400 



VAPOR-DENSITIES. 



would belong to each of these if existing by itself with the same 

 volume and temperature. These quantities will be connected by the 

 equations 



, 1 -. 



* 2-22v' 3 ~ 



where k denotes the same constant as on page 381. From the evident 

 relations 



we obtain 



and by substitution of these values in equation (14), 



5441 



log 



13-751. 



(16) 



In view of the relations (15), this may be regarded as an equation 

 between the pressure, the temperature, the volume, and the quantities 

 of protochloride of phosphorus and chlorine into which the gas- 

 mixture is resolvable. 



TABLE IX. PERCHLORIDE AND PROTOCHLORIDE OF PHOSPHORUS. 



EXPERIMENTS ON THE MIXED VAPORS BY WURTZ. 



It is in this form that we shall apply the equation to the experiments 

 of M. Wurtz, the results of which are exhibited in Table IX. The 

 first column gives the number distinguishing each experiment in the 

 original memoir ; the second, the temperature ; the third, the observed 

 pressure (p) of the mixture of PC1 5 , PC1 3 , and C1 2 , which is the 

 barometric pressure corrected for the small quantity of air remaining 

 in the flask ; the fourth, the pressure TT due to the possible perchloride, 

 found by subtracting the pressure due to the excess of protochloride 

 (this pressure is calculated from the theoretical density of the proto- 

 chloride) from the total pressure ; the fifth, the density 8 of the 

 possible perchloride calculated from its pressure TT with the tem- 

 perature and volume. The numbers of these five columns are taken 



