240

OXYGENATION.

giston, were not the copper present, which takes it

up.

The same author remarks, that a small excess ofacid is necessary, and that without it no precipitationbegins.

Now since water is decomposed by iron and sul-phuric acid, it must be allowed, that when iron isimmersed in a solution of sulphate of copper, thewater is decomposed by the iron and excess of acid,the iron attracting the oxygen of the water, whilethe hydrogen of the latter unites to the oxygen ofthe copper, reduces it, and forms a quantity of wa-ter equal to that decomposed.

The precipitation of silver in its metallic form byiron and other metals is to be explained in the samemanner, and not by a single affinity as the Antiphlo-gistians imagine.

The reduction of gold and seme other metals, bysolutions of sulphate of iron and muriate of tin, isreadily accounted for on the principles advanced here;for fresh made solutions of sulphate of iron and mu-riate of tin contain hydrogen, and have the power of

•Chem. Essays, Vol. II» p. 384, Eng. trans.