284: Messrs. F. Soddy and T. D. Mackenzie on the 



Purification of the Uranium. 



The uranyl nitrate, usually one kilogram, dissolved in about 

 one litre of water was thoroughly shaken in a bottle of 3 litres 

 capacity with an equal volume of ether to expel air, the 

 stopper then inserted and tied down. The bottle was fastened 

 in the shaking machine and shaken for an hour. The liquid 

 was allowed to stand for at least an hour to allow the two 

 solutions to separate, and the top ethereal solution drawn off 

 as thoroughly as possible by means of a siphon into a sepa- 

 rating funnel and allowed to stand in the funnel for two hours 

 when any separated aqueous liquid was removed. To the 

 aqueous solution in the bottle a further quantity of ether was 

 added, the mixture shaken and separated, and then a third 

 quantity was added and treated in the same way. Three 

 successive extractions removed nearly the whole of the 

 uranium, and the aqueous liquid was worked up as residues. 

 If expectations are fulfilled these residues should contain all 

 the intermediate parent of radium. 



The ethereal uranium solution was separated from ether- by 

 distillation. The usual precautions were taken in distilling 

 ether, the distilling-flask being kept about two-thirds full by 

 running in fresh solution as the ether evaporated. During the 

 first distillation the uranium nitrate in the flask was allowed 

 to collect in fairly large quantity, and owing to a sudden 

 evolution of oxides of nitrogen a violent explosion occurred 

 and much of the uranium was lost. In two subsequent 

 distillations an explosion was avoided by rapidly cooling the 

 flask as soon as gas began to appear. Thereafter, about 

 100 c.c. of water was kept in the flask and the uranium 

 nitrate not allowed to collect in large quantity. The contents 

 of the flask were poured out into a porcelain dish and heated 

 on the steam-bath. When the liquid got hot a sudden rapid 

 evolution of oxides of nitrogen took place lasting two or 

 three minutes. About 50 c.c. of concentrated nitric acid 

 were added, and the solution evaporated till a crust of crystals 

 formed. The solution was diluted and allowed to stand, when 

 a copious yellow precipitate, containing uranium and organic 

 matter, was thrown down. This was separated and ignited, 

 and the uranium oxide dissolved in nitric acid and added to 

 the rest of the solution. This solution constituted the 

 purified uranyl nitrate solution used in the experiments. 



An attempt to avoid decomposition of the ether by the use 

 of the purest ethyl ether obtainable met with no success. 

 The same strong smell of aldehyde and other bodies was 



