310 OBSERVATIONS ON MURIATIC ACID, 
There are, I believe, only two arguments to which any 
weight is due in support of the opinion that chlorine is a 
simple substance, which by combination with hydrogen forms 
muriatic acid. One is drawn from the analogy resting on the 
general fact, sufficiently established, that acidity is in different 
cases the result of the agency of hydrogen ; the other, from the 
analogy in the chemical relations of chlorine and iodine. 
Sulphur forms with hydrogen a compound unequivocally 
acid. The compound radical of prussic acid Cyanogen, disco- 
vered by the able researches of Gay Lussac, likewise acquires 
acidity when it-receives hydrogen. . Acidity, therefore, is a 
property not exclusively connected with oxygen; it is also 
communicated by hydrogen; and when chlorine with hydro- 
gen gas, forms muriatic acid gas, the agency exerted may be 
considered as similar to that arising in other cases, of the pro- 
duction of an acid from the action of hydrogen. 
This is confirmed by the relations of iodine. It, too, forms 
an acid by combination with hydrogen; and the chemical 
agencies of iodine are in several other respects similar to those 
of chlorine. When the one, therefore, is considered as a 
simple body, (and there is no absolute proof that iodine is a 
compound,) the other is, with probability, placed in the same 
class. And certain analogies existing between sulphur and io- 
dine, serve to connect and confirm these views. Each of them 
forms an acid with hydrogen; each of them also forms an acid 
with oxygen. But chlorine exhibits precisely the same points 
of resemblance: with hydrogen, it forms muriatic acid; 
with oxygen, it forms chloric acid. Its chemical relations, with 
regard to acidity, being thus similar, seem to require the same 
explanation to account for them. 
These facts lead undoubtedly to views of chemical theory, 
different from those which had before been established; and on 
which 
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