On Vegclalle and Animal Analysis. 63 



which we do not weigh, and whii-h 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 beforehand. 



If all the flasks are of the same capacity, they will be 

 filled with gas by equal weights of mixture; and if we 

 examine these gases, we shall find them perfectly identical, 

 an evident proof of the extreme accuracy of this method 

 of analysis. 



The tube ought to be kept during the whole operation at 

 the highest degree of heat which it can support without 

 melting, in order that the gasesiiiay not contain any oxy- 

 carburetted hydrogen gas. In all cases the analysis ouo-ht 

 to be performed over mercury. This is a proof to which it 

 is indispensable to subject them : for this purpose it is suf- 

 ficient to mix them with one-fourth of their volume of hy- 

 drogen, and to pass an electric spark into them. As they 

 contain a ^reat excess of oxygen, the hydrotien which 

 we add, and of which an account must be kept, burns as 

 well as the whole oxy-carburetted hydrogen which thev 

 may contain ; and we thus acquire the certainty that they 

 are no longer formed of any thing but carbonic acid and 

 oxygen, which must be separated by potash. 



But this necessity of raising the temperature obliifes us 

 on the other hand to take Ron)e precautions in order that 

 the stop -cock may not be healed. \Viih this view the 

 glass tube is passed through a brick to ^vhich it is fastened 

 with clay, and which at the same time gives solidity to the 

 apparatus: besides this, we must solder to the body of the 

 stop-cock a small hollow cylinder in which water is put, 

 or rather ice. 



Wc have thus all the necessary data for knowino- the 

 proportion of the principle* of the vegetable substance: we 

 know how much of this substance has been burnt, since wc 

 have the weight of it to a denii-miltigramme: we know 

 how nuich oxygen is wanted to trai:s!oim it into water 

 and into carbonic acid, since the quantity of it is given by 

 the diffeience which exists between that contained in the 

 hyper-oxygenated muriate and that contained in the nascs; 

 lastly, we know how nuich carbonic acid is formed, and 

 we calculate how nuich water ought to be furn-ed. 



By following the same order of analysis, we also succeed 

 in delcrnn'ning the proportion of ttie constituent principles 

 of all the animal substances. But as these substances con- 

 tain azote, and as there would be a formation of nitrous 

 acid gas, if we employed an cjccess of hyper-oxyiienaled 



muriate 



