ng chemist of Sweden, his first discovery--that of
tartaric acid, which he had isolated from cream of tartar. This was the
beginning of his career of discovery, and from that time on until his
death he sent forth accounts of new discoveries almost uninterruptedly.
Meanwhile he was performing the duties of an ordinary apothecary, and
struggling against poverty. His treatise upon Air and Fire appeared
in 1777. In this remarkable book he tells of his discovery of
oxygen--"empyreal" or "fire-air," as he calls it--which he seems to
have made independently and without ever having heard of the previous
discovery by Priestley. In this book, also, he shows that air is
composed chiefly of oxygen and nitrogen gas.

Early in his experimental career Scheele undertook the solution of
the composition of black oxide of manganese, a substance that had long
puzzled the chemists. He not only succeeded in this, but incidentally in
the course of this series of experiments he discovered oxygen, baryta,
and chlorine, the last of far greater importance, at least commercially,
than the real object of his search. In speaking of the experiment in
which the discovery was made he says:

"When marine (hydrochloric) acid stood over manganese in the cold it
acquired a dark reddish-brown color. As manganese does not give any
colorless solution without uniting with phlogiston (probably meaning
hydrogen), it follows that marine acid can dissolve it without this
principle. But such a solution has a blue or red color. The color is
here more brown than red, the reason being that the very finest portions
of the manganese, which do not sink so easily, swim in the red solution;
for without these fine particles the solution is red, and red mixed with
black is brown. The manganese has here attached itself so loosely to
acidum salis that the water can precipitate it, and this precipitate
behaves like ordinary manganese. When, now, the mixture of manganese and
spiritus salis was set to digest, there arose an effervescence and smell
of aqua regis."(6)

The "effervescence" he refers to was chlorine, which he proceeded to
confine in a suitable vessel and examine more fully. He described it as
having a "quite characteristically suffocating smell," which was very
offensive. He very soon noted the decolorizing or bleaching effects of
this now product, finding that it decolorized flowers, vegetables, and
many other substances.

Commercially this discovery of chlorine