The Two Calories


MUCH confusion is caused by the use of the word calorie in two different senses—one to signify the amount of heat required to raise the temperature of one gram of water 1°C., and the other to represent what is really a kilocalorie, or the amount of heat required to raise 1000 grams of water 1°C. The only difference between the means of distinguishing the two units is that the large Calorie is spelt with a capital initial letter, and unless great care is taken this may be set up as a ‘lower case’ letter by the compositor. May I suggest that the confusion could be avoided—at least so far as the printed word is concerned—by spelling the large unit with a capital letter K, thus, ‘Kalorie.’ The use of the letter ‘k’ in this way is in conformity with the principle adopted in the designation of metric units generally.

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MARKS, P. The Two Calories. Nature 121, 58 (1928).

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