22 6 Mr. Porrett’s experiments relative to the 
from his Paper on the definite proportions in which the ele- 
ments of organic nature are combined, published in Dr. 
Thomson’s Annals of Philosophy for December last. It is to 
this information that I principally attribute the success which 
has attended the experiments of a similar nature, which I have 
made. 
The method pursued by me, however, differs in several 
respects from that of either of the chemists just mentioned, 
ist. In the apparatus employed, which is much more sim- 
ple in my process 
2dly. In the nature of the oxygenised body employed to 
effect the combustion. 
3dly. In the method to which I had recourse, for propor- 
tioning the oxygenised to the combustible body, by making 
the former a multiple of that which enters into chemical union 
with the latter. 
4thly. In decomposing a much less quantity of the com- 
bustible body at a time, than either of the above chemists. 
In the present case, each of these alterations appeared to me 
to possess very decided advantages over the other methods. 
How far they may be applicable to other cases, I do not pre- 
tend to determine. 
Having thus generally stated in what my process differed 
from former ones, I proceed to rather a more particular de- 
scription of it. 
I prepare the peroxide of mercury which I employ, by de- 
composing with pure soda, a solution of corrosive sublimate. 
Having weighed out the proportions of prussiate of mercury, 
and of the peroxide which I intend to decompose, I triturate 
them together in a small polished mortar of porphyry or agate 
