OF ARTS AND SCIENCES : OCTOBER 13, 1868. 65 



of alcohol and sulphuric acid before the precipitate ceased to redissolve 

 as fast as it formed. 



In two other experiments where, instead of free sulphuric acid, 10 

 c. c. of the standard solution of sulphate of ammonium were mixed 

 with 10 c. c. of the citrate-of-ammonium solution, 30 c. c. of the 

 standard lead solution had to be added, in each case, before an)' per- 

 manent precipitate formed. 



Didtrate of Ammonium (C 12 H G (NH 4 ) 2 14 ) was prepared in crys- 

 tals, and 22.6 grms. of the salt were dissolved in 500 c. c. of the 18% 

 alcohol. 25 c. c. of the solution were mixed with an equal volume of 

 the standard sulphuric acid, and the acetate-of-lead solution was 

 dropped into the mixture in the usual way. After the addition of 8 

 c. c. of the standard acetate of lead, a permanent precipitate was pro- 

 duced. These 8 c. c. contained 0.3032 grm. of acetate of lead, cor- 

 responding to 0.2424 grm. of sulphate of lead. The 25 c. c. of 

 dicitrate-of-ammonium solution contained 1.13 grms. of the dry salt. 

 Hence, 1 part of sulphate of lead was held dissolved for every 4.6617 

 parts of the dicitrate. 



Tricitrate of Potassium. — 25 c. c. of a standard solution of ordi- 

 nary crystallized citrate of potassium, mixed with an equal volume of 

 the standard sulphuric acid, gave no permanent precipitate until 2 c. c. 

 of the solution of acetate of lead had been added to it. 



Sugar. — A standard solution of cane sugar, mixed with an equal 

 volume of the sulphuric acid, gave a permanent precipitate, on the ad- 

 dition of the first drop of the acetate of lead. 



These experiments show clearly that very considerable quantities of 

 sulphate of lead can be held in solution by weak alcohol charged with 

 various salts. It may, therefore, reasonably be inferred that wines 

 sometimes retain lead in solution, in consequence of this action of the 

 acids and salts peculiar to wine upon lead compounds ignorantly em- 

 ployed to correct acidity. 



DONATIONS TO THE LIBRARY, 



FROM JULY 21, 1866, TO JULY 1, 1868. 



Massachusetts Historical Society. 



Proceedings. 1866-67. 8vo. Boston. 1867. 

 Massachusetts Institute of Technology. 



Second and Third Annual Catalogues of the Officers, and the 

 VOL. VIII. 9 



