58 THE r.EHAVIOUK OF SOLUTIONS OF HVDRIOIMC ACID 



allowed to act for a couple of hour?; portiousof the residue from 

 the solution were heated with potassium cyanide and powdered 

 charoual, and with ])Owdere(l niai>nesinni ; and lastly some of the 

 residue was heated in a rnvrent of hydrogen to sncli a high tem- 

 perature, that the sodium sulphate Avas reduced to s\ilphide. In 

 neither of these instances was the slightest trace of iodine 

 obtained. 



As it was thought that an analysis of the solution might 

 throw some light on the ])rol»leni. the following deferminations 

 Avere undertaken. 



80 cc. of the colourless solution that had Ivecii acted 

 on l)y ])ure oxygen, and whicli, therefore, must have con- 

 tained all the ioiline originally in it, were exactly neutralized 

 Avitli potassium carhonate and evajiorated to dryness. The 

 residue after l)eing dried at 110° for an hour weighed 8.0530 

 grams. This I'esidiu' was used for tlie analysis, and the only 

 substances that it could contain besides the iodine, Avere potas- 

 sium, and sulphiTric acid in the form of sulphate, fit Avas 

 proA'ed that there was no carl)onate present). 



The amount of sulphuric acid fSO'^ ) was determined by 



])reci])itating Avitli bni'iuni cldoridc. 1'he folldwiijg :-,ie tlie 

 results (i])tained : 



(1 j 1.4!)]4 grams resichie yicdded 1,081:5 grams VrA^O ^ 

 (2) 1.4<»14 '' " ' " 1.9842^ " " 



mean 1,9827 



This weight of barium sul])hate corresi)onds to 0.81 G8 gram of 

 SO4, or to 54. TC) ])er cent, of the residue used. 



The ])otassium was estimated by ])recipitating- as double 

 potassium-platinum (ddoi-i(h'. This precipitate after being 

 thoroughly drie<l, Avas heated Avith oxalic acid and reduced 

 to a mixture of metallic platinum and potassium chloride, 



