“TERRIBLY COLD.”

Thames Star, Volume LVII, 11 September 1923, Page 6

“TERRIBLY COLD.”

WONDERS OF LIQUID AIR . Liquid air is so cold that ice is extremely “hot” compared with it, and a kettle filled with it will boil on a lump of ice! If some be poured into an open dish it looks as if it is being turned to steam, and quickly all disappears. It is much colder, as it were, than boiling water is hot, for water boils at 212 degrees F., but liquid air has a temperature of about—374 degrees F.—over 400 degrees below freezing point! So not even a finger must be put in it, or severe frostbite will ensue. In preparing it ordinary air, at high pressure, is forced through a very small nozzle and is thus cooled. This cooled air is passed back over more incoming air, the latter is thereby cooled and then passed back as before. And so on till the air gets so cold that it condenses in drops, just as steam condenses to water when cooled. Many wonderful experiments can be performed with liquid air, owing to its extreme coldness. A tube of milk placed in it becomes a solid block in a few seconds, and so does mercury. Grapes and flowers become hard, white, and brittle, so that they can easily be broken into fragments with a hammer. A child’s indiarubber ball is hardened in the same way, the air inside contracts and almost a vacuum is made, so that when trying to bounce it against a wall it explodes like an electric lamp would. If one end of a cigarette be dipped i*n the liquid and then a lighted match applied it burns furiously like a squib; a cigar gives even a better effect. A biscuit behaves similarly, and cotton wool burns up instantly with a great flare. Liquid air evaporates into the atmosphere so quickly—about a pint an hour from a large jar—that it has to be kept in special vessels which are just like thermos flasks; an ordinary cork or glass stopper is no s good,, so cotton wool is used instead.