ANALYTICAL EDITION
September 15, 1941
OF PHOSPHORUS I?; SYNTHETIC TABLE I. DETERMIXATION SAMPLES,
Ferromolybdenum 0 . 0 2 5 , 0 . 0 2 6 , O.OZS% (Si 0.647,) 0.026, 0.027, O.O2STc 0.025,0 . 0 2 7 , 0 027Y0 0 . 0 2 8 , 0.030%a (Si 0.77%) 0.038, 0.038% (Si 0.90%)
Calcium Molybdate 0.014, 0.015, 0 017y0 a
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precipitation takes place a t about 80" C. the yellow precipitate is (NH4)3P04.12M003.H?;Os, which requires 24 moles of sodium hydroxide per mole of phosphorus. Thus, the fact that there exists more than one yellow precipitate requires proof as to whether or not a new yellow precipitate forms under the new conditions of precipitation. The results indicate that the familiar (NH4)3P04.12M003forms. Two previous papers (4) have discussed the determination of sulfur and copper in ferromolybdenum.
llanufacturer'b analysis: P 0 OZS?, Si 0.74%.
iiom the hot plate and cooled, and 25 cc. of water are added, followed by 25 cc. of ammonium hydroxide. The mixture must be stirred to dissolve all the molybdic acid. Failure to do so leads to high results. Previously, solid ammonium nitrate had been used (because of its cooling effect) in conjunction with less ammonium hydroxide, but the technique vas changed to include 25 cc. of ammonium hydroxide to be certain that no deposits of oxide remained. The purpose of the "synthetic sample" is to check the yello^ precipitate, and to show that the standard sodium hyliroxide-hydrochloric acid solutions should be 0.148 A' as TI ith the usual precipitations for phosphorus a t 40" C. Ordinary yellow precipitate, (SH4),P04.12NoO3, requires 23 moles of -odium hydrouide for each mole of phosphorus P ; but when
Results The first synthetic sample was 1gram of ammonium molybdate plus 0.5 gram of Bureau of Standards No. 82 (0.102% P, 2.78% C, 2.09% Si), planned to represent a high-silicon high-carbon ferromolybdenum. This represented 0.051 per cent phosphorus. The recovery was 0.051 and 0.051 per cent. A second synthetic sample used Bureau of Standards S o . 19c (0.049% P, 0.21% C, 0.20'% Si). This represented 0.025 per cent phosphorus. The recovery was 0.023 and 0.026 per cent phosphorus. Results for routine determinations are found in Table I.
Literature Cited (1) Johnson, C.XI., "Chemical Analysis of Special Steels", 3rd ed., p. 42, iYew York. John Wiley & Sons, 1920. (2) Lundell, G. F., "Chemical Analysis of Iron and Steel", Chapter 11, New Tork, John Wiley & Sons, 1931. (3) I b i d . , Chapter 36. (4) Silverman, Louis, IND.ESG. CHEM.,ANAL.ED., 10, 433 (1938), 12,343 (1940).
Determination of Zirconium in Steel A Rapid Colorimetric Method W.kLTER G. 14.41 E S
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EDWARD W. JONES, Great Lakes Steel Corp., Chemical Laboratory, Ecorse-Detroit, Mich.
HE authors, needing a rapid routine method for the
determination of zirconium in steel and finding none t h a t n a s completely satisfactory, made a search of the general literature on zirconium determinations. After investigation of several methods, the precipitation of zirconium by p-dimethylaminoazophenylarsonic acid described by Feigl (I), together Jvith the colorimetric measurement of the precipitated reagent as reported by Kazarenko (Z), was selected as the most satisfactory approach. This determination can be made without preliminary separation of iron or other elements, although considerable amounts of manganese, silicon, chromium, etc., are present in the steel. This, however, necessitates standardization against similar steel of known zirconium content. The importance of this is shown in Figure 1, which was obtained by plotting milligrams of zirconium against the readings of a Cenco-Sheard-Sanford photelometer on semilog paper, When no considerable amount of other metals is present, and the solutions to be precipitated contain more than 5 micrograms in 10 nil. or less of 2 N hydrochloric acid, line C is obtained. The precipitate in this case probably contains the reagent and zirconium in the proportions of 2 to I, as indicated by [(CH& K o X = K(l>As0,l2Zr. X h e n the solutions contain the same amount of zirconium in 50 ml. of 2 S hydrochloric acid, line B is obtained. In this case, much of the zirconium probably precipitates as [ ( C ' H & S O Y = S a . % q03]Zr0. , Line A , which is
used with the proposed method, was obtained by precipitating the zirconium from 50 ml. of solution containing 0.1 gram of steel, which had been analyzed for zirconium by the selenious acid method. If extreme accuracy were desired, a preliminary separation of zirconium by means of a mercury cathode or other suitable method would make it possible to use line C, giving about twice as many scale divisions for the same amount of zirconium.
PHOTEL OMETER REARING FIGURE1
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Reagents Required Hydrochloric acid, 1 part to 1 part of water. Crystalline potassium hydrogen sulfate. Ammonium hydroxide, specific ravity 0.90. Hydrochloric acid wash, 10 ml. of concentrated ydrochloric acid er liter of water. Ammonium hydroxide wash, 333 ml. dilute! to 1 liter with water. p-Dimethylaminoazohenylarsonic acid, 0.250 gram of dye, 10 ml. of concentrated ydrochloric acid, diluted to 250 ml. with ethyl alcohol.
