ACETATES AND THEIR MANUFACTURE. 



291 



other places steam heat is employed for this purpose, which is 

 much to be preferred on account of its being more easily regu- 

 lated. 



Fig. 64. 



Fig. 65. 



When working on a large scale a centrifugal is advantageously 

 employed for the separation of the niother-lye in the same manner 

 as recommended for the preparation of sodium acetate (p. 243). 



Litharge being quite impure plumbic oxide never dissolves 

 entirely, and frequently contains over 10 per cent, of impurities, 

 consisting of sand, clay, red lead or minium (Pb 3 O 4 ), metallic lead, 

 traces of silver, cupric, and ferric oxides. The cupric oxide 

 passes into the sugar of lead solution and colors it slightly blue. 

 To separate the copper bright sheets of lead are dipped into the 

 solution, the copper separating upon them in the form of a dark 

 slime. The sheets of lead must be frequently cleansed (scraped), 

 as otherwise they lose their effect. When there is a large accu- 

 mulation of litharge residue, it can be worked for silver. 



Sugar of lead can also be prepared from metallic lead, the pro- 

 cess having been recommended first by Berard, and is said, by 

 Rtmge, to yield a good product with great economy. Granulated 

 lead, the tailings in the white lead manufacture, etc., are put in 

 several vessels, say eight, one above the other, upon steps, so 

 that the liquid may be run from one to the other. The upper 

 one is filled with acetic acid, and after half an hour let off into 

 the second, after another half an hour into the third, and so on 

 to the last or eighth vessel. The acid causes the lead to absorb 

 oxygen so rapidly from the air as to become hot. When the acid 

 runs off from the lowest, it is thrown on the uppermost vessel a 

 second time and carries off the acetate of lead formed ; after pass- 



