Vegetable oils consist their esters of glycerin and nonlimiting carbonic acids. Whereas lubricating oils are a mix of hydrocarbons. Therefore it is possible to distinguish them carrying out high-quality reactions to existence of nonsaturated double communication.
It is required to you
- - test tubes;
- - spirit-lamp or a water bath for heating;
- - bromic water;
- - potassium permanganate solution;
- - solution of hydroxide of copper (II).
Instruction
1. Take two identical test tubes and pour in them gradually one and second oil. One of high-quality reactions to double communication – decolouration of bromic water (the saturated water solution of bromine having yellow coloring). Add this reactant to both test tubes and stir up.
2. If in one of test tubes there is no decolouration, accurately heat them at a low temperature. For heating it is convenient to use a spirit-lamp and the holder for test tubes or use a water bath. In that test tube where yellow coloring disappeared, there is a vegetable oil. Respectively, in another – machine.
3. Pour new portions of oils in clean test tubes. Add potassium permanganate solution (potassium permanganate solution) to each of test tubes. Depending on concentration of permanganate in solution, the reactant can have color from light pink to bright crimson. For the analysis it is better to use more saturated solution of crimson color that it was easier to define coloring transition.
4. Heat a test tube on a water bath. Do not forget to observe safety measures – when heating direct a test tube from yourself. In case of liquid spraying it will help to protect a face and clothes. The test tube in which crimson coloring disappeared contains vegetable oil.
5. Take new samples of oils in two test tubes. Add approximately equal volume of water and the catalyst (acid or alkali) to everyone. At the same time air of glycerin decays under the influence of hydrolysis on glycerin and fatty acids. After that carry out high-quality reaction to glycerin, for example saponification reaction.
6. In both test tubes flow solution of hydroxide of copper (II). As glycerin is a polyatomic alcohol, in a test tube with vegetable oil the bright blue coloring is formed.