271 
SCIENTIFIC SUMMARY, 
CHEMISTRY. 
Synthesis of Ammonia. — Mr. G. S. Johnson, having observed the forma- 
tion of traces of ammonia while passing nitrogen gas over freshly hydro- 
genized copper at a red heat, was induced to make further experiments. He 
passed a mixture of hydrogen and pure nitrogen over spongy platinum at a 
low red heat. The hydrogen was produced first and passed through silver 
nitrate and sulphuric acid, over pumice moistened with sulphuric acid, 
through Nessler’s reagent, and finally over the spongy platinum. The plati- 
num having been heated to redness in the hydrogen, and the absence of am- 
monia proved, nitrogen was evolved from ammonium nitrite and passed 
through the apparatus with the hydrogen. When the mixed gases reached the 
hot platinum, ammonia was formed, characterized by its odour, by its render- 
ing the Nessler reagent brown, and red litmus blue, and producing white fumes 
with hydrochloric acid. 5'9 milligrammes of NH 3 were produced per hour in 
this way. Objections having been raised to this process, on the ground that 
the vapour of some ammoniacal salt might be carried through the apparatus 
by the rapid stream of gas, Mr. Johnson made further experiments. Hy- 
drogen was passed through the apparatus and over the spongy platinum, heat- 
ing the latter until it gave off no ammonia ; the platinum was then allowed 
to cool, and a current of nitrogen was passed through to displace the hydrogen, 
with the intention of heating the platinum afterwards in pure nitrogen, so 
that the ammonia salt, if present, might be dissociated and yield its ammonia. 
On the admission of the nitrogen to the cold platinum, however, ammonia 
was produced to the amount of 24 milligrammes in an hour. To avoid all 
chance of error, the author repeated the experiments with nitrogen obtained 
from atmospheric air, but without success; nor was any ammonia produced 
when 'the nitrogen evolved from nitrite of ammonium was passed over 
Seated copper before being brought in contact with the platinum. Hence 
it was to be inferred, either that the contact with the copper produced 
an inactive condition of the nitrogen, or that some nitrogen oxide present 
in the nitrogen was removed by the hot copper. The nitrogen produced 
from ammonium nitrite was found to contain some nitric oxide, to 
Remove which it was passed through ferrous sulphate, and then, to test its 
purity, through a tared tube containing freshly reduced copper heated to red- 
ness. When the gas has passed over a sufficient length of the ferrous 
