August 4, 1892] 



NATURE 



329 



magnesic sulphate, MgSOg, yOH, or SOHoMgo", 6OH0 would 



r/ 



H— O 



-Na 



Even alum, with its 24 molecules of water of crystallization, 

 may be expressed by an appalling formula : — 



although Graham found that crystallized alum at a temperature 

 of 61" lost 18 molecules of water; if he had used a tempera- 

 ture a few degrees lower he might have found that only 16 

 passed off ! 



By a little stretching of the imagination and altering the 

 atomicities of the elements to suit each particular case, no doubt 

 graphic formulae 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 in 1834. 



But since that time we have learnt that our formulae 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 Associa- 

 tion 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 applied to those phenomena which 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 alcohol contains CoHgO, and if from two molecules 

 of alcohol one molecule of water is subtracted a molecule of 

 ether results :— 2C2H60 = OH2 -I- C4HJ0O. As sulphuric acid 

 is known to have a great attraction for water, it is easy to imagine 

 that the acid combines with the water and ether passes off. 

 But it is found that a small quantity of sulphuric acid at the 

 temperature of 140°- 150° will transform a very large amount 

 of alcohol into ether and water, much more than can be ex- 

 plained .by assuming that the acid has combined with the water. 

 If a mixture of sulphuric acid and alcohol is heated to a tem- 

 perature of 140° -150°, and alcohol allowed to flow into the 

 liquid, a mixture of ether and water vapours passes over, and 

 after a large quantity of alcohol has been transformed, the 



H H 



o 



H— O— O— H H— O^ 



H H 



O O 



/\ /\ 



-O— O— H H— O— O— H 



II II 



H H H H 



There is certainly a symmetry about the formu.a, and it will 1 amount of sulphuric acid is found to be unaltered. At 



be found that 16 of the molecules of water are in a different first glance this seems very difficult to explain, but on 



position from the remaining 8 ; this probably has no significance, | further investigation it is found that alcohol and sulphuric 



NO. II 88, VOL. 46] 



