302 



Mr. W. Sutherland on the 





a. 



b. 



c. 



Ether 



CS 2 



•5195 



•229 



•198 



•0 3 887 

 •0 3 391 

 •0 3 136 



•0 4 123 

 •0 5 133 



CC1 4 



The numbers calculated for alcohol do not join on in a 

 continuous manner with those obtained from Regnault's ex- 

 periments, so that a single formula of the above type is not 

 competent to represent both series. 



Regnault's formula has been given at the beginning of this 

 paper, and may be considered to hold from —10° to 50° ; the 

 numbers tabulated above give for the specific heat of alcohol 

 from 80° to 140° the formula 



dq/d6 = 'U5 + '0026e + '0 5 926 2 . 



If the two series of values given by these formulae are to join 

 on to one another in a continuous manner, there must be a 

 point of inflexion between 50° and 80° in the curve which 

 represents the relation of specific heat to temperature. 



Now it is a noteworthy fact that Regnault, in his experi- 

 ments on the total heats of different liquids (that is, the 

 amounts of heat necessary to raise unit mass from 0° to t and 

 evaporate it at t) found that alcohol was the only exceptional 

 liquid giving a point of inflexion between 70° and 80° in the 

 curve representing the relation of total heat to temperature. 

 The agreement between the position of this point and of that 

 on the specific-heat curve is suggestive of some interesting 

 points in the molecular structure of ethylic alcohol. It would 

 be worth while for some experimenter to determine by actual 

 experiment how the specific heat of alcohol does vary between 

 50° and 80°. 



Addendum. — On Regnault's Determinations of the Specific 

 Heat of Water at temperatures above 100°. 



It is a rather remarkable fact in the history of Physics that 

 such complete uncertainty should reign to-day as to the spe- 

 cific heat of water, the standard substance in calorimetry, and 

 a fundamental quantity in the science of energy. Observer 



