368 HYDROBROMIC AND HYDRIODIC ACIDS. 
ART. XC. — ON THE PREPARATION OF HYDROBROMIC AND 
HYDRIODIC ACIDS. 
By C. H. Mene. 
Hitherto hydrobromic and hydriodic acids have been 
prepared by decomposing the phosphorets of bromine and 
iodine by a small quantity of water. Now without men- 
tioning the considerable loss of substance, the serious and 
frequent accidents which occur in this reaction frequently 
prevent chemists from preparing these gases, and conse- 
quently from studying their properties. The means recently 
proposed, as the essential oil of lemon, napthaline, being 
either rare, expensive or of difficult preparation, I have 
considered it of sufficient importance to describe a new 
method of preparation, which I have recently employed 
with success, and which presents no danger, and is not 
accompanied by any loss. 
To liberate hydrobromic acidgas, I employ the crystal- 
lized hypophosphite of lime obtained in the preparation of 
phosphuretted hydrogen from phosphuret of calcium. It is 
placed in a flask or retort with a small quantity of water ; 
after which I add, by means of a long funnel, some liquid „ 
bromine 5 the reaction takes place instantly, without the 
assistance of heat, and hydrobromic acid is disengaged, and 
may be collected over mercury. It is merely requisite to 
place in the neck of the retort or the flask some pieces of 
cotton or of amianthus, in order to retain any bromine 
vapor which might be volatilized by the heat. The reac- 
tion of the bromine upon the hypophosphite of lime in pre- 
sence of water will be easily understood ; the water is de- 
composed, 4 parts of oxygen pass to the hypophosphite of 
lime, converting it into neutral phosphate, and the 4 parts 
of hydrogen are transferred to the bromine, forming hydro- 
bromic acid : — 
4Br+PhO,CaO+4HO=Ph0 5 CaO + 4HBr. 
