Tartaric Acid. 215 



Acetic acid dissolves lead foil, and forms sugar of lead 

 or acetate of lead. It is a very useful salt, as will subse- 

 quently appear. 



For calico-printing, some dye-woods are boiled with 

 strong vinegar, instead of water. The boiling should not 

 be continued long in this case, as much acetic acid will be 

 driven off. It is better to dissolve the inspissated extract 

 of dye-wood in vinegar. 



The volatility of acetic acid just mentioned, exists in many 

 of its combinations. If we have solutions of acetate of alu- 

 mina, acetate of iron and acetate of copper, in an open dish, 

 and place it in a warm place ; a strong smell of acetic acid 

 can be perceived during the evaporation of the salt, and at 

 last a residue remains which is no longer soluble in water, 

 as the portion of acetic acid required to dissolve it is re- 

 moved. The same happens with these salts when they are 

 placed on cotton instead of the dish. A part of the acetic 

 acid flies off, and the salt with a little acetic acid remains 

 upon the fibres. 



Such compounds of acetic acid are, therefore, to be pre- 

 ferred for printing, which allow a portion of their acid to 

 be driven off, as those already mentioned, as well as the 

 acetate of tin. Acetates of manganese, zinc and chrome are 

 not to be used, as they lose no acetic acid by evaporation. 



The action of alkalies and of lime will be destroyed by 

 vinegar. Hence, vinegar removes from dyed pieces all spots 

 produced by the former. The brown spots which are pro- 

 duced by potash or lime upon Fernambuc-red, cochineal- 

 red, quercitron-yellow and logwood-blue are completely re- 

 moved by vinegar. The original colour generally returns 

 when the fresh spot and the stuff is not yet washed. If 

 it is so, the colouring matter will be washed out, and the 

 early colour cannot again appear. Pyroligneous acid, which 

 is impure acetic acid mixed with tar, may, when purified, 

 be employed instead of acetic acid. It is used, however, in 

 an impure, barely skimmed state, for the preparation of 

 pyrolignate of iron ; the formation of which is attended 

 with difficulty in this respect, that it requires a long time. 



Tartaric acid. — This acid occurs in commerce in trans- 

 parent crystals, and is so readily soluble in water, that 100 

 lbs. of a saturated solution contain (J4 lbs. tartaric acid. 



