slowly 5 
re 
ei 
{Fa “ 
_ by its oxygen being attracted by the metal, but its presence 
oxygen; some are oxydated rapidly, and exhibit ell the _ 
of combustion ; others undergo this operation much more’ 
and there are some (gold, silver, and platina) which can — 
‘dated inthis manner. Several of them are oxydated 
cy of water. It is thus that iron and some others, espe- 
when assisted by a high temperature, attract oxygen from | 
_ water, the hydrogen being disengaged. Lastly, all of them may be — 
oxydated by the action of acids. The acid itself is not only decom- 
es several of the metals to decompose the water present with 
~ = et ae t rapidity. 
_ The results of these combinations are compounds, which in gene- 
ral belong to the class of oxyds. They are destitute of the metal- 
lie qualities, and are more similar to earths, being in general insipid, 
_ insoluble in water, and vitrifiable by heat. Four metals, tungsten, 
_ molybdena, arsenic, and tin, can be so highly oxygenated as to pass. 
» the acid state. 
with only a small proportion of that 
up nearly their own weight. 
the oxyd produced by each proportion di 
$ attract very different quantities of oxygen. Some com- 
principle, while others can 
ti" 
Each metal, too, combines with certain different proportions, and — 
fiers in its properties from 
that produced by the others. The first degree of oxygenation — 
generally produces an oxyd, having a colour not mach different from 
that of the metal: by higher oxygenation, more brilliant colours” 
are produced. 
Metals also attract oxygen with very unequal degrees of force. 
_ Hence one metal can ofien be oxydated 
merely by heating it with 
: the oxyd of another. Some oxyds, too, as those of gold, silver, and 
_ Mercury, are decomposed by the mere agency of ealoric, at-a tem- 
__ Perature not raised very high, and even by the action of light at the. 
al temperature. 
oe 
derive their activity. They are, for inst 
og ‘It is principally from their combination with oxygen that metals” 
ance, incapable of combining: 
with the earths, unless they have been previously oxydated. The case 
is the same with respect to the acids, If the metal has not beem 
