68 Reo. J. E. Aahby [March 23, 



The definition given by the speaker as being, upon the whole, 

 in harmony with the prevailing ideas of catalysis, will be found to 

 include the following cases : — 



1. Galvanic action in relation to a finally unchanged platinode. 

 In every battery-cell containing an apparently unchangeable plati- 

 node, all the conditions of catalysis are perfectly fulfilled when the 

 platinode touches the zincode without the intervention of any other 

 metallic conductor ; and the truthfulness of the fulfilment is not 

 altered by the additional fact that similar action will ensue when a 

 metallic (or other) conductor is interposed. It is very doubtful 

 whether the platinode really undergoes no changes, but it remains 

 unchanged at last. 



2. A finally unchanged body produces in certain others no 

 decomposition, but only combination. 



Example. — Platinum combines hydrogen and oxygen into water. 



3. A finally unchanged body produces decomposition, but no 

 re-combination. 



Example. — Decomposition of chlorate of potash by metallic 

 oxides and heat. 



4. A finally unchanged body produces decomposition, and partial 

 or total recomposition, of the elements of a body. 



Example. — Alcohol passed into sulphuric acid at 300" passes 

 out as ether and water, the elements of water having been ab- 

 stracted by the acid, which cannot retain them at that temperature. 

 If we suppose that the acid removes water, as such, from the 

 alcohol, this case is resolved into the foregoing. 



5. A finally unchanged body produces the decomposition of 

 another substance, and causes some of its elements to enter into 

 combination with a third body, also present. 



Examples. — Heated platinum decomposes alcohol vapour, with 

 access of air. In illustration of this class of phenomena, the 

 speaker exhibited the continuous combustion of the vapour of strong 

 liquid ammonia by a fiat spiral of platinum wire (y^^^ inch thick) 

 evolving nitrous gas and water. 



Mr. Ashby then briefly adverted to the principal theories of 

 Catalysis. 



1. Berzelius, who introduced the term into chemistry, considers 

 that it represents a new force. 



2. Liebig dwells at great length upon cases in which the opera- 

 ting body does not remain finally unchanged. He supposes that if 

 A and B are in contact, and changes happen among the particles of 

 A, these may induce changes among the particles of B, by destroy- 

 ing the statical condition, and forcing the particles into motion, 

 whereupon they arrange themselves into new groups. This does not 

 explain at all the cases included under the definition given in this dis- 



