112 
Mr. Davy on some 
powder, I was limited to very minute quantities of it ; and I 
made several trials, before I gained any satisfactory evidences 
of its constitution. I decomposed the powder in long green 
glass tubes filled with mercury ; in such cases, by a gentle 
heat, the powder became ignited, the reduced platinum amal- 
gamated with the mercury, a little fluid appeared, and some 
gas was evolved. The fluid reddened litmus, and had an 
acid taste. The gas rendered lime water turbid, and was in 
part absorbed by water and by ammonia ; and the unabsorbed 
portion exhibited properties similar to those of nitrogen. 
These results seemed to prove, that the powder contained 
acid and inflammable matter ; but they were not sufficiently 
uniform to enable me to place much reliance on them. I then 
used very small glass retorts, varying in capacity, from to 
t 7 q of a cubic inch, and decomposed the powder over pure 
water and over mercury ; but the results were most satis- 
factory when I operated over mercury. From two experi- 
ments of this kind, which I beg briefly to detail, as they very 
nearly agree, I think I may venture to state the composition 
of the powder under examination. 
Experiment 1. Ten grains of the powder were decomposed 
in a little retort, over dry mercury, by the heat of a spirit 
lamp. On the first impression of the heat, gas was disengaged, 
and shortly after, the interior of the retort assumed a reddish 
yellow colour (like that exhibited by the vapour of fuming 
nitrous acid), and small drops of a colourless fluid condensed 
in the neck of the retort. After the utmost heat of the lamp 
had been given to the retort, it was suffered to cool, and the 
results were immediately examined. 
