200 



Ozone and the Atmosphere. 



Does the Electric Spark Decompose Potassium Iodide ? — One 

 of the most interesting points to be determined in connection 

 with the ozone tests, was whether the electric spark alone would 

 decompose potassium iodide, or whether the decomposition was 

 not due to the ozone produced whenever the electric spark is 

 taken in the ordinary manner. To settle this question it was 

 essential to submit the tests to the spark taken either in vacuo, 

 or in an atmosphere of some gas which, under the influence of 

 the spark, would neither suffer decomposition nor enter into 

 combination. The first method was attended with insurmount- 

 able difficulties, for which reason the second was adopted, 

 hydrogen being the gas selected. 



The hydrogen was purified by permanganate of potash solu- 

 tion, as proposed by the author, in an article entitled '■ Contri- 

 butions to the Chemistry of Hydrogen ;" American Ass'n 

 Adv. Science, Aug. 23d, 1876 ; American Chemist, Nov., 1876.* 

 It was dried in the usual manner by sulphuric acid, and 

 then passed over a length of 20 c. m. platinum sponge, which 

 was kept heated at the middle. The farther end of this tube 



* Later by Shobig. Jour, pr. Chem., II., XIV, ! 



Oct., 1876. 



