Saponification reaction
Saponification reaction: chemical reaction that occurs when fatty acids in oils and fats are mixed with alkaline aqueous solution.
Grease+caustic alkali (sodium hydroxide, potassium hydroxide)+water = soap+glycerol (saponification reaction)
The function of water in saponification reaction is to dissolve caustic soda.
Heating program (HP): When oil, caustic soda and water react, heating from outside is called heating program.
Cold program (CP): Soap is made without heating, and it is allowed to stand for about 1 month by using the heat generated naturally during the chemical reaction, so that it can mature gradually, which is called cold program.
Instruments and materials
Raw caustic soda can only be bought in shops specializing in chemical raw materials and chemical reagents. 500g/ box of caustic soda with 98% purity does not need more than 10 ~ 20 yuan, and many bars of soap can be made.
Caustic alkali will corrode copper, aluminum, tinplate containers and non-stick pans. Use non-corrosive plastic, glass, stainless steel and casserole containers.
Others: molds, measuring cups, scales, glass or stainless steel rods, used for placing soap.
For safety: use rubber gloves, glasses, long-sleeved clothes, scarves, gloves and masks when operating.
Matters needing attention in making soap
Matters needing attention in using caustic soda
Caustic alkali is a very corrosive chemical, and skin and eyes will burn if they contact caustic alkali. Clothes will also burn out. Therefore, the operation should be particularly careful. Bring latex gloves, glasses and a mask (gas will be generated when making lye). It is best to wear long-sleeved shirts and trousers to protect your eyes and skin. In case the skin is accidentally stained with caustic soda, rinse with plenty of water or go to the hospital for treatment. It is dangerous to splash caustic soda on your eyes. Rinse with cold water and go to the hospital for treatment.
● It is best to make soap outdoors or in the bathroom and kitchen. Use old newspapers or plastic sheets around to prevent the solution from flowing out. In addition, don't let children and pets near the operation site.
Caustic alkali absorbs water easily and can be kept in inexhaustible seals. Keep it out of the reach of cool children and write a dangerous goods sign.
● When dissolving caustic alkali, heat will be generated. Use heat-resistant containers. When using plastic bottles, put them in cold water and stir while cooling.
When dissolving caustic soda, a small amount of gas will be produced, and the operation should be carried out in a ventilated place.
Caustic alkali is a highly corrosive chemical. It was scary at first, and it was easy to have an accident if you were too nervous. After doing it many times, it will be very simple, and some precautions may be ignored. In a word, it is very important to understand the properties of caustic soda and the principle of chemical reaction process.
Other preventive measures
● Natural products are safer and do not contain preservatives, pigments and chemical raw materials. But the skin varies from person to person, especially those with sensitive skin. When using new soap, a simple allergy test should be carried out on the skin, and a little can be applied on the inside of the arm or neck. After staying for 24 hours, if there is no allergic reaction, you can use it safely.
Making soap can be said to be mixing "oil" and "water solution" (emulsification reaction). They are connected and cannot be separated by stirring, so stirring is very important.
● The first 15 minutes of stirring is very important, and the stirring is insufficient, so the chance of caustic soda and oil droplets meeting is low, the effect is poor, or the curing time is long.
● For other precautions, please refer to the "Q&A" of homemade soap.
Advantages and disadvantages of homemade soap
merits and demerits
○ Make solid soap in the factory to remove by-product glycerol. Glycerol is a good humectant with lubricating effect. It is a raw material for making cosmetics. Self-made soap retains glycerin, which has moisturizing effect and makes the skin feel smooth after use.
○ Does not contain preservatives, preservatives, metal sealing agents and other chemical raw materials. Unreacted oil in the production process may be oxidized, causing discoloration.
After fully drying, put it in a cool place, away from sunlight, high temperature, humidity and ventilation.
