50° Fahr. is equal to about forty atmospheres[1], he must have been mistaken. The following is his account:—"I now proceeded to the muriatic acid gas, and upon the condensation of a small quantity of it, a beautiful green-coloured substance adhered to the side of the receiver, which had all the qualities of muriatic acid; but upon a large quantity, four pints, being condensed, the result was a yellowish-green glutinous substance, which does not evaporate, but is instantly absorbed by a few drops of water; it is of a highly pungent quality, being the essence of muriatic acid. As this gas easily becomes fluid, there is little or no elasticity, so that any quantity may be condensed without danger. My method of collecting this and other gases, which are absorb able by water, is by means of an exhausted florence flask (and in some cases an empty bladder), connected by a stopcock with the extremity of the retort." xiii. 235. It seems probable that the facility of condensation, and even combination, possessed by muriatic acid gas in contact with oil of turpentine, may belong to it under a little pressure, in contact with common oil, and thus have occasioned the results Mr. North more describes.
Sulphurous Acid Gas.—With regard to this gas, Mr. Northmore says, "Having collected about a pint and a half of sulphurous acid gas, I proceeded to condense it in the three cubic inch receiver; but after a very few pumps the forcing piston became immovable, being completely choked by the operation of the gas. A sufficient quantity had, however, been compressed to form vapour, and a thick slimy fluid, of a dark yellow colour, began to trickle down the sides of the receiver, which immediately evaporated with the most suffocating odour upon the removal of the pressure." xiii. 236. This experiment, Mr. Northmore remarks, corroborates the assertion of Monge and Clouet, that by cold and pressure they had condensed this gas. The fluid above described wa evidently contaminated with oil, but from its evaporation on removing the pressure, and from the now ascertained low pressure of the vapour of sulphurous acid, there can be no hesitation in admitting that it was sulphurous acid liquefied.
The results obtained by Mr. Northmore, with chlorine gas and sulphurous acid gas, are referred to by Nicholson in his
- ↑ Philosophical Transactions, 1823, p. 198—or page 95.
