TRANSACTIONS OF SECTION B. 



667 



Even alum, with its twenty-four molecules of water of crystallisation, may be ex- 

 pressed by an appalling formula^ 



H H 



H H 



H_0— 0— H H— 0— 0— H 



o o 



H H H 



H— 0— O— H H— 0; 



O 



H— O— O— H H— O'^ 



I I 



n H H 



H H 



O O 



H— O— 0— H H— O— O— H 



H H 



H H 



There is certainly a symmetry about the formula, and it will be found that sixteeru 

 of the molecules of water are in a different position from the remaining eight ; this 

 probably has no significance, although Graham found that crystallised alum at a 

 temperature of 61° lost eighteen molecules of water ; if be had used a temperature 

 a few degrees lower he might have found that only sixteen passed off ! 



By a little stretching of the imagination and altering the atomicities of the 

 elements to suit each particular case, no doubt graphic formuL-e might be made for 

 all crystalline salts, but they would be perfectly artificial, and not much good is 

 likely to come from the attempt. *^'"^' '^* 



I fear we are driven to the conclusion that, notwithstanding all the progress 

 that has been made in chemical science during the last fifty-eight years, we have 

 not yet reached a method of notation that would have satisfied Dr. Dalton m 1834. 



But since that time we have learnt that our formulse ought to show even more- 

 than the number and position of the atoms of a compound ; we should like them to 

 indicate the amount of potential energy residing in a body, and our equations ought 

 to indicate the amount of heat generated by a chemical change. Let us hope that 

 before the next meeting of the British Association in Edinburgh these desirable 

 developments will have been accomplished. 



A short time ago I mentioned the word ' catalysis ' as being employed to express- 

 certain chemical actions which cannot be explained. It is apphed to those pheno- 

 mena wbich take place in the presence of a body which appears to be entirely un- 

 changed by the action. Happily these catalytic actions are being explained one 

 after another, so that soon the name itself may become obsolete. An example of 

 this action of presence may be given. When a mixture of sulphuric acid and 

 alcohol is heated to a temperature of about 140° to 150° ether passes over. Now 



