BROMINE.
Examine bromine, potassium bromide, sodium bromide, magnesium
bromide.
157. Preparation.
Experiment 96.--Pulverize 2 or 3 g. KBr, and mix it with about
the same bulk of MnO2. After putting this into a t.t, add as much
H2SO4, mix them together by shaking, attach a d.t., and conduct
the end of it into a t.t. that is immersed in a bottle of cold
water. Slowly heat the contents of the t.t., and notice the color
of the escaping vapor, and any liquid that condenses in the
receiver. Avoid inhaling the fumes, or getting them into the
eyes.
MnO2 + 2 KBr + 2 H2SO4 = ? Compare this with the equation for
making Cl from NaCl.
158. Tests.
Experiment 97.--Try the bleaching action of Br vapor as in the
case of Cl. Bleach a piece of litmus paper, and try to restore
the color with NH4OH. Explain its bleaching and disinfecting
action. Try the combustibility of As, Sb, and Cu.
159. Description.--Bromine at usual temperatures is a liquid
element; it is the only common one except Hg; it. quickly
evaporates on exposure to air. The chemistry of its manufacture
is like that of Cl; its bleaching and disinfecting powers are
similar to the latter, though they are not quite so strong as
those of Cl. Its affinity for H and for metals is also strongly
marked. A drop of Br on the skin produces a sore slow to heal.
Bromine salts are mainly KBr, NaBr, MgBr2. These in small
quantities accompany NaCl, and are most common in brine springs.
The world's supply of Br comes chiefly from West Virginia and
Ohio, over 300,000 pounds being produced from the salt (NaCl)
wells there in 1884. The water taken from these wells is nearly
evaporated, after which NaCl crystallizes out, leaving a thick
liquid--bittern, or mother liquor--which contains the salts of
Br. The bittern is treated with H2SO4 and Mn02, as above.
For transportation in large quantities, Br has to be made into
the salts NaBr and KBr, on account of the danger attending
leakage or breakage of the receptacles for Br.
160. Uses.--Its chief uses are in photography (page 167),
medicine, as KBr, and analytical chemistry.