232 



Dr. A. Holt. Colouring Matters in the 



hours with hot dilute sulphuric acid, fresh quantities of acid being used till 

 the yellow tint at first imparted to it was no longer visible. The mixture of 

 animal matter and sand was then boiled with several portions of water and 

 filtered. It was next extracted with alcohol. Finally, it was treated in 

 a Soxhlet with ethyl benzoate or acetylene tetrachloride. These solvents 

 acquired a fine blue colour, and exhibited a strong purple-red dichroism. 

 On cooling, the solutions gradually deposited a fine purple-black powder, 

 which after recrystallisation and washing with ether did not greatly differ in 

 tint from the violet colour of the Ascidian colony when preserved in alcohol. 

 When quite dry this purple powder had a distinct coppery lustre. It was 

 insoluble in water, alcohol, and ether, but soluble in aniline, pyridine, 

 quinoline, nitro-benzene, ethyl benzoate, and acetylene tetrachloride, though 

 the solubility varied with the liquid. Thus, though easily soluble in hot 

 acetylene tetrachloride, it was almost entirely reprecipitated on allowing the 

 cooled solution to stand for some hours. 



In every case the solution was blue with a greenish shade when very 

 dilute, changing to pure blue, and subsequently violet blue, on concentration. 

 "When hot both the violet colour and the dichroism were more pronounced. 



The absorption spectrum was determined in both hot and cold ethyl 

 benzoate and acetylene tetrachloride. 



The ethyl benzoate solution in the cold showed an absorption band with 

 a maximum about X = 611 llll, though absorption began at X = 617 llll. 

 When heated, the maximum was shifted to X = 605 llll, the band being very 

 indefinite towards. the green, the total absorption ranging from X 617 llll to 

 X 598 llll. In acetylene tetrachloride the maximum absorption both when 

 hot and cold was shifted towards the green, the maximum when cold being 

 X = 606 llll, and when hot X. = 598 llll. 



The pigment dissolved in concentrated sulphuric acid to form at first a 

 pinkish solution, which rapidly changed to a dirty purple colour. On standing, 

 or more rapidly on warming, this colour changed to a brown tint with a green 

 shade in it, or if sufficiently strong to a dull green. The pink colour appeared 

 to be of a transient nature, depending for its stability on concentration and 

 low temperature. 



Addition of water to the cold acid solution precipitated the pigment, so it 

 must be concluded that it does not form a soluble sulpho-salt, as is the case 

 with indigo, but after heating, the addition of water caused the separation of 

 a dull green flocculent precipitate, not the original pigment. 



The colouring matter was insoluble in alkali, but gave a colourless solution 

 with an alkaline reducing agent. Owing to the small quantity available it 

 was impossible to try its action on cotton satisfactorily, but a cotton cloth in 



