Wells and Johnston — Ammonium -Lead Halides. 25 



Quartz 6*10 



S0 3 28-46 



As„0 2-36 



Quartz deducted 



. 0. 



30-29 = 



•1817 



2-51 



•0087 



49*28 



•1478 



•42 



•0012 



4-62 



•0119 



I'RI 



•0027 



11-24 



•0999 



1904 12 



Fe 2 3 46-27 49-28 -J478 -1478 9-35 



CaO -39 



Na„0 4-35 4-62 -0119 J- -0158 



K o 1-4' 



HO 10-55 11-24 -0999 "0999 



9995 99-93 



The excess in O ratios for the iron and water is to be attrib- 

 uted to the presence of some ferric hydrate and the O ratios 

 for the sample is 1 : 9 : 12 : 6. 



State School of Mines, Rapid City, S. D. 



Art. III. — On the Ammonium-Lead Halides ; by H. L. 

 Wells and W. R Johnston. 



It is a well known fact that the ammonium double halides, 

 like other ammonium salts, are usually analogous to those of 

 the alkali-metals, especially to those of potassium. For example, 

 in connection with an investigation of the caesium-mercuric 

 halides, made by one of us,* it was noticeable that caesium com- 

 pounds were prepared, corresponding to all of the four types 

 of ammonium-mercuric halides that had been previously 

 described. 



A study of the caesium-lead and potassium-lead halides has 

 recently been made in this laboratory,-}- and, in view of the 

 fact that the existence of four very simple types of double salts 

 was established by that investigation, it seemed desirable to re- 

 investigate the ammonium-lead halides, since a considerable 

 number of these with very complicated formulae had been 

 described. These peculiar ammonium-lead halides have formed 

 the most noticeable exception to the similarity of the alkali- 

 metal and ammonium salts, and it seems probable that it was 

 chiefly on account of these that Kemsen has remarked :;£ " The 

 position of the double halides containing ammonium is cer- 

 tainly exceptional. They seem to be governed by some law 

 of their own." 



All of the extremely complicated ammonium-lead salts have 

 been described by Andre.§ 



The list of his alleged compounds is as follows : 



*This Journal, xliv, 221. f This Journal, xlv, 121. 



t Am Chem. Jour., xi. 296. 



£ Compt. Rend., xcvi, 435 and 1502; Bull. Soc. Chim., [2], xl, 14. 



