456 Walker and Gillespie — Application of 



amounts of hypoiodites that might otherwise be present, the 

 final action results in the formation of an exactly neutral mix- 

 ture of iodate and iodide, according to the equation : 



6ROII + :iI 2 = RIO, + 5RI + 3H a O. 



Phelps* has shown that in the case of barium hydroxide at 

 least this reaction is regular and complete under the conditions 

 of analysis, and is independent of the excess of iodine which 

 remains in the neutral mixture unacted upon, and may he esti- 

 mated by directly titrating with arsenious acid. Phelps not 

 only applies this principle of action to the standardization of 

 solutions of barium hydroxide by boiling with an excess of 

 iodine in a trapped flask, but also bases thereon a differential 

 method for determining carbon-dioxide, in which the liberated 

 gas is run into a measured amount of barium hydroxide, the 

 final excess of which is estimated by treating with iodine in 

 the presence of the precipitated barium carbonate. The good 

 result obtained by Phelps with barium hydroxide suggested 

 that the attempt be made to analyze alkali hydroxides, and 

 possibly carbonates, by a method, simpler than that devised by 

 Groger, based on the direct treatment of these compounds 

 with iodine in hot solution. It also seemed possible to apply 

 the differential method not only to carbon-dioxide but to any 

 acid or other compound that will act definitely and completely 

 with the metallic hydroxide employed, pr >vided the soluble or 

 insoluble product formed will not be attacked when heated in 

 the presence of iodine. It was decided to modify the Phelps 

 process, however, in order to obviate the necessity of handling 

 large measured amounts of iodine in a flask trapped to prevent 

 mechanical loss by heating. The flask was therefore dispensed 

 with altogether, and the hydroxide solution to be analyzed was 

 mixed with an approximately measured excess of iodine solu- 

 tion, in an Erlenmeyer beaker, the mouth of which was lightly 

 closed with a little trap to prevent loss by spattering. The 

 excess of iodine was then completely removed by boiling, and 

 the cooled colorless solution remaining, which contained a neu- 

 tral mixture of iodate and iodide, was acidified with a min- 

 eral acid and the liberated iodine titrated with sodium thio- 

 sulphate, the amount found being equivalent to the amount of 

 hydroxide taken for analysis. 



The present investigation was undertaken to study the limi- 

 tations and possible applications in analysis of the reactions 

 between iodine on the one hand, and barium hydroxide, potas- 

 sium hydroxide and sodium carbonate on the other. It was 

 soon found that the reaction in the case of sodium carbonate 

 is entirely dependent on conditions of time, mass and tempera- 



*This Journal, ii, 70. 



