ON SPONGIOPOHPHYRIN. 339 



689 ; second band, including shadings, A 577 to A 545, the 

 dai'ker part extending from A 574 to A 552 ; the centre of 

 darkest part being about A 563. 



Hydrochloric acid is quite as good a solvent for the pig- 

 ment as nitric acid, when added in very sliglit amount to 

 alcohol or even distilled water, and is really preferable for 

 many reasons; but alcohol acidulated witli sulphuric acid is a 

 very poor solvent. 



A solution of Spongiopoi'phyrin in absolute alcohol acidu- 

 lated slightly with hydrochloric acid, gave the following 

 measurements for the absorption bands : — First, A 602 to 

 A 574, including shadings, dark from A 598 to A 580 ; second, 

 A 566 to A 556-5; third, A 548-5 to A 535. 



The bands in an aqueous solution acidulated with hydro- 

 chloric acid, of which the spectrum is shown in sp. 5 (only 

 for another depth of solution), read — First baud, A 592 to 

 A 542, dark part A 586 to A 547, centre about A 566 ; second 

 band, A 533 to A 514, centre A 524. 



The pigment is gradually deposited from an aqueous solu- 

 tion acidulated with hydrochloric acid, and can be quickly 

 precipitated out by adding caustic potash solution drop by 

 drop until the fluid is slightly alkaline. In this way I found 

 that I could isolate Spongioporphyrin, as will be referred to 

 below. 



Mr. Kirkpatrick found, as I have done, that the pigment 

 is insoluble in benzol, ether, chloroform, and ammonia, but I 

 find that distilled water and glycerine take a little up as well 

 as water to which a little ammonia has been added. 



Neutral Solutions of Spongioporphyrin. — The 

 spectrum of a neutral aqueous solution is shown in sp. 7, 

 and that of the solid pigment mounted in balsam in 8. That 

 the very small amount of acid or of alkali required to extract 

 the pigment must exert some slight influence on the pigment 

 is shown by a comparison of the spectra of the alkaline and 

 acid solutions. Compare, for instance, sp. 5 and 6 with 3 

 and 4. Of course the alcohol acidulated extracts show a 

 different spectrum from that of the corresponding acidulated 



