Rapid Determination of Phosphorus in Ferromolybdenum and in Calcium Molybdate LOUIS SILVERRIAN, 5559 Hobart St., Pittsburgh, Penna.
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JI7O methods have been given for the
Remove from the hot plate, add about 10 Phosphorus in ferrodrops of hydrofluoric acid (20 drops for high determination of phosphorus in ferromolybdenum and in silicas) and 10 cc. of 70 per cent (technical) molybdenum ( 2 ) . perchloric acid, place in a no-bump beaker, calcium molybdate is heat to heavy fumes, and maintain for about In the first method, the solution of the alloy determined (without 5 minutes. is treated with ammonium or sodium hydroxide, to remove most of the molybdenum. Cool, add 25 cc. of water, shake, add 25 cc. previously filtering off Two separations are usually suggested; if of ammonium hydroxide (specific gravity 0.9), any compounds) as the only one separation is used a long process of and stir to dissolve all yellow precipitate. wmhine is rewired. With the bulk of the vellow DhosphomolybAdd 25 cc. more of cold water, place the remolybdYenum Iemoved, the iron precipitate action beaker in a larger beaker of water. add date’ can be dissolved and the hosphorus precipiconcentrated nitric acyd (sp. gr. 1.42) until the tated with ammonium mofvbdate, as in steels. ferric hydroxide is dissolved (approximately In a second method, the phosphorus is 20 cc.), and add just 10 cc. excess of acid. separated as magnesium ammonium phosphate in the presence of While adding the acid, the temperature of the solution should not citric acid. This method is no more satisfact?ry for phosphorus pass 45’ C. At once, add 50 cc. of molybdate solution ( 2 ) , stir than is the separation of magnesium under the same conditions. or shake, let stand 2 hours, filter, wash, and titrate as usual with Precipitation is slow (overnight) and not always complete. standard acid and alkali (0.148 N). 1 cc. = 0.02% P on a 1-gram With calcium molybdate, ferric chloride can be added t o the sample. solution of molybdate with subsequent separation by ammonium CALCIUM MOLYBDATE. Transfer a 1-gram sample to a tall hydroxide, as in the ferromolybdenum method. 300-cc. beaker, add a mixture of 15 cc. of 2 to 1 hydrochloric acid and 1 drop of nitric acid, and heat to nearly complete solution. This paper presents a more rapid routine method for the deRemove from the hot plate, add about 20 drops of hydrofluoric termination of phosphorus in ferromolybdenum and in calacid and 12 cc. of 70 per cent (technical) perchloric acid, place in a no-bump beaker, and heat to heavy fumes. cium molybdate. Complete as in the second paragraph for ferromolybdenum, noting that ammonium hydroxide yields a white precipitate with calcium molybdate instead of the red iron precipitate with ferroExperimental molybdenum. A 1-gram sample was transferred to a FERROMOLYBDEKUIII. Discussion tall form 300-cc. beaker, 10 cc. of (1 2) nitric acid were added, and the beaker was immediately covered with a watch glass. The obvious x a y to determine phosphorus in ferromolybhfter the first rapid reaction, the beaker was placed on a warm denum is to dissolve the sample in nitric acid and precipitate plate to complete solution of the alloy, then removed from the plate and hydrofluoric acid was adc‘ed (10 drops for low and 20 with molybdate. The fact that standard texts do not present drops for high-silicon alloys). Then 10 cc. of perchloric acid this method indicates that it has not been entirely successful. (70 per cent technical) were adc‘ed, and the beaker was set in a The problems are: to take care of interfering elements, t o “no-bump beaker” holder on the hot plate. The cover was reprevent the separation of free molybdic acid, ant1 to form the moved to distill out the nitric and hydrofluoric acids, then replaced. Heating was continued until considerable amounts of easily filterable “yellow precipitate”. molybdenum trioxide separated. Poor results were obtained on Of the interfering elements, silica and insoluble silicates those samples which were not fumed well. are taken care of by hydrofluoric acid. Organic matter is The beaker was cooled, and about 25 cc. of water were added. oxidized by nitric and perchloric acids. Vanadium, present From a graduate, ammonium hydroxide (specific gravity 0.9) was added. A volume of 15 cc. was found satisfactory to dissolve in only small amounts, is taken care of by the relatively high all the trioxide and precipitate ferric hydroxide. Another 25-cc. nitric acid content ( 1 ) . Likewise, the small amounts of portion of water WRS added t o cool the mixture. A thermometer tungsten are converted to ammonium tungstate by the excess was placed in the beaker, and in order to keep the temperature ammonium hydroxide, and upon acidification neither retard below 40” C. the reaction beaker was placed in a larger beaker containing cold water. Xitric acid (specific gravity 1.42) war precipitation of phosphorus nor precipitate as tungstic acid added from a buret, and the amount of acid required to dissolve in this large volume of solution (150 cc.]. Precipitation a t the ferric hydroxide was noted. Measured excess portions of 40” C. eliminates interference by arsenic. nitric acid (6, 8, 10, and 12 cc.) were added to a series of beakers T o prevent the precipitation of free molybdic acid, note to determine the optimum volume of nitric acid, 50 cc. of molybdate solution were added at once, and the mixture was stirred was taken of the technique in the preparat,ion of the “stock several minutes, or put in a shaking device. The cooling bath, molybdate solution” (3)-i. e., dissolve molybdic acid in an which was now warm, was not removed (for hand stirring) beexcess of ammonium hydroxide and water, then acidify in the cause it accelerated separation of tlie yellow precipitate. The presence of considerable excess of ammonium ion, and maintime of settling and the character of the- precipitate were noted. The precipitate was filtered and titratea as usual by the xlkalitain an excess of 10 per cent nitric acid by volume. metric method. Under these conditions of acidit’y and of concentrations of Since no standard ferromolybdenum was available, a synthetic ammonium nitrate and perchlorate the yellow precipitate mixture of 0.5 gram of standard steel and 1 gram of ammonium which formed vias dense and settled n-ithin 2 hours. The molybdate was used to check the composition of the oreripitate. CALCIUM MOLYBDATE.A 1-gram sample was used. The solcolor was not reddish, as would be the case if vanadium were vent was 2 to 1 hydrochloric acid (3)plus one drop of nitric acid. carried down. ;idditional precipitate did not form overnight Heat was applied till only a small residue was left. From this showing that free molybdic acid was not separating. point, the same procedure was followed as for ferromolybdenum. The above remarks also apply to calcium molybdate, for after solution in hydrochloric acid, addition of hydrofluoric Procedure acid, and subsequent, fuming with perchloric acid, the niaterial is found in the same state as the ferromolybdenum. FERROMOLYBDEKUM. Transfer a 1-gram sample to a tall 300One precaution must be emphasized. After the sample cc. beaker, add 10 cc. of 1 to 2 concentrated nitric acid, cover with has been fumed with perchloric acid, the heaker is remored a watch glass, and heat, if necessary, to effect complete solution.
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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., C h e m i c a l Laboratory, Ecorse-Detroit, M i c h .
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 i t possible to use line C, giving about twice as many scale divisions for the same amount of zirconium.
PHOTEL OMETER REARING FIGURE1
