New York AGRICULTURAL EXPERIMENT STATION. 267 
CaCl, combine, the pressure (concentration) of ammonia at equi- 
librium depends only on the temperature. The same is true of the 
reaction between PbO and NH,Cl, in which ammonia is formed. 
As examples in which the reaction is hydrolysis and therefore 
especially comparable to the hypothetical hydrolysis of insoluble 
acid-casein, the hydrolyses of mercurous sulphate and of the picrate 
of diphenylamine may be noted. The first reaction was studied by 
Gouy? and by Hulett.* It occurs in accordance with the equation. 
Pees 2 1) [He (OH) ], (Hg.50;) -- 2 HegHsO,. 
emit Oli ol), is relatively the only soluble substance and conse- 
quently the only one of varying concentration. Equilibrium is 
reached when hae constant, this constant concentration 
at 25° C. being 0.00225 molecular weights in grams per liter. 
When Hg,SO,, or a mixture of it with the basic salt, was shaken 
with water, hydrolysis always proceeded until the concentration of 
the HgHSO, reached this value, and no further hydrolysis occurred 
unless the mixture of salts was treated with fresh water, when the 
process again went to the same limit, and it could be repeated until 
all the Hg,SO, was changed. Hulett treated a portion of Hg,SO, 
thus with 43 successive portions of water and found at the end of 
each treatment (of 12 hours) the same concentration of HgHSO, 
in solution. The forty-third treatment exhausted the Hg.SO, and 
further treatment had no effect except to dissolve traces of the 
basic salt. 
The picrate of diphenylamine, like all salts of this base,* is hydro- 
lyzed by contact with water, with formation of picric acid and 
diphenylamine. Both diphenylamine and its picrate are, like casein 
and acid-casein, practically insoluble. The picric acid is, therefore, 
the only reagent of variable concentration. Walker® found that 
picric acid (saturated solution) placed in contact with varying excess 
portions of diphenylamine always combined with it until the con- 
Gentration of the acid was reduced to 13.8 mgs. per cc. If picric 
*Isambert. Compt. Rend. Acad. Sci. [Paris], 102:1313. 1886. 
*Compt. Rend. Acad. Sci. [Paris], 130:1399. 1900. 
*Zischr. Phys. Chem., 49:491. 1904. 
4 Meyer and Jacobson. Lehrbuch der Organishe Chemie, II (1) p. 177. 
1902. 
sJour. Chem. Soc. [London], Trans., 69:1341. 1806. 
