212 



Ozone mid the Atmosphere: 



NAME OP OZONOSCOPE. 



Polli's 



Moffat's 



Lowe's (with 0,03 gnn. calcium carbonate) 



Schonbein's 



Osann's 



Cadmium Iodide 1 grm 



POTASSIUM IODIDE. 



STARCH. 



2. grms. 



1 grm. 



4 " 



1 " 



0.2 " 



1 " 



0.1 



1.1 " 



0.1 " 



1 " 





1 " 



The preparation of the other tests is given elsewhere. The 

 tdsts prepared with great excess of potassium iodide, as recom- 

 mended by Dr. Polli, were not employed, since they turned 

 brown while drying. The sensitiveness of these tests, as will 

 be seen from the tables, increases, as a rule, with the percent- 

 age of potassium iodide. Those of Lowe, which occupy an in- 

 termediate position, and are not liable to change on drying, are 

 perhaps to be preferred. Calcium carbonate was aded in ac- 

 cordance with the recommendation of Mr. Lowe, in order to 

 secure greater uniformity of action and prevent souring, but 

 we were unable to perceive that the addition was of practical 

 value.* 



The tests were separately suspended in a capacious bell-jar, 

 through which a current of ozonized ozygen, containing 1 

 mgrm. ozone in the litre, was caused to flow very slowly. No 

 attempt was made to screen them from diffused light. In the 

 first place, they were simultaneously, exposed, while dry, for 

 certain intervals. The effects were noted, and expressed by 

 numbers, the ozonoscope which had experienced the most 

 striking change, being placed first. They were then moistened, 

 and the results indicated in like manner. Finally, in this 

 moistened condition, they were allowed to remain in the vessel, 

 and their changes noted at the expiration of times indicated in 

 the tables. The effect upon silver is not given, because of its 

 want of sensitiveness, and its inapplicability as an atmospheric 

 ozonoscope. 



* E T. Lowe, Proc. Royal Soc, [12], p. 518. 



