328 Dr Bischof s Examination of Three Inflammable Gases 



throughout its whole extent, was browner than in the former 

 experiment. It adhered strongly to the tube, so that it was 

 extremely difficult to get it out. Water did not remove it, 

 but oil of turpentine was a little more effectual. It could 

 only be scoured out with sand, and even then some dark por- 

 tions remained in the hollows of the porcelain tube. 



What can be the reason, that in this experiment so little 

 carbon was deposited I As all the circumstances were the 

 same, with this difference only, that, in the previous experi- 

 ment, the heated gas could move on without hindrance, where- 

 as in this one it was restrained by a column of sulphuric acid 

 two inches in height, one might be inclined to seek for the 

 cause of the difference of the result, in this difference of cir- 

 cumstances. In fact, by means of the flowing off of the wa- 

 ter from the collecting apparatus, the gas between it and the 

 receiving apparatus must always first be so much rarified, as 

 to be able to overcome the pressure of the acid. 



The flowing through of the gas can, therefore, take place 

 only by jerks, and it must remain longer exposed to the heat 

 of the tube than in the preceding experiment. But other 

 causes can be adduced for this difference of result. 



The greenish little drops of which mention was made above, 

 were partly hardened and partly formed a uniform coating to 

 the ball. It resembled a green-coloured solidified oil. On the 

 sulphuric acid in the first ball, viz., that one turned towards the 

 porcelain tube, a whitish pellicle floated, which, when a move- 

 ment was made, adhered to the inner surface. This pellicle so 

 entirely covered the acid, that it appeared swimming on it like 

 a solid body. Likewise on the mercury which preserved the 

 gas before it reached the apparatus, and also on the under 

 side of the receiver, there was a white covering.* This pel- 



* The absorbing apparatus terminated in a tube a ; and a similarly bent tube, 



r 



