36 7 
of simple alimentary substances, &c. 
ratus, and mode of analysing organic compounds. In the 
first and chief place, there is nothing to be apprehended from 
moisture. Whether the substance to be analysed be naturally 
a hydrate, or in whatever state it may be with respect to 
water, the results will not be affected ; and the great pro- 
blem, whether the hydrogen and oxygen exist in the sub- 
stance in the proportions in which they form water, or whether 
the hydrogen or oxygen predominates, will be equally satis- 
factorily solved, and that (of course within certain limits), 
independently of the weight of the substance operated on.* 
When however it is the object to ascertain the quantities of 
carbonic acid gas and water yielded by a substance, it is, of 
course, necessary to operate on a known weight ; but this 
being once determined, there is no fear, as in the common 
methods, of exposing the substance to the atmosphere as long 
as may be necessary. The hygrometric properties of the 
oxide of copper, as well as its property of condensing air, are 
also completely neutralised, for the whole, at the end of the 
experiment, being left precisely in the same state as it was at 
the commencement, the same condensation of course must 
take place, and any little differences that may exist are 
rendered quite unimportant from the bulk of oxygen gas 
operated on, which of course should, in all instances, be con- 
siderably greater than that of the carbonic acid gas formed. 
Another advantage of this method is, that more perfect com- 
bustion is ensured by it than by any other that I am acquainted 
* It is to be observed, that, throughout the experiments, great care is taken 
that the gases are saturated with moisture ; the errors from this cause are thus ren- 
dered definite, and are easily corrected by tables calculated for the purpose from 
the most accurate data, and which will be given in a subsequent communication. 
