Dry ice is solid carbon dioxide.
Dry ice is readily manufactured by the following process:
- Gases containing a high concentration of carbon dioxide are produced. Such gases can be a byproduct of some other process, such as producing ammonia and nitrogen from natural gas, or large-scale fermentation.
- Carbon dioxide-rich gas is pressurized and refrigerated until it changes into its liquid form.
- The pressure is reduced. When this occurs some liquid carbon dioxide vaporizes, and this causes a rapid lowering of temperature of the remaining liquid carbon dioxide. The extreme cold makes the liquid solidify into a snow-like consistency.
- The snow-like solid carbon dioxide is compressed into either small pellets or larger blocks of dry ice.