Frigorific mixture

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Frigorific mixture

A frigorific mixture is a mixture of two or more chemicals that achieve an equilibrium temperature independent of the temperature that the two chemicals started at. The temperature is also relatively independent of the quantities of mixtures as long as significant amounts of each original chemical are present in its pure form.

Liquid water and ice, for example form a frigorific mixture at 32 degrees Fahrenheit

Fahrenheit

Fahrenheit is a temperature scale named after the physicist Daniel Gabriel Fahrenheit , who proposed it in 1724. Today, the scale has largely been replaced by the Celsius scale; it is still in use for non-scientific purposes in the United States and a few other countries such as Belize....
or 0 degrees Celsius

Celsius

Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death....
.

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Encyclopedia

Fahrenheit

Celsius

Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death....
. A mixture of ammonium chloride

Ammonium chloride

Ammonium chloride is, in its pure form, a clear white water-soluble crystalline salt of ammonia. The aqueous ammonium chloride solution is mildly acidic....
and ice form a frigorific mixture at -17.8 degrees Celsius or 0 degrees Fahrenheit. Other examples of frigorific mixtures include :

Uses

The most common use of a frigorific mixture is to melt ice. When salt is placed on ice when the ambient temperature is greater than −17.8 °C (0°F), then the salt melts some of the ice and the temperature drops to −17.8. Since the mixture is colder than the ambient, heat is absorbed and the temperature rises. This causes the salt to melt more of the ice to drive the temperature down again. The process continues until all of the salt is dissolved in the melted ice. If there is enough salt present, then all of the ice will be melted.

Frigorific mixtures are commonly used in laboratories as a convenient way to generate reference temperatures for calibrating thermometer

Thermometer

The thermometer is a device that measures temperature or temperature gradient using a variety of different principles; it comes from the Greek language roots thermo, heat, and meter, to measure....
s.

They are also useful for creating cold temperatures when mechanical refrigeration is not available.

They can be used for shrink-fitting

Shrink-fitting

Shrink-fitting is a technique in which pieces of a structure are heated or cooled, employing the phenomenon of thermal expansion, to make a joint....
two items such as machined pieces of metal. One item is placed in a mixture to get it cold and shrink. The cold item is then placed into the other item. When the cold item warms up, it expands and fits tightly into the other item.

Additionally, salt dispersed across wintery roads uses the same principle.