Soap method

The preparation method of soap is as follows:

(1) In a beaker of 150ml, put 6g lard and 5ml 95% alcohol, and then add 10ml40% NaOH solution. Stir with a glass rod to dissolve it (heat it with low fire if necessary).

(2) Put the beaker on the asbestos net (or in a water bath), heat it with low fire, and stir it constantly with a glass holder. In the heating process, if the evaporation of alcohol and water decreases, it should be replenished at any time to maintain the original volume. Therefore, 20 ml of mixed liquor of alcohol and water (1: 1) can be prepared in advance for addition.

Take out a few drops of samples, put them into a test tube, add 5 ~ 6 ml distilled water into the test tube, and heat and oscillate. When standing, there is oil precipitation, which indicates that saponification is not complete, and alkali solution can be added dropwise to continue saponification.

(4) Slowly add 20ml of hot distilled water into the completely saponified viscous liquid, and stir to make them mutually soluble. Then slowly pour the viscous liquid into 150ml hot saturated salt solution, and stir while adding. After standing, the soap will salt out and float. After the soap is completely precipitated and solidified, it can be taken out with a glass rod, and the soap is made.

explain

(1) oil is insoluble in alkaline water. Alcohol is added to increase the solubility of oil in alkaline solution and accelerate saponification reaction.

(2) If you don't need water bath heating, you must use a small fire.

(3) During the saponification reaction, the original volume of the mixed solution should be kept, and the mixed solution in the beaker should not be boiled or overflowed.

I hope this helps.