CHLORINE. 231 



with hydrochloric acid, or a mixture of manganese dioxide and 

 sodium chloride with sulphuric acid : 



Mn0 2 + 4HC1 = MnCl 2 -f 2H 2 O + 2C1. 



MnO 2 + 2NaCl -f 2H 2 SO 4 = MnSO 4 -f Na 2 SO 4 -f 2H 2 O + 2C1. 

 Chlorine is liberated also by the action of sulphuric or hydrochloric acid on 

 bleaching-powder, which is a mixture of calcium chloride and calcium hypo- 

 chlorite : 



CaCl 2 .Ca(ClO) 2 -f 2H 2 SO 4 = 2CaSO 4 + 2H 2 O + 401. 



Chlorine is now also produced by electrolysis of sodium chloride solution in 

 suitably constructed apparatus. 



Experiment 17. Use apparatus as in Fig. 39, page 168. Conduct operation 

 in a fume-chamber. Place about 50 grammes of manganese dioxide in coarse 

 powder in the flask, cover it with hydrochloric acid, shake up well to insure 

 that no dry powder be left at the bottom of the flask, apply heat, and collect 

 the gas in dry bottles by downward displacement. Keep the bottles loosely 

 covered with pieces of stiff paper while filling them. Use the gas for the 

 following experiments : 



a. Fill a test-tube with chlorine, a second test-tube of same size with hydro- 

 gen ; place them over one another so that the gases mix by diffusion, then 

 hold them near a flame ; a rapid combustion or explosion ensues. 



b. Hold in one of the bottles filled with chlorine a lighted wax candle, and 

 notice that it continues to burn with liberation of carbon. The hydrogen con- 

 tained in the wax is in this case the only constituent of the wax which burns, 

 i. e., combines with chlorine. 



c. Moisten a paper with oil of turpentine, C 10 H 16 , and drop it into another 

 bottle filled with the gas ; combustion ensues spontaneously, a black smoke of 

 carbon being liberated. 



d. Drop some finely powdered antimony into another bottle, and notice that 

 each particle of the metal burns while passing through the gas, forming white 

 antimonous chloride, SbCl s . 



e. Pass some chlorine gas into water, and suspend in the chlorine water thus 

 formed colored flowers or pieces of dyed cotton, and notice that the color fades 

 and in many cases disappears completely in a few hours. 



Properties. Chlorine is a yellowish-green gas, having a disagree- 

 able taste and an extremely penetrating, suffocating odor, acting 

 energetically upon the air-passages, producing violent coughing and 

 inflammation. It is about two and a half times heavier than air, 

 soluble in water, and convertible into a greenish-yellow liquid by a 

 pressure of about six atmospheres. 



Chemically, the properties of chlorine are well marked, and there 

 are but few elements which have as strong an affinity for other ele- 

 ments as chlorine ; it unites with all of them directly, except with 

 oxygen, nitrogen, and carbon, but even with these it may be made to 

 combine indirectly. The act of combination between chlorine and 

 other elements is frequently attended by the evolution of so much 



