262 A. LIVERSIDGE. 



blue filtrate passes through, but on standing, a black precipitate 

 forms and the solution becomes colourless ; this black precipitate 

 gives a blue solution with acetic acid, so that the pigment is 

 sufficiently stable to resist the action of hot sulphuric acid. 



Organic Acids. — Formic acid dissolves it readily both hot and 

 cold to a beautiful blue colour similar to that yielded to acetic 

 acid ; on evaporating to dryness over a water bath it leaves a 

 greenish coloured residue, and this on ignition chars in much the 

 same way as the acetic residue and leaves a ferruginous-looking ash. 



The residue insoluble in acetic acid and the other above-men- 

 tioned solvents after repeated treatment, until the solvent no 

 longer became coloured, is practically black. On heating this 

 residue on platinum it burns slowly without flame, emits a nitro- 

 genous odour, and leaves a considerable amount of ash, which is 

 of a ferruginous colour, and appears to have much the same com- 

 position as that from the crude pigment itself. 



Propionic Acid. — Slightly soluble in the cold ; when boiled it 

 yields a bright blue solution equal to that in glacial acetic acid, 

 and as permanent. 



Propionitril. — Insoluble. 



Butyric Acid. — Insoluble in the cold but yields a pale greenish 

 solution when boiled. Isobutyric Acid takes up a little of the 

 blue on warming. 



Heptoic Caprylic and Nonylic Acids. — Insoluble. 



Lactic Acid (Ethylidene lactic acid). — Slightly soluble in the 

 cold, but when warmed the solution is a full bright blue, as good 

 as the acetic acid solution. The black residue insoluble in lactic 

 acid imparts no colour to acetic acid. On concentrating the 

 lactic acid solution over the water bath, the colour gradually 

 fades and acquires a light brownish tint. 



Gly collie Acid. — Gives light green solution, a little darker on 

 warming. 



Oleic Acid. — Insoluble, on boiling the acid becomes brown. 



