The Literature of Ozone, etc. L4S 



not take place with pure oxygen until a pressure of 300 atmo- 

 spheres is attained. The ozone must be compressed slowly and 

 with constant cooling, otherwise it will explode with evolution 

 of heat and light. By mixing the ozone with carbon dioxide. 

 and then submitting the mixture to great cold and pressure. 

 Hautefeuille and Chappuis succeeded in obtaining a deep blue 

 liquid, the blue color being due to the liquefied ozone. 



The same observers have studied the absorption-spectrum of 

 ozone, and accurate measurements of the same have been made by 

 \V. N. Hartley. The latter has extended the research to the ab- 

 sorption of certain parts of the sun's rays by atmospheric ozone. 

 By this new optical method he has arrived at the conclusions — 

 1st. That ozone is a constant constituent of the upper atmo- 

 sphere. 2d. That it is present in larger amounts in the upper 

 than in the lower part of the earth's atmosphere. 3d. That it 

 is the cause of the blue color of the sky. 



IV. Atmospheric Ozoxe. 



In a former paper published in the Annals of the Academy, 

 "Upon Ozone and the Atmosphere," I have detailed at length 

 the experiments by which I sought to show that the so-called 

 ozonoscopes, such as Schonbein's potassium iodide starch-papers, 

 and Houzeau's potassium iodide and litmus papers, were of no 

 value as tests for ozone per se, since they were equally affected 

 by hydrogen peroxide, which is also present in the air. Schone 

 has arrived at the same results. But he has also shown that whilst 

 even thallium papers are of no value as ozonoscopes, they are of 

 value in the determination of atmospheric hydrogen-peroxide by 

 exact chemical methods. Thus at the very time when the esti- 

 mation of atmospheric ozone by any known chemical method 

 had been found impossible, the researches of Hautefeuille, Chap- 

 puis and Hartley pointed out an entirely unlooked-for means of 

 overcoming the difficulty. But as yet the practical utilisation 

 of their discovery, and the influence of moisture, hydrogen per- 

 oxide, and other constituents of the atmosphere, in confusing or 

 rendering difficult the observation of the ozone absorption-spec- 

 trum, have not yet been made known. 



Hobokkn, December 15, 1883. 



