194 On Dimorphism of Arsenic, Antimony and Zinc. 
+ 
existence of these modifications is even more satisfactory evi- 
ence on this point than an actual measurement. 
It is well known that oxyd of antimony is capable of erystal- 
lizing in octahedrons belonging to the monometric system and 
although from the construction of the apparatus it was deemed 
impossible that any sensible amount of air could become mixed 
with the’ hydrogen in the tube, yet in order to remove all doubt 
on the subject, the crystals were exposed to the following rea- 
ents 
A portion of the glass tube covered with crystals was first 
boiled for a long time in water and subsequently treated with 
the strongest liquid hydrochloric acid; but although exposed to 
the action of the acid for several days in a warm room, the crys ; 
tals were not dissolved, They also resisted for some time the 4 
action of boiling hydrochloric acid, but after prolonged boiling 
they disappeared. Exposed to the action of chlorine gas at a very 
gentle heat, the crystals were immediately consumed, leaving no 
residue and rendering the gas cloudy from the fumes of chlorid 
of antimony. Lastly, a portion of the tube (on which was de- 
posited nothing but distinct octahedral crystals), was treated with 
a few drops of nitric acid, and a gentle heat applied. The 
: were at once attacked and the familiar white powder of 
antimonious acid was theresult. This dissolved on adding a few 
drops of hydrochloric acid and the solution evaporated nearly to 
dryness, diluted with a solution of tartaric acid and subsequently 
treated with a solution of sulphid of hydrogen, gave the famili 
red precipitate of sulphid of antimony. 
the metallic mirrors of arsenic and antimony obtained b 
Marsh’s test, the metals seem to be always in the octahedral mod- 
ification, and when deposited slowly are more or less crystalline. 
The author has obtained the best crystals by resubliming the me- 
tallic mirrors, after they were first formed, in a slow current 0 
hydrogen, and it is in this way very easy to obtain the crystals 
entirely isolated on the surface of the glass tube, and in the case 
of antimony the author has traced with the microscope every . 
dation between the distinct crystals and the granular coating, 
which forms the mass of the mirror. The process of crystalli- 
zation in the formation of the mirror is similar to that of sal- 
ammoniac on a glass plate and the lines of erystals shoot out in 
the same way parallel to the axis of the tube. 
Zinc.—In the “Annales de Chimie et de Physique,” vol. xxii, 
been questioned by Gustav Rose* on the grounds first thatthe 
* Poggendorff, Annalen, vol, Ixxxy, 293. os 
