Oil tho Food of Phnts. 
55') 
to a sufTicient extent, tlie gluten is dried and weighed. This is tlie 
method used by Davy in liis analyses. 
Boussingauh,* some years ago, having occasion to make a number of 
sucli experiments, in which accuracy was required, speedily found that 
this method could never be trusted ; he rejected it, and substituted the 
ultimate analysis, assuming from data of his own, that real gluten in a 
])ure and dry state contains 15 per cent, of nitrogen. 
This nitrogen analysis has hitherto, from its difficulty of execution 
and somewhat imperfect results, been the great stumbling-block of 
organic cliemistry: still, it was a happy thought to put it in the place of 
the still more imperfect plan of mechanical se])aration. 
Within the last few months a new mode of determining the nitrogen 
in organic substances has been devised and put into execution at Giessen, 
which promises to be of the greatest advantage to science by reason of 
the facility with which it is conducted, and of the sharp and beautiful 
results it affords ; residts which, so far as I can judge from my own ex- 
periments and those of the authors of the process, MM. Will and Var- 
rentrapp, equal at least in accuracy those of the carbon and hydrogen 
determination. The following is the principle : — When any organic 
substance containing nitrogen, except a nitrate, is heated to redness with 
excess of hydrate of potash or soda, the water of the hydrate suffers de- 
composition, its oxygen attacks the carbon of the substance, and its 
hydrogen the azote, which is thus wholly and entirely converted into 
ammonia. By collecting this ammonia, therefore, and ascertaining its 
weight, we could easily calculate the quantity of nitrogen in a given 
weight of the substance. 
The practice is as follows : — A mixture is made of about two parts 
quicklime and one part hydrate of soda, and reduced to fine powder ; a 
convenient quantity of the organic body is brought to a proper state of 
dryness, weighed and intimately blended with some sixty times its weight 
of the lime and soda mixture. The whole is then introduced into a tube 
of hard Bohemian glass, eight or nine inches long, drawn out to a point 
as in the carbon and hydrogen estimation. To this tube is connected, 
by means of a cork, a little glass apparatus on the principle of a Woulfe's 
bottle, containing dilute hydrochloric acid. 
Arrangements being thus made, the tube is gradually ignited from 
end to end by the aid of a charcoal fire, the ammonia disengaged is 
absorbed by the acid, and the hydrogen, carbonic acid, and other incon- 
densible gases escape. AVhen the operation is ended, the point of the 
tube being broken, air is drawn through the apparatus to sweep out any 
ammonia that may linger in the combustion tube. 
The acid liquid now contains, provided the experiment has been pro- 
perly conducted, the whole of the ammonia generated by the nitrogen of 
the organic substance analysed. It is transferred to a porcelain capsule, 
mixed with a quantity of pure chloride of platinum, and evaporated to 
dryness in a water-bath. Upon the residue is poured a mixture of 
alcohol and ether, which dissolves the excess of chloride of platinum, 
but leaves untouched the yellow double chloride of platinum and ammo- 
Aim. Chim. et Pliys., G5, 301. 
