Owing to the heat developed when carbide is in excess,
about half the water is converted into vapour; and so the reaction
proceeds in two stages: half the water added reacting with the carbide as
a liquid, the other half, in a state of vapour, afterwards reacting
similarly, [Footnote: This secondary reaction is manifestly only another
variety of the phenomenon known as "after-generation" (cf. _ante_).
After-generation is possible between calcium carbide and mechanically
damp slaked lime, between carbide and damp gas, or between carbide and
calcium hydroxide, as opportunity shall serve. In all cases the carbide
must be in excess.] or hardly reacting at all, as the case may be.
Suppose a vessel, A B, somewhat cylindrical in shape, is charged with
carbide, and that water is admitted at the end called A. Suppose now (1)
that the exit for gas is at the opposite end, B. As the lumps near A are
attacked by half the liquid introduced, while the other half is changed
into steam, a current, of acetylene and water vapour travels over the
charge lying between the decomposing spot and the end B. During its
passage the second half of the water, as vapour, reacts with the excess
of carbide, the first make of acetylene being dried, and more gas being
produced.
Pages:
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139