292 VINEGAR, CIDER, AND FRUIT-WINES. 



ing through the whole series the solution is so strong that it may 

 be evaporated at once so as to crystallize. 



Apparently this method has a considerable advantage over that 

 with litharge, metallic lead being cheaper and producing more 

 sugar of lead (entirely free from copper) than litharge, because 

 103.5 Ibs. of pure lead yield 189.5 Ibs. of sugar of lead, while 

 the same quantity is only obtained from 111.5 Ibs. of pure litharge. 

 Furthermore, commercial lead is always purer than litharge. On 

 the other hand, this process has the disadvantage of a consider- 

 able quantity of acetic acid being lost by evaporation on account 

 of it having to pass through several vessels. The manufacture 

 of sugar of lead is most suitably combined with that of white 

 lead, it being thus possible to utilize the tailings, etc. to greater 

 advantage than, as is frequently done, by melting them together 

 and remelting, which always cause considerable loss. 



Sugar of lead is further formed by boiling lead sulphate with 

 a very concentrated solution of barium acetate, barium sulphate 

 (permanent white) being thereby precipitated. For 100 parts of 

 lead sulphate 84 parts of anhydrous or 100 of crystallized barium 

 acetate are required, the yield being 125 parts of sugar of lead. 

 Sulphate of lead is obtained in large quantities as a by-product 

 in the preparation of aluminium acetate. 



For many purposes of dyeing and printing the use of pure 

 sugar of lead is not necessary, the brown acetate of lead answer- 

 ing all requirements. For its preparation ground litharge is 

 introduced in small portions, and with constant stirring into dis- 

 tilled pyroligneous acid in a vat until red litmus paper is colored 

 blue, and, hence, a basic salt is formed. The impurities separat- 

 ing on the surface are removed and the clear fluid is then trans- 

 ferred to a copper pan provided with strips of lead, and evaporated 

 to about two-thirds its volume, the brown smeary substances 

 rising to the surface during evaporation being constantly removed. 

 By again diluting and slightly acidulating the concentrated fluid 

 a further portion of the foreign substances can be removed. 

 Finally evaporation is carried to the crystallizing point, i. e., 

 until a few drops congeal when allowed to fall upon a cold 

 metal plate. An addition of animal charcoal for the purpose of 

 discoloration is of no advantage ; the coloration is not completely 



