When heated with hydriodic acid and phosphorus it forms phenylacetic acid; whilst concentrated hydrobromic acid and hydrochloric acid at moderate temperatures convert it into phenylbromand phenylchlor-acetic acids.
As in the case of quinine, the administration of small doses of hydrobromic acid often relieve the milder symptoms.
In persons who have a marked idiosyncrasy towards cinchonism, the symptoms may often be successfully averted if small doses of hydrobromic acid - io minims of the dilute solution - are given with the quinine.
The following table gives the heats of neutralization of the commoner strong monobasic acids with soda: - Hydrochloric acid Hydrobromic acid Hydriodic acid Nitric acid Chloric acid Bromic acid Within the error of experiment these numbers are identical.
Soc., 1900, 77, p. 648) prepares pure hydrobromic acid by covering bromine, which is contained in a large flask, with a layer of water, and passing sulphur dioxide into the water above the surface of the bromine, until the whole is of a pale yellow colour; the resulting solution is then distilled in a slow current of air and finally purified by distillation over barium bromide.
It may be obtained by brominating conine, and then removing the elements of hydrobromic acid with alkalis.
Gessner (Berichte, 1876, 9, p. 1507) removes chlorine by repeated shaking with water, followed by distillation over sulphuric acid; hydrobromic acid is removed by distillation with pure manganese dioxide, or mercuric oxide, and the product dried over sulphuric acid.
Thus, in the production of hydrochloric acid from hydrogen and chlorine 22,000 calories are developed; in the production of hydrobromic acid from hydrogen and bromine, however, only 8440 caloriesare developed; and in the formation of hydriodic acid from hydrogen and iodine 6040 calories are absorbed.
In ethereal solution it combines with bromine to form an unstable liquid dibromide; it also unites with one molecule of hydrobromic acid to form the same tertiary bromide as dimethylallylene; this points to its being Q-methyldivinyl, CH 2: C(CH 3) CH: CH 2 (V.
Thus, chlorine enters into reaction with hydrogen, and removes hydrogen from hydrogenized bodies, far more readily than bromine; and hydrochloric acid is a far more stable substance than hydrobromic acid, hydriodic acid being greatly inferior even to hydrobromic acid in stability.