COMPOSITION OF AMMONIUM AMALGAM. 173 



the adhesion to it of the gases ; and he cites the absorp- 

 tion of oxygen by melted silver as a similar case. 



Grove*, in 1841, made a few experiments on the amal- 

 gam, and advanced the idea that it is a chemical compound 

 of mercury and nitrogen, merely swelled up with hydrogen. 



In 1864 Dr Wetherillf performed several ingenious 

 experiments on the amalgam, but without attempting any 

 quantitative estimate of its composition. He concludes 

 that it is not an alloy of mercury and ammonium, and 

 that the swelling up of the mass is due to the retention 

 of gas bubbles by virtue of some unexplained action which 

 he somewhat vaguely refers to catalysis. 



In the ' Annalen der Chemie u. Pharmacie' for 1868 J 

 is a paper by Landolt, in which, after pointing out the dis- 

 cordance of the quantitative results obtained by Davy, and 

 by Gray-Lussac and Thenard, he describes a method by 

 which he attempted a new determination of the relative 

 quantities of ammonia and hydrogen. He prepared the 

 substance from a solution of sal-ammoniac, separated from 

 the mercury (which formed the negative pole) by a porous 

 cell. The amalgam, when removed from the circuit, was 

 washed in a stream of water to get rid of the adhering 

 solution of sal-ammoniac, which always contains free am- 

 monia. It was then immediately plunged into dilute 

 hydrochloric acid of known strength; and the hydrogen 

 evolved was received in a graduated cylinder placed over 

 it, while the ammonia was estimated by determining the 

 amount of unneutralized acid in the liquid. Two experi- 

 ments gave results corresponding respectively to 2*15 and 

 2*4 volumes of ammonia to 1 of hydrogen. These figures 

 of Landolt's cannot be considered satisfactory, neither 

 nearly agreeing with each other nor approximating to the 



* Phil. Mag., United Series, xix. p. 97. 

 t Silliman's Amer. Journ. [2], xl. p. 160. 

 \ Supp. Bd. vi. p. 346. 