○ 100% saponified soap on the market is added with some chemical raw materials such as synthetic surfactant, preservative, preservative, synthetic perfume and metal sealing agent. Self-made soap, using high-quality oil, does not contain 100% saponification, deliberately leaving more oil beneficial to the skin. Leave it for a while, let it mature slowly, and make high-quality soap containing natural moisturizing ingredient glycerin. It is beneficial to skin and suitable for allergic skin.
○ Soap tends to soften because it contains glycerol which is easy to absorb water. Foam may not be as much as commercial soap, but it will be more when put in a net bag (such as a small net bag selling garlic in a supermarket) or when using sponge glue. Don't soak in water after use, hang it to dry.
○ You can choose materials freely and make soap suitable for your skin. You can choose a soap with suitable hardness, foam, moisture retention and fragrance.
○ Low cost. Hand-made high-grade soap is very expensive, 1 block costs 40 ~ 100 yuan, and it is much cheaper to make it yourself. Homemade soap lovers make all kinds of soaps themselves and give them to relatives and friends to play with.
○ Commercially available soaps are very cheap and there are many kinds. Homemade soap takes time. Self-made soap is a kind of healthy soap with various colors and curative effects, which is beneficial to the health of family members and can be given to relatives and friends for appreciation.
○ The use of strong alkali caustic soda in the production process requires careful operation.
Calculation method of oil, alkali and water for soap making
When various oils and fats are saponified, the amount of caustic alkali required is different.
Saponification value of sodium hydroxide solid soap and potassium hydroxide liquid soap.
Saponification value of common oils and fats
Product name (English) Product name (Chinese) NaOH (sodium hydroxide) KOH (potassium hydroxide)
Almond almond oil 0. 136 0. 189
Avocado avocado 0. 133 0. 1862
Bear fat bear oil 0. 139 0. 1946
Beeswax beeswax 0.069 0.0966
Butter (beef) butter 0. 16 19 0.2266
Camellia oil 0. 136 0. 1904
Rapeseed oil 0. 124 (note) 0. 1736
Castor oil 0. 1286 0. 18
Cocoa butter cocoa oil 0.137 0.1918
Coconut coconut oil 0. 19 0.266
Coconut, virgin coconut oil 0. 1946 0.273
Corn corn 0. 136 0. 1904
Cottonseed oil 0. 1386 0. 194
Evening primrose oil 0. 136 0. 1904
Flaxseed oil 0. 1357 0. 1899
Grape seed oil 0.1265 0.1771
Hazelnut oil 0. 1356 0. 1898
Linseed oil 0. 1345 0. 1883
Horse fat horse oil 0. 14 0. 196
Jojoba oil 0.069 0.0966
Kukuinut antique oil 0. 135 0. 189
Lanolin 0.074 1. 1037
Lard lard 0. 138 0. 193
Macadamia nut 0. 139 0. 1946
Mango butter mango oil 0. 128 0. 1792
Mink mink oil. 0. 14 0. 196
Neem oil 0.1387 0.1941
Olive oil 0. 134 0. 1876
Palm kernel palm kernel coarse powder 0. 1560.438+084
Palm oil 0.141.1974
Palm stearin palm stearin 0.141.1974
Peanut and peanut oil 0. 136 0. 1904
Pumpkin seed pumpkin seed oil 0.133/kloc-0.1863
Rice bran and rice sugar oil 0. 128 0. 1792
Safflower safflower oil 0. 136 0. 1904
Sesame oil 0. 133 0. 1862
Shea butter resin 0. 128 0. 1792
Soybean oil 0. 135 0. 189
Sunflower seed oil 0. 134 0. 1876
Sweet almond oil 0. 136 0. 1904
Beef tallow 0. 1405 0. 1967
Walnut oil 0. 1353 0. 1894
Wheat germ oil from Germany 0.131.1834
Chicken oil 0. 138
Source:
Catalogue of rainbow grassland. Rainbow meadow. Catalogue of Rainbow Meadows, 2000. Rainbow meadow. 200 1
The amount of sodium hydroxide needed to calculate the saponification value.
