Glycerol.
Glycerol or 1,2,3-propanetriol is the almost of import trihydric alcohol. It was formerly known equally Glycerine. Glycerol is constitute inwards all-natural fats together with oils equally glycerol esters of long-chain carboxylic acids.
Manufacture. Glycerol is manufactured:
(1) From Fats together with Oils.
Natural tits together with fats are triesters of glycerol together with long-chain carboxylic acids (mainly palmitic, stearic, together with oleic acid). On hydrolysis amongst alkali, the fatty together with oils gain glycerol together with the sails of the long-chain acids which are called soaps.
In the inwards a higher house equation, R is nine to 17 carbons. The hydrolysis of fats together with oils is carried originally for lather manufacture, together with glycerol is obtained equally a by-product. This is even so a commercial source of glycerol.
Glycerol from Soap Manufacture.
In lather manufacture, the fatty is hydrolyzed past times boiling amongst an alkali solution. The carboxylic acids produced past times hydrolysis react amongst the alkali to cast enterprise lather spell the glycerol is left inwards the solution. The lather is filtered out. The filtrate is called Spent Lye.
Spent lye contains 4 to half-dozen per cent glycerol, unused alkali, soluble soaps, together with suspended impurities. It is allowed to stand upward inwards a tank where almost of the suspended impurities settle down. The clear solution is transferred to a novel tank where it is commencement treated amongst HCL to neutralise excess alkali. It is so treated amongst alum (aluminium sulphate) together with steam (Fig 16:2). The remaining excess alkali is precipitated equally aluminium hydroxide together with the soluble soaps are converted into insoluble aluminium soaps. These impurities are filtered out. The filtrate is side past times side concentrated nether vacuum when almost of the sodium chloride separates out. This is filtered together with the filtrate is treated amongst fauna charcoal to take coloured impurities. After filtration, it is over again subjected to vacuum distillation. The glycerol thence obtained is ninety per cent pure. To obtain pure glycerol, it is redistilled nether vacuum until distillate has a specific gravity of 26.
From Propane.
Large quantities of glycerol are obtained equally a by-product inwards the industry of soap. However, this provide is non sufficient. Today much of glycerol is manufactured from propene obtained past times the catalytic corking of petroleum. Following 4 steps are involved :
Step 1.
Propene is treated amongst Cl2 at 600C to ambit allyl chloride.
Step 2.
Allyl chloride is treated amongst dil. NaOH to ambit allyl alcohol.
Step 3.
Allyl alcohol is treated amongst dilute hypochlorous acid to ambit a chlorohydrin. The add-on of HOCL to the carbon-carbon double bond takes house according to the Markovnikov rule.
Step 4.
The chlorohydrin is treated amongst dil. NaOH to yield glycerol.
Physical properties.
Glycerol is a colourless, odourless sweet-tasting together with syrupy liquid, bp 200°C. it is non-toxic. Glycerol is soluble inwards H2O together with ethanol, simply insoluble inwards ether. It is hygroscopic, that is, it absorbs wet from the air.
Chemical properties.
Glycerol molecule contains 2 primary -OH groups together with ane secondary -OH group. It undergoes many of the reactions to live expected of these types of alcohols. The carbon atoms inwards glycerol are indicated as α, β and α.
Uses.
Glycerol is nontoxic together with an first-class humectant (moisture-retaining agent). It is used inwards bakery products, paw lotions, vanishing creams, shaving soaps together with toothpaste s. Glycerol is used inwards the production of plastics, synthetic fibres, together with surface coatings. It is used inwards the industry of explosives similar Dynamite together with Cordite.
Formula: C3H8O3
Density: 1.26 g/cm³
Boiling point: 290 °C
IUPAC ID: propane-1,2,3-triol
Molar mass: 92.09382 g/mol
Melting point: 17.8 °C
