FERMENTS AND FERMENTATION. 95 



metals while these are held in a large dish of absolutely 

 pure water, The metal emanates in a cloud irom one of 

 the electrodes and remains suspended in the liquid. The 

 colloidal solution is therefore not a true solution, but rather 

 a suspension of very fine particles. The coarser particles 

 are filtered off, and the sql (a term applied to a colloid in 

 the liquid state) which remains behind shows properties 

 exceedingly like those of the ordinary ferments. For this 

 reason these sols have been called inorganic ferments by 

 BREDIG. Depending upon the metal from which the sol 

 is prepared, we speak of platinumsol, goldsol, etc. 



A large number of ferments from different sources have the 

 power of catalyzing the decomposition of hydrogen peroxide 

 into water and oxygen. Colloidal solutions of platinum 

 have the same power. Interestingly enough, as is the case 

 with the true ferments, this inorganic ferment also is active 

 in exceedingly small quantities. Thus one gram-atom of 

 platinum (194.8 grams) diluted with seventy million liters 

 of water is still able to accelerate the decomposition of 

 more than a million times its amount of hydrogen peroxide. 

 One cubic centimeter of the solution which still shows 

 'fermentative" properties therefore contains only 1/300000 

 milligram of platinum. It would be difficult to rival this 

 with figures taken from any of the organic ferments. 



The rapidity of the decomposition of hydrogen peroxide 

 by platinumsol is dependent upon the concentration of the 

 platinum, just as in the case of a true ferment. If infinite 

 time is allowed, a small amount of platinumsol will bring about 

 as much decomposition as a larger amount. In shorter periods 

 the velocity of the catalysis is definitely dependent upon 

 the concentration of the colloidal plaoinum, very much 

 as in the case of the ordinary ferments which have the 

 | power of catalyzing the decomposition of hydrogen peroxide. 



Even though not sensitive to the same degree as organic f er- 

 Iments, the inorganic ferments are exceedingly sensitive to heat. 

 In the preparation of the sols great care has to be exercised to 



