The action of hot and strong
sulphuric acid is altogether different; it acts as an oxidising agent,
and is itself reduced to sulphur dioxide or even to sulphur. The
following metals are attacked in this way:--copper, bismuth, mercury,
silver, antimony, tin, and lead. Gold, platinum, and arsenic are not
affected. This property is made use of in parting silver from gold and
platinum. Metallic sulphides are similarly attacked; but this method of
opening up minerals has the disadvantage of giving rise to the formation
of anhydrous sulphates of iron, &c., which are not readily dissolved
when afterwards diluted. The use of sulphuric acid in assaying is (for
these reasons) to be avoided. Its chief use is as a drying agent, since
it has a strong affinity for water. Air under a bell jar may be kept dry
by means of a basin of sulphuric acid, and gases bubbled through it are
freed from water-vapour.
~Dilute Sulphuric Acid.~--This is made by diluting 1 volume of the
strong acid with 4 of water.
~Tartaric Acid~, H_{2}[=T] or C_{4}H_{6}O_{6}.--A crystallised organic
acid, soluble in less than its own weight of water, or in less than
three parts of alcohol. It is used for the same purposes as citric acid
is. The solution is made when required.
BASES, SALTS, &c.
~Alcohol~, C_{2}H_{6}O. (Commercial alcohol of sp.
Pages:
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125