230 THE SO-CALLED INORGANIC ENZYMES 



of being unity, is a constant, the value of which lies between 1-6 

 and 1-3. Hence we see that there are abnormalities in the action 

 of these inorganic catalysts, similar to those already described 

 in the case of the enzymes. The abnormalities are explained upon 

 the basis of intermediate compounds between catalyst and sub- 

 stratum, or products of reaction. 



Even equal platinum concentrations do not always lead to the 

 same velocity of reaction, this depending upon variations in fine- 

 ness of subdivision of the platinum, and upon the previous history 

 of the solution, such as its age, the temperature at which it has 

 been preserved, etc. ; to this variation van Bemmellen has in ana- 

 logy with similar phenomena in magnetisation applied the term 

 " hysteresis." 



The dilutions in which these colloidal platinum solutions exert 

 their catalytic effects are enormous. Thus a solution containing 

 only 0-000,01 grm. that is, ^J^ mgrm. per c.c. acting upon a 

 solution of hydrogen peroxide containing 0-06 grm. per c.c., con- 

 verted more than the half in forty minutes. The action of -ioioir 

 to TyiroWd nigrm. of colloidal platinum upon more than 1,000,000 

 times its weight of hydrogen peroxide could still be detected. 



Ernst also found that T V mgrm. of colloidal platinum cata- 

 lysed 50,000 times its own weight of hydrogen and oxygen to water 

 at ordinary temperature without losing its activity in the least. 



The retarding action (or so- Galled " poisoning " action) of 

 certain substances upon the catalytic action of these inorganic 

 colloidal catalysts is also remarkable on account of the minute 

 quantities required to stop the reaction. 



For example, the addition of 0-000,000,014 grm. per c.c. of 

 hydrocyanic acid, to the above-mentioned experiment, in which 

 0-000,01 grm. per c.c. of platinum was acting upon 0-06 grm. 

 per c.c. of peroxide, served to decrease the rate of change by one 

 half, and the addition of 0-000,000,001 grm. per c.c, of hydro- 

 cyanic acid in another experiment had an equal effect upon the 

 velocity of conversion by a colloidal platinum solution in con- 

 centration of 0-000,006 grm. per litre. It is to be noted that the 

 hydrocyanic acid produces its marked effect in amounts of -^ini 

 to T ^Q- of that of the platinum in these experiments, so that there 

 cannot be an ordinary chemical compound between the catalyst 

 and the " paralysator." It must be remembered, however, that 

 even at these dilutions the platinum is present not in molecular 



