In some cases, however, they are filled with fused acetate of soda; this salt is solid when cold, but when the can containing it is heated by immersion in hot water it liquefies, and in the process absorbs heat which is given out again on the change of state back to solid.
It liquefies at 7° C. It is an exceedingly reactive compound, combining with water to form malonic acid, with hydrogen chloride to form malonyl chloride, and with ammonia to form malonamide.
It readily liquefies at 0° C. under a pressure of four atmospheres, the liquefied acid boiling at -34.1 4° C. (730.4 mm.); it can also be obtained as a solid melting at -50 8° C. It is readily soluble in water, one volume of water at To° C. dissolving 425 volumes of the acid.
The metal as obtained in this process is lustrous and takes a polish, does not melt in the oxyhydrogen flame, but liquefies in the electric arc, and is not affected by air at ordinary temperatures.
On these occasions the substance contained in the phial liquefies, and the Neapolitans see in this phenomenon a supernatural manifestation.
On the other hand, if a gas be sufficiently cooled and compressed, it liquefies; this transition is treated theoretically in the article Condensation Of Gases, and experimentally in the article Liquid Gases.
It is a colourless gas 42 times heavier than air, and liquefies at 15° under 40 atmospheres, solidifying when the pressure is diminished.
It is a colourless fuming gas, which liquefies under ordinary pressure at -50°, and under a pressure of 15 atmospheres at 16°; it may be solidified to a snow-like mass.
It liquefies when heated under pressure, and its melting point lies between 446° C. and 457° C. The vapour of arsenic is of a golden yellow colour, and has a garlic odour.