1849.] Dr. Murray’s Defence of his New Theory of Acids. 328 
ARTICLE VI. 
Defence of Dr. Murray’s New Theory of Acids. 
By Toke Murray, M.D. F.R.S. Edin. 
(To Dr. Thomson.) 
SIR, Edinburgh, Dec, 8,.1818. 
In the account which you give in your number for Dec. of the 
mutual action of sulphurous acid and sulphuretted hydrogen, and 
in which an important experimental result is established, you 
remark of the compound which you find to be formed of these 
two gases, that though containing both oxygen and hydrogen, 
united to a combustible base, it possesses the properties of 
acidity in a very weak degree, and you consider this as affording 
a proof that my notion of the greatest degree of acidity being 
given to bodies by the joint union of oxygen and hydrogen is 
not countenanced by chemical facts, nor consistent with the 
phenomena of the science. 
Unwilling to engage in controversial discussion, I should not 
probably have alluded to the subject, with the view merely of 
obviating an objection. But the fact becomes more interesting 
when it affords, as I am led to believe it does, an important 
illustration and confirmation of the truth of my opinion. 
In a memoir read at the close of last session before the Royal 
Society of Edinburgh, on the Relation of the Law of Definite 
Proportions to the Constitution of Acids, and which I have 
published lately as an appendix to the new edition of my System 
of Chemistry, I had given the example of sulphuric acid (oil of 
vitriol) as affording an argument in support of my views. It is 
composed of 100 of sulphur with 150 of oxygen, and 56:7 of 
combined water; that is, of 100 of sulphur with 200 of oxygen, 
and 6°7 of hydrogen. Sulphurous acid is a compound of 100 of 
sulphur with 100 of oxygen. The proportion of 200 of oxygen, 
therefore, in sulphuric acid is the regular multiple conformable to 
the usual law. . The proportion of hydrogen is that which consti- 
tutes sulphuretted hydrogen. It appears, therefore, I remark, 
that the proportions of both these elements are determined by 
their relation to the sulphur as the radical of the acid, and are 
those which the quantity of sulphur would separately require. 
This, so far as theory can discover, is not a necessary result. 
The oxygen and hydrogen might each have required,the quantity 
of sulphur with which they combine ; that is, the existing rela- 
tions might have been those of sulphur to oxygen, and sulphur 
to hydrogen, in their several proportions. It is otherwise ; there 
is the relation of sulphur to oxygen, and in addition to this of 
hydrogen to the same sulphur. And thus, since the same 
quantity of sulphur receives the acidifying influence of both 
elements, we discover the source of the higher degree of acid 
