26 Wells and Johnston — Ammonium-Lead Halides. 



PbCl 3 .18NH 4 CUH 9 2PbBr 2 .14NH 4 Br.3H 2 



PbCl 2 .10NH 4 Cl.H 2 O PbBr 2 .6NH 4 Br.H 2 



2PbCl 2 . 1 8NH 4 C1.3H 2 7PbBr Q .l 2NH 4 Br.7H a O 



PbCI 2 .6NH 4 Cl.H 2 3PbBr 3 .2NH 4 Br.H.O 



4PbCl 2 .22NH 4 C1.7H 2 



4PbCl 2 .18NH 4 CI.5H 



4PbCl 2 .2NH 4 C1.6H 2 



From Andre's original articles, it appeared that lie made no 

 mention of having ever prepared any of his remarkable 

 products more than once, and it seems probable that whenever 

 he obtained a crop of crystals or a precipitate he described it 

 as a new compound, without regarding the number of differ- 

 ent substances that it might contain. Andre operated in two 

 ways. A part of his salts were made by dissolving a lead hal- 

 ide in a hot solution of the corresponding ammonium halide 

 and cooling, while the rest were made by dissolving lead mon- 

 oxide in boiling solutions of ammonium chloride or bromide. 

 From the products made by the last method he obtained lead 

 oxy chlorides or oxybromides by heating them with water in 

 sealed tubes. This peculiarity of these products caused him to 

 remark that all the chlorides made in this way seemed to con- 

 tain some oxychloride. This is the only evidence of any sus- 

 picion on his part that he was obtaining mixtures. In a 

 number of instances Andre describes his products as " crystal- 

 line precipitates," " brilliant plates with pearly lustre," " crys- 

 tallized bodies " etc , so that it would seem that they should 

 have been pure, but after having repeated his experiments, fol- 

 lowing his methods as closely as his descriptions permitted, 

 with many variations and repetitions, we are convinced that 

 not one of the salts described by Andre exists. 



Our work has resulted in the preparation of the following 

 series of salts : 



Type 2 : 1 



Type 1 : 1 



Type 1 : 2 





3NH 4 PbCl,.H 9 



NH 4 Pb 2 Cl 5 



(NH 4 ) 2 PbBr 4 .H 2 



NH"PbY.2HO 



NH 4 Pb 3 Br 5 



For comparison, the potassium series, already referred to, is 

 given : 



Type 2:1 Type 1 : 1 Type 1 : 2 



3KPbCl 3 .H 2 KPb 2 Cl 5 



K 2 PbBr 4 .H 2 3EPbBr 3 .H 2 KPb 2 Br 5 



KPbBr 3 .H 2 



KPbI„.2HO 



It is to be noticed that the two series correspond exactly, ex- 

 cept that no ammonium-lead bromide of the 1 : 1 type was 



