136 



Sir B. C. Brodie on the Calculus of 



[May 3, 



bitter, and astringent taste. A substance with exactly the same properties 

 was obtained from the acid which was used to act upon the hydrocarbons 



I am at present engaged upon experiments to isolate the hydrocarbons 

 Cn H2«_2 contained in coal-tar. 



IV. The Calculus of Chemical Operations ; being a Method for 

 the Investigation^ by means of Symbols,, of the Laws of the 

 Distribution of Weight in Chemical Change. Part I. — On 

 the Construction of Chemical Symbols." By Sir B. C. Brodie^ 

 Bart.^ E.E.S.^ Professor of Chemistry in the University of 

 Oxford. Beceived April 25, 1866. 



(Abstract.) 



In chemical transformations the absolute weight of matter is unaltered, 

 and every chemical change, as regards weight, is a change in its arrange- 

 ment and distribution. Now this distribution of weight is subject to 

 numerical laws, and the object of the present method is to facilitate the 

 study of these laws, by the aid of symbolic processes. The data of the 

 chemical calculus, as indeed of every other application of symbols to the 

 investigation of natural phenomena, are supplied by observation and ex- 

 periment ; and its aim is simply to deduce from these data the various 

 consequences which may be inferred from them. The province of such 

 a method commences where that of experiment terminates. 



This part comprises the consideration of the fundamental principles of 

 synibolic expression in chemistry, and also the application of the method 

 to the solution of perhaps the most important of all chemical problems, 

 namely, the question of the true composition, as regards weight, of the units 

 of chemical substances. 



Section I. In the first section certain definitions are given of those weights 

 and relations of weight, of which the symbols are subsequently considered. 

 It may be regarded as containing an analysis of the subject of chemical 

 investigation. The definitions are of "a chemical substance," "a weight,'* 



a single weight," *' a group of weights," *' identical weights," " a com- 

 pound weight," " a simple weight," and "an integral compound weight." 



The unit of a chemical substance is defined as that weight of the sub- 

 stance which at 0° Centigrade, and 760 millims. pressure and in the con- 

 dition of a perfect gas, occupies the volume of 1000 cubic centimetres. 

 This volume is termed the unit of space. 



Section II. The second section treats of symbolic expression in chemistry. 

 A " chemical operation " is]^defined as an operation of which the result is a 

 weight. These operations are symbolized by letters, x, y, &c. An inter- 

 pretation is assigned to the symbols -f and — , as the symbols of aggregation 

 and segregation, that is, of the mental operations by which groups are formed. 

 The symbol = is selected as the symbol of chemical identity ; the symbol 