Understand the calculation method by using the amount of various materials of orange cocoa soap.
○ The total amount of grease is 500g, and four oils (olive oil 200g, palm kernel oil 120g, cocoa oil 30g, coconut oil 150g) are used this time.
○ Calculation method of sodium hydroxide consumption (the saponification value of various oils is selected from the above table, and the red data is the saponification value of the oil selected this time).
200g olive oil 0. 134 X 200 = 26.8.
Coconut oil 150g 0. 19 X 150 = 28.5.
Palm oil120g0.141x120 =16.92.
Cocoa oil 30g0.137x30 = 4.11.
○ Total amount of sodium hydroxide required for complete saponification of 500 grams of four oils: 76.33 grams.
○ In the process of making soap, in order to improve the moisturizing effect and avoid residual alkali, a large amount of grease was used, and the reaction was only 85% ~ 95%. 100% saponification reaction does not proceed.
○ Reduce the dosage of 10% sodium hydroxide by 76.33 X 0.9 = 68.697, totaling * * * 68.70g (45%).
It is better to use less oil, but soap with less oil is easy to oxidize, so it is more appropriate to reduce the amount of caustic soda.
Calculation method of water quantity
Water accounts for about 30 ~ 40% of oil. The amount of water includes aqueous solutions of flowers and plants to be added. Here, 35% of 500g is175g, and an aqueous solution of175g is needed.
○ Free choice of auxiliary materials, such as favorite color, fragrance, etc. Cocoa powder and oranges are used here to add color and flavor.
The formula of orange cocoa soap using 500 grams of various oils and fats is as follows.
Water175g
68.7 g of sodium hydroxide (reduced by 10%)
200 grams of olive oil
Coconut oil150g
Palm oil 120g
Cocoa oil 30g
Cocoa powder (for color matching) spoon 1
Small spoonful of orange essential oil (fragrance enhancement) 4 (orange flavor is light, so it is often used)
bribe
Grease is the basic material of self-made soap, and soap is made by saponification reaction between fatty acid in fat and caustic alkali, so oil quality has a great influence on the characteristics of soap, so it is very important to understand the characteristics of various oils. The representative oil of homemade soap is olive oil (moisturizing); Coconut oil (foam); Palm oil (hardness). A more balanced soap can be made by using these three oils in balance.
In addition to the above oils, you can freely choose various vegetable oils and animal oils according to your family situation. All natural animal and vegetable oils can be made into soap.
Hardness, foam, detergency and moisture of soap.
The hardness, foam, detergency and humidity of soap vary with the type and proportion of fatty acids, such as stearic acid, linolenic acid, oleic acid, lauric acid, myristic acid and palmitic acid.
In terms of hardness, every oil has an iodine value. The lower the iodine value, the higher the hardness of soap.
Soaps made from solid oils such as butter and lard have higher hardness than liquid oils such as rapeseed oil and sunflower oil.
Soap with high stearic acid content has less foam and poor foaming power; Soap with more oleic acid has better moisture retention, foam retention and cleaning power.
The characteristics of common oils and fats are introduced as follows. If you want to know the detailed properties of various oils, please see the natural beauty self-made cosmetic materials.
Foam foam (coconut oil, palm kernel oil)
Improve foam (castor oil, palm oil, lard, butter, etc. )
Hardness increases the hardness of soap (palm oil, coconut oil, lard, butter, cocoa butter, etc.). )
Increase the softness of soap (soft oil, oil that is liquid at room temperature)
Melting is difficult to melt (palm oil, lard, butter, etc.). )
Soluble (soft oil)
Moisturizing feeling, cleaning power, moisturizing feeling (avocado oil, olive oil, etc. Soft oil with viscosity)
Super moisturizing feeling (cocoa butter, shea butter, etc. )
Good washing effect (coconut oil, palm kernel oil)
Oxidized oil is not easy to oxidize (coconut oil, palm oil, etc.). )
Easily oxidized (grape seed oil, etc.). )