ON SPONGIOPORPHYIUN. 



340 



II. 



Feebly Acid Spongiopoephyrin (a little HCl in distilled 



water) . 

 \ = wave-leugths iu jujtt (1 = O'OOl n). 



See Curve II (Fig. 2). 

 FIG. 2. 



These numbers express the mean of five readings for each. I may mention 

 that I have repeated these measurements over and over again for solutions of 

 tiie same strength, and I find tliny agree to within 0"5 per cent, fur tlie midiile 

 of tiie spectrum, and to below abi)ut 2 per cent, for the red end. 



