654 
MR. H. B. DIXON ON CONDITIONS OF CHEMICAL CHANGE 
Table XXI.—Pressure = 1000 milliras. 
Reference 
No. 
Length of 
Column. 
D ,• CO., 
Ht> 
Temperature. 
miilims. 
° C. 
70 
25 
•90 
8-0 
71 
50 
•91 
8-4 
69 
400 
•98 
io-o 
As the general result of these pressure experiments, it appeared that the law of mass 
might be tested by the incomplete combustions of carbonic oxide and hydrogen, pro¬ 
vided that each mixture of gases was exploded above its critical pressure. It will, 
perhaps, be most convenient, before proceeding to describe the experiments made with 
this view, to give here an account of Horstmann’s second paper, which advanced the 
inquiry another stage. 
Horstmann’s experiments. 
Horstmann* having shown that no sudden alterations occur in the ratio of carbonic 
acid and water produced by the combustion of carbonic oxide and electrolytic gas 
mixed in various proportions, and that Bunsen’s earlier experiments were vitiated 
by the presence of varying proportions of aqueous vapour in the eudiometer, proceeded 
to repeat v. Meyer’s experiments, in which mixtures of carbonic oxide and hydrogen 
were exploded with successively increasing quantities of oxygen. 
Horstmann found in these experiments that, for a given mixture of carbonic oxide 
and hydrogen, the proportion of carbonic acid formed gradually diminishes at first with 
increase of oxygen, reaches a minimum when between 30 and 40 per cent, of the com¬ 
bustible gases is burnt, and then gradually increases towards the limit that would be 
reached if all the gases are burnt. Nowhere did he find any alteration per saltum in 
the proportion of the products of combustion. But an examination of the numbers 
given by these experiments led Horstmann to detect a remarkable relation between 
the ratio of the unburnt carbonic oxide to the unburnt hydrogen, and the ratio of the 
burnt carbonic oxide to the burnt hydrogen. He found that when mixtures of car¬ 
bonic oxide and hydrogen in any proportions are exploded, with the same quantity of 
oxygen, the ratio between the quantities of the two gases burnt is proportional to the 
ratio between the quantities of the two gases left unburnt. Thus, if A and B are the 
quantities of carbonic oxide and hydrogen in any mixture exploded with a certain 
quantity of oxygen, then the quantity of carbonic acid formed («) and the quantity of 
steam formed (h) are given by the equation 
A —a a 
B"- 6 = i XK 
where k is a constant depending on the quantity of oxygen taken. 
* Verb, des Heidelb. nafcurf. med. Yereins., N.S. II., 1 ; Liebig’s Annalen, 190-228. 
