84 Mr Johnston on a solid form of Cyanogen. 



There can remain little doubt, therefore, that the coal ob- 

 tained by Scheele, was one of the carburets of azote above- 

 mentioned ; and the decomposition of uric acid by heat would 

 probably give these substances more abundantly, and with 

 greater ease than either of the methods I have pointed out. 

 Other animal and azotized vegetable products, when decom- 

 posed by heat, may possibly leave similar compounds of car- 

 bon and azote. 



A knowledge of the existence of such compounds will ena- 

 ble us often to state more distinctly the composition of animal 

 and vegetable substances, as well as to reconcile to atomic 

 proportions the presence of small quantities of azote among 

 the other results of analysis, which, as in the case of mineral 

 coal, some chemists have ascribed to the presence of foreign 

 matter. 



The external characters of these two compounds, so similar 

 to those of coal, render more probable also those analyses of 

 the various kinds of this mineral product, which show the pre- 

 sence of a large per centage of azote. Some chemists give 

 only a small quantity of jazote as the result of their analysis, 

 while others find in some varieties, as in that of Newcastle, no 

 less than 16 per cent. This estimate may probably be too 

 high, yet, if one might judge from appearance, that of the bi- 

 carburet would justify us in assigning to some varieties of coal 

 a still larger proportion of azote. The slow combustion of 

 these compounds, however, would lead us to expect much less 

 azote in the caking coal of Newcastle, than in some of the less 

 inflammable species called by mineralogists non-bituminous 

 coal. The progress of analysis will probably soon put us in 

 possession of results agreeing more with each other, and upon 

 which, therefore, more entire reliance can be placed than upon 

 those hitherto published.* 



Edinburgh, \^th April 1829. 



• The experiments above detailed were performed in a small tube ap- 

 paratus, the cubical contents of which were from .3 to .5 of an inch. In 

 separating the gases, the carbonic acid was absorbed by caustic potash ; 

 the oxygen in the unabsorbed portion estimated by deutoxide of azote, 

 after the method of Gay-Lussac, and the residue, allowing for the common 

 air, was considered to be azote. 



