338 C. A. MAOMUNN. 



This pigment is characterised by possessing a very well- 

 marked banded absorption spectrum, and by certain other 

 chaiacteristics which distinguish it from other pigments 

 which have been hitherto described. 



An inspection of the accompanying plate shows the remark- 

 able spectra which the various solutions of Spongioporphyrin 

 present. Looking at sp. 5 or 6, one is reminded of oxy- 

 hsemoglobin, of carminic acid, of turacin, and of antedonin, 

 etc. ; but a closer inspection reveals differences between the 

 spectrum of Spongioporphyrin and that of any known animal 

 or vegetable pigment, and, as will be seen further on, the 

 wave-length measm-ements of the absorptive bands of the 

 solutions of this pigment, and the chemical characters of 

 these solutions, show that it is a pigment not identical with 

 any hitherto described. 



Acid Solutions of Spongioporphyrin.^ — Professor 

 Lankester had suggested various solvents to Mr. Kirk- 

 patrick, and among others alcohol acidulated with nitric 

 acid, and the spectrum of this solution was mapped by the 

 latter observer correctly, and is shown in sp. 1. 



This represents the spectrum of a suitable depth, or suit- 

 able concentration of solution. In a deeper layer, or in a 

 more concentrated solution, the absorptive bands coalesce, 

 and one can see a broad black band occupying the middle of 

 the spectrum, the red rays and some of the blue being trans- 

 mitted, while in a deeper layer still, or in a more concentrated 

 solution, only some of the red rays are transmitted. 



All the acid solutions of Spongioporphyrin have a red- 

 pui'ple colour, while the alkaline solutions have a bluer tinge. 

 This difference is especially well marked when the solutions 

 are filtered ; the filtering paper being coloured reddish purple 

 in the case of the acid solutions, and bluish purple in the case 

 of the alkaline solutions. 



Taking the readings of a suitable depth of a rectified (90 

 per cent.) spirit solution acidified with a couple of drops of 

 nitric acid we get, — First band, from X 595 to X 583, centre 

 • Of course all these solutions were filtered. 



