202 Ozone and the Atmosphere. 



ployed still contained oxygen, was negatived by the positive 

 results obtained by the platinum sponge guard-tubes, and not 

 less so by the absence of any smell of ozone, this last being in 

 fact one of the most delicate tests which we possess. But the 

 burnt smell noticed each time the apparatus was opened, ren- 

 dered it extremely probable that the paper, containing, as it 

 does, the elements of water, had undergone some decomposition. 



To eliminate these sources of error, a tube was partially 

 filled with pure potassium iodide, and hung upon the elec- 

 trodes. After dessication in a current of hydrogen for many 

 hours, sparks were passed through the iodide for a very long- 

 time. The magnificent color of the spark in hydrogen changed 

 whenever the particles of potassium iodide were rendered in- 

 candescent. On testing the iodide afterwards, there was not 

 the slightest indication of liberated iodine. From this it would 

 appear that it is not the electric spark, but the ozone generated 

 under its influence, which produces the chemical effects of de- 

 composition in this and similar instances. 



Collection and Preservation of Ozone. — A bottle with 

 mouth partially covered, may be filled with ozonized ox} 7 gen 

 by displacement. It is noticeable that even when the en- 

 trance tube extends quite to the bottom of the bottle, the 

 smell and iodo-starch reaction of ozone are obtained almost 

 immediately, while quite an interval elapses before the air is 

 so perfectly displaced that the issuing gas relights a spark at 

 the orifice. Bottles so filled may be sealed with paraffine, and 

 the contained ozone be preserved for hours. Great difficulty 

 was encountered in making tight joints. It has been recom- 

 mended to insert the ends of tubes to be joined, into a wider 

 tube, and fill in with paraffine. But the adhesion of the 

 paraffine is so slight, that such a joint easily comes apart. A 

 better plan is, to take a strip of cotton cloth about 1| in. wide, 

 and of suitable length, wrap it tightly round the tubes to be 

 joined, fasten with soft flower or copper wire, and then render 

 it impervious by melted paraffine applied with a feather or 

 brush. Tubes of very different diameters, and vessels of vari- 

 ous dimensions, can be joined by suitably modifying this plan, 



