Cooling baths are generally one of two types: (a) a cold fluid (particularly liquid nitrogen , water , or even air ) — but most commonly the term refers to (b) a mixture of 3 components: (1) a cooling agent (such as dry ice or water ice ); (b) a liquid 'carrier' (such as liquid water, ethylene glycol, acetone, etc.), which transfers heat between the bath and the vessel; ; and (c) an additive to depress the melting-point of the solid/liquid system.