210 Ozone and the Atmosphere. 



exposed to the disturbing influences of the other bodies which 

 may be present in the atmosphere, we found that it was unaf- 

 fected by nitrous acid, if we except one trial in which the 

 paper turned yellow. This was apparently due to some other 

 cause than the formation of peroxide, which is of a brown 

 color. This confirms the result previously arrived at by 

 Bottger.* 



In an atmosphere containing hydrogen peroxide, the thallous 

 hydrate remained white, or if immersed, after having been 

 turned brown by ozone, was bleached. Carbonic anhydride is 

 rapidly absorbed by thallous hydrate, carbonate being formed, 

 which is not decomposed with formation of peroxide in pres- 

 ence of ozone. Thallous hydrate is therefore not applicable to 

 the detection of ozone in the atmosphere, though in the labora- 

 tory, to detect ozone in the presence of nitrous acid, it is of 

 great service.* 



Manganons sulphate is altogether inapplicable as an atmo- 

 spheric ozonoscope, whether dry or moist ; in the former con- 

 dition it was scarcely affected at all, in the latter it occupied 

 one of the lowest places in the scale. That there might 

 be no error, from want of care in the preparation of the salt, the 

 recrystallized sulphate was precipitated from its solution in alco- 

 hol, and used in making the tests. Thinking that the manganous 

 oxide might be more easily converted into peroxide, if it were 

 in combination with a feeble acid like acetic, some manganous 

 acetate was prepared from the former salt by conversion into 

 carbonate and then into acetate. Tests prepared with this salt 

 did not appear more sensitive than those with manganous sul- 

 phate. They had the further disadvantage of being powerful- 

 ly affected in a dilute atmosphere of nitrous acid, turning dirty 

 brown, while the sulphate was little changed. They likewise 

 became light brown in an atmosphere containing a trace of 

 hydrogen peroxide. The manganous sulphate ozonoscopes 

 contained 10 mgrms. of the salt in each square centimeter of sur- 

 face. Of the manganous acetate papers, some were dipjDed in 



* Bottger, Jour. pr. Cheruie, 95, 311. 



t See Lamy, Bull. Soc. Chim., [2], 11, 210; March, 1869. 



