igii] Louis Hussakof and William H. Welker 219 



acid media, whereas that of the Port Jackson shark capsule, while 

 more resistant to botli types of reagents, was somewhat more solu- 

 ble in strong acid than in concentrated alkaline media. 



V. GENERAL QUALITATIVE TESTS 



Both types of capsules gave the same general reactions when 

 the powdered substance as well as the washed and dried fragments 

 of the original material were tested. These tests showed the pres- 

 ence of sulfur^ and nitrogen,^ and the absence (or presence in ex- 

 ceedingly slight proportions) of phosphate.^" Hydrolysis with boil- 

 ing dilute hydrochloric acid for 30 minutes failed to yield sulfate or 

 a reducing substance. The capsular material did not respond to the 

 Molisch test for carbohydrate, but gave the typical colorations in 

 the general protein color tests. 



VI. PIGMENTS 



Pigments from egg capsules of the skate. About five capsules 

 were completely dissolved in boiling 5 per cent. potassium hydroxide 

 Solution, by which process a deep wine-red fluid was produced. This 

 was filtered and the filtrate carefully neutralized with hydrochloric 

 acid. A heavy, flocculent, gray precipitate resulted, which was 

 filtered off.^^ The filtrate containing the coloring matter was then 

 spontaneously evaporated to dryness in a warm place. When dry, 

 a concentrated aqueous Solution was made of the residue. This 

 Solution was placed in a parchment bag and dialyzed. The coloring 

 matter did not pass through the bag and after several days' dialysis, 

 the colored Solution was obtained free from salts. The Solution was 

 again filtered and evaporated to dryness as before. The residue 

 was a shiny, translucent, scaly, reddish-black solid. 



Solubility tests applied to these scales showed them to be soluble 

 in water, acid and alkali. Solutions of this pigment are delicately 

 responsive to change in reaction ; when acid, the Solutions are straw 

 colored; when alkaline or netural, they are dark brown. 



* The material was fused with metallic sodium and the aqueous Solution of 

 the residue was tested with sodium nitroprusside. 



' Determined with the aid of the Lassaigne test. 



"The material was decomposed with nitric acid and the resultant Solution 

 was tested with molybdate Solution. 



" The further treatment of this precipitate is described on page 220. 



