474 



NATURE 



ject, perpetually perplexed with new problems, to 

 have at its command the unerring judgment of Lord 

 Rayleigh and his knowledge of theory and his keen 

 instinct for practice. During the war, when any 

 specially important or specially difficult point arose 

 in connection with the application of science for 

 the use of the Army or Navy, Lord Rayleigh was 



[December 8, 192 1 



very often consulted, and never in vain. Lord Ray- 

 leigh, I believe, has had every honour that this 

 country can bestow, and he deserves that place on the 

 walls of the Abbey close by the memorials to Davy 

 and to Young, for, like them, he increased the 

 prestige of this country in science, and widened the 

 bounds of our knowledge of nature. 



International Physico-chemical Symbols. 

 By Prof. Alex. Findlay. 



IN the years prior to the war endeavours were 

 made by various internationally constituted 

 bodies to secure greater uniformity in the symbols 

 used in different countries and by different writers 

 to represent physical, physico-chemical, and 

 electrotechnical quantities. As part of the general 

 movement to this end the International Associa- 

 tion of Chemical Societies, founded in 191 1, set 

 up a Commission for the Unification of Physico- 

 chemical Symbols, and in 1913 this commission 

 submitted to the council of the International Asso- 

 ciation of Chemical Societies a list of symbols 

 for quantities especially of physico-chemical im- 

 portance. At this point, however, the need was 

 felt for co-ordinating the work of the commission 

 with that of other bodies, and a small "working 

 committee," consisting of Sir William Ramsay 

 (chairman), Dr. Friedrich Auerbach, Profs. P. A. 

 Guye, P. J. Walden, and Alex. Findlay (secre- 

 tary), was therefore set up in order to secure this 

 co-ordination and to suggest methods of organ- 

 isation and work. 



The list of symbols drawn up by the Com- 

 mission for the Unification of Physico-chemical 

 Symbols was submitted for consideration and 

 criticism to the chemical societies of the different 

 countries represented on the International Associa- 

 tion, to the Ausschuss fiir Einheiten und Formel- 

 grossen, and to the International Electrotechnical 

 Commission. The criticisms and suggestions re- 

 ceived from these bodies were considered in May, 

 1914, by the working committee to which refer- 

 ence has been made above, and a list of symbols 

 was then drawn up for the approval of the Inter- 

 national Commission. Unfortunately, however, 

 before the meeting of the International Commis- 

 sion took place, international scientific relations 

 were ruptured by the outbreak of war, and the 

 list of symbols recommended unanimously by the 

 members of the working committee could not, 

 therefore, receive the approval of the parent com- 

 mission. As it is not to be doubted that this 

 approval would have been given, and as it would 

 have been a misfortune if the labours of the com- 

 mittee on which Great Britain, France, Germany, 

 Russia, and Switzerland were represented had 

 been in vain, the council of the Chemical Society, 

 with the approval of the recently constituted Inter- 

 national Union of Pure and Applied Chemistry, 

 authorised the publication of the committee's 



NO. 2719, VOL. 108] 



report and list of symbols in the Transactions of 

 • the Chemical Society, April, 1921.1 



As regards the general principles adopted by 

 the working committee it may be said that in 

 drawing up its list the committee restricted itself 

 to symbols for quantities of chemical or physico- 

 chemical importance and approved the general 

 principle adopted by the International Commission 

 that Greek letters should be used as sparingly as 

 possible. In respect of symbols for quantities 

 used, especially in mathematics, physics, and 

 the various branches of mathematics and physics, 

 the committee restricted itself to noting the 

 symbols which had been recommended or adopted 

 by the scientific bodies specially interested in these 

 quantities, and there were included in the com- 

 mittee's list only those symbols about which there 

 was general agreement among the specially com- 

 petent bodies. As it was not possible, in the case 

 of symbols which are employed in different 

 branches of pure and applied science, always to 

 obtain agreement among the representatives of 

 different sciences, the committee adopted the 

 symbols which find, or are likely to find, general 

 acceptance by chemists or physico-chemists. 



Although a practically universal agreement 

 already obtained regarding many of the symbols, 

 there were a number of quantities for which diverse 

 symbols were employed by different writers or 

 were suggested by various bodies. It was neces- 

 sary, therefore, for the committee to examine, 

 carefully and critically, the different suggestions 

 and to make a decision as to the symbols to be 

 recommended for use. The reasons for the choice 

 of symbol made by the committee in the debated 

 cases are appended to the list of symbols. 



Although it is not possible to refer specifically 

 to all debatable cases, reference may be made to 

 a few important quantities. For entropy and for 

 maximum work the committee recommends the 

 symbols S and A respectively, although in doing so 

 regret is expressed at having to depart from the 

 classical symbols <^ and \p employed by Willard 

 Gibbs. The committee, however, states that it felt 

 such departure to be advisable on the twofold 

 principle of disturbing existing usage as little as 

 possible and of employing Greek letters as 

 sparingly as possible. For degree of dissociation 



1 Copies of the report and list of symbols may be obtained on applica- 

 tion to the Assistant Secretary of the Chemical Society, Burlington House, 

 London, W. i. 



II 



