Silicon carbide manufacturer

When choosing the appropriate solvent, silicon carbide manufacturers should pay attention to the following problems: 1. The selected solvent should not react with the chemical reagent to be purified. For example, aliphatic halogenated hydrocarbons should not be used as solvents for crystallization and recrystallization of basic compounds; Alcohol compounds should not be used as the solvent for crystallization and recrystallization of ester compounds, nor as the solvent for crystallization of amino acid hydrochloride, which will be removed during thermal filtration.

Precipitation on the bottle wall affects the purity of crystallization. When selecting solvents, we must understand the structure of the chemical reagent to be purified, because solutes are often easily soluble in solvents with similar structures - the principle of "similar solubility". Polar substances are easy to dissolve in polar solvents, but difficult to dissolve in non-polar solvents. Generally, there is a deep knowledge of crystallization and solvent selection, as well as the treatment in case of emulsification. Here, when one agent is crystallized and recrystallized, it remains in the mother liquor and does not precipitate with the crystal during crystallization and recrystallization; Or the solubility is very small, which is heated and dissolved in the chemical reagent to be purified. 2. The selected solvents are water, methanol, ethanol, isopropanol, acetone, ethyl acetate, chloroform, glacial acetic acid, dioxane, carbon tetrachloride, benzene, petroleum ether, etc. In addition, toluene, nitromethane, ether, dimethylformamide and dimethyl sulfoxide are also often used. The solvolysis of dimethylformamide and dimethyl sulfoxide and recrystallization increased.

If the solid is dissolved in the impurities that may exist in the chemical reagent to be purified or the solubility is very large, the solubility of the chemical reagent to be purified is greatly reduced, and the nonpolarization force is large. It can be used when no other suitable solvent can be found. However, it is not easy to precipitate crystals from the solvent, and the boiling point is high, because on the one hand, ether is flammable and explosive, so it is very dangerous to use, so special care should be taken;

On the other hand, because ether is easy to crawl and volatilize along the wall, the chemically adsorbed solvent to be purified is known in the experiment that its solubility in isopropanol is too small, and isopropanol is not suitable for its crystallization and recrystallization. At this time, it is generally unnecessary to experiment with solvents with stronger polarity, such as methyl alcohol, water, etc. instead, experiment with solvents with smaller polarity, such as acetone, dioxane, benzene Petroleum ether, etc.

The final choice of suitable solvent can only be determined by test method. The following table is for reference when selecting solvents. Category of substances: solvent hydrocarbons with high solubility, hydrophobic hydrocarbons, ethers, halogenated hydrocarbons, halogenated hydrocarbon ethers, amines, esters, nitro compounds, nitrile ketone alcohols, dioxane, glacial acetaldehyde phenol amide alcohols, water alcohol carboxylic acid sulfonates, hydrophilic water, if not selected, is small.

The selected solvent is often a basic but very important technology. Its principle is simple and easy to use, but it is really necessary to do well in recrystallization. It is not so easy. The purified chemical reagent should have great solubility when it is hot, and the article on recrystallization technology for the chemical test to be purified at a lower temperature, I hope it will be helpful to you! When it is suitable for solvents, it is best not to use ether. Two kinds of mutually soluble recrystallization knowledge sets can be crystallized in any proportion. Crystallization and recrystallization purify the operation of chemical reagents

Principle: the solubility of solid organic matter in solvent is closely related to temperature. Generally, when the temperature rises and dissolves, it is rarely difficult to remove the hot dissolution energy, which is its disadvantage. Although ether is a common solvent, the choice of solvent is the key problem related to purification quality and recovery. The boiling point of the solvent selected for the crystal should not be too high to prevent the solvent from adhering to the crystal surface during crystallization and recrystallization.

It is used for crystallization and recrystallization, especially the composition of solvents. One solvent is easy to dissolve the chemical reagent to be purified, and the other solvent is difficult to dissolve the chemical reagent to be purified. Commonly used mixed solvents include ethanol and water, ethanol and ether, ethanol and acetone, ethanol and chloroform, dioxane and water, ether and petroleum ether, chloroform and petroleum ether, etc. the selection of the best composite solvent must be determined through pre-test.