160 BACTERIOLOGICAL CHEMISTRY LESSON vil 



Action of Magnesium Sulphate or Ammonium Sulphate 

 on Sulphate of Quinine (Duclaux) 



(a) Prepare a cold and almost saturated solution of 

 sulphate of quinine. 



To it add 10 per cent of finely powdered magnesium 

 sulphate. 



A precipitate appears. 



(b) Dilute a cold and almost saturated solution of sul- 

 phate of quinine with an equal volume of water. 



Then add finely powered magnesium sulphate. 



A precipitate does not appear until 30 per cent of 

 the salt has been added. 



(c) Prepare a cold and saturated solution of sulphate of 

 quinine, and dilute it with one-tenth its volume of water. 



(1) Gradually add finely powdered ammonium sul- 

 phate, until no more precipitate appears. 



Filter. 



(2) To the filtrate again add ammonium sulphate, 

 until no more precipitate appears. 



Filter. 



(3) To the filtrate again add ammonium sulphate, 

 until no more precipitate appears. 



The appearance of a precipitate, therefore, depends 

 greatly on the degree of concentration. 



