KICHARDS AND ROWE. — THE SPECIFIC HEATS OF LIQUIDS. 477 



the time required to secure thermal equilibrium, gave the necessary 

 data. The uncertainty of the true law ot cooling is enough to seri- 

 ously impair the accuracy of any results thus obtained, however. 



Quite a different procedure was adopted by Hesehus, 12 who balanced 

 the heating effect of the calorifer in a calorimeter at room temperature 

 by the additions of successive portions of cold water. In this way 

 he eliminated any cooling of the calorimeter. Waterman 13 improved 

 this method, and made a series of apparently excellent determinations 

 of the specific heats of metals. Using a Pfaundler resistance coil as a 

 source of heat, Litch 14 has studied in this way the specific heat of 

 water. Satisfactory as these methods may appear upon first sight to 

 be, however, the unavoidable warming of the cold water during its 

 transference to the warm calorimeter introduces an element of uncer- 

 tainty just as great as the uncertainty in the ordinary cooling cor- 

 rection ; hence no real gain was made. The method is not really 

 adiabatic. 



In 1905 a new method was described by Richards and Lamb, 15 

 eliminating most of the earlier sources of error while maintaining all 

 the advantages of the older procedure except simplicity. Two por- 

 tions of liquid — one hot, the other cold — were rapidly discharged 

 from their respective containers and mixed in a calorimeter, the tem- 

 perature of the mixture being that of the environment. Obviously, 

 the cooling experienced by the warm liquid during transference is bal- 

 anced by the warming of the cold liquid. The method involves a 

 somewhat high degree of mechanical complexity, and is further com- 

 plicated by the necessity of making supplementary determinations of 

 the heats of solution or dilution where the two liquids possess any 

 degree of mutual solubility. 



More recently a new method of calorimetry, by a strictly adiabatic 

 procedure, has been described by Richards, 16 and its applicability has 

 been experimentally proved by the same investigator with the assist- 

 ance of Forbes, 17 Henderson, 18 and Frevert. 19 Here the environ- 

 ment of the calorimeter is caused to increase in temperature as the 

 calorimeter itself becomes warmer. The studied transformation in the 

 calorimeter thus takes place without interchange of heat with the sur- 

 roundings. Further, since both the initial and the final temperatures 

 are stationary, the error due to the lag of the thermometer disappears. 



12 Jour. Soc. Ph. Chim. Russ., Nov., 1887 ; Jour, de Phys., 7. 489 (1888). 



13 Phys. Rev., 4, 161 (1896). " Ibid., 41, 10 (1905). 



" Ibid., 5, 182 (1897). " Ibid., 41, 10 (1905) ; 42, 573 (1907). 



» These Proceedings, 40, 659 (1905). 19 Ibid., 42, 673 (1907). 

 « Ibid., 41, 8 (1905). 



