372 Dr. A. Ransome on some of the 



4. The Molecules of the Catalyte must be free — 



That is, must be untainted by any stain of vapour or of any 

 other substance ; otherwise the molecular power of the catalyte 

 will be in some measure neutralized by being exerted upon the 

 substance which soils it. This condition is a very important 

 one. It is probable that upon all bodies, and especially upon 

 detached molecules, there exists a layer of vapour. As I have 

 before stated, Professor Magnus has shown that the most various 

 vapours condense on the surface of solid bodies ; and this fre- 

 quently takes place to such an extent that, by careful thermo- 

 electric measurements, he could detect the rise of temperature 

 due to their condensation. The experiments of Messrs. Jamin 

 and Bertrand on the condensation of gases and vapours by pow- 

 dery substances have also been quoted ; and the extreme diffi- 

 culty of thoroughly cleansing glass and silver plates from stain 

 is familiar to all photographers. Professor Faraday's well-known 

 experiment of producing union of oxygen and hydrogen by 

 means of a platinum plate, requires for its success the most ac- 

 curate cleansing of the plate. 



When heat quickens a molecular action, as in most catalytic 

 experiments, familiarly in the ordinary platinum lamp, the in- 

 tensity of the subsequent action, when the heat is withdrawn, is 

 probably partly owing to the cleansing-power of the heat, which 

 drives off the layer of vapour with which the catalyte was sur- 

 rounded. The same favouring condition is also probably pre- 

 sent when an acid is assisted in its attack upon a metal for which 

 it has little affinity, by the presence of another more attractive 

 metal alloyed with it. 



To take one instance, when nitric acid dissolves the platinum 

 in an alloy of platinum with another metal, apart from galvanic 

 action, it seems likely that during the operation the acid is 

 brought into much closer contact with separated particles of the 

 indifferent material than would otherwise be possible, and thus 

 comes within the sphere of chemical combining-forces. 



duced in, or which at any rate are accompanied by a decomposition of, the/er- 

 ment, it is probable that the want of chemical energy in the products of the 

 decomposition may permit molecular forces to play their part. Ferments are 

 bodies containing nitrogen, a substance which not only displays very little 

 combining-power, but confers the same indifference upon many of its com- 

 pounds. An observation of the eminent chemist Berthelot gives peculiar 

 point to this remark. He noticed that in fermenting sugars, having the 

 general formula Cen m(HO), by means of animal nitrogenous substances, 

 such as caseine (together with an alkaline carbonate to neutralize any acid 

 as it is formed), decomposition took place simultaneously in the sugar 

 (glycerine, mannite, &c.) and in the ferment. The ferment, however, did 

 not rot, but lost the whole of its nitrogen. (Chemist, vol. iv. p. 580.) 



