230 0, S. Pulman — Determination of Uranium and 



n 



The potassium permanganate solution, approximately — 



(containing about 3*16 grams of the crystals to the liter), was 

 standardized against an exactly — arsenite solution by allow- 

 ing a measured amount of the permanganate to act upon an 

 acidified solution of potassium iodide (containing enough of the 

 salt to hold the iodine set free in sohition), the iodine thus set 

 free being taken up by adding an excess of the arsenite and 

 neutralizing with acid potassium carbonate, the excess of the 

 arsenite then being titrated by standard iodine, with starch as 

 an indicator. The total amount of arsenite employed, less the 

 excess which is indicated by the iodine, corresponds to the 

 amount of permanganate taken. 



For each experiment a measured amount of the standard 

 uranyl nitrate solution was converted into the sulphate by 

 evaporating it with lO'"^' of sulphuric acid (I'SA) in a 300"'"' 

 flask, placed in a slanting position on an iron radiator to pre- 

 vent any loss by spattering, until dense white fumes were 

 formed. The liquid was then cooled, and water and more sul- 

 phuric acid were added in sufficient amount to make the 

 volume of the solution up to that desired (generally from 100 

 to ISO^""^), and the proportion of the free sulphuric acid to the 

 total volume to between the ratios of 1 to 5 and 1 to 7. Before 

 passing the solution through the reductor, a small amount of 

 warm acid was sent through, and, in order that the proportion 

 of the acid in the uranium solution might not be changed by 

 the liquid thus left in the reductor, care was taken to have the 

 dilute acid of the same strength of acidity as in the uranium 

 solution. The warm acid was followed by the uranium solu- 

 tion, and this was washed through by a little of the acid and 

 by 250'^'°^ of hot water. The solution was collected in the 

 flask, diluted, and titrated with potassium permanganate. This 

 was the general procedure in preparing and treating the ura- 

 nium solution. 



It was found that it required about an hour, instead of ten 

 minutes, as Kern said, for 100^°"' of a solution, containing sul- 

 phuric acid even in the ratio of 1 to 7, and 250'=™' of water to 

 pass through a reductor prepared exactly according to Kern's 

 directions. The apparatus, therefore, was arranged so that 

 suction could be applied, but with suction the carbon dioxide 

 generated by a gram of sodium carbonate would be very quickly 

 exhausted. In view of this fact, it was thought best to con- 

 nect the apparatus with a carbon dioxide generator, to pass a 

 current of gas through the apparatus before starting the oper- 

 ation, and then after the operation to fill up the partial vacuum 

 formed by the suction with carbon dioxide before disconnec- 



