METHOD OF KJELDAHL 347 



after this he attempted to extend the method so as to estimate 

 the quantity of proteid matter in a sample by treatment with an 

 alkaline solution in presence of the permanganate salt. One gram 

 of the finely pulverized sample was treated in a liter flask with 

 one-tenth normal potash lye. According to the supposition of 

 Wanklyn, pure albuminoid matters thus treated yielded o.i of 

 their weight of ammonia, or about 50 per cent, of the total nitro- 

 gen appeared as ammonia. The ammonia content of the sample 

 was determined by the colorimetric process devised by Nessler. 

 It is needless to add that the process of Wanklyn proved to be 

 of no practical use whatever, acting differently on different al- 

 buminoid matters, and even on the same substance. No other 

 attempt was made to perfect the moist combustion process until 

 Kjeldahl introduced the sulfuric acid method in 1883. The sim- 

 plicity, economy, and adaptability of this method have brought it 

 into general use. At first the process was only applied to organic 

 nitrogenous compounds in the absence of nitrates, but especially 

 by the modifications proposed by Asboth, Jodlbauer, and Scovell 

 it has been made applicable to all cases, with the possible exception 

 of a few alkaloidal and allied bodies. The moist combustion pro- 

 cess for determining nitrogen is now generally employed by 

 chemists in all countries, not only for fertilizer control, but also 

 for general work. 



309. The Method of Kjeldahl. The process originally pro- 

 posed by Kjeldahl is applicable only to nitrogenous bodies free 

 of nitric nitrogen. The principle of the process is based on the 

 action of concentrated sulfuric acid at the boiling-point in de- 

 composing nitrogenous compounds without producing volatile 

 combinations and the subsequent completion of the oxidation by 

 means of potassium permanganate. The original process has 

 been modified by many analysts, but the basic principle of it has 

 remained unchanged. It will, therefore, prove useful here to 

 describe the process as originally given. 97 



The substance is placed in a small digestion flask of resistant 

 glass. Liquids which are not decomposed on heating are evap- 

 orated in a thin glass dish, which can be ground up and placed 



7 Zeitschrift fur analytische Chemie, 1883, 22 : 366. 



