194 II. L. Wells — Halides of Potassium and Lead. 



halogens in these compounds is in excess, so that, if all the 

 iodine is in this condition it amounts to about one- third of this 

 excess. 



The crops A and B had a dark bronze color. They were 

 successive crops made by adding bromine to a strong solution 

 of potassium iodide containing lead iodide. The exact condi- 

 tions are unknown, but it is probable that insufficient bromine 

 was used to set free all the iodine which the solution contained. 

 These products were apparently as stable as the iodide. 



C and D were successive crops made by continuing the addi- 

 tion of bromine to a somewhat similar solution until a change 

 of color showed that the free iodine had been converted into 

 BrI. These salts were red. An analysis of the mother-liquor 

 from D gave, KBr = 31-3, PbBr 2 = 1-8, Br = 6*7, I = 8'3, 

 H 2 (difference) = 51-9. 



E was made by adding 31 s of bromine to 430 g of the above- 

 mentioned, analyzed solution. This crop was also red, but it 

 was not quite as bright in color and not as stable as the others. 

 On continuing the addition of bromine, still less stable crops 

 were obtained which approached the pure bromide in color. 

 These were not analyzed. 



The analyses of the five crops are as follows : 





K 



Pb 



Br 



I 



H 2 



A 



9-41 



31-57 



41-40 



12-06 



5-09 = 99*53 



B 



9-24 



31-55 



39-27 



14-57 







C 



9-90 



32-88 



48-66 



3-40 



5-24 = 100-08 



D 



9-99 



32-74 



48-70 



3-30 



5-02 = 99-75 



E 



10-24 



32-26 



49-97 



2-07 







he 



ratios calculated fr 



om the above analyses are as folk 







K : 



Pb : 



Br + I 



H 2 





A 



1-57 



1- 



3'99 



1-83 





B 



1-55 



1- 



3-99 









C 



1-59 



1- 



4-00 



1-82 





D 



1-61 



1- 



4-00 



1-76 





E 



1-68 



1- 



4-16 







The ratio required for the formula K 3 Pb 3 (Br,I) 8 .4H 2 is, 



K : Pb : Br + I : H 2 



1-50 1- 4- 2' 



The analyses agree well with this formula, except that the 

 water is somewhat low. Although 3J- molecules of water would 

 correspond more closely to these analyses than 4, the latter 

 number is considered more probable on account of the fact that 

 the analyses of the iodide show some excess over four mole- 

 cules. 



