HYDROLYSIS (Gr. 6Swp,

See also:

• WATER

water, Anew, to loosen)  , in chemistry, a decomposition brought about by water after the manner shown in the equation R•X-{-H'OH=R•H+X•OH . Modern research' has proved that such reactions are not occasioned by water acting as H2O, but really by its ions (hydrions and hydroxidions), for the velocity is proportional (in accordance with the law of chemical mass action) to the concentration of these ions . This fact explains the so-called " catalytic " action of acids and bases in decomposing such compounds as the esters . The term " saponification " (Lat. sago, soap) has the same meaning, but it is more properly restricted to the hydrolysis of the fats, i.e. glyceryl esters of organic acids, into glycerin and a soap (see CHEMICAL ACTION) . in small quantities to a cold dilute solution of the acid . It is catalyst; for example, formic, glygollic, lactic, tartaric, malic, necessary that it should be as pure as possible since the commercial product usually contains traces of ferric, manganic and aluminium oxides, together with some silica . To purify the oxide, it is dissolved in dilute hydrochloric acid until the acid is neatly neutralized, the solution is cooled, filtered, and baryta water is added until a faint permanent white 'precipitate of hydrated barium peroxide appears; the solution is now filtered, and a concentrated solution of baryta water is added to the filtrate, when a crystalline •precipitate of hydrated barium peroxide, BaO28•H2O, is thrown down . This is filtered off and well washed with water . The above methods give a dilute aqueous solution of hydrogen peroxide, which may be concentrated somewhat by evaporation over sulphuric acid in vacua . H, P . Talbot and H . R .

Moody (Jour . Anal . Chem., 1892, 6,p . 65o) prepared a more concentrated solution from the commercial product, by the addition of a 1o% solution of alcohol and baryta water . The solution is filtered, and the barium precipitated by sulphuric acid . The alcohol is removed by distillation in vacua, and by further concentration in vacuo a solution may be obtained which evolves 58o volumes of oxygen . R . Wolffenstein (Ber., 1894, 27, p . 2307) prepared practically anhydrous hydrogen peroxide (containing 99•a% 11202) by first removing all traces of dust, heavy metals and ' alkali from the commercial 3% solution . The solution is then concentrated in an open basis on the water-bath until it contains 48% H202 . The liquid so obtained is extracted with ether and the ethereal solution distilled under diminished pressure, and finally purified by repeated distillations . W .

Staedel (Zeit. f: avegew, Chem:, 1902, 15, p . 642) has described solid hydrogen peroxide, obtained by freezing concentrated solutions . Hydrogen peroxide is also found as 'a product in many chemical actions, being formed when

carbon monoxide and cyanogen burn in air (H . B . Dixon); by passing air through solutions of strong bases in the presence of such metals as do not react with the bases to liberate hydrogen; by shaking zinc amalgam with alcoholic sulphuric acid and air (M . Traube, Ber., ' 1582, 1 5, p . 659); in the oxidation of zinc, lead and copper in presence of water, and in the electrolysis of sulphuric acid of such strength that it contains two molecules of water to one molecule of sulphuric acid (M . Berthelot, Comptes rendus, 1878; ' 86, P . 71)• The anhydrous hydrogen peroxide obtained by Wolffenstein boils at 84-85°C . (68 mm.); its specific gravity is 1.4996 (1.5° C.) . It is very explosive (W . Spring, Zeit. anorg .

Chem.; 1895, 8, p . 424) . The

explosion risk seems to be most marked in the preparations which have been extracted with ether previous to distillation, and J . W . Briihl (Ber., 1895, 28, p . 2847) is of opinion that a very unstable, more highly oxidized product is produced in small quantity in the process . The solid variety prepared by Staedel forms colourless, prismatic crystals which melt at -2° C.; it is decomposed with explosive violence by platinum sponge, and traces of manganese dioxide . , The dilute aqueous solution is very unstable, giving up oxygen readily, and decomposing with explosive violence at loo° C . An aqueous solution containing more than 1.5% hydrogen peroxide reacts slightly acid . To-wards lupetidin [ace dimethyl piperidine, C5H9N(CH3)21 hydrogen peroxide acts as a dibasic acid (A . Marcuse and R . Wolffenstein, Ber., 1901, 34, p .

2430; see also G . Bredig, Zeit . Electrochem., 1901, 7, p . 622) . Cryoscopic determinations of its molecular

weight show that it is H202 . [G . Carrara, Rend. delta Accad . dei Lincei, 1892 (5), 1, ii. p . 19; W . R . Orndorff and J . White, Amer .

Chem . Journ., 1893, 15, p . 347.] Hydrogen peroxide behaves very frequently as a powerful oxidizing

agent; thus lead sulphide is converted into lead sulphate in presence of a dilute aqueous solution of the peroxide, the hydroxides of the alkaline earth metals are converted into peroxides of the type MO2BH20, titanium, dioxide is converted into the trioxide, iodine is liberated from potassium iodide, and nitriles(in alkaline solution) are converted into acid-amides (B .