NOTES
576
Since v/Bp = a,it is seen that Eq. (9) is equivalent
to
da dP
--e-
a
(1
+
ap) =
(1
+ );
P P which may also be expressed in the form
or
d In cu d In p
--e
1 +cup = 1
+;
(10)
Vol. 58
water and benzene were required. Daniel2 has g./ml. for the solupublished a value of 1.4 X bility of cupric stearate in benzene at 23”, but this value seemed much too large. Determination of these solubilities at 25’ gave values of 7 2 X 10-9 g./100 g. of water and 8 f 2 X lo-’ g./lOO g. of benzene. Experimental
(12)
Finally, one obtains the following expression for the change of compressibility with volume at extreme pressures by differentiating Eq. (8) with respect to Y
SOLUBILITY OF CUPRIC STEARATE IN WATER AND BENZENE AT 2501 BYALANDOBRY Westinohouee Research Laboratoriee, East Piflsburgh,Pa. Received March $0. 1864
In the course of some thermodynamic calculations, values for the solubility of cupric stearate in (1) This work is taken from a paper presented before the 9th Meeting of the American Society of Lubrication Engineers, April. 1954, and is Scientific Paper No. 1812 from the Westinghouse Research Laboratories.
Cupric stearate was prepared by treating sodium stearate (made from stoichiometric amounts of reagent grade sodium hydroxide and reagent grade stearic acid) in water with the stoichiometric amount of reagent grade CuS0~5H20. The precipitated soap was recrystallized twice from benzene and dried. Anal. Calcd. for CasHtoOaCu: C, 68.68; H, 11.19; Cu, 10.08. Found: C, 68.62, 68.68; H, 11.42, 11.42; Cu, 9.81, 9.82. Mixtures of excess copper stearate with the respective solvents (reagent grade benzene or doubly distilled water) were boiled in flasks with ground glass joints. The flasks were tightly stoppered and shaken, along with similar mixtures which had not been boiled, for several days at room temperature. The flasks were then ke t overnight at 25’ and the mixtures filtered through S. and No. 507 filter aper. The benzene filtrates were extracted with 10% H,S& and the acid solutions analyzed for copper; the aqueous solutions were analyzed directly. Analysis was carried out by a colorimetric method employing sodium diethyl dithiocarbamate.8
8
(2) 5. G . Daniel, Trans. Faraday SOC.,4T, 1351 (1951). (3) E. B. Sandell, “Colorimetric Determination of Traces of Metals,” 2nd ed.. Interscience Publishers, Inc., New York, N. Y., 1954, p. 309.
