Nomenclature and Notation in Calorimetry 4 1 7 



common use in chemical laboratories ; these are the gramme 

 and the Celsius degree. 



The heat given out by one gramme of water cooling by 

 iC. at ordinary temperatures is the unit most used in such 

 researches ; and it received the name of calorie, sometimes 

 now called small calorie. 



For many purposes this unit proved itself inconveniently 

 small, and several larger units have been used, such as the 

 heat given out by one kilogramme of water cooling iC. at 

 ordinary temperatures, or the heat given out by one gramme 

 of water cooling from 100 C. to o C; but the name of calorie 

 was retained in connection with them all, and in the specifica- 

 tion of a quantity of heat by a number, the nature of the unit 

 was indicated by the syllable cal. or the letter K, neither of 

 which of itself gives any information. 



In my own work, and in the study of the writings of 

 others, I have adopted a form of notation which I have 

 found so useful that I propose to lay it before the readers 

 of Nature. I do not doubt that others who interest them- 

 selves in calorimetric work have been driven to adopt some 

 similar, perhaps the same, perhaps a better form of notation ; 

 and I think they will agree with me that some system of self- 

 interpreting notation should be universally adopted without 

 loss of time. 



Just as, when dealing with work, we use currently the 

 expressions foot-pound and kilogramme-metre, so in calori- 

 metry it is quite common to talk of a gramme-degree, or 

 a kilogramme-degree ; and what I propose is to use no 

 other expression than these compound and self-explaining 

 ones, and, in writing, to express them shortly by g and k 

 respectively, to which for clearness the symbol of the thermo- 

 metric scale must be added, so that they become gC. and 

 k C, when Celsius' scale is used, or g F. and k F. when 

 Fahrenheit's scale is used. 



On this system the expression gC. would replace the 

 ordinary "cal." and Ostwald's K would be represented by 

 ioogC. or O'l kC, or by h C., to mean hectogramme- 

 degree C. With perfect exactness K would be expressed by 



B. 27 



