484 
SIR B. C. BRODIE ON THE ACTION OF ELECTEICITT ON GASES. 
according to hypothesis (2) the density of ozone is twice that of oxygen. The experi- 
ments are perfectly consistent with either of these two assumptions, and both hypotheses 
are equally tenable. 
Case III. R=f, r=f, 
jp(4— 3n)=%qn. 
The experiments with hydriodic acid at zero, and also the experiments with hydro- 
sulphide of sodium, given in Section III., are to be referred to this case; only one 
hypothesis is possible : 
Hypothesis, n= 1, p=oq; whence 
4?=? + 10[g. 
Case IV. 11= 2, r= 3, 
p(l —7i)=qn. 
The experiments comprised in Section IV. (namely, the oxidation of neutral and 
slightly alkaline solutions of hyposulphite of soda, the oxidation of oil of turpentine 
and of protochloride of tin) are examples of this class. 
But one hypothesis is possible : 
Hypothesis, n—\, q=§ ; whence 
r=3[g. 
The hypothesis, therefore, that the unit of ozone is constituted of three “ simple 
weights” | is both necessary and sufficient for the explanation of the total system of 
phenomena, and no other hypothesis of this order is tenable. 
