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Mr. W. B. Hardy and Miss E. G-. Willcock. [July 21, 



On the Oxidising Action of the Kays from Radium Bromide as 

 shown by the Decomposition of lodoform." By W. B. 

 HAEDY, F.B.S., Caius College, Cambridge, and Miss E. G. 

 WILLCOCK, Newnham College, Cambridge. Eeceived July 21, 

 1903. 



In the course of certain experiments one of us noticed that a solution 

 of crystals of pure iodof orm in chloroform rapidly became purple. The 

 colour change is due to the liberation of iodine, and the purple solution 

 readily gives the starch test, and is decolourised by thiosulphate. 

 This decomposition of iodoform occurs in a variety of solvents, namely, 

 in chloroform, benzene, carbon bisulphide, carbon tetrachloride, pyri- 

 dene, amyl alcohol, and ethylic alcohol. In alcohol the change is 

 shown only by a deepening of the original yellow tint of the solution 

 to brown ; iodine when dissolved in alcohol having a yellow-brown tint. 



As the reaction itself seems not to have been described, a few words 

 may be devoted to it before passing to the main point namely, the 

 influence of the rays from radium upon this chemical change. 



The liberation of the iodine needs the presence of oxygen though 

 exceedingly minute amounts are sufficient and some form of radiant 

 energy. When oxygen is washed out by a stream of COo, or the 

 vapour of the solvent, no change takes place ; the solution of iodoform 

 retains its faint yellow tint in full daylight. 



If a minute quantity of oxygen be left behind, the colour deepens in 

 daylight to a brownish-yellow, but iodine is not liberated the solution 

 will not give the starch test. That is to say, there is an intermediate 

 stage of chemical change which is reached in presence of minute 

 amounts of oxygen, and which falls short of the actual liberation of 

 iodine. 



If a pair of platinum electrodes be dipped in a solution which is in 

 process of changing to purple, and a field ( 4 volts per centimetre) be 

 established, a heavy, oily, colourless liquid slowly drips from each 

 electrode. The nature of this liquid has not yet been determined, but 

 from its specific gravity probably it is methylene iodide. 



In the complete absence of any radiant energy, and in presence of 

 abundant oxygen, the solution of iodoform undergoes no change at 

 ordinary temperatures. When heated to near the boiling point, 

 however, the solutions change even in the dark. 



Salts, when present, have a remarkable influence on the reaction, 

 although they can hardly be said to be soluble in the reagents employed. 

 For instance, if a solution of iodoform in benzene be divided into two 

 parts, and to one part solid sodium chloride be added, and then both 

 be heated, the one with the salt decomposes much more rapidly. 

 Compared in this way, it was found that 



