Elements of chemistry, in two volumes / by John Murray.

  • Murray, John.
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Elements of chemistry, in two volumes / by John Murray. Source: Wellcome Collection.

    24/768 (page 12)
    quicksilver, as it is instantly absorbed by watei. So strong, indeed, is its attraction to humidity, that it is dif- ficult to obtain the gas dry ; one object in using an excess of lime is to absorb the water produced in the decompo- sition, and it is advantageous to use even a larger quan- tity of lime. To dry the gas thoroughly, it should be exposed to the action of fused potash ; chloride of calcium can scarcely be used, as it absorbs the gas. Ammonia, in the state of gas, has an odour extremely pungent, and is so acrid as to inflame the skin. It is one of the rarest of the elastic fluids, being, as has been sta- ted, little more than half as heavy as atmospheric air. 100 cubic inches weigh 18 grains. It is permanently elastic at natural temperatures, but when exposed to a cold of—56° of Fahrenheit, it is said to condense into the liquid state, probably from the presence of a small poi- tion of water. The dry gas has been reduced, however, to the fluid form, by Mr Faraday, by evolving it in close glass tubes. To obtain it dry, advantage was taken of a peculiar property belonging to chloride of silver. This substance, when immersed in ammoniacal gas, is found to absorb a large quantity of it, 100 grains ol the chlotide condensing no less than 130 cubic inches ; the compound thus formed is decomposed at a temperature of 100°. A quantity of it was placed in one leg of a bent glass tube, which was then hermetically sealed and heated; the other leg was cooled by the application of ice. Ammoniacal gas was evolved, and part of it, by the pressure of the elas- ticity of the remainder, was reduced to the liquid state. Thus condensed, it formed a colourless transparent fluid, of the specific gravity of .76 to water as 1; supeiioi in refractive power to any of the other condensed gases, and to water itself. The pressure of vapour, which had thus rendered it fluid, was found to be equal to six at- mospheres and a half at the temperature of 50 .