Synthetic Inorganic Chemistry

NOTES AND PROBLEMS 37

ment is taken in each case the weights of the second element
which combine with this definite weight of the first element to form
the respective compounds are to each other in the ratio of small
whole numbers.
For example, two different substances are known which contain
copper and chlorine. In cuprous chloride 63.6 grams of copper
are combined with 35.46 grams of chlorine; in cupric chloride
63.6 grams of copper are combined with 70.92 grams of chlorine.
The weights of chlorine are in the simple integral ratio of 1 .2.
The law of combining weights covers not only the behavior
described by the laws of definite and multiple proportions, which
apply to specific compounds and to specific pairs of elements, but
it covers the combining ratios in all compounds. In the illustra-
tion above we chose apparently arbitrarily 63.6 grams of copper
and found that the corresponding weights of chlorine were 35.46
and 70.92 in the respective compounds. Without stopping to
inquire why we chose 63.6 grams rather than 1 gram or 100 grams,
let us inspect the following tabulation of combining weights.

Cuprous chloride

Mercurous chloride

Mercuric oxide

Sulphur dioxide

Cupric sulphide

Hydrogen sulphide

Water

Carbon monoxide

Carbon tetrachlonde

Chlorine monoxide

Cu

63 6

31 8

Cl

35 46

35 46

70 92

70 92

Hg

200 6

200 6

O

. 16
16

8

8

. 16

S

16

16

16

H

1 008

1 008

C

6

. 6

It is obvious that the combining weights of the elements are in

every case small whole multiples of recurring numbers: Cu 31.8;

Cl 35.46; Hg 200.6; O 8; S 16; H 1.008; C 6. If we had taken

any other weight, say 100 grams of oxygen, as a starting point

it is evident that the same uniformity would be manifest, but the

fundamental weight of each element would be different.

The law of combining weights may be stated as follows: For

every element a combining weight may be chosen such that in all

pure compound substances the ratio of the number of combining

weights of the different elements is the ratio of simple integrals.

The Atomic Theory. Dalton was impressed by the significance

of the facts generalized in these three laws, particularly the law