326 
SELECTED ARTICLES. 
Now, as the mean quantity of the latter gas is known to be 
loioo °f tne whole, we have, by deducting this, 21.01 for the 
proportion of oxygen. 
100 parts of air, taken from an elevation of 10,000 feet 
above the ocean, contained, after having been deprived of their 
carbonic acid by pure potash, 20.903 parts of oxygen. Air 
collected in a crowded ball room at the theatre in Geneva, was 
found to contain 20.81 per cent, of oxygen, and t 2 q 4 ^ of one 
per cent, of carbonic acid. 
Jour, de Phar. and Bib. Univ. of Geneva. 
ART. LIII.— ON THE PREPARATION OF PROTOIODIDE OF 
MERCURY. By P. H. Boutigny. 
Iodine and its combinations have furnished medicine with 
several energetic preparations. Most of these combinations 
have been studied by chemists and are w T ell known and de- 
fined; I wish, however, to say a few words on the protoiodide 
of mercury. 
This is one of the surest remedies in the treatment of sy- 
philitic affections, few of which resist its influence, though it 
has failed in some instances owing in my opinion to errors in 
its preparation. 
The principal modes which are employed in making it are: 
1st, mixing together one atom of protochloride of mercury, 
and one atom of hydriodate of potassa; this mixture is placed 
in a porcelain capsule and boiling water added; on cooling, 
the precipitate is collected on a filter, washed and dried. 2d, 
precipitating the protonitrate of mercury by means of hydri- 
odate of potassa. 3d, using the protoacetate instead of the 
protonitrate of mercury. Finally, the fourth plan, which is 
the most simple and direct, but also the most liable to error, 
is by triturating together two atoms of mercury and one atom 
of iodine with a little alcohol, till the mercury disappears. 
The protoiodide prepared in this way always contains metal- 
