Wells and Johnston — Ammonium- Lead Halides. 29 

 The analyses were as follows : 



Ammonium. Lead. Bromine. Water. 



A 6*01-5-86 37'12-36'84 55-06-55'10 2'60 



B 37-06-36-94 54'94 



C 37*26 



Calculated for 



(NHJ a PbBr,H,0' 617 85 ' 63 55 ' 08 3 ' 10 



1 : 2 Ammonium-Lead Bromide, NH^Po^Br^ : — On slightly 

 diluting solutions from which the preceding salt would be 

 deposited, this salt is obtained. Repeated trials were made to 

 obtain a 1 : 1 salt intermediate between the two, but these were 

 without success. The salt forms square plates, often several 

 millimeters in diameter. The crystals darken somewhat on ex- 

 posure to light, but they do not lose their luster on drying, and 

 are evidently originally anhydrous. The compound is formed 

 under rather wide limits of conditions. A single sample was 

 analyzed. 



Calculated for 

 Found. XH 4 Pb 2 Br 5 



Ammonium 2-17-2-17 2-16 



Lead 49-26-49-12 49-76 



Bromine 48'28-48'22 48*08 



« 



1 : 1 Ammonium- Lead Iodide, NH^Pbl^H^O : — This was 

 the only double iodide obtained, although a thorough search 

 was made for other salts. It forms hair-like crystals of a pale 

 yellow color. Sample A was made by disssolving 100 s of 

 NH 4 I and 10 s of Pbl 2 in sufficient hot water to make a 

 volume of 108 cc , and cooling. Sample B was obtained by 

 slightly diluting the solution which gave A. It was noticed 

 that, where lead iodide was deposited from a moderately con- 

 centrated hot solution of ammonium iodide, the lead iodide 

 disappeared on cooling and in its place was formed a compact, 

 silky mass of crystals. Sample C was such a crop as just 

 described, which was carefully separated from the usual form 

 of the double salt which formed above in the solution. 



Calculated for 

 A B C NH 4 PbI 3 .2H 2 



Ammonium _ 2-40- 2*25 2-97- 2-97 2-80 



Lead 31-08-31 -46 31-36-31-20 31-76 32-24 



Iodine 59-76-59-70 59'85-59'75 62-45 59*36 



Water 5'60 5*65 5-60 



On Andre's Products. 



Andre* prepared some of his most complicated products, such 

 as 2PbCl a .18NH 4 C1.3H a O and 4PbC] Q ,22NH 4 C1.7H a O, by dis- 



