84 CHEMISTR V FOR A GRICUL TURAL STUDENTS 



cork down the tube so as to fit loosely into the flask and 

 prevent loss of chlorine. Invert the whole apparatus for a 

 moment to get rid of any air which has got into the tube. 

 Set the apparatus in bright sunlight for a few hours. Note 

 that two or three inches of gas collect in the tube and that 

 the liquid becomes colourless. When the gas ceases to be 

 evolved, test it with a glowing splint. Is it oxygen? Has 

 the hydrogen of the water been attacked by the chlorine 

 forming hydrochloric acid and liberating oxygen, thus : — 



Cl2 + H20 = 2HCl + 0? 



Test the liquid for hydrochloric acid with silver nitrate solu- 

 tion, and with blue litmus paper. 



Bleaching Agents and Disinfectants. — The strong attraction that the 

 foregoing experiment shows to exist between chlorine and hydrogen causes 

 chlorine to be a powerful oxidising agent^ and upon this depends its use 

 for bleaching, and as a disinfectant and deodoriser. A piece of turkey-red 

 cloth, when placed in a jar of chlorine, is bleached if moistw-e be present ^ 

 the red dye being oxidised to colourless substance by the oxygen set free 

 from the water by the action of chlorine upon it. Chlorinated lime, which 

 may be produced on a small scale by passing chlorine gas through a glass 

 tube containing a layer of slaked lime, and which consists of a compound 

 of calcium chloride and calcium hypochlorite (the salt derived from the hypo- 

 chlorous anhydride mentioned on p. 52), is more conveniently used. On 

 the addition of dilute acid to the powder chlorine is rapidly evolved, and even 

 the carbonic acid gas of the air very slowly liberates chlorine, so that it is 

 sufficient to sprinkle the powder wherever it may be required as a disin- 

 fectant or deodoriser. Another powerful oxidising agent and disinfectant 

 is the permanganate of potash, KgCMngOY, contained in Condy's Fluid, 

 for the heptoxide of manganese easily gives up oxygen, and is reduced to 

 a lower oxide. Ozone, a condensed form of oxygen occurring in sea and 

 country air, and the peroxide of hydrogen, are also powerful oxidising and, 

 therefore, bleaching and disinfecting agents. It must be remembered that 

 sulphurous acid owes its bleaching power partly to its reducing action, 

 and therefore acts in the opposite way to the substances now under con- 

 sideration. 



