n6 SCIENCE PROGRESS 



as dimercury diammonium chloride, N 2 H 4 Hg 2 Clj, as dimercury 

 ammonium chloride plus ammonium chloride, NHg 2 Cl, NH 4 C1, 

 and as mercuric chloramide, NH 2 HgCl. Franklin (13) obtained 

 this compound by the action of liquid ammonia on HgCl 2 , 

 and he regards it as ammono-basic mercuric chloride, 



NH-. . Hg . CI. Cf. basic mercuric chloride, HO . Hg . CI. 



In accordance with this view, the dimercuri-ammonium 

 salts are represented by the general formula Hg = N = Hg— X 

 where X is any monovalent acid radicle. 



Cf. HO - Hg - O - Hg - X. 



The fusible white precipitate is regarded by Franklin as 

 a salt with ammonia of crystallisation, while the numerous 

 mercury ammonia compounds containing oxygen are regarded 

 as mixed hydro and ammono basic compounds. According to 

 this view the well-known Nessler's precipitate is regarded as 



NH,.Hg.O.Hg.I 



These somewhat intricate details are given to show the new 

 light that has been thrown upon the nature of well-known 

 compounds by the study of interactions in liquid ammonia. In 

 addition to these compounds Franklin, by the use of liquid 

 ammonia solutions, prepared mercuric nitride, Hg 3 N 2 , lead 

 imide, PbNH and bismuth nitride, Bi N, as well as the previously 

 mentioned silver amide, AgNH 2 . These compounds were pre- 

 pared by adding the solution of the metallic iodide in ammonia 

 to a solution of potassium amide. Silver amide was obtained 

 as a white precipitate but the others are of different shades 

 of brown and all of them are extremely explosive. An excess 

 of KNH 2 was used to prevent contamination with ammono- 

 basic salts but this cannot be done in the case of lead imide, 

 as it is soluble in excess of potassium amide. 



Many " double decompositions " take place in liquid ammonia, 

 just as in water : 



e.g. Zn(N0 3 ), am + (NH ( ), S am = ZnS ppt + 2 NH,NO :1 am, 



but in many cases precipitations occur which have no counter- 

 part in aqueous solutions : 



e.g. Zn(N0 3 ), am + 2NH, CI am = ZnCL ppt + 2NH 4 NO i am 



There are many other cases in which insoluble chlorides are 

 precipitated. 



