Calorimetric Absolute Measurements. 195" 



ways, and employing three quite different natural laws — when, 

 further, this result but very slightly differs from that of another 

 group of observers who worked according to a fourth, essen- 

 tially different method, certainly it can be pretty safely main- 

 tained that the result so found is correct. 



In instituting this last series of experiments, besides ascer- 

 taining the absolute value of the S. M. XL, I pursued also, as I 

 have already intimated, another aim, which, in conclusion, I 

 will briefly explain. 



M. Favre has repeatedly determined with the aid of the 

 mercury calorimeter the quantities of heat developed by the 

 most various electromotive forces in their circuits during the 

 time in which they consume equal quantities of zinc — namely, 

 the quantity which is chemically equivalent to the unit of mass 

 of hydrogen. As the result of his experiments, he found that 

 the ratio of those quantities of heat gives quite another value than 

 does the ratio of the corresponding electromotive forces when 

 measured galvanometrically. Thus, according to M. Favre, 

 the quantities of heat which the elements of Daniell and Grove 

 produce in their circuits during the time within which they 

 consume 1 equivalent of zinc are 23993 and 46447 units. 

 The ratio of these numbers is 1 : 1*93, while the electromotive 

 forces of the Daniell and Grove elements stand (according to 

 all galvanometric measurements hitherto executed) in the ratio 

 of from 1 : 1-68 to 1 : 1-70. This result of M. Favre's directly 

 contradicts certain galvanic laws which are universally re- 

 garded as resting on a secure foundation, as will be evident 

 from the following consideration : — 



If E denotes the hydroelectromotive force of a circuit, w the 

 sum of all the resistances of the circuit, and Q the sum of all 

 the quantities of heat which the constant current i calls forth 

 in the circuit during the time z, then, according to Joule's 

 law (which we have demonstrated under section III. to be 

 correct), 



JQ = i 2 ivz; 



or, if, according to Ohm's law, we put no = 'E f 



JQ=iEz. 



If « denotes the electrochemical equivalent of zinc, the quan- 

 tity m of zinc which is consumed within the element during 

 the time z becomes, according to Faraday's law of electrolysis, 



m=*iz. 



Therefore the total heat Q produced in the entire circuit by the 



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