Page:Experimental researches in chemistry and.djvu/143

128 second balloon. This balloon was then cooled to -43°.75 C., and then drops of a fluid lined its interior, and ultimately united at the bottom of the vessel. When the thermometer in the cooling mixture stood at -36°.25 C., the fluid already deposited preserved its state, but no further portions were added to it; reducing the temperature again to -41° C., and hastening the disengagement of ammoniacal gas, the liquid in the second balloon augmented in volume. Very little gas escaped from the last flask, and the pressure inwards was such as to force the oil of the lute into the balloon, where it congealed. Finally, the apparatus was left to regain the temperature of the atmosphere, and as it approached to it, the liquid of the second balloon became gaseous. The ice in the first balloon became liquid, as soon as the temperature had reached -21°.25 C.

M. Morveau remarks on this experiment, that it appears certain that ammoniacal gas made as dry as it can be, by passing into a vessel in which water would be frozen, and reduced to a temperature of -21° C., condenses into a liquid at the temperature of -48° C., and resumes its elastic form again as the temperature is raised; but he proposes to repeat the experiment and examine whether a portion of the gas so dried, when received over mercury, would not yield water to well-calcined potash, for as it is seen that water charged with a little of the gas, remained liquid in the first balloon, at a temperature of -21°, it is possible that a much smaller quantity of water united to a much larger quantity of the gas, would become capable of resisting a temperature of -48° C."

Sir H. Davy, who refers to this experiment in his 'Elements of Chemical Philosophy,' p. 267, urges the uncertainty attending it, on the same grounds that Morveau himself had done; and now that the strength of the vapour of dry liquid ammonia is known, it cannot be doubted that M. Morveau had obtained in his second balloon only a very concentrated solution of ammonia in water. I find that the strength of the vapour of ammonia dried by potash, is equal to about that of 6°5 atmospheres at 50° F., and according to all analogy it would require a very intense degree of cold, and one at present beyond our means, to compensate this power and act as an equivalent to it.