ELEMENTARY SUBSTANCES. 57 
6. Sudphur.—In combination with other bodies, sulphur 
exists in considerable abundance in animal substances. It 
can scarcely be said to occur in a separate state in animals ; 
at least the experiments which may be quoted as encourag- 
ing such a supposition, are by no means decisive. United 
with oxygen, in the form of sulphuric acid, it exists in com- 
bination with potash, soda, and lime. 
7. Flworic Acid.—BeErzetius has detected this acid in 
bones and in urine, in a state of combination with lime *. 
8. Muriatic Acid.—This acid exists, in combination with 
an alkali, in a great number of the animal fluids, as with 
soda and ammonia in urine. I have observed, that several 
species of the genus Julus, when taken by the hand, emit 
an odour so much resembling this acid, as to render the 
opinion probable, that they secrete it, when irritated, in a 
free state. 
9. odine.—This interesting substance has been obtained 
by Dr Fyre +, from the residue of the incineration of the 
common sponge of the shops. The water in which sponge 
had been infused, and which, consequently, contained its 
gelatinous ingredient, yielded no traces of it. The portion 
which remained, after infusion in water, or its albuminous 
part, afforded, after being burnt to ashes, distinct traces of 
its existence. We may conclude, therefore, that the iodine 
is in combination with the albumen or insoluble portion. 
In the sea-weeds, on the other hand, the portion which is 
soluble in water contains the iodine; thereby furnishing a 
very striking point of difference in its mode of combination 
in the Vegetable and Animal Kingdoms. 
10. Potash.-This alkali exists in combination with the 
sulphuric, muriatic, or phosphoric acids; but it is far from 
* Annals of Philosophy, ii. p. 416. 
+ ‘On the Plants from which Iodine can be procured.”—Edin. Phil. 
Journ. i. 256. 
