BLUE PIGMENT IN COKAL AND OTHEK ANIMAL ORGANISMS. 259 



acid and digested on a water bath for five or six hours. During 

 extraction in the percolator the original blue colour gradually 

 changed to a dark green. 



The extract was evaporated to dryness in a platinum dish over 

 a water bath, the dried extract weighed -171 gramme or 26*45% 

 on the above, or '268% on the original coral, hence the acetic acid 

 extracts a larger proportion of matter than alcohol, but the 

 amount of pigment dissolved may not be proportionately greater; 

 the residue was dark green in colour, with a resinous appearance, 

 closely adherent to the dish, without blisters, and somewhat 

 deliquescent. 



On heating, the residue melted and assumed purple, blue and 

 other iridescent tints \ it also gave off a disagreeable nitrogenous 

 odour like burnt fish, similar to that from the crude pigment set 

 free by hydrochloric acid and by the alcoholic extract ; dense 

 white inflammable fumes were also emitted. 



The fixed residue or ash was of a brownish colour and weighed 

 •0123 gramme equal to 1*90%. It was found to consist principally 

 of iron, phosphoric oxide, lime and magnesia. Hence the acetic 

 acid extracts more organic matter and less ash or mineral matter. 



No traces of crystal form could be detected even under the 

 microscope in any of the residues left by the acetic acid solutions. 



On evaporating the glacial acetic acid solution of the pigment 

 to dryness over a water bath and taking up with hot glacial acetic 

 acid a second time, the solution was of a light brown colour 

 instead of blue. The ash from this brown extract also contained 

 iron and phosphoric acid. 



When solutions of the coral blue and of indigo in acetic acid 

 are compared side by side the former is seen to be brighter and to 

 have a green shade as compared with the indigo blue. The colour 

 is between that of indigo and copper sulphate solution. 



When a luminous flame is viewed through it the flame appears 

 of a bluish-green, but when viewed through sulphindigotic acid 

 or indigo in acetic acid, the flame is more or less reddish-purple. 



