on the fixed Alkalies. 
39 
taking the spark, and a black film from the mercury appeared 
on the sides of the tube. It was probable that some ammonia 
had been absorbed by the metallic oxides both upon the iron 
and the mercury, which might again have been given out in 
the progress of the operation. 
I now used recently distilled mercury, which did not leave 
the slightest film on the glass tube, and wires of platina. The 
ammonia had been exposed to dry caustic potash, and proved to 
be equally pure with that mentioned in page 36. 60 measures of 
it, each equal to a grain of water, were electrized till no farther 
expansion could be produced, the gas filled a space equal to 
that occupied by 1 08 grains of water. The thermometer in 
this experiment was at 56°, and the barometer at 30.1 inches. 
The wire of platina transmitting the spark was slightly 
tarnished.* The 1 08 measures of gas carefully analyzed, were 
found to consist of 80 measures in volume of hydrogene, 
and 28 measures of nitrogen e. 
o 
The results of an experiment that I made in 1799,‘f give 
the weight of 100 cubic inches of ammonia, as 18.18 grains 
at the mean temperature and pressure. I had reasons however 
for suspecting that this estimation might be somewhat too. 
low, and on mentioning the circumstance to Messrs. Allen 
and Pepys, they kindly undertook the examination of the 
subject, and Mr. Allen soon furnished me with the following 
data. “In the first experiment 21 cubic inches of ammonia 
weighed 4.05 grains ; in a second experiment the same quantity 
weighed 4.06 grains, barometer 30.65. thermometer 54 0 
Fahrenheit.” 
* This most probably was owing to oxydation. When platina is made positive in 
the Voltaic circuit in contact with solution of ammonia, it is rapidly corroded. 7 his 
is an analogous instance. 
■\ Researches Chem. and Phil. p. 62. 
