468 LECTURE XX. 



end-products of the reaction, and both are effective when present in very 

 minute quantities. Thus, a very small amount of nitrous acid is sufficient 

 to convert relatively large quantities of sulphur dioxide and atmospheric 

 oxygen into sulphuric acid. To.^znr to ^o^tfuo milligram of colloidal 

 platinum or manganese dioxide, or ^.TTOO m illig r am of gold, will cause 

 the decomposition of more than one million times as much hydrogen 

 peroxide. Ernst 1 has shown that T V milligram of colloidal platinum 

 will catalyze 50,000 times as much oxyhydrogen gas without losing any 

 of' its efficiency. It is of great significance for the conception of the 

 action of catalyzers to know that there are substances which have the 

 opposite effect, and retard reactions which are already in progress. Bredig 2 

 calls these negative catalyzers. Thus, we know that traces of ethylene, 

 alcohol, ether, oil of turpentine, and ethyl iodide will tend to prevent the 

 oxidation of phosphorus. 3 Bigelow 4 for instance, has shown that the 

 presence of 0.000,0014 gram of mannitol per cubic centimeter will reduce 

 the rate of the oxidation of 800 times as much sodium sulphite in aqueous 

 solution to one-half its former value. On the other hand, we also know of 

 substances which will directly prevent catalysis. These are known as 

 anti-catalyzers or paralyzers. As an example of this may be mentioned, 

 that 0.000,000,001 gram of hydrocyanic acid per cubic centimeter 

 will reduce the catalytic effect of 0.000,006 gram of colloidal plati- 

 num in the decomposition of hydrogen peroxide to one-half its original 

 value. 



Not only do we have the above analogies between the ferments and 

 catalyzers, but there are other similarities, such as the effect of external 

 conditions upon their activity, e.g. temperature, etc. Certain laws have 

 also been worked out showing how the rate of the reaction depends upon 

 the amount of ferment present and upon the temperature, etc., and these 

 relations illustrate the analogy between the ferments and the above- 

 mentioned catalyzers. It would be beyond the scope of these lectures to 

 dwell longer upon these interesting observations. We can abandon the 

 subject the more readily because if we were to attempt to apply these 

 principles to the processes in the animal and vegetable organisms, it would 

 further our insight into the cell processes but little. We must not be 

 deceived by the little knowledge we have gained regarding catalysis, for, 

 generally speaking, we know nothing at all concerning the way in which 

 the catalyzers act. We know merely that their presence is necessary. 

 We must admit that the relations between catalyzers and ferments are 

 to be regarded only as analogies, there being no proof that their actions 



1 Z. physikal. Chem. 37, 448, 454 (1901). 



2 Bredig and v. Berneck: Ibid. 31, 324 (1899); Bredig and Ikeda, 37, 1, 63 (1901). 



3 Centnerszwer: Ibid. 26, 1 (1898). 



4 Ibid. 26, 493, 503 (1898). 



