256 Determifiation of Nitrogen in Organic Compounds. 



with a flat bottom, (which has been previously slightly warmed,) 

 and with a very gentle movement of tbti^pestle. If these pre- 

 cautions are strictly observed, no loss of material will result by 

 its sticking to the sides of the mortar, or bottom of the pestle. 

 If the mixture be pressed too hard, or if it be rubbed too fine, or 

 if the mortar be not perfectly dry, a portion of the substance will 

 adhere to its sides. After introducing the mixture into the burn- 

 ing tube in the ordinary way, the mortar is rinsed with the alka- 

 line powder, with which we fill the tube to within an inch of its 

 mouth, in which is placed a loose stopper of asbestus that has been 

 heated to redness and cooled." 



The use of the asbestus is to prevent the gas that is generated, 

 from projecting any of the powdered alkali into the apparatus con- 

 taining the hj^'drochloric acid, which accident would of course 

 cause a serious error in the result. 



" With a tight cork we unite the tube containing the mixture 

 to the acid apparatus, and. by warming slightly the bulb a, by 

 bringing an ignited coal beneath it, we are able to ascertain whe- 

 ther the apparatus is tight, for if so, the liquid will be chased from 

 the bulb a. The tube is now heated as in the case of ordinary 

 organic analysis, by placing ignited coals at the front part of the 

 furnace, that contains none of the organic substance. The cork 

 must be kept as warm as possible, so that it may contain no mois- 

 ture, which by absorbing ammonia, may cause a loss of nitrogen. 

 So soon as the first part of the tube is red hot, we carry the fire 

 slowly back upon that part containing the substance." 



"Carbonic acid is formed, the oxygen in the water of the hy- 

 drated alkali combining with the carbon of the substance, the free 

 hydrogen combines with its nitrogen, and ammonia is formed, 

 which is absorbed by the hydrochloric acid. Hydrogen or carbu- 

 . retted hydrogen (according as the substance contains more or less 

 carbon) is evolved, and this passing through the acid without being 

 absorbed, enables us to see the progress of the burning." 



" It may be well to remark, that a continued current of gas is 

 evolved, but there need be no apprehension of the escape of the 

 ammonia, for its absorption is so complete and goes on with such 

 rapidity, that one has rather to apprehend a recoil of the fluid ; 

 if the current of gas is only stopped for a moment, the fluid rises 

 in the bulb a, and if the fire be carelessly attended to, it will 

 enter the tube d, and thence the burning tube, rendering the ex- 

 periment useless." 



