BROMINE IODINE- FLUORINE. 123 



3. Chlorates deflagrate when sprinkled on red-hot charcoal. 



4. Hypochlorites evolve a peculiarly smelling gas (hypochlorous 

 acid) on the addition of acids, and are strong bleaching agents. 



17. BEOMINE IODINE -FLUORINE. 



Bromine, Bromum, Br = 79.8. This element is found in sea- 

 watex and many mineral waters, chiefly as magnesium bromide, 

 which compound, however, represents in all these waters a compar- 

 atively small percentage of the total quantity of the different salts 

 present. Most of these salts are separated from the water by evapo- 

 ration and crystallization, and the remaining mother-liquor, contain- 

 ing the magnesium bromide, is treated with chlorine, which liberates 

 bromine, the vapors of which are condensed in cooled receivers : 



MgBr 2 -f 2C1 = MgCl 2 + 2Br. 



Bromine is at common temperature a heavy, dark reddish-brown 

 liquid, giving off yellowish-red fumes of an exceedingly suffocating 

 and irritating odor ; it is very volatile, freezes at about 24 C. 

 ( 11 F.), and has a specific gravity of 2.99; it is soluble in 30 

 parts of water, more freely in alcohol, abundantly in ether and bisul- 

 phide of carbon ; it is a strong disinfectant, and its aqueous solution 

 is also a bleaching agent. 



Hydrobromic acid, Acidum hydrobromicum, HBr = 80.8. 

 This acid cannot well be obtained by the action of concentrated sul- 

 phuric acid upon bromides, since the hydrobromic acid first formed 



QUESTIONS. 151. State the names and general physical and chemical prop- 

 erties of the four halogens. 152. How is chlorine found in nature, and why 

 does it not occur in a free state ? 153. State the general principle for liberating 

 chlorine from hydrochloric acid, and explain the action of the latter on man- 

 ganese dioxide. 154. Mention of chlorine : its atomic weight, molecular weight, 

 valence, color, odor, action when inhaled, and solubility in water. 155. How 

 does chlorine act chemically upon metals, hydrogen, phosphorus, water, am- 

 monia, hydrocarbons, and coloring matters ? 156. Mention two processes for 

 making hydrochloric acid ; state its composition, properties, and tests by which 

 it may be recognized. 157. What is aqua regia ? 158. State the composition 

 of hypochlorous and chloric acids. 159. What is the difference in the action 

 of chlorine upon a solution of potassium hydroxide at ordinary temperature 

 and at the boiling-point? 160. How many pounds of manganese dioxide, 

 and how many of hydrochloric acid gas are required to liberate 142 pounds of 

 chlorine ? 



