Method of determining Nitrogen in Organic Compounds. 221 



bonic acid, in order that sufficient hydrogen be set free to form 

 ammonia with the vvhole of the nitrogen ; and we are not ac- 

 quainted with a single nitrogenous organic substance in which 

 the nitrogen is not present in the form of nitric acid, that does 

 not contain carbon at least sufficient for this purpose. To the 

 last class belong niellon, mellamin, &c. ; these also give, as 

 well as the sulphuret of cyanogen, perfectly accurate results if 

 the following precaution be taken. As in this case the greater 

 part of the air is expelled from the tube by the first action of 

 the heat, nearly pure ammonia is given oft', which is absorbed 

 with such violence by the acid, that let the bulb next the tube 

 be ever so large, a returning back of the acid is scarcely avoid- 

 able. This evil is easily remedied by adding about an equal 

 weight of some organic substance free from nitrogen (sugar 

 for instance) to the substance to be analysed. This affords 

 permanent gases by its decomposition, which dilute the am- 

 monia and render its absorption by the acid less rapid. After 

 the tube has been gradually brought to redness the whole of 

 its length, and the evolution of gas has entirely ceased, which 

 occurs when all the carbon has become oxidized and the mix- 

 ture again appears white, the extreme erect point is broken 

 off", and a current of atmospheric air drawn through the ab- 

 sorbing apparatus, that the au)monia still in the tube may be 

 condensed. In doing this a lube containing potash is fixed 

 on to the extremity of the absorbing apparatus by which the 

 air enters ; this perfectly secures it against acid vapours which 

 may accompany the current of atmospheric air. The be- 

 coming white of the mixture in the tube is of importance, as 

 ammonia in contact with alkali and carbon, at a high tempe- 

 rature, easily forms prussiate of ammonia, which would cause 

 a loss of nitrogen in the analysis. All the carbon, however, 

 is burnt when sufficient heat is employed, and not the least 

 fear need be entertained of the formation of cyanogen. 



Such is the course to be followed in the conversion of nitro- 

 gen into ammonia with solid organic bodies. The number of 

 fluid nitrogenous substances is not very considerable, and 

 their combustion offers no difficulties. Some of the mixture 

 is first introduced into the tube, then a small bulb with a 

 known quantity of substance, the point of which has been 

 broken off' previous to its introduction; the remainder of the 

 tube is filled with the alkaline mixture and asbestos. When 

 tlie first third portion of the tube has been heated to redness, 

 it is best to drive a portion of the substance out of the bulb 

 by means of a glowing coal ; it is then diffused in the midille 

 portion of the tube and is burnt gradually. 



When the burning is finished, the contents of theabsorbino- 



