86 



CHEMISTRY FOR AGRICULTURAL STUDENTS 



Is ammonia set free ? Fit up the apparatus figured. Fill the 

 U tube with small lumps of quicklime to serve as a drying 

 agent. In the Florence flask place a 

 mixture of 20 grams of powdered 

 sal - ammoniac with twice its weight 

 of powdered quicklime, then fill up 

 the flask with lumps of quicklime, 

 and, having connected the U tube, 

 warm gently. Collect the gas in an 

 inverted jar by upward displacement 

 Note the colour, smell, and lightness of the pure 

 ammonia. Of its two component gases, neither are supporters 

 of combustion, and hydrogen alone is combustible. Examine 

 the properties of ammonia in these respects. Pass a rapid 

 stream of the gas into a flask containing a little cold water. 

 Is it soluble? Prepare a saturated solution. Neutralise a 

 little of the solution with hydrochloric acid, and evaporate 

 to dryness. Is sal-ammoniac left? 



Fig. 38. 



of air. 



With respect to the combustibility of ammonia, it must be remembered 

 that while heat will be produced by the combustion of the hydrogen, heat 

 must first be absorbed in order to decompose the ammonia into its elements. 

 Hence, while there is a tendency for the gas to burn while the lighted taper 

 is held at the mouth of the jar, the combustion immediately ceases when 

 the heat of the burning taper is removed. 



Determine the relative density of ammonia gas by means of 

 the density flask (Fig. i). To do so recharge the ammonia 

 apparatus and attach a second U tube filled with quicklime to 

 dry the gas thoroughly. Pass a slow stream of the ammonia 

 into the top of the density flask until the gas issuing from the 

 long tube is completely soluble in water. Compare the 

 density (i) with air as unity, and (2) with hydrogen as unity. 



Ammonia differs from the bases so far considered in not 

 being an oxide. Its action on acids to form salts must there- 

 fore be different from that of caustic potash or caustic soda. 



