*

140. CoDBtitaentB of Water. — Water, tbough a fluid, is
composed of two gaseous elements. With the properties
of one of these, oxygen, you have already become well ac-
quainted. The other gas is hydrogen, so called because
when chemically united with oxygen it produces water, the
name being derived from two Greek words — Awefor, water,

and ^ennao, I form. Inform-
ing water, two volumes of
hydrogen unite with one vol-
ume of oxygen, or two parts
2 vols. + ivoL = 2 vols. by weight of the former with

n^««m, ooo X sixteen parts by weight of

Oxygen 88.9 per cent. ^, _ ^ .„ ,. ?

Hydrogen ii.i " " ^"® latter. All this is pre-

Water looo sented to the eye in the di-

P,g3^ agram,Fig. 34 — the spaces

representing the proportions
of the two ingredients in bulk, and the figures their propor-
tionate weights. You will notice that owing to the con-
traction which takes place, two volumes of water result



H

1


► +


^




o

16


=


H,0 18


U

1







Digitized



byGoogk



THE CHBMISTEY OF WATBE. — HYDROGEN.
Ill



from the combination of three volumes of the component
gases.
141. Decomposition of Water. — Water may be decora-
posed — that is, resolved into the two gases of which it is
made — in a variety of ways, both physical and chemical
We will first describe a method in which electricity is used,
and then give you some chemical methods.
A current of electncity from a galvanic battery, gener-
ated as explained in Pait I., decomposes water very readily.
By employing the apparatus. Fig. 35, the gases may be col-



1 r

M






Fig. 85.
