water
A colorless or faintly blue-green liquid (H
2 O). Molecules of water enter into the
constitution of many crystalline salts, e.g.,
alum—K 2 SO 4 .Al
2 (SO 4 ) 3 . 24H
2 O, in which they may be reversibly
held. The outstanding chemical reactions of water
are: 1) its reaction with certain metals, e.g.,
Na, Ca, Fe, more or less easily, with the
liberation of hydrogen, such as, Na + H
2 O --> NaOH + H; 2) its reaction with
oxides of non-metals, e.g., with SO 3
to form acids, such as, SO 3 + H
2 O --> H 2 SO 4
; 3) with halides of nonmetals, to form hydrogen
halides and an oxyacid, such as PCl 3 +
3H 2 O --> H 3 PO
3 + 3HCl; 4) with dissolved salts of
weak acids or weak bases, forming solutions with
an alkaline or acid reaction (hydrolysis), such as
Na 2 CO 3 + H 2 O
<==> NaOH + NaHCO 3 ; and 5) with coke
at high temperature to form water gas, C + H
2 O --> CO + H 2 . (235 )