Journal of 



Applied Microscopy 



and 



Laboratory Methods. 



VOLUME IV. MARCH, 1901. NUMBER 3 



MICRO-CHEMICAL ANALYSIS. 

 XL 



AMMONIUM. 



The salts of the radical NH^ resemble so closely, in their behavior, those 

 of the alkalies that it is more convenient to discuss ammonium in connection with 

 the elements of Group I than under the head of Nitrogen. 



As has already been seen from the preceding work, ammonium reacts with 

 most of the reagents used for the detection of potassium, rubidium, and cesium. 

 Hence it is usually not practical to test for ammonium directly in the substance. 

 It follows, therefore, that it is generally necessary to first volatilize the ammonia 

 and test for this substance after its separation. 



Although the salts of ammonium are easily driven of¥ by heat, any attfempt to 

 sublime them and then to test the sublimate will be found unsatisfactory. A far 

 better plan is to expel the NH, by the action of an alkali and heat and to absorb 

 the evolved gas in dilute acid. The method of procedure is as follows : 



Place in a deep 25 mm. watch glass a tiny bunch of fibrous asbestos which 

 has just been ignited to redness by being held, with the forceps, in the flame of 

 the Bunsen burner.- In the absence of asbestos, a tiny piece of thick filter paper 

 can be employed, but in this case the paper must be tested for ammonia. 



On the absorbent place a small amount of the substance to be tested and 

 sufficient water to just thoroughly moisten the mass, but no more. Now add a 

 fragment or two of sodium hydroxide so as to obtain an alkaline reaction. Invert 

 over the watch glass thus prepared, a glass slide bearing at its center a minute 

 drop of water acidified with hydrochloric acid. 



Hold the watch glass thus covered (by grasping 

 its edges between the thumb and fore-finger) over a 

 small flame (see diagram, Fig. 39) so as to expel the 

 ammonia. The heating is kept up until the slide 

 becomes bedewed with moisture. Heating to boil- 

 ing should be avoided, since in such cases there is 

 danger of some of the contents of the watch glass 

 spirting upon the slide. Pm ^g 



(1189) 



