52 
On Vegetable and Animal Analysis « 
Tims we know accurately that a given weight of this 
mixture represents a known weight of hyper-oxygena 
ted muriate, and of the substance which we wish to ana- 
lyse. 
Now in order to finish the operation, nothing more is 
requisite than to make the bottom of the tube red hot : to 
drive off all the air by means of a certain number of balls, 
which we do not weigh, and which we throw in one after 
another ; then to decompose in the same manner a weight 
of them precisely determined, and carefully to collect 
all the gases in flasks full of mercury and gauged before- 
hand. 
If all the flasks are of the same capacity, they will be; 
Hied with gas by equal weights of mixture ; and if we 
examine these gases, we shall find them perfectly identi- 
cal, an evident proof of the extreme accuracy of this me- 
thod of analysis. 
The tube ought to be kept during the whole operation 
at the highest degree of heat which it can support with- 
out melting, in order that the gases may not contain any 
oxy- earbiir e tied hydrogen gas. In all cases the analysis 
ought to be performed over mercury. This is a proof to 
which it is indispensable to subject them : for this purpose 
it is sufficient to mix them with one fourth of their volume 
of hydrogen, and to pass an electric spark into them. 
As they contain a great excess of oxygen, the hydro- 
gen which we add, and of w hich an account must be 
kept, burns as well as the whole oxy-carhuretted hydro- 
gen which they may contain; and we thus acquire the 
certainty that they are no longer formed of any thing but 
carbonic acid and oxygen, which must he separated by 
potash. 
But this necessity of raising the temperature obliges us 
on the other hand to take some precautions in order that 
the stopcock may not be heated. With this view the glass 
