Approached from a
theoretical standpoint, it will be seen that this method of generation
entirely sacrifices the advantages otherwise accruing from the use of
liquid water as a means for dissipating the heat of the chemical
reaction, but on the other hand, inasmuch as the substances are both
solid, the reaction presumably occurs more slowly than it would in the
presence of liquid water; and moreover the fact that the water employed
to act upon the carbide is in the solid state and also more or less
combined with the rest of the sodium carbonate molecule, means that, per
unit of weight, the water decomposed must render latent a larger amount
of heat than it would were it liquid. Experiments made by one of the
authors of this book tend to show that the gas evolved from carbide by
the dry process contains rather less phosphorus than it might in other
conditions of generation, and as a fact gas made by the dry process is
ordinarily consumed without previous passage through any chemical
purifying agent. It is obvious, however, that the use of the churn
described above greatly increases the labour attached to the production
of the gas; while it is not clear that the yield per unit weight of
carbide decomposed should be as high as that obtained in wet generation.
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