SOLID SOLUTIONS 



79 



remaining: the quantities being calculated by means of 

 the known volume of the apparatus (provided with marks 

 at k, i, k) and the pressure and temperature. 



It was already known, from the experiments of Troost 

 and Hautefeuille, that the amount of hydrogen absorbed 

 first rises with the pressure, whilst on further absorption 

 the pressure becomes constant, which suggests the forma- 

 tion of a compound. We may quote the data for 150; 

 the pressure (P) in millimetres, the number of hydrogen 

 atoms absorbed by one palladium (H), and the ratio between 

 the increase of pressure (AP) and the quantity absorbed 



Troost and Hautefeuille's opinion in favour of the forma- 

 tion of a compound was strengthened by the fact that 

 at the temperature they employed the maximum hydrogen 

 taken up in the interval of nearly constant pressure cor- 

 responded to the formula Pd 2 H. It appears, however, from 

 the newer researches discussed here, that this quantity does 

 not represent any definite atomic ratio, and especially that 

 it varies with the temperature. 



At io concentration about Pd H . 6 . 

 180 PdH . 37 . 



The possible explanation of these facts is that at constant 

 pressure two solid solutions are present in the palladium. 



