ACETATES AND THEIK MANUFACTURE. 277 



air. It quickly oxidizes and by pouring back the solution and 

 several times repeating the drawing off and pouring back, a quite 

 concentrated solution of a dark red brown, nearly black color is 

 in a short time obtained. Heat must not be employed in the 

 preparation of this salt, as in such case it readily decomposes. 



Neutral ferric acetate may be obtained in the pure state by 

 decomposing a solution of lead acetate by addition of ferric sul- 

 phate in slight excess. In the course of 24 hours the excess of 

 ferric sulphate precipitates as a basic salt. It is also produced, 

 though more slowly, by dissolving ferric hydrate or ferric car- 

 bonate obtained by precipitation, in strong acetic acid. This 

 method occupies more time, but affords better guarantees for the 

 purity of the compound. 



By dissolving one part of nitric acid or aqua regia, precipitating 

 the solution with ammonia and dissolving the washed ferric 

 hydrate in 10 parts of acetic acid of 1.042 specific gravity and 

 evaporating the solution at from 140 to 176 F. an amorphous 

 salt soluble in water and alcohol remains, which is, however, not 

 neutral, as it contains only 2 instead of 3 equivalents of acetic 

 acid for 1 equivalent of ferric oxide. By dissolving this amor- 

 phous salt in acetic acid and exposing the dark red solution to a 

 low temperature, the neutral salt crystallizes out in hydrated, lus- 

 trous, dark red laminae. 



On heating the strongly diluted solution of this salt nearly to 

 the boiling point its color becomes more intense and it evolves 

 a distinct odor of acetic acid without, however, producing a precipi- 

 tate. The salt has nevertheless become more basic, and an addi- 

 tion of any soluble sulphate or even of free sulphuric acid immedi- 

 ately precipitates the whole of the iron as insoluble basic ferrous 

 sulphate. By heating, however, the dilute solution of the pure 

 acetate to boiling it disengages acetic acid and separates a basic 

 salt, which, if boiling be continued, also loses its acid so that ferric 

 hydrate remains behind. The properties of this hydrate differ, 

 however, from those of ordinary ferric hydrate, it being only 

 dissolved in concentrated hydrochloric acid by long-continued 

 digestion or boiling and scarcely attacked by boiling concentrated 

 sulphuric acid. In acetic acid or dilute nitric acid it dissolves, 

 however, to a red fluid, transparent to transmitted, but opaque to 



