408 Berzelius on a new Mineral Body, [JuneE, 
microscope both surfaces present a crystalline aspect; that of 
the upper surface is irregular, but on the under surface it is easy 
to distinguish the small faces of crystals with right angles, which 
appear cubes or parallelopipeds. In the liquid we sometimes 
find the selenium deposited on the sides of the vessel below the 
surface of the liquid. In that case there is formed a kind of 
metallic vegetation, which, when viewed through a glass, appears 
composed of prismatic crystals, terminated in pyramids; but 
always too small to enable us to determine the figure with 
recision, 
The colour of selenium varies a good deal, I have said that 
when rapidly cooled, its surface has a very dark brown colour, 
and that its fracture has the colour of lead. If by means ofzinc 
or of sulphurous acid we precipitate it cold from a diluted solu- 
tion, it assumes a cinnabar red colour; and if we boil the liquid 
with the precipitate, this last diminishes in bulk, and becomes 
almost black. If we mix an aqueous and very weak solution of 
selenic acid with sulphite of ammonia, or with sulphurous acid, 
in a glass which is only half filled with it, and expose it to the 
light, the sulphurous acid gradually reduces the selenium, and 
the liquid becomes covered with a brilliant pellicle, which, after 
some days, assumes the lustre of a pellicle of gold, If we remove 
it by a piece of paper or glass, and allow it to dry on these 
bodies, 1t resembles a pale gilding, and preserves the appearance 
without alteration. 
The powder of selenium has a deep red colour, but it sticks 
together readily when pounded, and then assumes a grey colour 
and a smooth surface, as happens to antimony and bismuth. In 
very thin coats selenium is transparent, with a ruby red colour. 
When heated, it softens ; and at 212° it is semiliquid, and melts 
completely at a temperature a few degrees higher. During its 
cooling, it retains for a long time a soft and semifluid state. 
Like Spaniah wax it may be kneaded between the fingers and 
drawn out into long threads, which have a great deal of elasti- 
city, and in which we easily perceive the transparency when they 
are flat and thin. These threads viewed by transmitted light 
are red; but by reflected light they are grey, and have the 
metallic lustre. 
When selenium is heated in a retort, it begins to boil at a 
temperature below that of a red heat, It assumes the form of 
a dark yellow vapour, which, however, is not so intense as that 
of the vapour of sulphur; but it is more intense than chlorine 
gas. The vapour condenses in the neck of the retort and forms 
black drops, which unite into larger drops, as in the distillation 
of mercury. 
If we heat selenium in the air, or in vessels so large that the 
vapour may be condensed by the cold air, a red smoke is 
formed, which has no particular smell, and which is condensed 
in the form of a cinnabar red powder, yielding a species of 
