Dr. E. J. Mills on the Chemical Activity of Nitrates. 135 



a is deduced, namely, certain weights of argentic chloride and 

 magnesic pyrophosphate, are, if singly considered, new with each 

 experiment ; they depend on time, rate of heating, the state of divi- 

 sion of the nitrate, and other conditions. But, assuming the results 

 to have heen brought about under a law of chemical action, the values 

 of a must be independent of those circumstances, by which the pri- 

 mitive numerator and denominator could have been only pari passu 

 affected ; they are related only to the actual occurrence of the re- 

 action. This property, in a chemical ratio, has not, it is believed, 

 been previously observed. 



After describing the means employed for obtaining a current of dry 

 air, the apparatus required for the reaction, and the individual ex- 

 periments which were severally made, the following Table of results 



2 

 is given, S being the symbolic value of a nitrate, and Q= — • 



a 2 Q 



fThallous nitrate 876 265-30 30*29 



i Argentic nitrate 5*48 169*94 31*01 



[ Plumbic nitrate 5*17 165*56 32*02 



Rubidic nitrate 2*38 147*40 61*93 



Csesic nitrate 221 19501 88*24 



J Potassic nitrate 1*99 101*14 5082 



\ Sodic nitrate 1*70 85*05 50*03 



Lithic nitrate 1*61 69*00 42*86 



The above list probably contains all the metallic nitrates that can 

 be completely dried, excepting nitrates derived from amines and 

 amides, which, in the present state of our knowledge of the phos- 

 phamides, it was evidently advisable to exclude. 



In the silver group, the mean value of Q is 31*11 ; and the fol- 

 lowing equation may be accepted therefor: — 



_ S 

 a 31*11* 

 In the potassium group we have likewise 



2 

 a== 50-42' 



Hence, within each set of nitrates, chemical activity is in direct 

 proportion to symbolic value. It is further sufficiently apparent that 

 (excepting rubidic nitrate) a and 2 increase and diminish in the same 

 general oider. 'Within the limits of error, the Q column is an in- 

 complete arithmetical series, the most probable value of whose first 

 term is 6*258, so that 



Q=m 6*258, 



m being integral. Reasons are then adduced for identifying the 

 number 6*25 with Dulong and Petit's constant of specific heat. 

 Moreover, since the product of specific heat and symbolic value is, 



