sodium bicarbonateSee sodium
hydrogencarbonate.sodium bisulphateSee sodium
hydrogensulphate.sodium bisulphiteSee sodium hy-
drogensulphite.sodium bromide A white crys-
talline solid, NaBr, known chieÛy as
the dihydrate (monoclinic; r.d. 2.17),
and as the anhydrous salt (cubic; r.d.
3.20; m.p. 747°C; b.p. 1390°C). The di-
hydrate loses water at about 52°C
and is very slightly soluble in alcohol.
Sodium bromide is prepared by the
reaction of bromine on hot sodium
hydroxide solution or of hydrogen
bromide on sodium carbonate solu-
tion. It is used in photographic pro-
cessing and in analytical chemistry.sodium carbonateAnhydrous
sodium carbonate (soda ash, sal soda)
is a white powder, which cakes and
aggregates on exposure to air due
to the formation of hydrates. The
monohydrate, Na 2 CO 3 .H 2 O, is a white
crystalline material, which is soluble
in water and insoluble in alcohol; r.d.
2.532; loses water at 109°C; m.p.
851 °C.
The decahydrate, Na 2 CO 3 .10H 2 O
(washing soda), is a translucent
efÛorescent crystalline solid; r.d.
1.44; loses water at 32–34°C to give
the monohydrate; m.p. 851°C.
Sodium carbonate may be manufac-
tured by the *Solvay process or by
suitable crystallization procedures
from any one of a number of natural
deposits, such as:
trona (Na 2 CO 3 .NaHCO 3 .2H 2 O),
natron (Na 2 CO 3 .10H 2 O),
ranksite(2Na 2 CO 3 .9Na 2 SO 4 .KCl),
pirsonnite(Na 2 CO 3 .CaCO 3 .2H 2 O),
gaylussite(Na 2 CO 3 .CaCO 3 .5H 2 O).
The method of extraction is very sen-
sitive to the relative energy costs and
transport costs in the region in-
volved. Sodium carbonate is used inphotography, in cleaning, in pH con-
trol of water, in textile treatment,
glasses and glazes, and as a food addi-
tive and volumetric reagent. See also
sodium sesquicarbonate.sodium chlorate(V)A white crys-
talline solid, NaClO 3 ; cubic; r.d. 2.49;
m.p. 250°C. It decomposes above its
melting point to give oxygen and
sodium chloride. The compound is
soluble in water and in ethanol and
is prepared by the reaction of chlo-
rine on hot concentrated sodium
hydroxide. Sodium chlorate is a pow-
erful oxidizing agent and is used in
the manufacture of matches and soft
explosives, in calico printing, and as
a garden weedkiller.sodium chloride (common salt)A
colourless crystalline solid, NaCl, sol-
uble in water and very slightly solu-
ble in ethanol; cubic; r.d. 2.17; m.p.
801 °C; b.p. 1413°C. It occurs as the
mineral *halite (rock salt) and in nat-
ural brines and sea water. It has the
interesting property of a solubility in
water that changes very little with
temperature. It is used industrially as
the starting point for a range of
sodium-based products (e.g. Solvay
process for Na 2 CO 3 , Castner–Kellner
process for NaOH), and is known uni-
versally as a preservative and sea-
soner of foods. Sodium chloride has a
key role in biological systems in
maintaining electrolyte balances.
sodium chloride structure See
rock salt structure.
sodium cyanideA white or
colourless crystalline solid, NaCN,
deliquescent, soluble in water and in
liquid ammonia, and slightly soluble
in ethanol; cubic; m.p. 564°C; b.p.
1496 °C. Sodium cyanide is now made
by absorbing hydrogen cyanide in
sodium hydroxide or sodium carbon-
ate solution. The compound is ex-
tremely poisonous because it reactssodium bicarbonate 488s