Upon a Daguerreotype plate, from which an impression has been effaced by rubbing or otherwise, the picture may be made to reappear by merely coating it over with iodine.
c.

Place in a vessel a little water, into which put the smallest possible quantity of free iodine and add a little starch, and the liquid will instantly assume a blue color.

Advantage is taken of this fact in the laboratory to detect the presence of iodine in liquids.
The starch should be dissolved in boiling water and allowed to cool.
There are numerous other interesting experiments that can be performed by the aid of iodine, but it is unnecessary here to consume more space.
CHLORINE.
History .-- The Swedish chemist, Scheele, in 1774, while examining the action of hydrochloric acid on peroxide of manganese, first noticed this element.

He called it dephlogisticated muriatic acid.

It was afterwards, by the French nomenclaturists, termed oxygenated muriatic acid, conceiving it to be a compound of oxygen and muriatic acid.