Transactions of the Kansas 



atmosphere. Tlie extent to which this paper is blued by tlie action of the caustic 

 potassa produced affords a basis for determining the amount of atmosplieric Ozone 

 present. 



For my own uses, however, I have preferred a test of Schonbein's own devising. 

 It is dependent on the well-known property which free Iodine possesses of turning 

 starch an intense blue color; a reaction so delicate that it will detect one part in a 

 million. In the manufacture of the test paper I use the proportion, 1 part of Potas- 

 sium Iodide to 10 of starch ; first, boiling the starch in an excess of 200 parts of 

 distilled water, and, when the mixture is cold, adding the Potassium Iodide. In 

 this, strips of unsized paper are soaked and afterward dried carefully in the dark 

 and in air as absolutely free from impurities as possible. As a basis of comparison 

 I employ a color scale, by which the proportion of Ozone, varying from the merest 

 t-race to an abundant presence, is indicated by a series of ten corresponding blue 

 colors, gradually deepening from the first to the tenth. Now, on exposing a slip 

 of this prepared paper to the action of the atmospheric Ozone for a period of twelve 

 hours, free Iodine will become liberated in it to an extent proportionate to the quan- 

 tity of Ozone in that atmosphere. If the exposed slip be then dipped in water, a 

 blue color from the resulting action of the Iodine upon the starch will then be pro- 

 duced, and by comparing this with our color scale the number of the corresponding 

 color may then be recorded as the result of the observation. Thus a basis is formed 

 by which observers in different countries are enabled by the use of these numbers 

 to compai'e the results of their investigations. As a necessary precaution the test 

 paper must be preserved in the dark, as the action of intense light itself will in time 

 decompose the Potassium Iodide. When exposed also it must be carefully protected 

 from violent wind, from direct sun-light or even from directlj' reflected sun-light. 

 This I find is easiest to accomplish by suspending the slip in a plain wooden box 

 without bottom and drilled abundantly with holes to allow a free access of air. 



Employing this test of Schonbein's as a basis, the observations upon the quantity 

 of Ozone, which for the year past have been in progress at the Agricultural College,, 

 have been most interesting and gratifying. They have established beyond a doubt 

 the existence of an abundance of Ozone in the atmosphere of Kansas. While such 

 observations can of course prove of value only when extended through a long 

 period of years, results of great interest have already been obtained. Two series 

 of daily observations have been made. First, a day observation, the result obtained 

 by exposing tlie paper from 7 a. m. to 2 p. m. Second, a night observation, tlie 

 result of which is best obtained by an exposure from 9 p. m. to 7 a. m. The rela- 

 tions of the two are well shown in the means of the observations for the month of 

 January. The average of the day records for this month was 6.03 ; that of the night 

 7.50. In four observations for the night records of January, the scale gave the max- 

 imum number 10. During the succeeding months these numbers slowly decrease. 

 For the month of May, for instance, the daily average has become 5 ; for tiiat of 

 July it has fallen to 3.53; in August, to 3.77; while in September it has again risen 

 to 4.75; and thus it will go on increasing until the succeeding January. Moreover, 

 during the summer months the difference between the day and night observations 

 becomes less and less, those of the day sometimes even exceeding those of the night. 



Probably one of the most extensive series of observations of this character in the 

 United States has been that conducted by the Chemical Department of the State 

 Agricultural College of Michigan, and I have been much interested in noticing by 

 comparison how uniformly the results obtained in Kansas exceed those of Mich- 

 igan. I liere append a table giving the means of the day and night observations in 



