ACETATES AND THEIR MANUFACTURE. 287 



Dibasic cupric acetate and mercuric chloride (corrosive subli- 

 mate) combine to a blue crystallizable combination which dis- 

 solves with difficulty in water it is decomposed by boiling with 

 water. 



Lead Acetates. 



With plumbic oxide acetic acid gives a neutral as well as sev- 

 eral basic salts. The most important of these combinations are 

 the neutral salt, known in commerce as sugar of lead, and a basic 

 salt by means of which white lead is obtained. 



Neutral acetate of lead (sugar of lead), Pb(C 2 H 3 O 2 ) 2 + 3 HO. 

 According to VolckePs method, acetic acid prepared from wood- 

 vinegar and rectified over potassium bichromate is saturated with 

 litharge, filtered or decanted, and after a further addition of acetic 

 acid until a slightly acid reaction takes place, evaporated to the 

 crystallizing point. 



By saturating acetic acid with litharge, a solution of basic salt 

 is obtained, which is later on converted into neutral salt by the 

 addition of acetic acid. This is more suitable than using only as 

 much litharge as the acetic acid requires for the formation of the 

 neutral salt, because the litharge dissolves with greater ease in 

 solution of sugar of lead than in acetic acid. 



Solution of sugar of lead, like solution of neutral cupric acetate, 

 permits the evaporation of acetic acid in boiling ; and, hence, it is 

 best to use strong acetic acid, because less will have to be evapo- 

 rated and the loss of acetic acid be consequently smaller. By 

 taking, for instance, acetic acid of 1.057 specific gravity, for 100 

 Ibs. of it 82 Ibs. of litharge are required for the formation of the 

 neutral salt. A larger quantity is, however, taken (from 100 to 

 180 Ibs.), so that a basic salt is formed, or, with 100 Ibs., a mix- 

 ture of neutral and basic salts. To recognize the point of neu- 

 tralization in the subsequent addition of acetic acid, litmus paper 

 is used, or, still better, dilute solution of corrosive sublimate (1 

 part of corrosive sublimate in 100 of water), which does not 

 change the neutral salt, but produces turbidity' in the basic 

 (Biichner). Hence, by from time to time testing the lead solu- 

 tion with this reagent, the point of neutralization is reached the 



