INDUSTRIAL AND EhTGINEERING CHEMISTRY
July 15, 1931
1.19). Cool, add 3 cc. of 0.0344 N silver nitrate, and then add ammonium hydroxide (sp. gr. 0.90) from a buret until the precipitate formed is just dissolved and the solution is clear. If the solution is warm a t this point, cool again before titrating. Now add 10 cc. of potassium iodide (4 per cent solution in water), dissolve the precipitate with an excess of 0.0344 N potassium cyanide, and titrate back with 0.0344 N silver nitrate until one drop produces a permanent white turbidity. The silver nitrate solution equivalent to the 0.0344 N potassium cyanide solution is obtained by titration in the same solution in which the nickel was determined. The 0.0344 N silver nitrate is standardized by the method of Mohr (2) against a 0.0344 N solution of sodium chloride. The nickel is calculated by the following formula: ( A X B ) - c X 0.1 X D Weight of sample cc. of 0.0344 N potassium cyanide nitrate equivalent of 0.0344 N cyanide cc. of 0.0344 N silver nitrate normality factor of 0.0344 N silver nitrate
Per cent nickel
A = B = C =
D
=
259
quite vigorously for 20 minutes. Cool, add 50 cc. of water, filter on paper pulp with suction, and wash with a 1 per cent solution of perchloric acid. Determine the chromium and nickel in the filtrate as described in the method for steel. The accuracy of the results expected with the above procedure are shown in Tables I and I1 iii which are tabulated determinations for chromium and nickel for B. 8. chromenickel 32, B. s. nickel-chromium iron 82, and stainless steel No. 1 which was standardized by the procedures ordinarily used for this purpose.
SAMPLE 32a 82 1
Table I-Chromium Determinations -----CHROMIUM OBTAINED----1 2 3 4 Av.
CHROMIUM PRESENT
%
%
%
%
%
%
0 87 0 21
0 88 0 23 7 57
0 86 0 20 7 48,
0 87 0 22
0 87 0 21
0 88 0 24
7.66
7 57
7 57
7.63
=
SAMPLE
Table 11-Nickel Determinations -----NICKEL OBTAINED------. 1 2 3 4 Av.
NICKEL PRESENT
Method for Nickel-Chromium Iron
Dissolve a 1-gram sample in a 500-cc. tall-forni beaker with the same solution as used for steel, add 30 cc. of perchloric acid (60 per cent), boil until the fumes given off are white rather than yellowish in color, and then continue to boil
Literature Cited (1) Lord and Demorest, “Metallurgical Analysis,” 1913. (2) Treadwell and Hall, “Analytical Chemistry,” Vol. 11, Wiley, 1915. (3) Willard and Cake, J. IND. ENG. CHEM.,11, 480 (1919).
A Modified Vacuum Regulator‘ Arthur A. Sunier and Chester M . White UNIVERSITY OF ROCHESTER, ROCHESTER, N. V.
HE vacuum regulator described herewith, which is a modiT fication of one described by Cox ( I ) , has been found especially useful when a set of predetermined pressures are to be maintained in rotation in a given apparatus. The figure shows the regulator before filling with mercury. By tilting it, about 15 cc. of pure niercury are introduced through A into flask B (about 100 cc. capacity). The apparatus is then firmly clamped in an upright position with the mercury container resting on a sand bath. A Hyvac oil pump is attached a t A by a three-way stopcock. During evacuation the entire apparatus is strongly flamed for an hour. Then mercury is slowly distilled into the manometer. When the mercury stands a t about 39 em. in both arms, the barometer tube is sealed off a t the constriction, C. After air has been admitted through A , the distillation apparatus can be cut off a t some point on D. This method of filling the manometer, which was suggested by Weatherill ($), has been found very satisfactory. The side tubes with sealed-in lengths of tungsten wire (No. 24 B. and S.) are filled with mercury. The position of each has been calculated to correspond approximately to some desired pressure-thus F , 700 mm.; G, 650 mm.; H , 600 mm.; etc. The exact values, which can be determined with a cathetometer or by other suitable means, will of course always remain the same, and thus these predetermined pressures may always be duplicated a t will. The lowest side tube, E, which is connected to a relay, is beneath the mercury surface a t all times. The electrical circuit and precision of regulation of this modified regulator are similar to that described in Cox’s article (f), where further details may be obtained. 1
Received February 13, 1931.
3 A Modified V a c u u m Regulator
Literature Cited (1) C o x , IND. ENG.CHBM.,Anal. Ed., 1, 7 (1929). (2) Weatherill, J. A m . Ckem. Soc., 47, 1947 (1925).
