It is found in the ley of ashes of sea-weeds, after the soda has been separated by crystallisation; and it is disengaged by means of sulphuric acid, which expels it from the alkaline ley in the form of a violet gas, which may be collected and condensed in the way you have just seen.—This interesting discovery was made in the year 1812, by M. Courtois, a manufacturer of saltpetre at Paris.
CAROLINE.
And pray, Mrs. B., what is the proof of iodine being a simple body?
MRS. B.
It is considered as a simple body, both because it is not capable of being resolved into other ingredients; and because it is itself capable of combining with other bodies, in a manner analogous to oxygen and chlorine. The most curious of these combinations is that which it forms with hydrogen gas, the result of which is a peculiar gaseous acid.
CAROLINE.
Just as chlorine and hydrogen gas form muriatic acid? In this respect chlorine and iodine seem to bear a strong analogy to each other.
MRS. B.
That is indeed the case; so that if the theory of the constitution of either of these two bodies be true, it must be true also in regard to the other; if erroneous in the one, the theory must fall in both.
But it is now time to conclude; we have examined such of the acids and salts as I conceived would appear to you most interesting.—I shall not enter into any particulars respecting the metallic acids, as they offer nothing sufficiently striking for our present purpose.