62 PROCEEDINGS OF THE AMERICAN ACADEMY 



out at my suggestion by Mr. A. H. Pearson, of Haverhill, a student in 

 the Laboratory of the Massachusetts Institute of Technology. 



A considerable quantity of dilute alcohol, of the usual strength of 

 sherry wine (18 per cent) having been prepared, standard solutions of 

 acetate of lead, of sulphuric acid, and of sulphate of ammonium were 

 made by dissolving weighed quantities of these substances in portions 

 of the 18% alcohol. Each of the solutions was made of such strength 

 that 500 c. c. of the liquid contained one tenth of an equivalent of the 

 salt or acid, reckoned in grammes, on the hydrogen scale. 



Alcoholic solutions of several salts of ammonium and of the fixed 

 alkalies were also prepared, as will be described below. 



In each experiment, equal quantities of the standard solution of 

 sulphuric acid, or of sulphate of ammonium, and of the saline solution 

 to be tested were mixed in a glass flask, and the standard solution of 

 acetate of lead was made to fall from a burette drop by drop into the 

 mixture until a persistent precipitate of sulphate of lead was perceived. 

 The burette was graduated so that two drops from it were equal to 

 one tenth of a cubic centimetre ; and the flask was constantly shaken 

 while the drops of acetate of lead were falling into it. 



The results of the experiments are as follows : — 



Acetate of Ammonium was prepared by neutralizing ordinary acetic 

 acid with ammonia-water, and the strong aqueous solution thus obtained 

 was mixed with alcohol. It appeared, however, that this alcoholic solu- 

 tion of the acetate exerted no solvent action upon sulphate of lead, for 

 a permanent precipitate of the latter was produced in the mixture of 

 acetate of ammonium and normal sulphuric acid by the first drop of 

 the standard solution of acetate of lead. The same negative result 

 was obtained in several repetitions of the experiment, even when new 

 portions of dilute alcohol and a second set of the standard solutions 

 were employed. 



When, however, the solution of acetate of ammonium was mixed 

 with an equal bulk (10 c. c.) of the standard solution of sulphate of 

 ammonium, instead of the sulphuric acid, a considerable quantity of 

 sulphate of lead was held in solution by it. In two distinct trials, the 

 precipitate formed by dropping acetate of lead into the mixed solution 

 of acetate and sulphate of ammonium continued to redissolve until 3 

 c. c. of the standard solution of acetate of lead had been added to the 

 liquor. These 3 c. c. of the standard solution contained 0.1137 grm. 

 of acetate of lead, corresponding to 0.0909 grm. of sulphate of lead. 



