BLEACHING BY CHLORINE. 153 



Put an ounce of bleaching powder (chloride of lime) in a bottle 

 with half a tumblerful of water, and shake up well; now filter off 

 (Expt. 56) a portion of the solution formed ; a quantity of lime 

 and other substances will usually be left undissolved, whilst a 

 clear solution will be obtained, containing amongst other things a 

 compound called hypochlorite of calcium. Add to a little of this 

 solution some diluted hydrochloric acid; a chemical action will 

 take place, the result of which is that a peculiar gas termed chlorine 

 is evolved. 



Caution. This gas is extremely injurious to breathe, producing 

 great irritation of the lungs ; all experiments made with it are best 

 performed in a draught closet (Expt. 145, fig. 67), or failing this, 

 in the open air, or in a room permitting of free ventilation by 

 opening doors and windows, and great care must be taken not to 

 inhale the gas in any quantity. Should small quantities be acci- 

 dentally inhaled, and distressing coughing and irritation of the 

 throat be consequently produced, this may be a good deal relieved 

 by pouring a few drops of ether in the palm of the hand and 

 breathing in the vapour. The chlorine gas evolved in this experi- 

 ment has a greenish-yellow tint (whence the name from the Greek 

 XpoAws = pale green) ; if the solutions used are weak, little or no 

 gas will be evolved as such, almost all being retained in solution 

 in the water present, which will take up a yellow colour. 



Expt. 163. To illustrate the Bleaching Action of Chlorine 

 Solution. To a wine-glassful of water add a few drops of litmus tinc- 

 ture, so as to tint the water purple ; now add a little of the chlorine 

 solution prepared as in the last experiment, by adding hydrochloric 

 acid to bleaching powder solution; the colour will be discharged or 

 bleached by the action of the chlorine. 



Instead of litmus tincture, a little solution of indigo may be used 

 with the same result ; or some claret, or a little of the red liquid 

 obtained by pickling red cabbage or beetroot. Almost all vegetable 

 colours, in fact, are destroyed by chlorine, and to this circumstance 

 is due the use of bleaching powder for whitening paper, calico, 

 &c., in the arts. Koses and other coloured flowers may be 

 bleached by immersing them for some time in chlorine water or 

 in a jar of the gas. 



Dip a piece of pink blotting-paper into the solution obtained by 

 dissolving bleaching powder in water, and then dip it into water to 

 which a little hydrochloric acid has been added; the chlorine thus 

 set free in contact with the colouring matter in the paper will 

 rapidly discharge the pink colour. Instead of pink blotting-paper, 

 a piece of calico soaked in claret and then dried so as to be 

 reddened, may be employed with the same result. 



