64 PROCEEDINGS OF THE AMERICAN ACADEMY 



That sulphuric acid is a more efficient precipitant of lead in pres- 

 ence of tartaric acid than sulphate of ammonium was shown in another 

 way. 30 c. c. of the standard alcoholic acetate of lead were mixed 

 with an equal volume of the standard solution of tartrate of ammonium. 

 The precipitated tartrate of lead was filtered, and the filtrate mixed 

 with a' quantity of the sulphate of ammonium solution. No precipi- 

 tate was produced, though on the subsequent addition of sulphuretted 

 hydrogen a slight precipitate of sulphide of lead was formed. In a 

 similar experiment, where sulphuric acid was substituted for sulphate 

 of ammonium, a slight precipitate was produced by the sulphuric acid, 

 and no precipitate could be obtained afterwards with sulphuretted 

 hydrogen. 



In two other experiments where 5 c. c. of the acetate-of-lead solu- 

 tion were mixed with 30 c. c. of the tartrate of ammonium, no precipi- 

 tate was produced by sulphate of ammonium in the filtrate from the 

 tartrate of lead, while sulphuric acid gave a slight precipitate as before. 

 In this case, however, sulphuretted hydrogen gave a slight precipitate 

 after sulphuric acid, as well as after sulphate of ammonium. 



Normal Tartrate of Potassium mixed with the solution of sulphuric 

 acid exerted no solvent action on sulphate of lead. 



Succinate of Ammonium, prepared by neutralizing a solution of suc- 

 cinic acid with ammonia-water, exerted no solvent action when mixed 

 with the free sulphuric acid ; but when mixed with the solution of sul- 

 phate of ammonium, 6 c. c. of the acetate-of-lead solution were added 

 to the liquor before a permanent precipitate fell. 



Normal Citrate of Ammonium was prepared by neutralizing a 

 weighed equivalent portion of crystallized citric acid with ammonia- 

 water. 10 c. c. of the solution were mixed with an equal volume of 

 the standard sulphuric acid, and the standard solution of acetate of 

 lead was dropped into the mixture in the usual way. No permanent 

 precipitate was formed until 16 c. c. of the lead solution had been 

 added. These 16 c. c. contained 0.6064 grm. of acetate of lead, 

 corresponding to 0.4848 grm. of sulphate of lead. The 10 c. c. of 

 citrate-of-aminonium solution contained 0.42 grm. of crystallized citric 

 acid. Hence, 1 part of sulphate of lead was held dissolved in the mix- 

 ture of alcohol and dilute sulphuric acid for every 0.8663 part of citric 

 acid in the liquor. 



On repeating the experiment, a precisely similar result was obtained: 

 16 c. c. of the standard lead solution had to be added to the mixture 



