Catalysts of Organic and Inorganic Origin. 307 



If a dilute solution of copper sulphate and salt is mixed thoroughly with an 

 excess of egg albumin, a greenish-white precipitate is formed, but the liquid 

 will still give a strong blue with guaiacum. After boiling, the filtrate gives 

 no blue with guaiacum, and the coagulum gives a greenish colour only. 

 Boiling with coagulable proteid would apparently in this case practically 

 destroy the " oxidase " reactions of copper sulphate and salt, and would 

 entirely remove the oxidase from its solution in water. 



Where, however, a cell oxidase is a metallic salt not combined with or 

 associated with proteins, the oxidase properties may be retained after boiling. 

 Instances of these are already known,* and where boiling removes the direct 

 oxidase action of an extract but this returns slowly after cooling, this may be 

 due to the conversion of a " per " salt into a " proto " salt or vice versd. 

 Further, a solution of potassium ferrocyanide on standing in light develops 

 traces of ferricyanide and then becomes able to give a direct blue with 

 guaiacum. 



The Resistance of Oxidases to Drying and Keeping. 



According to Moore and Whitley (I.e.), apple and carrot gratings dried at 

 45° C. for eight and three days respectively lost all their oxidase. Potato pulp 

 was ground up, the excess moisture pressed off and the pulp spread in thin 

 layers to dry in air at 15° C. This formed a grey powder when ground. It 

 decomposed H 2 2 moderately actively, mixed with water gave a very faint 

 blue with guaiacum, with ursol tartrate and H2O2 the liquid darkened slowly 

 to brown and ultimately purplish. Drying makes the oxidase cling firmly to 

 the proteids of the pulp. These properties were shown by the powder even 

 when three months old. Similarly mere drying did not destroy the oxidase 

 in apple ptdp from which the sap had been pressed out before pounding and 

 drying, and the properties were retained uninjured for over three weeks in 

 the dry condition. Moore and Whitley's results may have been due to the 

 non-removal of the sap or to the higher temperature used. 



Even in solution oxidases may retain their properties for a long time. The 

 glycerine extract of potato oxidase, covered, 1 but in contact with air, darkened 

 slowly at 12-15° C, gave after two months a distinct reaction with guaiacum, 

 a slow change through brown to purple with guaiacum, a slow change through 

 brown with ursol tartrate, and a moderately active decomposition of H 2 2 . 

 At three months it gave no blue with guaiacum alone, a faint blue with 

 guaiacum and salt, stronger with guaiacum and H 2 2 , and very slow browniug 

 with salt and ursol tartrate, stronger with H 2 2 . At four months it gave a 

 faint blue with guaiacum and H 2 2 and a moderately active decomposition of 



* See Lafar, ' Techni.sche Mycologie,' vol. 1, p. 675 (1907). 



