APPENDIX.

151

proportion of a great number of other substances. The numberswhich are in this manner obtained are called combining weights,proportionals, equivalents, etc.; they express the relative propor-tions in which substances combine together. Compounds consistof a single proportional of each of these elements, but more com-monly they contain one of one element, and two, three, or more,of the other; organic substances, for the most part, consist ofnearly ten or a dozen proportionals of each of their elements.The following tables show the proportions or combining weightsof the most important substances, whether simple or compound,which have been previously described.

COMBINING OR EQUIVALENT WEIGHTS OF THE MOST IMPORTANT

SIMPLE SUBSTANCES.

Oxygen

. 8

Hydrogen

. . 1

Carbon

. 6

Nitrogen

. . 14

Chlorine .

. 35

Phosphorus .

. . 31

Sulphur

. 16

Iron

. . 27

When a compound is formed by the union of two elements, theequivalent or combining proportion of the compound is exactlythe sum of the equivalent of its elements ; thus, for example,Carbonic Acid consists of one equivalent of Carbon , the numberof which is 6, and two equivalents of Oxygen , weighing 16 ; thesum of 6 and 16 is 22, this then is the weight of Carbonic Acid ,which combines to an equivalent weight, of any base, with 28 partsof Lime, 47 of Potash , and so on.

In the following table the combining weight of some of themost important compounds is exhibited :—

Water .

9

Carburetted Hydrogen

. 8

Nitric Acid

54

Ammonia.

. 17

Carbonic Oxide

14

Potash .

. 47

Carbonic Acid .

22

Soda

. 31

Sulphurous Acid

32

Lime

. 28

Sulphuric Acid .

40

Magnesia

. 20

Phosphoric Acid

71

Silica .

. 46

Muriatic Acid .

36

Alumine .

. 51

Sulphuretted Hydrogen

17

Prot-oxide of Iron

. 35