204 



Ozone and the Atmosphere. 



discovery of a new method of generating ozone. "When potas- 

 sium permanganate and crystallized oxalic acid are pulverized 

 together in a mortar, the heat developed is so considerable as 

 to convert into steam much of the water formed during the 

 course of the reaction. If the salts are introduced into a test- 

 tube, and water added, the escape of gas at first is slow, but it 

 rapidly increases with a corresponding elevation of tempera- 

 ture. Iodo-starch papers held at the mouth of the tube, show 

 the presence of ozone in the escaping gases ; so do those of 

 guaiacum. Potassium iodide is little affected until the tem- 

 perature is kept down by holding the test-tube in cold water, 

 when the amount of ozone liberated is so c onsiderable that the 

 papers turn brown at once. Here, then, we have two solid 

 substances, which may be kept together for any length of time 

 without change, but on the addition of water liberate ozone. 

 The practical as well as theoretical interest of this discovery is 

 such that a careful study of this and similar reactions is now 

 being made. 



Critical Examination of Ozonoscopes. 



Potassium Iodide : — As the potassium iodide manufactured 

 in this country, and sold for chemically pure, has presumably 

 been employed in the preparation of ozone tests by American 

 observers, it was important to examine into its purity. The 

 principal manufacturers are four in number, and their goods 

 were examined with the following results : 



Atalyses of C. P. Potassium Iodide manufactured in the 

 United States. 



SAMPLE. 



REACTION. 



CAKBONATES, 



SULPHATES. 



CHLORIDES. 



IODATES. 



IODINE. 



I. 



II. 

 III. 



IV. 



Alkaline 

 Neutral 



Absent 

 Present 

 Absent 



Absent 

 Present 

 Absent 



Absent 

 Present 



Absent 



Absent 

 Present 

 Absent 



It will be seen from this table, that of the goods purchased 

 at the time the analyses were made, those of but one manufac- 

 turer were free from foreign salts, and had a neutral reaction. 