%
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Method Dissolve 1 gram of sample in 50 ml. of 1 to 1 hydrochloric acid. When solution is complete, dilute to 75 ml. with water and filter. Save the filtrate. Wash the residue 3 times with hot water, 3 times with hot 1 to 1 hydrochloric acid, and 3 times with hot water. Ignite paper and residue in a platinum crucible, fuse ash with as little potassium hydrogen sulfate as needed, dissolve cooled melt by heating the crucible, and melt in a beaker containing 100 ml. of water and a few drops of sulfuric acid. Now remove the crucible, washing well with hot water, and to the solution of dissolved melt add 2 drops of methyl orange indicator and a slight excess of ammonium hydroxide; boil a minute, filter, and wash the precipitate with cold water. Put paper and recipitate back into the beaker, add 50 ml. of 1 to 1 hydrochgric acid, break paper into pulp, and heat to boiling. Boil a minute and filter into original filtrate saved from first filtration. Wash well with hot water, transfer to a 500-ml. volumetric flask, cool, and dilute to the mark with water. Mix well and ipet 50 ml. of the combined filtrates into a 250-ml. beaker. bring the measured 50 ml. of solution to the boiling point, add 15 ml. of dye solution, cover with a watch glass, boil 1 minute, and remove from plate. Let stand at room temperature for a t least 30 minutes. Filter through 3 close-texture filter pa ers, wash excess dye from papers, and precipitate with hydrochforic acid wash solution. After washings are absolutely colorless, set the funnel containing washed paper and precipitate into the neck of a 100-ml. volumetric flask. Now remove dye combined with zirconium by washing with ammonium hydroxide wash, about 3 to 4 washes. Dilute to the mark with water, mix well, and fill absorption cell by filtering through cotton. Photoelectric reading is read in milligrams of zirconium on plotted curve.
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In this case, weight in grams X 10 X 100 = per cent zirconium. The solution of dye which is colorimetered is yellow. A blue filter is used in the photelometer.
In the authors’ laboratory this determination is made in less than 2 hours. The results do not deviate by more than 0.005 per cent from those obtained by the selenious acid method. This method is subject t o the same necessity for fusion of the insoluble zirconium with potassium pyrosulfate that is met in all other methods. It is possible, however, t o eliminate the usual sodium carbonate fusion when working with steel containing less than 0.05 per cent of phosphorus. The authors have added phosphorus t o the original solution of the steel in amounts equivalent to 0.170 per cent without producing any significant change in the results for zirconium. However, with some steels a sodium carbonate fusion of the residue should be made before fusion with potassium pyrosulfate. Titanium interferes with this method by reacting in the same manner as zirconium, but this can be prevented by adding 3 drops of 3 per cent hydrogen peroxide before the precipitation, if the titanium is not more than 10 times the airconium content. The p-dimethylaminoazophenylarsonic acid obtained from the Paragon Testing Laboratories, Orange, N. J., has been found very satisfactory. The authors were handicapped in their work by the fact that there is no Bureau of Standards steel sample of certified zirconium content. Literature Cited (1) Feigl, F., Krumhols, P., and
Rajman, E., Mikrochemie, 9, 395
(1931). (2) Nasarenko, V. A.,
J. Applied Chem. (U.S. S. R.),10, 1696-9
(1937).
A Study of the Ferric Thiocyanate Reaction CHARLES A. PETERS AND CHESTER L. FRENCH, Massachusetts State College, Amherst, Mass.
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HE thiocyanate method for iron is much used. However, it has some disadvantages. Kitrates generally in-
tensify the color, although small amounts may be tolerated with some concentrations of thiocyanate (14, 16). Phosphates change and decrease the color (4, 6) and salts may interfere (1,3, 6,9,13). I n view of these facts a study of the optimum conditions for the development of the red ferric thiocyanate color and the effect of salts on the color was undertaken. It has been assumed by Schlesinger and VanValkenburgh (12) that the red substance is the complex ion, Fe(CNS)G---; however, the work of Bray and Hershey (2) and Lamb and Jacques (6), indicating the existence of FeOH++ and FeCl++, leaves the authors ready t o accept evidence that the complex may contain less than six thiocyanate ions.
Procedure and Reagents Dilutions of an iron wire solution, oxidized with hvdrogen peroxide, were prepared daily and had a pH of 2.5. The reagents were added in the following order: thiocyanate, dilution water, acid, hydrogen peroxide, iron, and water to the mark. Hydrogen peroxide, when used, was added in quantity to make the solution either 0.0032 or 0.0064 molar. Inasmuch as the formula weights of CNS and Fe are nearly the same, the figures agp. p. m. may be read as molar quantities with only slight loss in accuracy.
Interfering Substances Nitric acid intensifies the color with thiocyanate in t h e presence of iron, Experiments in the absence of iron showed that solutions 0.1 N with nitric acid also developed a color when the thiocyanate concentration exceeded 0.1 N and, if the acid were changed to hydrochloric, solutions 1.26 N with this acid developed a color when the thiocyanate exceeded 0.05 N ; when the hydrochloric acid was weaker, 0.1 N , the thiocyanate had to be 0.4 N t o develop color. I n a previous article (11) the amounts of hydrogen peroxide necessary to make a colored substance from thiocyanate were given, but no limit for a safe maximum was set. Further work showed that the peroxide could be increased to 0.0064 M without significant error, but greater concentrations intensified the yellow color produced.
Thiocyanate-Iron Influence on Color From the formula Fe(CNS)G--- one would expect to obtain a colored solution when the molar ratio of CNS/Fe equaled or exceeded 6. In order to find out if the amount of thiocyanate necessary t o produce a color bore any relation t o this ratio, several experiments were performed in which various amounts of thiocyanate were added t o iron in 5 0 4 . Nessler tubes, the acidity being 0.01 N . The least amount of
