16 Dr THOMAS THOMSON on a New Combustible Gas. 



ago, when I attempted to substitute pyroxylic spirit for alcohol 

 in some processes which I had occasion to perform during a set 

 of experiments on protoxide of chromium, in which I was at that 

 time engaged. The gas in question may be easily procured by 

 the following process. 



Put into a flask a mixture of 1^ ounce of muriatic acid, half 

 an ounce of the nitric acid of commerce, and half an ounce of py- 

 roxylic spirit, all by measure. By means of a perforated cork in- 

 sert a bent glass-tube into the mouth of the flask. The cork 

 must fit so tight, that nothing can escape from the flask ex- 

 cept through the tube. Heat the mixture over a spirit lamp 

 till it begin to effervesce, and till the colour of the liquid changes 

 to red. The flask must then be withdrawn from the lamp, and 

 the extremity of the bent tube plunged into a mercurial trough. 

 The gas issues in torrents for five or six minutes, and may be 

 collected in any quantity, in glass jars, previously filled with 

 mercury, and inverted on the trough. From the quantity of 

 materials stated above, I think at least 200 cubic inches of the 

 gas are extricated. 



The gas, as it comes over, acts with considerable energy on 

 the mercury ; both calomel and corrosive sublimate being form- 

 ed in abundance. But this is owing to the presence of some 

 chlorine, with which the gas, as it issues from the flask, is mixed. 

 For when we transfer the gas into a clean jar, it may be left for 

 any length of time on the trough, without acting in the least on 

 the mercury, or changing its volume. 



The gas thus obtained possesses the following characters : 



1. It is transparent and colourless, and possesses the mecha- 

 nical properties of common air. 



2. Its smell is exceedingly pungent and disagreeable ; but so 

 peculiar, that I can compare it to nothing else. It acts with 



