Potassium Trihalides, with their Crystallography. 485 



Kl.I n _. 



This body can be made in a few hours by dissolving the 

 theoretical amount of iodine in a hot saturated aqueous solu- 

 tion of potassium iodide and exposing the resulting solution to 

 a winter temperature. It can also be made as Johnson states* 

 by evaporating the solution in a desiccator for a long time. 

 Johnson states that he always obtained a crop of potassium 

 iodide before the tri-iodide separated. We have never obtained 

 such a product, undoubtedly because we have invariably used 

 a sufficient amount of iodine. 



It was not considered necessary to make a new analysis of 

 this body. 



K Br. Br I. 



This compound can be prepared by making a very concen- 

 trated, warm solution of the calculated amounts of potassium 

 bromide, bromine and iodine, and exposing it for some time to 

 a low temperature. The product used for analysis was well 

 crystallized, but it suffered rapid decomposition on exposure 

 to the air. 



Calculated for 

 Analysis gave KBr . BrI. 



Potassium .. 12-21 11-99 



Bromine... 51-25 51-61 49-06 



Iodine 30-42 29*11 38'94 



KCl. ClI. 



To prepare this substance, chlorine is passed into a warm 

 mixture of calculated quantities of potassium chloride and 

 iodine in the presence of an amount of water insufficient to 

 dissolve the potassium chloride even when hot. The stream 

 of chlorine is stopped as soon as the iodine has been converted 

 into the monochloride, for otherwise Filhol's well-known com- 

 pound KCl . C1 3 I will be formed. Everything is then dis- 

 solved by warming and cautiously adding water if necessary 

 and the solution is exposed to a low winter-temperature. The 

 crystals are very unstable, but apparently not quite as much so 

 as KBr . BrI. 



Calculated for 

 Analysis gave KCl . ClI. 



Potassium 15-29 15-35 1649 



Chlorine 27'53 27-50 29-94 



Iodine.. 50-37 50-12 53*56 



Other Double-halides. 



The double-salt Csl . Agl was described in connection with 

 the caesium trihalides as being isomorphous with them as far 



* Loc. cit. 



