This principle can be applied to all elements whose
specific heats in the solid state are accurately known,
but will not aid us to confirm the atomic weight of many
of the non-metallic elements. To do this we must con-
sider the other facts. Take a diatomic molecule such
as chlorine and compare the weight of a liter of this
with the weight of a liter of hydrogen, at the same tem-
perature and pressure. According to the law of
Avogadro these volumes contain the same number of



ATOMIC WEIGHTS. 7

molecules. Let x=number of molecules in a liter, then
weight X chlorine molecules : weight x hydrogen mole-
cules : : weight one chlorine molecule : weight one hydro-,
gen molecule. And as one chlorine molecule and one
hydrogen molecule each contain two atoms, we have,
weight liter of chlorine : weight liter of hydrogen : :
atomic weight of chlorine : atomic weight of hydrogen :
or 3.1673 : 0.0896: : X : I. x=35.35. A result which con-
firms with sufficient accuracy our equivalent 35.5 as the
atomic weight of chlorine,

To determine the atomic weight of mercury,

1. Ignite 5 grams of mercuric oxide and weigh the
resulting mercury — 4.62 grams. The loss in weight
0.38 gram is oxygen and the equivalent of oxygen is 8
so 0.38 : 4.62 : : 8 : x. x = 97.26. The equivalent of mer-
cury.
