384 
Abstract of Mr Faraday’s Experiments. 
would be. In the course of some days, action had taken place, the water haf 
become black, and changes, probably such as are known to take place in an 
aqueous solution of cyanogen, occurred. The pressure of the vapour of cya- 
nogen appeared to be 3.8 dr 3.7 atmospheres at 45* Fahr. Its specific gravity 
was nearly 0.9. 
44 Ammonia — iWhen dry chloride of silver is put into ammoniacai gas, as dry 
as it can be made, it absorbs a large quantity of it ; 100 grains condensing 
above 130 cubical inches of the gas: but the compound thus formed is de- 
composed by a temperature of 100® F., or upwards. A portion of this com- 
pound was sealed up in a bent tube, and heated in one leg, whilst the other was 
cooled by ice or water. The compound thus heated under pressure, fused at a 
comparatively low temperature, and boiled up, giving olf ammoniacai gas, 
which condensed at the opposite end into a liquid. 
44 Liquid ammonia thus obtained was colourless, transparent, and very 
fluid. Its refractive power surpassed that of any other of the fluids described, 
and that also of water itself. When the chloride of silver is allowed to cool, 
the ammonia immediately returns to it, combining with it, and producing the 
original compound. During this action a curious combination of effects takes 
place : as the cloride absorbs the ammonia, heat is produced, the temperature 
rising up nearly to 100^ ; whilst a few inches off, at the opposite end of the 
tube, considerable cold is produced by the evaporation of the fluid. When 
the whole is retained at the temperature of 80°, the ammonia boils till it is 
dissipated and re-combined. The pressure of the vapour of ammonia is equal 
to about 8.5 atmospheres at 50°. It specific gravity was 0-76. 
44 Muriatic Acid ,-— When made from pure muriate of ammonia and sulphu- 
ric acid, liquid muriatic acid is obtained colourless, as Sir Humphry Davy had 
anticipated. Its refractive power is greater than that of nitrous oxide, but 
less than that of Water ; it is nearly equal to that of carbonic acid. The pres-' 
sure of its vapour at the temperature of 50°, is equal to about 40 atmo- 
spheres. 
“ Chlorine .— The refractive power of fluid chlorine is rather less than that 
of water. — The pressure of its vapour at 60® is nearly equal to 4 atmospheres. 
Mr Faraday has made many similar experiments on other 
gases, But though he has not succeeded in condensing any others 
than those which we have mentioned, yet there is reason to hope 
that he will ultimately succeed with some of them. 
Art. XXXIII . — Analysis of a Black Mineral from Candy , 
in Ceylon . By Dr C. G. Gmelin of Tubingen. (Commu- 
nicated by the Author.) 
1 HIS mineral is very Bard ; it scratches rock-crystal. Its 
colour velvet-black ; its fracture conchoidal ; its lustre glassy. 
12.145 grammes, when weighed in water, experienced a loss 
of 3.65 gr., temp. 17° li. The specific gravity of this mineral 
is therefore 3.617, temp'. -4 17° B 
