ACETATES AND THEIR MANUFACTURE. 275 



agitating the liquor to decompose the whole of the manganese 

 salt. 



It sometimes happens that a portion of the manganese salt is 

 not acted upon by the acetate of lime ; in this case a concentrated 

 solution of acetate of lead is employed towards the end of the 

 process to effect the complete decomposition. The mixed precip- 

 itate of sulphate of lime and lead is filtered off, and the filtrate 

 evaporated and crystallized. The best acetate of manganese is 

 made by adding to 4 parts of manganous sulphate dissolved in 

 3 parts of water, 7 parts of crystallized acetate of lead dissolved 

 in 3 parts of water, agitating the solution, and drawing off the 

 clear liquor for use. 



Acetate of manganese is used in dyeing and calico printing to 

 give a brown color to fabrics. Its principle of action depends 

 upon the further oxidation of the manganese. 



Iron acetates. Acetic acid combines with ferrous oxide (FeO) 

 as well as with ferric oxide (Fe 2 O 3 ), but only the ferrous acetate 

 crystallizes in small greenish white needles, very prone to oxi- 

 dation ; ferric acetate is a dark, brownish red, uucrystallizable 

 liquid, of powerful and astringent taste. Both salts dissolve 

 freely in water, and are of importance for dyeing and calico 

 printing. 



Ferrous acetate, Fe(C 2 H 3 O 2 ) 2 . For dyeing purposes this salt is 

 prepared by dissolving wrought-iron turnings in wood-vinegar, 

 care being had that some iron remains undissolved, as otherwise 

 the salt, on exposure to the air, is gradually partly converted into 

 the ferric salt. This oxidation proceeds, however, but slowly, 

 the empyreumatic substances contained in the wood-vinegar ren- 

 dering the conversion rather difficult ; the pure salt oxidizes with 

 greater rapidity. For commercial purposes this compound is 

 manufactured as follows : Into a large wooden vat or into barrels 

 a quantity of iron turnings, hoops, or nails are introduced, and hot 

 crude wood-vinegar, freed by distillation from wood-spirit, is poured 

 upon them. During the solution of the iron much tarry matter 

 separates which is skimmed off, and the solution is frequently 



cible until no more vapors escape. The residue is dissolved in water, filtered, 

 and allowed to crystallize at an ordinary temperature. The solution of the 

 salt when decomposed with crystallized soda gives a precipitate of manganous 

 carbonate. 



