Catalysts of Organic and Inorganic Origin. 



313 



to etiolin. The pulp gives strong oxidase reactions, but only decomposes 

 H2O2 feebly or not at all. If allowed to dry in the air the oxidase reactions 

 are feebler, but the decomposition of H2O2 a little more active. If the 

 potato pulp ground up with ether is left in contact with it and tested at 

 hourly intervals, it ceases to give distinct oxidase reactions in the following 

 order: — Ursol tartrate and H 2 2 , guaiacum, ursol and H2O2, guaiacum and 

 H2O2, decomposition of H 2 2 . Hence a substance which is at first 8l 

 " peroxidase," an oxidase and a " katalase," as it is attenuated, becomes a 

 " peroxidase " and " katalase," and finally a " katalase " only. 



Chloroform. — Apple pulp pounded with an excess of chloroform turns a 

 yellowish-brown, deepening slowly on exposure to air. The pulp does not 

 decompose H2O2 ; it gives feeble or doubtful oxidase reactions, which in the 

 case of guaiacum are rendered more distinct by the addition of H2O2, but not 

 in those of ursol or its tartrate. If the chloroformed pulp is dried in air 

 and powdered up, it regains a weak power of decomposing H2O2, and shows 

 stronger but still feeble oxidase reactions. Potato pulp triturated thoroughly 

 with excess of chloroform, after the latter had been allowed to evaporate, 

 gave no oxidase reactions with ursol or with the tartrate and H 2 2 , a pale 

 blue with guaiacum on standing, given at once in the presence of H 2 2 , and 

 produced a very feeble decomposition of H 2 2 . The chloroform apparently 

 attenuates or retards oxidase action much more than ether does. 



Neither chloroform nor ether inhibits the action of metallic oxidases such 

 as copper sulphate and salt, ferric chloride, black oxide of manganese, 

 potassium permanganate, or potassium ferricyanide, but in certain cases 

 chloroform retards or inhibits the decomposition of hydrogen peroxide^ 

 Thus if a mixture of copper sulphate and salt is shaken up with an excess of 

 chloroform a temporary precipitation film like an exaggerated surface tension, 

 film forms on the surface of the chloroform, and on adding H2O2 an 

 occasional large bubble may form beneath this film, lifting it up like a skin,, 

 but in the liquid above no decomposition of the H2O2 takes place. If, 

 however, the chloroform is removed by evaporation or the liquid warmed 

 to start the decomposition it continues indefinitely. Chloroform itself does- 

 not decompose H 2 2 , and saturation with ether slightly lessens the decom- 

 position without arresting it. Similar results were given with ferric chloride,, 

 except that the action of the ether is stronger, and if the ether or chloroform 

 is removed by boiling the liquid becomes reddish-brown and loses the power 

 of decomposing H2O2, whereas if removed by evaporation at a low tempera- 

 ture the power of decomposing fresh hydrogen peroxide is regained. 

 Chloroform added to potassium ferrocyanide and H2O2 merely changes a 

 rapid stream of small bubbles into a slow stream of occasional larger 



