258 A. LIVERSIDGE. 



On ignition the pigment gives off nitrogenous odours, intumesces 

 greatly and the charred residue acquires deep blue, green, and 

 other iridescent colours, similar to those sometimes seen on coke 

 and specimens of haematite : this sheen did not readily burn off. 

 No crystalline structure could be detected in the intumesced char — 

 (indigo, if present, would probably have been sublimed and 

 deposited in the cavities, it was accordingly specially searched for) 

 finally a bulky ferruginous-looking ash was left. The ash was 

 found to contain much phosphoric acid, together with iron, lime, 

 and magnesia. 



Moseley states that the blue colouring matter left by hydro- 

 chloric acid can be at once dissolved off the filter by alcohol; this 

 may be the case with the perfectly fresh coral, but I found that 

 the colour from the old dead coral is only slightly soluble, and 

 even absolute alcohol only dissolves it in part. On evaporation, 

 this extract leaves a dark olive-green residue ; (indigo leaves a 

 "blue residue) which intumesces on ignition and leaves a little ash. 



To ascertain its solubility -648 gramme of the blue residue left 

 by hydrochloric acid was extracted for some hours with 75 c.c. of 

 absolute alcohol in a percolator over a water bath ; the dark 

 green alcoholic extract when evaporated to dryness in a platinum 

 dish over a water-bath, left a dull dark green coloured and blistered 

 residue weighing *115 gramme, equal to 17*8% on the crude 

 pigment, and to "18% on the original coral. 



On warming, it melts and becomes very fluid, but solidifies on 

 cooling; at higher temperatures it gives off much fume and a 

 disagreeable nitrogenous odour like burnt fish and finally 

 inflames ; the carbon burns off very quickly and some ash is left, 

 viz., the above '115 gramme of pigment left *0061 gramme or 

 5-33%. This ash dissolved in hydrochloric acid to a pale yellow 

 colour and was found to contain iron, phosphoric oxide, lime and 

 magnesia; the quantity (-0061 gramme) was insufficient for a 

 complete examination. 



Next, -648 gramme of the blue colouring matter left by hydro- 

 chloric acid was placed in a percolator with 60 c.c. glacial acetic 



