Hydrocarbon- compounds contained in the Atmosphere, 545 



potash. The latter opinion has in fact been maintained by very 

 able chemists, for example, by Messrs. Eliot and Storer ; and it 

 was with a view of proving the accuracy of it that they under- 

 took the experiments which they have published in the { Pro- 

 ceedings of the American Academy of Arts and Sciences ' for 

 September 1860. 



As has been already stated, these chemists do not appear to 

 have observed the precautions necessary for keeping the air from 

 contact with organic matter during its passage through the 

 apparatus, so that the result of their experiments is affected by 

 a twofold source of error*. The first of these sources of error 

 was avoided in my experiments by disposing the apparatus in 

 the manner already described. The presence of the second was 

 demonstrated by my second experiment, which consisted in 

 passing the air, before allowing it to enter the apparatus where 

 it was washed with potash and lime-water, through a red-hot 

 platinum tube, 1 metre long and 15 centimetres wide, filled 

 with oxide of copper, so as to convert any volatile compounds of 

 carbon and hydrogen which might be contained in it into car- 

 bonic acid and water. 



In this experiment, as in the first, the heated air to be experi- 

 mented upon was passed through three bulb-apparatus, such as 

 that shown in the figure, containing potash before it came in 

 contact with the lime-water. The quantity of air passed through 

 the apparatus was also, as before, 120 litres, and the rate of 

 passage about 5 litres in twelve hours. 



At the end of this experiment all the vessels containing lime- 

 water were found to be perfectly unchanged, except that the 

 quantity of liquid in them was somewhat smaller, and hence a 

 little gelatinous hydrate of lime was deposited in them, but no 



* During the passage of atmospheric air through a caoutchouc tube, the 

 formation of carbonic acid by the oxidation of the caoutchouc takes place 

 to a very considerable extent. I placed at the end of the apparatus above 

 described a piece of so-called vulcanized india-rubber tubing, 1 foot in length, 

 and of the diameter of a raven's quill, which was connected with a bulb- 

 apparatus filled with lime-water, wherein the air, which entered the india- 

 rubber tube free from carbonic acid, was again washed. At the conclusion 

 of the experiment above described, the whole surface of the bulb -apparatus, 

 with which the lime-water came in contact, was covered with crystals of 

 carbonate of lime. In order to form an approximate idea of the quantity 

 of carbonic acid formed in the caoutchouc tube, I allowed a very slow 

 stream of air, deprived of carbonic acid, to flow during fourteen weeks 

 through a caoutchouc tube 3*2 metres in length, and 4 7 millimetres 

 internal diameter, the air as it issued being made to pass through a weighed 

 quantity of solution of potash, and then through a weighed chloride-of- 

 calcium tube as described in PoggendorfPs Annalen, vol. cix. p. .'J4 ( J. At 

 the end of the experiment the potash apparatus and chloride-of-calcium 

 tube had together increased in weight by - 116(> gramme. 



Phil Mag. S. 4. No. 157. SuppL Vol. 23. 2 



