RICHARDS AND ROWE. — SPECIFIC HEATS OF LIQUIDS. 199 



From this table it is clear that the molecular heat increases with 

 the molecular weight in the case of the halogen acids. The further 

 increase in the case of nitric and perchloric acid is only to be expected 

 from the increasing size and complexity of these molecules. On the 

 other hand it is noticeable that in the case of the alkalies the molecular 

 heats diminish as the atomic weight of the metal increases. 



Of course many circmustances lie at the basis of these phenomena; 

 the degree of ionization, the degree of hydration of both the ions and 

 of the undissociated substance; and indeed all those other as yet 

 undetermined factors which together produce the specific volumes 

 and all the other properties of solutions come into play here also. 

 Whatever may be the ultimate interpretation of these matters, it is 

 clear that the data just given must receive consideration in the final 

 estimate of the situation. 



It is a pleasure to express our indebtedness for the generous subsidy 

 of the Carnegie Institution of Washington, upon which we have de- 

 pended for the purchase of the apparatus and chemicals needed in 

 this investigation. 



Summary. 



In this communication an improved apparatus for the determina- 

 tion of the specific heats of solutions or other liquids has been described. 

 The method depends upon the liberation of definite quantities of heat 

 by the neutralization of definite quantities of pure sulphuric acid. 



The apparatus is capable of giving results of great accuracy. The 

 individual deviations are such that with five or six experiments the 

 "probable error" of the average specific heat is usually less than 

 0.0001. Because of this high degree of accuracy, it is evident that 

 the mercury thermometers used are an adequate means of measuring 

 temperature for this purpose. 



With this apparatus the specific heats of dilute solutions of hydro- 

 chloric, hydrobromic, hydriodic, nitric, and perchloric acids, as well 

 as of lithium, sodium, and potassium hydroxides have been deter- 

 mined. 



From these results the molecular heats of the solutions have been 

 calculated, and relations between them pointed out. It is shown that 

 the molecular heats varv in a svstematic manner. 



