ON THE ATOMIC WEIGHT OF CHLORINE. 199 



The solvent action of liquid chlorine, if any, on soft glass was also examined. The 

 same bulb was employed. After its weight had been determined as above, 10 cub. 

 centims. of liquid chlorine were condensed in it by means of a freezing mixture of 

 solid carbonic acid and ether. The bulb was then separated from the chlorine 

 apparatus by fusion between the ground-glass joint and the bulb, and was laid aside 

 for a week. The ground-glass portion was cleaned and dried, a mark was cut with a 

 clean glass cutter in the glass capillary tubing attached to the bulb, and a clean 

 fracture effected. When the chlorine in the bulb had been totally replaced by air, 

 the three parts of the original apparatus, i.e., the bulb, the piece of glass broken off 

 from it, and the inner portion of the ground-glass joint were weighed, the companion 

 bulb acting as a counterpoise. 



Weight of bulb before exposure 1 32464 grammes. 



after 1-32466 



A similar apparatus was constructed, and, after being subjected to the action of 

 pure dry gaseous chlorine for a week, the last experiment was repeated, the time of 

 exposure being a month. 



Weight of bulb before exposure 3 49842 grammes. 



after 3-49839 



There seemed to be no appreciable action of liquid chlorine on soft glass. 



Though the combined effect of gaseous and liquid chlorine on soft glass was so 

 exceedingly small, the bulb of the chlorine condensation bulb was subjected, before 

 use, to the action of pure dry gaseous chlorine for a fortnight. 



2. The Reaction between Iodine and Sodium Thiosulphate in Presence of 

 Carbonic Acid and of Hydrochloric Acid. 



Titrations of sodium thiosulphate by iodine in potassium iodide, carried out in an 

 atmosphere of carbonic acid, showed that the gas had no influence on the accuracy of 

 the residual iodine determinations. A known volume of sodium thiosulphate solution 

 was run into a small Erlenmeyer flask and titrated with the standard solution of 

 iodine in potassium iodide. An equal volume was run into another flask and pure 

 carbonic acid (from sodium hydrogen carbonate) was passed through the solution for 

 ten minutes, it was then titrated as usual. No difference in the volumes of iodine in 

 potassium iodide solution required to combine with the thio in the two flasks could be 

 detected. Several repetitions gave similar results. 



S. U. PICKERING* has shown that iodine in potassium iodide solution can be 

 correctly titrated by thiosulphate in presence of hydrochloric acid, if allowance is 

 made for the slow oxidation of the liberated hydrogen iodide by the oxygen from the 



* ' Jouru. Chem. Soc.,' 1880, p. 134. 



