BROMINE. 105 



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



4. Hypochlorites evolve a peculiarly smelling gas (h}-po- 

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



agents. 



QUESTIONS. 



151. State the names, and general physical and chemical properties 

 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 hydro- 

 chloric acid, and explain the action of the latter on manganese 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, phos- 

 phorus, water, ammonia, 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 acid. 



159. What is the difference in the action of chlorine upon a solution 

 of potassium hydrate at ordinary temperature or 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? 



17. BROMINE IODINE FLUORINE. 



Bromine, Bromum, Br = 80. This element is found in sea- 

 water and many mineral waters, chiefly as magnesium bromide, 

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

 paratively small percentage of the total quantity of the different 

 salts present. Most of these salts are separated from the water 

 by evaporation and crystallization, and the remaining mother- 

 liquor, containing the magnesium bromide, is treated with 

 chlorine which liberates bromine, the vapors of which are con- 

 densed in cooled receivers: 



MgBr 2 + 2C1 = MgCl, + 2Br. 



Bromine is at common temperature a dark, reddish brown 

 liquid, giving off brown fumes of an exceedingly suffocating 

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



