342 C. A. MACMUNN, 



and ammonia added to alkalinity ; the precipitate wliicli 

 formed was separated by filtration and a part digested in 

 alcohol and ammonia, but this merely showed the ordinary 

 alkaline spectrum as shown in sp. 3, Another part was digested 

 in alcohol acidulated with sulphuric acid, but this only showed 

 a spectrum similar to sp. 1. Hence Spongioporphyrin is not 

 allied to haemoglobin or to haematin. 



Isolation of Spongioporphyrin. — After trying various 

 methods of isolating the pigment, I have come to the con- 

 clusion that by far the easiest and best method is as follows : 

 — Extraction of portion of sponge with distilled water, to 

 which a little hydrochloric acid has been added, filtering, 

 precipitating the filtrate with caustic potash to feeble alka- 

 linity, collecting the precipitate on a Schleicher and Schiill's 

 toughened filter-paper, washing on the filter-paper with 

 abundance of distilled Avater, collecting precipitate, drying, 

 and washing with alcohol and ether. The amorphous pre- 

 cipitate can thus be obtained fairly pure, or it may be further 

 purified by re-solution and precipitation. So far I cannot 

 obtain it in crystals, and on incineration on platinum foil it 

 leaves a little greyish ash. I have not yet been able to get 

 enough pigment for a series of combustions, nor to determine 

 more closely its chemical characters, but I find that it is 

 soluble in distilled water acidulated with hydrochloric acid, 

 and insoluble in ether, chloroform, benzol, absolute alcohol, 

 liquorice, distilled water, aqueous solutions containing caustic 

 potash, and in alcohol containing caustic potash. Like the 

 pigment as it exists in the sponge, it is soluble slightly in 

 alcohol acidulated with hydrochloric acid. Solutions of the 

 isolated pigment give the same spectra as those obtained 

 from the coloured sponge itself. 



11. The Pigment of Polyopogon gigas. 



Whereas Spongioporphyrin is very stable, even when 

 treated with strong mineral acids, the colouring matter of 



