V O L U M E 2 8 , NO. 9, S E P T E M B E R 1 9 5 6 Table 11.
Analysis of Phosphorus Nitride by Single- and Double-Precipitation Methods
Phosphorus Taken, Xg. 0.25 0.50 1.33 2.86 4.19 5,58
Phosphorus Found, Mg. Single Double 0.30 0.50 1.33 2.86 4.15 5.50
0 29 0.51 1.34 2.99 4.19
5.57
moved in several evaporations with hydrochloric acid, and the sample finally was boiled with hydrochloric acid and ammonium bromide to remove arsenic. Ferrophosphorus was fumed with perchloric acid. The results obtained with the rocks and alloys are shown in Table I. Application to Phosphorus Nitride. The oxine method was applied to a sample of phosphorus nitride (PJj) that assayed 55.0’$& phosphorus by the magnesium pyrophosphate method. Portions of the nitride weighing about 0.35 gram were digested t o complete solution in 15-ml. charges of concentrated sulfuric acid, and the solutions were fumed a n additional 15 minutes. The aliquots contained approximately 5 mg. of phosphorus. Their sulfuric acid content was not enough to interfere in a single precipitation. Six determinations yielded an average of 55.22% phosphorus with a range of variation of 0.47%. When one result n-as rejected statistically, the average was 55.15% phosphorus with a maximum variation of 0.18%. The oxine method thus gave results comparable to those obtained by the magnesia method in the analysis of macro samples.
1487 llicro samples of the phosphorus nitride were weighed into tared microbeakers and transferred to 250-ml. beakers for decomposition. Phosphorus n-as determined by single- and doubleprecipitation methods on aliquots representing 50% of each sample. The results are shown in Table 11. The last two entries in the double-precipitation column of Table I1 indicate minor losses of phosphorus, presumably through volatilization ( 7 ) . The losses were offset by the effect of the sulfate in the single precipitations. Slthough the sample must be decomposed completely, the total time of fuming with sulfuric acid should not exceed 2 hours. LITERATURE CITED
(1) Alimarin, I. P., .Ilekseeva, 0. .A,, J . A p p l . Chem. (U.S.S.R.j 1 2 , 1900 (1939). (2) Berg, R., “Das o-Oxychinolin (Oxin),” vol. XXXIV in series, “Die Chemische Analyse,” F. Enke, Stuttgart, 1936. (3) Brabson, J. A , , Mattraw, H. C., ;LIaxwell, G. E., Darrow, 1., Needham, 1’1.F., AXAL.CHEM.20, 504 (1948). (4) Deitz, V. R., Higginson, H. R . , Parker, C., J . Research S a t l . Bur. Standards 40. 263 (1948). ( 5 ) Duval, C., ”Inorganic Thermogravimetric Analysis,” pp. 130, 132, Elsevier, Houston, 1953. (6) Huffman, E. O., Tarbutton, G., Elmore, K. L., Cate, TI7. E.. Walters, H. K., Jr., Elmore, G. V.. J . Am. Chem. Soc. 75. 6239 (1954) (7) Kolthoff, I. 11., Sandell, E. G., “Textbook of Quantitative Inorganic Analysis,” 3rd ed., p. 377, lIacmillan, Kew York, 1943. (8) Lorenz, h’. von, Landwirtsch. 1’ers.-Sta. 55, 183 (1901). (9) Scharrer, E., Biochem. 2. 261, 444 (1933). (10) Shik, I. R., Zazodskaya Lab. 8 , S o . 10-11, 1179 (1939). ,
I
RECEIVED for rerien 1Iarch 19, 1955. Accepted M a y 12, 1956.
Precipitation of lead Chromate from Homogeneous Solution WILLIAM A. HOFFMAN’ D e p a r t m e n t o f Chemistry,
and
Purdue
WARREN W. BRANDT
University, West Lafayette,
Homogeneous generation of chromate, by bromate, from chromium(II1) is used to precipitate lead chromate. The procedure is relatively free from interferences and can be used for the quantitative recovery of lead or chromium. The crystals recovered are large and easily handled, and exhibit maximum purity. The volume of the precipitate is half that obtained by standard procedures. Purity is the same as of lead chromate recovered by the careful use of standard procedures, but lead chromate can be more easily precipitated and handled by this procedure.
Ind.
Lead nitrate was recove1 ed by recrystallization. The lead nitrate so obtained \vas dissolved and recrystallized twice from O,lyc nitric acid. The resultant material was dried at 120” C. and weighed, as needed, as a primary standard, Pb(SOa),. Lead content was checked by recommended procedures (1,3) as the sulfate, chromate, and electrolytically deposited dioxide.
Table I.
iinalysis of Precipitate from Hydrolysis of Urea Calculated PbgOa, 0
Pb CrO4 Ratio (Pb-CrOa)
62.11 35,89 1.000
1
Found, To
63.26 27.83
Average, 2-
