VAPOR-DENSITIES. 



and for perchloride of phosphorus, 



403 



< 22 > 



By these equations the values of L are easily calculated. " The values 

 of A may then be obtained by inspection (with interpolation when 

 necessary) of the following table. From A the value of D may be 

 obtained by multiplying by D x , viz., by T589 for peroxide of nitrogen 

 or formic acid, by 2*073 for acetic acid, and by 3'6 for perchloride of 

 phosphorus.* 



TABLE X. 



For the solution of the equation: W 100Q ( A ~ 1 )_ T 



(2-A) a 



The constants of these equations are of course subject to correction 

 by future experiments, which must also decide the more general 

 question in what cases, and within what limits, and with what 

 degree of approximation, the actual relations can be expressed by 

 equations of such form. In the case of perchloride of phosphorus 

 especially, the formula proposed requires confirmation. 



* The value of A diminished by unity expresses the ratio of the number of the mole- 

 cules of the more complex type to the whole number of molecules. Thus, if A=l-20, 

 in the case of peroxide of nitrogen there are 20 molecules of the type N 2 O 4 to 80 of the 

 type N0 2 , or in the case of perchloride of phosphorus there are 20 molecules of the type 

 PC1 5 to 40 of the type PC1 3 and 40 of the type CLj. A consideration of the varying 

 values of A is therefore more instructive than that of the values of D, and it would in 

 some respects be better to make the comparison of theory and experiment with respect 

 to the values of A. 



