306 Dr. Pearson's Experiments for 
(b) These three grains (a) being placed upon an iron plate, 
red hot, again emitted a little green and blue flame, with 
the like, but a weaker smell than before ; the substance re- 
maining continued ignited but a few seconds of time, though 
the iron was red hot much longer. The residuum, which 
was black, weighed two grains and a half. 
(c) The residuum ( b ) was exposed in a silver spoon red hot ; 
it soon ignited, and sparkled ; but though this heat was applied 
six minutes, on cooling, a blackish matter remained, which 
weighed 1,3 grains. 
(d) The 1,3 grains of residue (c), under the flame applied 
with the blow-pipe, gave some indications of fusion, yet it re- 
mained black : but 
(e) Being thrown into boiling nitre, a slight detonation ensued; 
this salt was not coloured by it, and it was dissolved in water, 
leaving scarcely a visible quantity of matter upon the filter. 
I think I may safely conclude that but a small part of these 
ten grains of residue was charcoal : and as the proportion is 
so much smaller than has been shown to be afforded by an 
equal weight of alkali saturated with carbonic acid, this ex- 
periment confirms the conclusion, that the charcoal produced 
in the preceding experiments is from the decomposition of 
that elastic fluid. The small quantity of charcoal in the above 
ten grains of residuum was, perhaps, intimately mixed with 
phosphorus and alkali ; but more experiments are required to 
determine satisfactorily the nature of this compound. 
To corroborate the inference concerning the source of the 
charcoal above described, I add, that not a grain of it was 
produced by applying phosphorus to vegetable alkali and fos- 
sil alkali saturated with vitriolic and marine acid. 
