AMMONIA DERIVATIVES— ALKALOIDS AND AMIDES i6i 



wash the ethereal solution by shaking with a little water, and 

 finally pour into a dish and evaporate off the ether over warm 

 water. Moisten the white residue with water, and test its 

 alkalinity with red litmus paper. 



These reactions show that in all chemical respects an 

 alkaloid behaves like ammonia. The reactions may be 

 expressed as follows. Since quinine has the complex molecular 

 formula C20H24N2O2, it is symbolised in the equations by the 

 letter A. 



A2.H2S04 + H2S04 = 2(A.H2S04) 



like (NH3)2.H2S04 + H2S04- 2(NH3.H2S04) ; 

 A.H2SO4 + 2NaOH = A + Na2S04 + 2H2O 



like NH3.H2SO4 + 2NaOH = NH3 + Na2S04 + 2H2O. 



The ammonia derivatives in which hydrogen has been re- 

 placed by an acid radicle are termed amides. To this group 

 belong caffeine or theine, the stimulating constituent of tea and 

 coffee; the theobromine of cocoa; asparagine, an abundant 

 constituent of asparagus and many root crops ; and the uric acid 

 of urine. 



Another amide is the urea or carbamide, CO(NH2)2, of urine. 

 Evaporate half a liter of urine to about one quarter its bulk, 

 and after cooling add nitric acid until crystals of the nitrate 

 of urea begin to separate. Allow to stand, till the precipita- 

 tion of crystals is complete. Filter, dissolve the crystals in a 

 very little water, and then add strong nitric acid in wiiich the 

 salt is only slightly soluble. Collect the crystals which are 

 deposited, press between filter paper to dry them, and preserve. 

 A stable or urinal frequently smells strongly of ammonia. 

 This is due to the hydrolysis of the urea of the urine by the 

 action of a micro-organism, ammonia and carbonic acid gas 

 being formed. 



CO(NH2)2 + H2O = CO2 -f 2NH3. 

 The hydrolysis may also be effected by heating with strong 

 caustic potash, ammonia and carbonate of potassium being 

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