Friday, July 8, 2011


The first line of this post is concerned with the reactions which take place when an ester of an unsaturated fatty acid of the kind occurring in many suitable textile oils is oxidised by air or oxygen . For the sake of simplicity such an ester may be represented as R1 C H:C H-R 2 COOR 3 an example being ethyl oleate.

When a saturated carbon chain is oxidation takes place mainly at elevated temperatures such as occur in the Mackey  test or in vapour phase oxidation or due to bacterial action.

The most common type of oxidation is attack on the double bond which takes place rapidly even at normal room temperatures . The first stage is peroxide formation by addition of a molecule of oxygen at the double bond the subsequent stages may be shown diagram manically as follows

                                                                 splitting products
                                                                 condensation products
When monophthongs fatty acids E g Leica acid are involved the condensation products will be limited to dimers which will be soluble in the oil. This is what happens in a non drying oil.
          When diethenoid fatty acids E g Linotype acid are involved the possibility of trio or higher polymers arises as Linotype may form a double peroxide and each such compound con condense with two othe peroxides . In the case of Linotype acid such condensation products are likely to be relatively simple and will at first from dispersion or microscopically small aggregates in the mass of unoxidised oil.
As oxidation becomes more extensive these aggregates may link up to form al loose structure which will be viscous and sticky .If the oxidation has taken place on a textile fibre the oil. will not readily split up into small droplets during scouring and will be difficult to scour out .This is a description of the behaviour of a semi drying oil E g cotton seed oil.

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