124 Wheeler and Penjield — Alkaline lodates. 



The compound which separated from the solution of the 

 potassium pentahalide has already been described, but since 

 this is a new method of preparation and since there are con- 

 flicting statements concerning its state of hydration, it has 

 been re-investigated. 



The results of the investigation of the rubidium salts show 

 that the normal iodate is the only one of the series that can 

 be recrystallized unaltered from an aqueous solution. In the 

 case of the caesium compounds, the normal iodate and the salt 

 2CsI0 3 . I 2 5 are not decomposed by water. The other caesium 

 iodates give 2CsI0 3 . I 2 O when recrystallized from water and 

 not the normal iodate, thus showing an interesting difference 

 between the rubidium and caesium compounds. 



It is the tendency of the acid rubidium iodates to separate 

 in a higher state of hydration than the corresponding caesium 

 compounds. 



It is also an interesting fact that the formation of the com- 

 pounds of normal chloride and iodic acid was not observed on 

 mixing the constituents. In the case of rubidium, products 

 were obtained which proved to be RbI0 3 , RbI0 3 . HI0 3 or 

 RbI0 3 . 2HI0 3 according to the concentration of the solutions 

 and the excess of RbCl or HI0 3 . On the other hand by add- 

 ing hydrochloric acid to a solution of rubidium iodate, if the 

 acid is dilute RbIO s , 2HI0 3 is formed, if concentrated the 

 iodate is completely decomposed. Similar experiments under- 

 taken with caesium chloride and iodic acid, did not give the 

 peculiar double compound CsCl . HI0 3 but resulted, in each 

 case, in the formation of 2CsI0 3 . I 2 B . 



Method of Analysis. 



After the substances were prepared for analysis as described 

 in detail beyond, the halogens were determined by first reduc- 

 ing the solution of iodate with sulphur dioxide then precipi- 

 tating with silver nitrate in the presence of nitric acid. This 

 precipitate was then heated in a stream of chlorine, thus com- 

 bining the test for chlorine and its determination in one opera- 

 tion. In the filtrate from the silver precipitate the alkali 

 metal was determined as sulphate after the removal of the 

 excess of silver by means of hydrogen sulphide. Oxygen was 

 determined in a separate portion by precipitation with silver 

 sulphate, drying the precipitate at 100° and then determining 

 the loss on ignition. Duplicate halogen determinations were 

 then made in this residue. In the case of the compounds con- 

 taining the group I./) 6 , where an error would be introduced 

 if the oxygen was determined in this manner, the substance 

 itself was "ignited and the oxygen calculated from the loss. 



