In practice
this phenomenon of a secondary production of gas, which is known as
"after-generation," is regularly met with in all generators where the
carbide is in excess of the water added; but the amount of acetylene so
evolved rarely exceeds one-quarter or one-third of the main make. The
actual amount evolved and the rate of evolution depend, not merely upon
the quantity of undecomposed carbide still remaining in contact with the
damp lime, but also upon the rapidity with which carbide naturally
decomposes in presence of liquid water, and the size of the lumps. Where
"after-generation" is caused by the ascent of water vapour round lumps of
carbide, the volume of gas produced in a given interval of time is
largely governed by the temperature prevailing and the shape of the
apparatus. It is evident that even copious "after-generation" is a matter
of no consequence in any generator provided with a holder to store the
gas, assuming that by some trustworthy device the addition of water is
stopped by the time that the holder is two-thirds or three-quarters full.
In the absence of a holder, or if the holder fitted is too small to serve
its proper purpose, "aftergeneration" is extremely troublesome and
sometimes dangerous, but a full discussion of this subject must be
postponed to the next chapter.
Pages:
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109