CORAL PIGMENTS. 187 
not quite as soluble in alcohol; soluble in chloroform, forming a reddish-orange solution, and 
in carbon disulphide. In none of these solutions were any bands detectable. This residue 
(quite free from any traces of alcohol) became redder with strong nitric acid and with 
sulphuric acid, and a marked red with iodine in iodide of potassium solution. Hence this 
pigment is not a lipochrome. 
The coral was decalcified by means of hydrochloric acid as before. The acid however 
Bietcnes of —differing in this respect from the above corals—took up some pigment, the 
decalcified solution after filtermg being of a brown or reddish-brown tint. In this solution 
aa no absorption-bands could be seen: the violet end of the spectrum only being 
absorbed. If caustic soda be added in excess to this solution the pigment may be 
precipitated out. 
The colouring matter seems mainly to occur in the superficial layer of the coral: as 
taught by the action of hydrochloric acid. The decalcified masses of pigmentary substance 
when examined in a compressorium showed no bands; hence no polyperythrin was present: 
they are black in thick, and brownish in thin layers. 
By extracting the pigmented masses with alcohol a solution of a pale greenish colour 
a was obtained which absorbed the violet end of the spectrum abruptly: no 
extract of de- bands could be seen. On evaporation this left a yellow residue, which seemed 
calcified coral. +0 become brown by prolonged heating on the water-bath. Ether only took 
up part of this residue, leaving yellow flocks of pigment undissolved. This ether solution 
was yellow and showed a faint band at D; so that this pigment had changed by heating. 
This band read (about) from 2580 to 2615. On evaporating the ether a yellow and in 
part greenish residue was left: this was only partially soluble in chloroform, and this on 
evaporation left a residue partly yellow and partly dark brown. This residue was now only 
partially soluble in alcohol: so that the heating as stated had decomposed the pigment. 
The residue left from the evaporation of this last alcohol solution became distinctly 
red with nitric acid, gave no distinct coloration with sulphuric acid, and gave a fine 
brilliant red with iodine in potassic iodide solution. This last reaction was very remarkable, 
and was yielded by both the brown and the yellow portions of the residue. 
Caustic soda in aqueous solution extracted—after the decalcified coral had been already 
extracted with alcohol—the dark pigment in considerable amount. The solution 
perce or being almost black, but by transmitted incandescent (electric) light it appeared 
Saas coral reddish or brown-reddish. In a deep layer this let through the red rays, in 
less deep the red and green, and in less deep still the violet end of the spectrum 
only was absorbed. No band was seen, nor on the addition of ammonium sulphide. 
By adding hydrochloric acid to this solution to acidity a precipitate fell. This was 
filtered off and washed, and was of a brown colour: insoluble in ether, soluble in alcohol, 
insoluble in water, and soluble in aqueous solutions of caustic soda. 
I stated above that hydrochloric acid extracted some dark pigment also from this coral 
which was partially precipitated by adding caustic soda to alkalinity. Now this latter pigment 
differs from that just described in some respects, as it is insoluble in alcohol, and insoluble 
in aqueous solution of caustic soda. Hence there appear to be two dark pigments colouring 
this coral; and no lipochromes are present in it. 
