How many types of glycerin are there?
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There is a bucket in the laboratory labeled “Glycerin”; the substance inside it is immiscible with water and has a density lower than that of water. I checked the manual, which stated that \"glycerin is miscible with water and has a density of 1.26\". I then asked the people in the laboratory, and they said that the glycerin was of proper quality, and as far as they knew, glycerin is less dense than water. In confusion, who can answer this?
In a narrow sense, glycerol is simply glycerin; in a broader sense, glycerol includes similar alcohols such as ethylene glycol.
The person the original poster is asking about either has no idea what glycerin is, or is talking nonsense. Below is the information on glycerin; please refer to it. Glycerin; Propanetriol; 1,2,3-Glycerol; Glycerin; 1,2,3-Propeatriol; 1,2,3-Trihydroxyopropane; Glycerol; Glycyl alcohol; Propenyl alcohol; 1,2,3-Propanetriol. Molecular formula: C3H8O3; Molecular weight: 92.09; CAS number: 56-81-5. Properties: Colorless, transparent, viscous liquid. It has a sweet taste, is hygroscopic, and is flammable. Melting point 17.8°C (18.17°C, 20°C). Boiling point: 290°C (decomposition), 263.0°C at 53.2 kPa, 240.0°C at 26.6 kPa, 167.2°C at 1.33 kPa, 153.8°C at 0.665 kPa, 125.5°C at 0.133 kPa; flash point (open cup): 177°C; relative density: 1.26362 (20/20°C); autoignition temperature: 392.8°C; refractive index: 1.4746; viscosity (20°C): 1499 mPa·s; vapor pressure (100°C): 26 Pa; surface tension (20°C): 63.4 mN/m. Glycerol is miscible with water and ethanol, and its aqueous solution is neutral. 1 part of glycerol can dissolve in 500 parts of ether or 11 parts of ethyl acetate. Insoluble in benzene, chloroform, carbon tetrachloride, carbon disulfide, petroleum ether, and oils. It can absorb moisture from the air, as well as hydrogen sulfide, hydrogen cyanide, and sulfur dioxide. No odor. When pure glycerin is exposed to a low temperature of 0°C, it forms shiny rhombohedral crystals with a melting point of 17.8°C; the presence of even a small amount of water hinders crystallization. The freezing points of glycerin aqueous solutions at different concentrations (by weight%) are as follows: 10%, -1.6℃ ； 30%, -9.5℃ ； 50%, 23.0℃ ； 66.7%, -46.5℃ ； 80%, -20.3℃ ； 90%, -1.6℃. In nature, glycerol is widely present in animals and plants mainly in the form of glycerides. Preparation method: The industrial production methods of glycerin can be divided into two main categories: methods that use natural fats and oils as raw materials, with the glycerin obtained in this way commonly referred to as natural glycerin ； The synthesis method using propylene as a raw material yields glycerol that is commonly known as synthetic glycerol. 1. Production of natural glycerin: Before 1984, glycerin was entirely recovered as a by-product of soap production from animal and plant fats. To date, natural oils remain the main raw materials for producing glycerin; approximately 42% of this natural glycerin is obtained as a by-product of soap manufacturing, while 58% comes from the production of fatty acids. The saponification of fats and oils in the soap-making industry. The products of the saponification reaction form two layers: the upper layer consists mainly of sodium fatty acid salts (soap) along with a small amount of glycerin, while the lower layer is an aqueous waste solution containing salts and sodium hydroxide; this solution typically contains 9–16% glycerin and 8–20% inorganic salts. Fat reaction. Glycerin water obtained from the hydrolysis of oils and fats (also known as sweet water) has a higher glycerin content than soap-making waste liquid, at around 14-20%, with inorganic salts accounting for 0-0.2%. In recent years, the continuous high-pressure hydrolysis method has been widely adopted; no catalyst is used in the reaction, and the resulting sweet water generally contains no inorganic acids, making the purification process simpler than that for waste alkaline solutions. Whether it is soap-making waste liquid or the glycerin contained in water obtained from oil hydrolysis, the amount of glycerin present is not high, and both contain various impurities. The production process of natural glycerin involves purification and concentration to obtain crude glycerin, as well as refining steps such as distillation, decolorization, and deodorization of the crude glycerin. This process is described in detail in some books and publications. 2. Production of synthetic glycerol: The various methods for synthesizing glycerol from propylene can be divided into two main categories, namely chlorination and oxidation. The propylene chlorination method and the intermittent acetic acid oxidation method of propylene are still in use in industry today. (1) Propylene chlorination method: This is the most important production method for synthesizing glycerin, and it comprises four steps, namely high-temperature chlorination of propylene, hypochlorination of chloropropene, saponification of dichloropropanol, and hydrolysis of epichlorohydrin. The hydrolysis of epichlorohydrin to produce glycerol is carried out at 150°C and a carbon dioxide pressure of 1.37 MPa, in an aqueous solution containing 10% hydroxide and 1% sodium carbonate; this process yields a glycerol-containing aqueous solution with sodium chloride present, in which the glycerol content ranges from 5% to 20%. Through concentration, desalination, and distillation, glycerol with a purity of over 98% is obtained. (2) Propylene peracetic acid oxidation method: Propylene reacts with peracetic acid to produce propylene oxide, which is then isomerized into allyl alcohol. The latter then reacts with peracetic acid to produce propylene oxide (i.e., glycidol), which is finally hydrolyzed to glycerol. The production of peracetic acid does not require a catalyst; it is obtained through the gas-phase oxidation of acetaldehyde with oxygen, under normal pressure, at 150–160°C, with a contact time of 24 seconds. The conversion rate of acetaldehyde is 11%, while the selectivity for peracetic acid is 83%. The last two reactions mentioned above proceed continuously in a reaction distillation column with a special structure. After the raw materials, allyl alcohol and an ethyl acetate solution containing peracetic acid, are fed into the tower, the bottom temperature of the tower is maintained at 60–70°C and 13–20 kPa. Ethyl acetate solvent and water are distilled off at the top of the tower, while a glycerin aqueous solution is obtained at the bottom of the tower. This method features high selectivity and yield; peracetic acid is used as the oxidant, no catalyst is required, the reaction proceeds rapidly, and the process is simplified. To produce 1 ton of glycerin, 1.001 tons of allyl alcohol and 1.184 tons of peracetic acid are consumed, with 0.947 tons of acetic acid produced as a by-product. Currently, the production of natural glycerin and synthetic glycerin accounts for almost 50% each, while the propylene chlorination method accounts for about 80% of synthetic glycerin production. Natural glycerin accounts for over 90% of the total production in our country. Uses: Glycerin is an important basic organic raw material with a wide range of applications in industry, medicine, and daily life. Currently, there are around 1,700 different uses for it, primarily in the fields of medicine, cosmetics, alkyd resins, tobacco, food, acid resins, celluloid, and textiles for printing and dyeing. The consumption of solvents in areas such as alkyd resins, celluloid, and ** is on the decline.
No way – glycerin is miscible with water and ethanol; how could it not be miscible? It’s impossible, right?
No way – glycerin is miscible with water and ethanol; how could it not be miscible? It’s impossible, right?
No way – glycerin is miscible with water and ethanol; how could it not be miscible? It’s impossible, right?