Dry+Ice

Dry ice, sometimes referred to as "Cardice" or as "card ice" (chiefly British English), is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue (other than incidental frost from moisture in the atmosphere). It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable. The extreme cold makes the solid dangerous to handle without protection due to burns caused by freezing (frostbite). While generally nontoxic, the outgassing from it can cause asphyxiation due to displacement of oxygen in confined locations.

Dry ice is pure, solid carbon dioxide (CO2). As a gas, CO2 exists naturally in our environment. It's called "dry ice" because it does not melt. Dry ice goes directly from a solid to a gas in a process called sublimation. Dry ice keeps items colder for much longer than traditional “wet ice” because dry ice is extremely cold, -109 degrees F (-78.5° C).

In laboratories, a slurry of dry ice in an organic solvent is a useful freezing mixture for cold chemical reactions and for condensing solvents in rotary evaporators. The process of altering cloud precipitation can be done with the use of dry ice.] It was widely used in experiments in the US in the 1950s and early 60s before being replaced by silver iodide. Dry ice has the advantage of being relatively cheap and completely non-toxic. Its main drawback is the need to be delivered directly into the supercooled region of clouds being seeded

It is generally accepted that French chemist, Thilorier was the first to record the appearance of solid CO2 - dry ice. In 1835 he opened a cylinder with a large amount of liquid carbon dioxide to observe it in liquid form. Enough of it evaporated to leave a solid dry ice block at the bottom of the container. (more) For the next 60 years it was observed in university labs but not used for any practical applications. Even today anyone can take a metal cylinder of liquid CO2 (like a CO2 fire extinguisher) open the valve and observe the escaping gas cloud with part of it turning into dry ice snow flakes. In 1897 a patent was granted in England to Herbert Samuel Elworthy, a doctor in the British Army Medical Corps for solidification of carbon dioxide. His purpose was to make soda water to mix with his whisky. Liquid CO2 worked fine but the metal cylinder bottles were too heavy to take on excursions. A 100 pound cylinder carried only 50 pounds of CO2. He preferred to make solid dry ice for his soda water. Unfortunately the dry ice didn't last long as it sublimated into gas before it could all be used. Thereafter, few used dry ice for this patented purpose. From time to time a few doctors used dry ice to remove warts.

Dry Ice's sublimation process is fascinating and has been used in the entertainment industry as a stage prop. Dry ice, coupled with fans can give the stage/theatre a foggy effect that makes for an interesting effect. Many introductions to rock 'n' roll concerts and play scenes have been decorated with dry ice to increase the aesthetic appeal and increase the dramatic aspect. .

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