The name olation has been given to the combination of two or more molecules of basic chrome compounds with one another producing a bigger molecule.The mechanism of simple olation of 33.3% basic chrome chloride is represented as follows -
In this olation OH is combined with one chromium atom with the primary and with another chromium atom with the secondary valency. Thus Cr - OH - Cr. Two molecules of water have been eliminated and the positive charge of the olated molecule has been doubled. OH group held between the chromium atom is called the Ol group, as in alcohol, phenol. OH group or groups therefore held between the chromium atom are not simply titratable with acid, as in un-olated OH groups within the complicated can be titrated directly by acid. The method of olation is favoured by heating, increasing concentration, increasing basicity or storing wet 'chromed leather' for a length of time.
In this olation OH is combined with one chromium atom with the primary and with another chromium atom with the secondary valency. Thus Cr - OH - Cr. Two molecules of water have been eliminated and the positive charge of the olated molecule has been doubled. OH group held between the chromium atom is called the Ol group, as in alcohol, phenol. OH group or groups therefore held between the chromium atom are not simply titratable with acid, as in un-olated OH groups within the complicated can be titrated directly by acid. The method of olation is favoured by heating, increasing concentration, increasing basicity or storing wet 'chromed leather' for a length of time.
Polymerization:
The increase in the size of the molecules of basic chrome salt is not restricted by their olation as a result of they'll also grow to a larger size by polymerization subsequent to olation.
There is a difference between olation and polymerization. In the former water is eliminated from the molecule but in the later there is no such water elimination but the molecules simply join up forming bigger molecules.
Both olation and polymerization are affected with a similar factors, viz. increase in basicity, ageing, temperature etc.
There is a difference between olation and polymerization. In the former water is eliminated from the molecule but in the later there is no such water elimination but the molecules simply join up forming bigger molecules.
Both olation and polymerization are affected with a similar factors, viz. increase in basicity, ageing, temperature etc.
Oxolation:
Under certain conditions olated chromium compounds are become into oxolated ones. The modification is represented as follows-
In this the OH link of the olated compounds is modified into oxygen link of the oxolated compounds with the liberation of acid. Oxolated compounds could also be formed by the continuous heating of the olated compound.
In this the OH link of the olated compounds is modified into oxygen link of the oxolated compounds with the liberation of acid. Oxolated compounds could also be formed by the continuous heating of the olated compound.
The terms oil and lipid
Oils: Generally refers to a fat with short or unsaturated fatty acid chains that is Liquid at normal temperature. Oils have a high carbon and hydrogen content and are normally flammable slippery.
Fat: Fat may refer to fats which are solids at normal temperature. Fats that are saturated fats don't have any double bonds between the carbon within the chain. Unsaturated fats have one or additional double bonded carbons within the aliphatic chain.
Lipid: Lipid is the normal term as a lipid is not necessarily a triglyceride. Fats as like other, lipids are usually hydrophobic and are soluble in organic solvents and insoluble in water.
Triglyceride and phosphates are esters which form the major components of most commercial oils and fats, derived from vegetable and animal kingdom.
Esters which in oils and fats are combination products of alcohols (glycerol, compounds containing alcoholic -OH groups) and acids (fatty carboxylic acids).
RCO2H + R'OH = RCO2R' + H2O
Fatty acids of higher molecular weight, such as solid saturated steric acid, C12H35-COOH; pamitic acid, C15H31-COOH; or liquid unsaturated oleic acid, C17H33-COOH are widely disseminated in animal and plant organisms as esters.
The chemical reactions which takes place to form say, stearin by esterification of stearic acid and glycerol may be written as:
Chrome tanning and Objectives of chrome tanning and Confirmation test of chrome tanning
Chrome tanning:
The process of tanning hides and skins into leather with basic chromium salt is known as chrome tanning. It is a quick process.
Objectives of chrome tanning:
- To convert the putrescible hides/ skins into non - putrescible leather.
- To raise the shrinkage temperature ( Tâ‚›)/ hydrothermal stability.
- To reduce the power to swell once wet back.
- To increase the strength property of leather.
- To protect from microbial attack.
Confirmation test of chrome tanning:
Chrome tanning process is usually considered to be completed when a piece of tanned leather does not shrink in boiling water for 3 or 5 minutes.
For this a sample is cut from the thickest part of the tanned skin or hide, smoothed out on a piece of wooden board and its boundaries outlined with a pencil. It is thus placid in a bowl of water kept at boiling point for three minutes. The sample is then taken out, cooled, ironed out once more and if no shrinkage or any curling lip on the sides and corners be noticeable the tanning should be considered as complete.
The test is followed by the tanners who follow one bath chrome tanning process.
For this a sample is cut from the thickest part of the tanned skin or hide, smoothed out on a piece of wooden board and its boundaries outlined with a pencil. It is thus placid in a bowl of water kept at boiling point for three minutes. The sample is then taken out, cooled, ironed out once more and if no shrinkage or any curling lip on the sides and corners be noticeable the tanning should be considered as complete.
The test is followed by the tanners who follow one bath chrome tanning process.
I don not understadn where the Cl- comes from?
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