transmutation” and was interested to learn (on p. 664) that the aim of the alchymist has been reversed. It is now profitable to transmute gold into mercury. A quantity of the stable mercury isotope lg8Hg has been prepared in an atomic pile from gold, which occurs naturally as the single isotope 19’Au; this isotope of mercury gives a strong narrow spectral line a t 5461 A., which may well become the primary standard of length in preference to the cadmium red line, which is about double the width and requires a higher temperature of excitation. As natural mercury is a mixture of seven stable isotopes each giving its own spectral line of slightly different wavelength, it cannot be used for accurate measure- ment.John Wley & Sons Inc. London: Chapman & Hall, Ltd. 1948. Price $5.00; 40s.508 REVIEWS [Vol. 75 The scope of the book is wide, and covers all aspects of physical chemistry at degree level; there are many clear diagrams and a large selection of problems at the ends of the chapters. The text ranges from the correct pronunciation of “entropy” (p. 143) to an appendix which includes the mathematical development of the Debye -. Huckel theory (p. 680). In the usual three-letter abbreviation for ‘ I ‘ electro-magnetic units ” (p. 396), the omission of both punctuation and spacing produces a sligh.tly zoological effect. J. B. ATTRILL THE ANALYTICAL CHEMISTRY OF INDUSTRIAL POISONS, HAZARDS AND SOLVENTS. By M. B. JACOBS, Ph.D. Second Edition. Pp. xviii + 788.New York and London: Interscience Publishers Inc. 1949. Price $12. This book was first published in 1941 (Review, Analyst, 1941, 66, 477); it has now been considerably enlarged, and it aims to cover the field of analytical chemistry of industrial poisons exhaustively. In his first edition, Dr. Jacobs modestly hoped that his work would be useful in industry . . . and for chemists and toxicologists. The book is most useful and indeed the reviewer knows of no other book covering this ground that is so com- prehensive and contains so much information. To the analyst who has occasion to work in this field it is indispensible, not only describing all the appropriate methods of testing, but also giving information on the physiological effects, limits of tolerance and toxicity of a great range of products from the point of view of an industrial hazard.The author has greatly extended the analytical parts of the work; he has called in aid all kinds of newer techniques, electrical and mechanical, as well as physico-chemical and chemical methods. The enumeration and study of dust particles is well described; so also are questions of fire and explosion risks as well as purely physiological effects. The range of compounds covered and the enumeration of specific sensitive reactions for so many of them is a most valuable feature; the author has evidently roamed very thoroughly over the literature to find and describe with an intimacy of detail so many specific and useful methods. Notable, also, is the inclusion of newer reactions-or should one say newer applications of old reactions-for the detection of traces of elements such as arsenic, lead, antimony, fluorine; and methods suitable for residues from fumigation gnd to compounds new to industry, such as tetramethylsuccinonitrile, which is used in the blowing of sponge rubber.Altogether the work contains a wealth of information-which is of great value to the practising chemist in very many fields, He was certainly right. H. E. Cox MODERN SYNTHETIC RUBBERS. By HARRY BAKRON. Third Edition. Pp. xix + 636. London: The two previous editions of this book have been reviewed in The Analyst (1943, 68, 97; 1944, 69, 199). Their arrangement and style are closely followed by the third edition, but this is very considerably expanded by the inclusion of knowledge gained during the war and subse- quently released in a large number of publications, notably by the Combined Services Intelligence Reports on German industry. The value of the book has been greatly enhanced by these additions but they are also, at least partly, responsible for an increase in price of 17s., which must deter many who would otherwise buy the new edition. Methods of analysis of synthetic rubbers are discussed in the final chapter, which is now expanded from 17 to 29 pages. The extent of this increase is, however, somewhat illusory because the extra space is largely occupied by tabulated properties of various materials. There are only three additional references to the literature, and one of these-Ministry of Supply, Users’ Memorandum No. U.9-is not discussed in the text. This pamphlet shows how to estimate natural rubber by oxidation to acetic acid, a reaction not undergone by GR-S, so that Barron’s statement (p. 580) that “analysis will not show up any marked difference” is not justified-in fact, on pp. 591 and 593 he himself describes colour tests to distinguish between them! Chapman & Hall Ltd. 1949. Price 45s. G. H. WYATT

ISSN:0003-2654    

DOI:10.1039/AN950750505b

出版商:RSC    

年代:1950

数据来源: RSC