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Rh apparatus, have been equal to many atmospheres, but that being condensible, a part became liquid, and thus assisted in reducing the force within, to what it was found to be.

Ammonia.—I find the condensation of ammoniacal gas referred to in Thomson's System, first edition, i. 405, and other editions; Henry's Chemistry, i. 237; Accum's Chemistry, i. 310; Murray's Chemistry, ii. 73; and Thenard's Traité de Chimie, ii. 133. Mr. Accum refers to the experiments of Fourcroy and Vauquelin, ''Ann. de Chimie'', xxix. 289, but has mistaken their object. Those chemists used highly saturated solution of ammonia, see pp. 281, 286, and not the gas; and their experiments on gases, namely, sulphurous acid gas, muriatic acid gas, and sulphuretted hydrogen gas, they state were fruitless, p. 287. "All we can say is, that the condensation of most of these gases was above three fourths of their volume."

Thomson, Henry, Murray, and, I suppose, Thenard, refer to the experiments of Guyton de Morveau, ''Ann. de Chimie'', xxix. 291, 297. Thomson states the result of liquefaction at a temperature of -45°, without referring to the doubt, that Morveau himself raises, respecting the presence of water in the gas; but Murray, Henry, and Thenard, in their statements notice its probable presence. Morveau's experiment was made in the following manner: a glass retort was charged with the usual mixture of muriate of ammonia, and quick lime, the former material being sublimed, and the latter carefully made from white marble, so as to exclude water as much as possible. The beak of the retort was then adapted to an apparatus consisting of two balloons, and two flasks successively connected together, and luted by fat lute. The balloons were empty, the first flask contained mercury, the second, water. Heat was then applied to the retort, and the first globe cooled to -21.25°C., aqueous vapours soon rose,