Ml 



OZONOMETER 



OZONOMETEU. 



immediately ascertained by it* blue colour : it i right, however, to 

 add thnt the sufficiency of the tet i< not unquestioned. [OZONE.] 



Schbnbein, who originally described ozone, proposed this tart and 

 made u*e of it, by saturating na)ier with a solution of iodide of potas- 

 sium and starch. As the result of using this paper was to indicate the 

 quantity of ozone in the atmosphere by the intensity of the blue colour 

 produced on the test paper, it was necessary for comparison to use the 

 same test paper; hence Schonbein undertook to supply this paper 

 from his own laboratory, and pieces of I>aper for every day in the year 

 are sold in boxes under the name " Schonbein's ozone test paper." In 

 this country Mr. Moflatt has distinguished himself by his researches 

 in atmospheric ozone, and he also prepares a paper for supplying those 

 who wish to measure the presence of ozone in the atmosphere. With 

 these papers a scale of colour is supplied, each shade of colour showing 

 the action of the ozone on the iodide and starch being marked from 

 to 10 In using this paper a slip is taken and exposed i.i some place 

 to which the air has access, and there it is left for twenty-four hours. 

 At the end of this time the paper is compared with the scale, and 

 according to the intensity of its colour it is marked from to 10. 



Although this method indicates the existence of ozone at some time 

 within the twenty-four hours, it fails to indicate the exact time at 

 which the ozone was present, and prevents also any accurate comparison 

 with other meteorological phenomena, as heat, wind, moisture, &c. 

 In order to render the registration of ozone more accurate, Dr. 

 Lankester has invented an ozonometer, by which a strip of ozone 

 paper 24 inches in length is exposed successively for an hour to the 

 action of the atmosphere. In this way the ozone of each hour can be 

 indicated, and the sum of its effect on the paper more easily ascer- 

 tained. Dr. Lankester's instrument consists of a box (jig. 1} : the 



Section of Lankester's Ostonometcr. 



iodised paper a a n is first carried round the wheel 6, and passed on to 

 the two cylinders cc. When the lid of the box, which is made of 



brass, dd, is down, it covers the whole box except a small space, ea, 

 one inch in length and half an inch in width, which is cut in the lid, 

 and through this the paper a is exposed to the action of the air. The 

 strip, after this exposure, is carried from the cylinders c c to the wheel 

 t, on which it is wound up. The machinery which moves the wheels 

 is precisely similar to that of a clock, and tie instrument is wound up 

 in the same way. The following table will illustrate the method of 

 registering the intensity of the ozone by this instrument : 



The results of ozonometric experiments show that ozone is seldom 

 present in the atmosphere of great cities. It is generally present in air 

 coming from the ocean, and in rural and mountainous districts, where 

 the air is free from the contamination of animal and vegetable mattor. 

 On the sea-coast of Great Britain it appears to be more abundantly 

 present than away from the sea. It has also been observed in larger 

 quantities on the southern and eastern coasts of England when the 

 wind blows from the south, or west, or south-west. As the wind veers 

 from went to north, or from south to east, it diminishes. 



