SOLUBILITY AND ELECTROLYTIC CONDUCTANCE O F MESITYLENE PHOSPHIKOUS ACID BY H. J. M. CREIGHTON
Mesitylene phosphinous acid, (CH3)3C6Hz. P(OH)2, which was first prepared by Michaelis’ by the action of water on mesitylene dichlorphosphine, which in turn was produced by the interaction of phosphorus trichloride and mesitylene in the presence of aluminium chloride, forms salts of the type, [ (CH3)GH2(PO2H)1 MI, [ (CH3)3C6HZ(POzH)] *MI1, etc. Hence, it is a monobasic acid. The mesitylene phosphinous acid2 used in the following experiments had, after repeated recrystallization from hot water, a melting point of 147.3j0 (corr.). The solubility of mesitylene phosphinous acid was determined as follows : A large excess of the finely powdered acid was placed in each of two bottles, which were three-quarters filled with “conductance water’’ and closed with tight-fitting glass stoppers. The bottles were then agitated in a large thermostat, the temperature of which was kept constant to within 0.05”. At the end of the period of agitation the bottles were removed from the shaking device and allowed to remain in the thermostat, until the finely divided acid had settled. The weight of acid contained in a known weight of saturated solution was determined by titration against a standardized solution of barium hydroxide. The values obtained for the solubility of mesitylene phosphinous acid at a number of temperatures are as follows: Temperature C”,
I .o
Grams acid per roo grams soh.,
0.289
35.0
25.0
0.299
45.0
0.324
0.385
65.0
0.525
85.0
0.700
The conductance of aqueous solutions of mesitylene phosphinous acid and its sodium salt was measured at 2 5 =tO.OI’, by means of Kohlrausch’s alternating current bridge method. The sodium salt of the acid was prepared by exactly neutralizing the acid with a saturated solution of “carbonate free” sodium hydroxide. The conductance data obtained with solutions of the salt are given in Table I. The limiting value of the equivalent conductance (A”), given in the table, has been calculated by means of the equation3:
A, =
Az - +V,.AI
vx- vv,
hlichaelis: Bnn., 294, 36 (1897).
* The writer is indebted to a former colleague, Dr. A. P. Tanberg, for this acid. 3
Kohlrausch-Holborn: “Leitvermogen der Elektrolyte”, 107 (1898).
