Hartiey— Occurrence of Cyanogen Compounds in Coal-Gas. 297 
On examining the liquid it was found to possess a strongly 
ammoniacal odour. On the addition of a few drops of ferric 
chloride and acidifying the mixture with dilute hydrochloric acid, 
there was a voluminous precipitate of Prussian blue, sufficient to 
make some 15 c.c. of liquid thick with the solid substance. 
This completely sets at rest the question of the possibility of 
the lines being due to cyanogen. Irrespective of this evidence it 
should be mentioned that a very peculiar yellow and yellowish- 
green colour tinged the oxy-coal-gas flame in a,manner similar to 
the coloration which may be observed like a halo on the edges of 
the mantle of the peach-blossom coloured flame of cyanogen. This 
at the time seemed to be probably due to the synthesis of cyanogen 
or of hydrocyanic acid by the action of intensely heated hydro- 
carbons in contact with nitrogen. 
It should be stated that, in testing the coal-gas, an alkaline 
solution without the addition of ferrous sulphate did not absorb so 
much of the cyanogen compound, and that plain water gave merely 
a very distinct Prussian blue colour. From this it would appear 
that the substance is either ammonium cyanide or some other 
cyanogen compound that splits up into ammonia and hydrocyanic 
acid. 
It is of no little interest that the presence of cyanogen com- 
pounds in the gas supply of a large city like Dublin should first 
have been indicated by the bands and lines observed in the spectrum 
photographed from the flame of the burning gas. 
