What is Dry Ice
WHEN some-one makes a lot of money from a simple, invention, one asks one’s self, “Now why didn’t I see the possibilities of that thing myself?” About fifteen years ago students saw a professor conduct an experiment before a physics class. Into a peculiar double-shelled vessel he emptied carbon-dioxide snow-white, clean, fluffy. The vessel was a Dewar flask. Its double walls contained nothing-a vacuum. That was its secret, the carbon-dioxide snow would not soon melt. Air, as every one knows, is a poor conductor of heat. Nothing is still better. The snow was said to be about 100 degrees below zero. An interesting experiment. Well -what of it?
Somebody with practical brains saw possibilities in the Dewar flask, which had already been used by scientists for several previous decades, and the “thermo bottle” was the outcome. Now the carbon dioxide that was kept frozen in the Dewar flask is making more money for some other hard-headed man who doubtless saw that experiment. It, too, has gone into business-“dry ice.”
Dry ice may be a trade name. But so is Ford-yet we don’t hesitate to mention it in editorial comment. Some commercial products burrow their way into the warp and woof of modern life. Kodak is an example. Dry ice has already become a valuable refrigerant, and the reason is that its temperature stands some 112 below zero. Pound for pound it refrigerates fifteen times as much as common frozen water, and when it disappears it goes directly from a solid into a non-poisonous, inert gas, leaving not a sign of moisture. Think of being able to lay a piece of ice on a choice bedspread or-tablecloth, allow it to vanish, and find no sign that it was ever there! That is the kind of ice we get when we freeze carbon dioxide, and the reasons given account for the fact that it is attracting considerable attention. With dry ice you can transport a car of fish in summer without the costly necessity of re-icing the car at frequent intervals. You can ship ice-cream from New York to Cuba, and that is just what is now being done in immense quantities. You can put a small piece in the bottom of a cylindrical cardboard container of ice-cream and take it with you on a picnic and it will stay solid through all of a hot day.
A couple of years ago we saw such containers in ice-cream store windows. To most of us it then seemed a stunt. The stunt has spread into industry and is still spreading. Ice manufacturers are sitting up to take notice, for, though dry ice costs ten times what wet ice costs, it refrigerates fifteen times as much. The stunt of the store window and the entertaining experiment of the professor of physics have gone to work in earnest.
Source: The Outlook, 31 August 1927