544 M. H. Karsten OH the Oxidation of Gaseous 



In the first experiment, that of leading through the apparatus 

 atmospheric air which had not been heated to redness, the 

 supposition with which I started required that a certain amount 

 of carbonate of lime should be deposited in each vessel, but 

 especially in the first, and, further, that the vessel following a 

 large tube of 200 cubic centims. capacity, which was substituted 

 for one of the small tubes b, should contain more carbonate of 

 lime at the end of the experiment than the vessel immediately 

 preceding it. 



120 litres of air were pressed through the apparatus, a single 

 bubble at a time, so slowly that about 5 litres went through in 

 twelve hours. 



The air used in the experiment was freed from carbonic acid 

 by being passed through three vessels containing hydrate of 

 potash before it came in contact with the lime-water. 



As I have already pointed out*, the white opake precipitate 

 of carbonate of lime does not form (especially in the cold) on the 

 sides of the glass tube where it dips into the lime-water, if only 

 a very small quantity of carbonic acid is contained in the gas 

 which bubbles through the liquid, but only crystals of hydrated 

 carbonate of lime, which collect at the bottom and against the 

 sides of the glass bulbs together with a little gelatinous-looking 

 hydrate of lime. And since the air employed in this case was 

 very strongly dried by being previously passed through a con- 

 centrated solution of potash, it carried away water from the 

 saturated solution of caustic lime, and so occasioned the pre- 

 cipitation of a certain quantity of hydrate of lime. 



When 60 litres of air had been passed through the apparatus, 

 the first tube of the lime-water-vessel immediately following the 

 large tube filled with air showed already the well-known deposit 

 of carbonate of lime, whereas all the other tubes in the apparatus 

 remained free from it even at the end of the experiment. This 

 vessel also contained a larger quantity of crystallized carbonate 

 of lime than the others, in which, however, were distinct (though 

 not weighable) traces of it, recognizable by the evolution of gas 

 bubbles when a few drops of hydrochloric acid were brought in 

 contact with it after the lime-water had been removed by a 

 stream of air free from carbonic acid. 



The result of this one experiment is not alone sufficient to 

 prove the accuracy of the supposition that a continual oxidation 

 of compounds of carbon and hydrogen goes on in the atmosphere. 

 It might be urged that the potash solution was not sufficient to 

 keep back the whole of the carbonic acid already existing in the 

 air, or even that it is altogether impossible to free air completely 

 from carbonic acid by means of lime-water or of solution of 

 * Poggendorff's Annalen, vol. cix. p. 349. 



