Intelligence and Miscellaneous Articles. 545 



cause in the state of mechanical aggregation of oxygen atoms, a 

 course which is certainly not ver)^ probable in my case, as I enter- 

 tain doubts as to the correctness of the dogmas of our modern 

 atomic doctrines. — Journ. fiir prakt. Chem. 1852. 



ON THE QUANTITATIVE DETERMINATION OF OZONE. 

 BY C. F. SCHONBEIN. 



Since ozone combines even in the cold with silver forming per- 

 oxide, while ordinary oxygen behaves indifferently towards this 

 metal, I have endeavoured to determine the quantity of ozone in a 

 given volume of air by means of the peroxide of silver formed. 



If, for example, 60 litres of artificially ozonized air afforded 100 

 milligrms. of peroxide, I assumed that it contained 13 milligrms. of 

 ozone, presupposing that ozone was nothing more than allotropic 

 oxygen. 



This method, besides its tediousness, is otherwise objectionable, 

 and I endeavoured to discover a more convenient process, in which 

 I believe I have succeeded. Instead of silver I employ a solution of 

 indigo in sulphuric acid ; and numerous experiments have convinced 

 me that this reagent admits of accuracy and rapid operation, for the 

 quantity of ozone in several litres of air may be determined by it 

 within a few minutes, even to a small fraction of a milligramme. 

 This method depends upon the property possessed by ozone of de- 

 colorizing the indigo solution, a property which ordinary oxygen 

 is altogether destitute of ; and, likewise, upon the fact that the most 

 minute quantity of this solution colours a large volume of water. 

 The strength of the indigo solution, which I find the most con- 

 venient, is when 10 grammes of it are decolorized by 1 milhgrm. of 

 oxygen. 



In preparing this test solution, I take 100 grms. solution of indigo 

 prepared according to Berzelius's directions, add an equal quantity 

 of hydrochloric acid, and heat the whole until it boils. I then add 

 to the hot liquid small portions of a dilute solution of chlorate of 

 potash of known strength (one per cent.), shaking the mixture 

 continually until it has become brownish yellow. If, for example, 

 100 milligrms. of chlorate have been employed to decolorize the 

 indigo solution, I infer that this effect has been caused by the 39 

 milligrms. of oxygen contained in that quantity of the salt, and 

 consequently that 1 milligrm. of oxygen is capable of decolorizing 

 10039 grms. of the solution of indigo. To render this solution of 

 such a strength that exactly 10 grms, of it are decolorized by 

 1 milligrm. of oxygen, I mix 100 parts with 290 parts of water and 

 preserve it in stoj)i)ered bottles. 



In order to determine the quantity of ozone in a flask of air con- 

 taining for example 30 litres, and acted upon to the greatest pos- 

 sible degree by phosphorus, I pour 300 grms. of the test-solution 

 into a glass, and add about one-half to the gas at once. The closed 

 flask is then shaken for some minutes, and a small quantity of the 

 liquid poured out to see if it is decolorized. If so, I dip a small 



Phil. Mag. S. 4. No. 28. Suppl. Vol. 4. 2 N 



