It was far more difficult for man to discover how to produce artificial cold than it was for man to discover how to produce artificial cold than it was for him to produce warmth.

In olden days man tried to keep things cool during the summer by using snow or ice. This was a very difficult process. The snow and ice had to be carried down from the high mountain tops and stored in specially built places.

The ancient Romans, for example, brought their snow and ice from the Apennine Mountains. They dug large chambers in the ground which they called officinae reponendae nivis. This meant snow store. The store was covered in wooden boards and the ice was brought to the towns from the Apennine region near Rome and in Sicily from Mount Etna.

The first Experiments to produce ice artificially began in the seventeenth century. It was later discovered that in specified condition certain substances changed from a solid into liquid state. This fusion, or melting process, was found to be caused through the absorption of heat by those substances. As the heat was absorbed it was accompanied by a steady cooling of the temperature. Further experiments showed that the same absorption of heat could be carried out by evaporating and liquid. An example of this is when a sudden breeze evaporates the perspiration from our faces and makes us feel quite chilly. It is on this principle of heat absorption that ordinary household refrigerators work. The most commonly used liquid to bring about cooling is ammonia gas in solution. This solution runs through coiled tubes. It starts as a liquid and through compression becomes a gas which absorbs the surrounding warmth. This process is repeated over and over again until ice begins to form.

The first household refrigerator was made early in the nineteenth century. Since 1918 their use has becomes more and more widespread.


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