The Romance of Chemistry 733 



not take place. A thing which has this commanding power 

 is a catalyst, and the process is catalysis. 



The peculiar feature is that the substance which exerts a catalytic 

 influence is not affected by what it does ; it can be used over and 

 over again. The presence of a very small quantity of platinum 

 causes the combination of large quantities of oxygen and hydro- 

 gen, but it is not exhausted in the process. Prof. Duncan gives a 

 good example. 



Chromic chloride is a curious substance that exists in two 

 forms, soluble and insoluble. The "insoluble" violet crystals 

 may be left under water for days unaffected; but drop into 

 the test-tube a trace of chromous chloride, even 0.000025 of 

 a gram, and the violet crystals hasten to bury themselves in 

 the water, the temperature rises, and an indigo-blue liquid 

 results. The mere presence of a trace of the catalyst has 

 suddenly let loose the powerful affinities lying latent in the 

 violet crystals, and the substance is dissolved. It is almost 

 as curious as though a pound of salt thrown off the Battery 

 should dissolve Manhattan Island. This is an example of 

 what is called physical catalysis, for the chemical properties 

 of the chromic chloride are the same after as before; it has 

 simply passed into solution. 



Ferments 



To be included among catalytic substances, yet conveniently 

 separated, are the ferments or enzymes produced by living crea- 

 tures (e.g. yeast plant and bacteria) or by living cells like those 

 of the digestive glands. The fact that the yeast cell, the diameter 

 of which is only one three-thousandth part of an inch, is capable 

 of so many chemical changes is one of the unexplained wonders 

 of the world. As in the case of inorganic catalysts, so with these 

 organic ferments, minute quantities can bring about chemical 

 transformations of great magnitude and at a very rapid rate. The 

 number of ferments is legion and they work like magic; quickly 

 and quietly they bring about changes which in the laboratory 



