He,
however, contends for it, and tries, on this solitary occasion, to
strengthen his opinion by authority, though the proof, if it could be
given, that ammonium chloride at the temperature of volatilization is
decomposed into its two constituents, would be insufficient to uphold
the theory.
The ground on which Mr. Greene assumes a partial decomposition at 350 deg.
C. is the slight excess of the observed density (14.43) over that
corresponding to four vols. (13.375). There is, however, a similar
slight excess in the case of the vapor of ammonium cyanide, the same
values being respectively 11.4 and 11; and as this compound is volatile
at 100 deg. C and, at the same time, is capable to exist at a very high
temperature, being formed by the union of carbon with ammonia, nobody
has ever, as far as I am aware, maintained that it is completely or
partially decomposed at volatilization. The excess of weight not being
due, therefore, to such cause in this case, it cannot be due to it in
the other.
The question being whether the molecular weight of ammonium chloride
is two vols. or four vols., an idea of the magnitude of the assumed
decomposition is conveyed by the proportion of the volume of the
decomposed salt to the volume of the non-decomposed, and Mr. Greene's
quotation of the percentage of weight is irrelevant and misleading, and
his number not even correct. A mixture containing
1.
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