194-197] TESTS FOR ACID-RADICALS 6l 



REACTIONS FOR THE ACIDS. 



SULPHATE ("S0 4 ). — Use sodium sulphate 

 (Na 2 S0 4 .i2H 2 0) solution. 



194. Barium Chloride (BaCl 2 ) gives a white precipi- 

 tate of barium sulphate (BaS0 4 ), insoluble in acids. 



CARBONATE ("CO a ).— Use sodium carbonate 

 (Na 2 C03.ioH 2 0) solution. 



195. Hydrochloric Acid (HC1) causes carbon dioxide 

 gas (C0 2 ) to come off with effervescence. This gas may 

 be recognised either by dipping a glass 

 rod into lime-water and holding the 

 wet end of it just inside the test-tube ; 

 the adhering lime-water will be ren- 

 dered milky from the formation of cal- 

 cium carbonate (CaC0 3 ) ; or better by Fig. 23 

 pouring the C0 2 gas into another test-tube containing a 

 little lime-water (fig. 23), and then shaking up, when the lime- 

 water will become milky. 



NITRITES ('N0 2 ).— -Use potassium nitrite (KN0 2 ) 

 solution. 



196. Dilute Sulphuric Acid (H 2 S0 4 ) on warming 

 gives off brown nitrous fumes. 



197. Potassium Iodide (KI) Solution and several 

 drops of starch solution on addition to the liquid made acid 

 with acetic acid gives a deep-blue coloration. 



