40 
SELECTED ARTICLES. 
not without difficulty, and always require a series of correc- 
tions for temperature, pressure, and the hygrometric condi- 
tion of the gas. It appears to me to be preferable to receive 
the chlorine in a clear solution of sulphurous acid, mixed with 
muriate of baryta. The sulphate of baryta, which is the re- 
sult of the reaction of the chlorine upon the solution, will 
serve to designate the corresponding quantity of oxygen. 
The operation is to be performed in the following manner: 
The substance under examination is to be powdered very fine, 
especially if it be attacked with difficulty, and mixed with a 
known weight of oxide of manganese. The quantity of oxy- 
gen likely to be absorbed, may be nearly estimated before- 
hand, and by doubling the quantity of manganese which may 
be supposed sufficient to furnish the necessary oxygen, we 
may be satisfied that we will obtain a complete solution of the 
metallic matter. The operation is to be conducted in nearly 
the same manner as the analysis of the minerals of manganese 
themselves, only it is proper to carry on the process more 
slowly, so that time may be allowed for the brown solution 
of manganese to act upon the substance to be analysed. When 
the solution is finished, and all the chlorine has passed into 
the vessel containing the liquid sulphurous acid, an excess of 
muriate of baryta is to be added, and the excess of sulphurous 
acid driven off by boiling; the sulphate of baryta precipitated 
is then to be separated by a filter, calcined and weighed. 
One atom of sulphate of baryta, 1458.09 is equivalent 
To one atom of oxygen, 100. 
And to two atoms of chlorine, 442.64 
We should know, in advance, the quantity of sulphate of 
baryta which the oxide of manganese should produce by 
itself; the difference will correspond to the quantity of chlo- 
rine, and to the quantity of oxygen remaining in the metallic 
solution. 
One gramme of pure peroxide of manganese loses 0.18 of 
oxygen when reduced to protoxide; it will consequently pro- 
duce 2 gr. 62 of sulphate of baryta. 
