October 27, 1911] 



SCIENCE 



547 



ingly, a device was adopted which at one 

 stroke annihilates the pernicious "cooling 

 correction" — the worst foe to accuracy — 

 by merely causing the temperature of the 

 jacket around the calorimeter to change in 

 temperature at the same rate as the calor- 

 imeter itself. There are several ways in 

 which this may be accomplished; among 

 these ways the following was chosen as the 

 best method for a chemical laboratory. 

 The calorimeter, enclosed in a slightly 

 larger water-tight vessel, with tubes above 

 - — a kind of submarine — is immersed under 

 the surface of dilute crude alkali in a pail. 

 Thermometers inside and out enable one to 

 adjust the temperatures at the same point. 

 The reaction is then started in the calorim- 

 eter, and at the same moment and at a 

 corresponding rate acid is dropped into the 

 dilute alkali in the pail, so that the two 

 temperatures inside and out keep pace with 

 one another. Thus there is no loss of heat 

 from the inside vessel ; the thermochemical 

 reaction is strictly adiabatic. This method 

 has already been used at Harvard with 

 very encouraging outcome in determining 

 a wide variety of thermochemical data, 

 heats of combustion of hydrocarbons, of 

 solutions of metals in acids and of neutral- 

 ization, specific heats of solutions, and also 

 of the elements at very low temperatures, 

 and finally latent heats of evaporation.^^ 

 It has proved itself especially valuable in 

 the study of slow reactions, where the cool- 

 ing correction may become a large portion 

 of the total result. The effort is being 

 made to apply to this experimentation con- 

 cerning chemical energetics the same de- 

 gree of care which has recently been at- 

 ^ Eichards, in collaboration with Henderson, 

 Forbes, Frevert, Mathews, Eowe, Jesse, Burgess 

 and Jackson, Froc. Amer. Acad., 1905, 41, p. 3; 

 1907, 42, p. 573; 1908, 43, p. 475; 1911, 46, p. 

 363; /. Amer. Chem. Soc, 1909, 31, p. 1275; 1910, 

 32, pp. 268, 432, 1176; Zeitsch. physilcal. Chem., 

 1905, 52, p. 551; 1907, 59, p. 531; 1909, 70, p. 414. 



tempted in the revision of the atomic 

 weights, and although on account of the 

 greater complexity of the problem the per- 

 centage accuracy thus far reached has not 

 equalled that in the case of atomic weights, 

 one can not help thinking that the propor- 

 tional gain over previous investigations is 

 perhaps as great in this case as in the other. 



In thermochemical reasoning particu- 

 larly, accurate data possess a significance 

 wholly denied to cruder results. The rela- 

 tions between the heat of formation of 

 organic substances, if determined accu- 

 rately enough, may be hoped to throw light 

 on organic structure and the nature of 

 valence. Approximate values are of no use 

 at all for such a purpose. Enough has 

 been done already to suggest relations of a 

 highly interesting sort between heats of 

 combustion, heats of evaporation, compres- 

 sibility and many other properties; and to 

 add support to the theory of compressible 

 atoms.^* Moreover, taken in connection 

 with more precise knowledge of the free 

 energy of chemical changes, the new results 

 will permit the evaluation of bound energy, 

 and give results which may decide whether 

 or not bound energy is really a simple 

 function of change of heat capacity, as has 

 been more than once intimated.^" There is 

 time now only to suggest possibilities, each 

 of which would take hours to elucidate. 



How can we collate all the varying prop- 

 erties so as to show their many-sided rela- 

 tionships ? How can we piece together the 

 scattered evidence so as to synthesize an 

 adequate conception of the ultimate nature 



"Richards, Froc. Amer. Acad., 1908, 39, p. 581; 

 also Zeitsch. physikal. Chem., 1904, 49, p. 15. 



^Helmholtz, Lewis, van't Hoff, Nemst and 

 Haber, as well as the author and many others, 

 have contributed to this discussion. An interest- 

 ing resume, with references to many of the original 

 papers, will be found in Haber 's "Thermody- 

 namics of Technical Gas Reactions " (translated 

 by Lamb), London and New York, 1908. 



