284 ON PRUSSIAN BLUE 



If more of the precipitating liquor be added, the precipitate 

 will be redissolved, and this solution will be colourless. 

 This precipitate likewise dissolves in volatile alkali without 

 any colour. If more of the solution of vitriolated copper be 

 added, the precipitate likewise disappears, and the solution 

 assumes a green colour. Acids dissolve a portion of this 

 precipitate, and what remains of it is white. The muriatic 

 acid dissolves the yellow precipitate completely ; but it is 

 again precipitated by water. (/) The solution of vitriol of 

 zinc in water yields a white precipitate, which is not redissolved 

 on adding more of the precipitating liquor ; but it is soluble 

 in acids. These solutions have the smell of the colouring 

 matter, which latter may really be separated from them by 

 distillation. (m) Vitriol of iron is first precipitated of a 

 yellowish brown colour, which soon changes to green, and 

 then becomes blue on the surface. Some hours afterwards 

 the precipitate subsides to the bottom of the vessels, and 

 then the whole mixture turns blue ; but on adding any acid 

 the precipitate becomes instantly blue. If a very small 

 quantity of vitriolated iron be put into the precipitating 

 liquor, the precipitate entirely dissolves, and imparts to the 

 mixture a yellow colour (Sec. n. (a), (c)). (n) From the 

 solution of cobalt a brown-yellow precipitate is thrown down, 

 which does not dissolve on adding more of the precipitating 

 liquor ; neither will it dissolve in acids. (0) Lead dissolved 

 in vinegar is precipitated in the form of a white powder, 

 which more liquor does not dissolve ; but when well 

 edulcorated it is soluble in acids. If the solution be 

 distilled, the colouring matter goes over into the receiver. 

 (p) Vitriolated manganese suffers no decomposition. 



