MAY 15, 1935
ANALYTICAL EDITION
familiar with vacuum-tube circuits consult a radio engineer for ininor details of construction before an attempt is made to build such a n assembly. The approximate costs of the various parts are: amp1ifier resistors, tubes, $4; paper condensers, $1; mica condenser, $ 5 ; condenser discharge key, $3; batteries, $4; filament transformer, $2; microammeter and shunt, $15; accessory potentiometer, $2; shunt and
s5;
205
series resistors for main potentiometer (with dials), $4; student potentiometer, $70.
Literature Cited (1) Hemingway,A., IND. ENa. CHEM.,Anal. Ed., 5, 278 (1933). (2) Morton, J. Chem. sot., 1930,2, 1528. (3) Morton, C., Ibid., 1931, 2977. R~~~~~~~December 26,1934.
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Determination of Sulfur in-Plain and Allov
Steels A Perchloric Acid Modification of Meineke's Method LOUIS SILVERMAN, 1118 North Euclid Ave., Pittsburgh, Pa.
T'
HE time required for gravimetric determination of sulfur in steels by Meineke's method may be decreased by substituting perchloric acid evaporation for hydrochloric evaporation. The steel is dissolved in the potassium-copper chloride solution which leaves insoluble all the sulfur, carbon, some chromium, iron, molybdenum, etc. The residue may be taken u p in acids, and fumed down with perchloric acid. T h e insoluble material is then separated from the soluble sulfates which are precipitated after reduction of chronnates. When running a batch of sulfurs the points which deserve consideration are: the substitution of paper for Gooch crucibles; a single evaporation with perchloric acid, instead of several with hydrochloric acid, to get rid of nitric acid; and 8, slight danger of spattering during evaporation of the acid. The determination of sulfur after fuming a sample by perchloric acid has been applied for some time to sulfur in rubber, so th,at it is only a matter of application to steels. The steels under consideration were those containing molybdenum or selenium which give low results b y the evolution method, and any high-sulfur steels which may tend to give low results by that method.
Procedure Five grams of steel are transferred to a 600-CC.beaker or flask and covered with 500 cc. of the potassium-copper chloride solution. The solution is kept at about 90' C., as on a steam bath. Copper immediately comes out of the solution, and the reaction is complete when the bright red metal has redissolved. The solution is kept covered a t all times, but agitated frequently to hasten solution if desired. With hand stirring, the time required is 2 or more hours. The hot solution is filtered through a fast filter paper, and washed with hot water. The paper is removed from the funnel, placed in a beaker, covered with strong bromine water, and agitated with a glass rod. Now 10 cc. of zinc oxide-nitric acid, and 8 cc. of c. P. perchloric acid are added. The beaker is heated to destroy the paper and drive out the nitric acid and the excess perchloric acid. Upon completion of heating, as indicated by the formation of chromic acid (if chromium is presenl;), or by the clarification of the fumes in the beaker, and condensation of perchloric acid on the sides of the beaker, the beaker is removed from the heat and cooled. As carbon does not interfere, heating need not be continued to oxidize it. The residue, usually solid, is dissolved in water, diluted to about :LOO to 150 cc., and boiled to remove chlorine. The silica (and carbon) is filtered off on paper and washed with water. To the filtrate are added 10 cc. of peroxide (to reduce chromic acid), t,he solution is diluted to 200 cc. and boiled, and sulfates are prr:ci itated with barium chloride, as is customary. The weight otbarium sulfate in grams divided by 5 and multiplied by 0.1373 gives the weight of sulfur found per gram.
This perchloric acid modification for the determination of sulfur checks Meineke's method. T o show that various reagents encountered in analysis of sulfur do not interfere. a series of four sets was run as follows: 1. 25 cc. of approximately 0.1 N sulfuric acid, run for sulfates. 2. 25 cc. of approximately 0.1 N acid plus 10 cc. of zinc oxide-nitric acid reagent and 8 cc. of perchloric acid. 3. 25 cc. of approximately 0.1 N acid plus 1 gram of potassium chlorate and 5 cc. each of nitric and hydrochloric acids and 8 cc. of perchloric acid. 4. As in 2, and in addition 0.0586 gram of potassium chromate (0.0200 pram of chromium). and ueroxide. ' ResulG (grams of sulfur): (11 0.0403, 0.0402; (2) 0.0403, 0.0402; (3) 0.0403; (4) 0.0403, 0.0402.
TABLE I. TYPICAL ANALYSES C % Author's laboratory 0utsidelaborat.ory
Mn
%
P %
9
%
Si
%
Ni
Cr
Mo
%
%
%
0.62 0,1690.082 2 . 3 7 1.80 0 . 3 7 0 . 6 0
3.00 3.00 3.10 3.00
0.70 0.56 0.68 0.43 0.086 0 . 4 0 0.11 0.37 0 . 1 5 0.37
...
0.11 0106 2 . 3 1 0.085 2.35 0.051 0 . 0 6 4 2 . 3 0 0.021 b 0.34 0.022 0 . 2 2 1 0 . 2 7 0.014 0 0.30 0.016 .,. 0.25
1.91 0 . 3 7 1.82 0 . 3 5 1.87 0.40 . . 13.14 0.22 13.3 13.1 13.1
....
0.70 0.60 0.62
..
0:55 0.56
Evolution, 0.034; gravimetric, 0.087, 0.068 (author) : 0.071. 0.072 (R. C. Coburn). b Evolutioo 0.256. gravimetric 0.348, 0.344. c Gravimetiic, O.O$, 0.08 (authorj. 0.089, 0.089 (R. C. Coburn). Meineke, 0.077 (author); 0.08, 0.09 (R. C. doburn).
Analysis of a selenium steel by the gravimetric method gave 0.246 and 0.245, and by the evolution method 0.132 per cent. Another gave 0.256 and 0.112 per cent, respectively. Bureau of Standards steels analyzed for sulfur gave the following results: No. 10d, 0.030; author, 0.026, 0.026; No. 22b, 0.041; author, 0.034, 0.034.
Solutions Used The following reagents were used: 500 grams of (KC1)2.CuC12.2Hz0; 100 cc. of hydrochloric acid; and 2000 cc. of water. The zinc oxide-nitric acid reagent was prepared by sifting 200 grams of zinc oxide into 1 liter of concentrated nitric acid.
Conclusion A modified method for the Meineke gravimetric sulfur determination, suggested because of greater speed in operation, has been applied successfully to molybdenum, selenium, and high-sulfur steels. R I D C E W EFebruary D 18, 1935.
