INDUSTRIAL A N D ENGIiVEERING CHEMISTRY
April, 1927
present, superheating and "bumping" occurred and the distillate contained excessive and variable amounts of bromine. COMPOSITION OF VAPOR-In determining the composition of the vapor given off by a boiling mixture of bromine and water which contained both liquid phases, the apparatus shown in Figure 2 was used. Into each of two bubbling tubes, as shown, was placed a mixture of water with excess of bromine. The second tube was immersed in a water bath which was maintained at a temperature only slightly
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nFas transferred completely to the longer cylindrical arm. The wider bulb containing the saturated aqueous solution was then cut off, transferred immediately to a large weighing tube containing an excess of a strong solution of potassium iodide, and weighed. The bromine solution was determined by titration with thiosulfate in the usual manner. The results obtained were as follows: TEMPERATURE O
c.
30.1 36.0 41.0 44.8 48.8 52.8 5 3 . 6 (b. p.)
GRAMSBROMINE IN 100 GRAMS SOLUTION 3.341 3.357 3.387 3.414 3.447 3.496 3 . 5 0 (est.)
From these various determinations it appears that the mutual boiling point of bromine and water is 53.6" C. a t 748.8 mm. pressure, and that a t this mutual boiling point the aqueous layer contains 3.50 grams of bromine per 100 grams, while the vapor that is given off contains 98.85 grams of bromine per 100 grams. Figure 2
below the mutual boiling point (50-53" C.). By passing steam into the first bulb the mixture therein was heated to its boiling point and vapor was given off which was practically in equilibrium with the two liquid layers. I n passing from the first to the second tubes, this vapor was partially condensed, so that the material that entered the second bulb consisted of a mixture of the two liquid phases and a vapor in equilibrium with the two liquids. This vapor, in passing through the solution in the second tube, heated it to boiling and produced a vapor in true equilibrium with the two liquid layers. When the liquid in each bulb was boiling, the weighed absorption tube, C, containing a strong solution of potassium iodide, was attached and a sample of the distillate was collected. This sample was weighed and analyzed as described above. From several individual determinations which agreed closely among themselves, a n average value of 98.85 per cent was obtained as the bromine content of the vapor in equilibrium with the mutually saturated solutions of bromine and water. __ DETERMINATION OF BOILIKG POIKT _-_ -A mixture of water and excess -~ __ __ . _ bromine was placed in a large test = - ~- tube, which was surrounded by a still z-~ - y larger tube to provide an air jacket. __- The outer tube was placed in a water _ _ - - bath which was kept a t about 50" C. - __~__ ___ _ The mixture of bromine and water -_ __ _ -Z was heated to boiling and kept boiling by passing into it the vapor from a similar mixture which was boiled in a separate flask. The boiling point was indicated by a n accurate thermometer placed in the boiling mixture Figure 3 i n t h e t u b e . The mutual boiling point was found to be 53.6' C. a t 748.8 mm. pressure. SOLUBILITY-The solubility of bromine in water a t the mutual boiling point was estimated by extrapolation from the curve representing the solubilities a t slightly lower temperatures. I n making these solubility determinations, a mixture of water and excess bromine was sealed in a U-shaped tube (Figure 3) and shaken in a thermostat at constant temperature until equilibrium was reached. The tube was then allowed to stand in an upright position in the thermostat until the excess of liquid bromine had settled into the lower U-bend, after which it was slowly inverted so that the bromine layer ~
~
a condenser is sealed and a Soxhlet thimble placed over the end of the outlet tube in the flask. I n order to secure a saturated filtered solution, dry air or other suitable gases can be applied a t the capped outlet to force the solution out of the Soxhlet thimble into the flask several times before pressure is applied at the top of
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