Volume 2

The elements of experimental chemistry / by William Henry.

  • Henry, William, 1774-1836.
Date:
1815
Catalogue details

Licence: Public Domain Mark

Credit: The elements of experimental chemistry / by William Henry. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

    61/586 (page 43)
    by the escape of gas. Iron, it has ah-eady been stated, effervesces strongly during its solution in dilute sulphuric acid; but the black oxide of that metal is taken up silently, and without any discharge of gas. III. The metals may be oxidized by the transfer of oxy- gen fi'om other metallic oxides. Thus when iron filings are distilled with the red oxide of mercury, the oxygen passes to the iron, and the mercury is revived or appears in a me- tallic state. In a similar manner, the oxides held in solu- tion by acids, are decomposed by immersing, in the solution, other metals. When copper, for example, is immersed in a solution of nitrate of mercury (consisting of oxide of mer- cury and nitric acid) the latter metal is deprived of its oxygen by the former, and appears on the surface of the copper in a revived state. The nitrate of copper, which is thus produced, is precipitated by iron, which has a stronger affinity than copper for oxygen. A variety of similar ex- amples might be given, in which the precipitating metal takes oxygen from that which is precipitated. In cases of this sort, it must be confessed that the comparative affinities of the acid for the oxides of the two metals have some share in the effect, but much less than the affinities of oxygen se- parately considered. The precipitated metal, also, is seldom quite pure, but contains a portion of the metal, which has caused the precipitation. By an attentive examination of facts of this kind, Lavoi- sier has been able to deduce the proportion of oxygen ne- cessary to the solution of different metals, according to this analogy: As the quantity of the precipitant is to that of the PRECIPITATED metal, so is the quantity of oxygen necessary for the solution of the precipitated to that necessary for the 50- lution of the precipitant. Thus it has been found by expe- riment that 135 grains of mercury are necessary for the precipitation of 100 grains of silver from the nitric acid. It is evident, then, that l.'iS grains of mercury require, to be- come soluble, the same quantity of oxygen as 100 grains of silver; and, therefore, as 100 to 135, so is the quantity, necessary to render soluble 100 grains of mercury, to that necessary