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Use of extraction and separation funnel

 Extraction is one of the common operations for separating and purifying organic compounds. The application of extraction allows the extraction of desired substances from liquid or solid mixtures, the former called “liquid-liquid extraction” and the latter called “solid-liquid extraction”.

Extraction is an operation in which a substance is separated, extracted, or purified by a difference in solubility or partition ratio between two immiscible (or slightly soluble) solvents.

Working principles of extraction:

(1) The first two liquid phases in contact are completely insoluble (or slightly soluble);

(2) the solubility of the solute components in the two phases is different, so the extracting agent should have a greater solubility to the solute;

(3) Another situation is that the extractant can react with the extracted substance. This extraction method often uses acid-base neutralization reaction, generally using 5% sodium hydroxide, sodium carbonate, sodium bicarbonate or dilute hydrochloric acid, dilute sulfuric acid, etc. The alkaline extractant can remove the acidic material of the organic phase, and the acidic extractant can remove the alkaline material of the organic phase. Usually used in the post-treatment process of organic chemical reactions.

Selection principle of extraction agent:

(1) Generally, organic matter extraction from water requires that the solubility of water in the solvent is very small or almost insoluble

(2) The solubility of the extracted substance in the solvent is greater than that in water, and the solubility to impurities is smaller. The solvent does not react with water and the extracted substance

(3) The solvent after extraction is easy to be recovered by atmospheric distillation

(4) cheap and easy to get, easy to operate, low toxicity, boiling point should not be too high, chemical properties are stable

The method to judge the organic layer and the water layer: take a small amount of liquid in either layer and drop a small amount of tap water in a test tube. If it is divided into two layers, it means that the liquid is an organic phase. If there is no stratification after adding water, it is an aqueous solution.

Operating principles of extraction:

Using the same component of solvent, following the principle of a small amount of multiple times, the extraction efficiency is higher than using the full amount of solvent at one time.

1. Liquid-liquid extraction

Separating funnels are often used in liquid-liquid extraction.

The main uses of liquid separation funnel:

(1) Separation of two liquids that are delaminated and do not react

(2) Extract a component from a solution

(3)Wash the product with water or alkali or acid

(4)replace the drip funnel, drop reagent

Points needing attention when using a separating funnel:

(1) Leakage must be checked before use

(2) the lower port of the separating funnel can not be held by hand

(3) in the process of operation, the right hand holding the funnel, the index finger to resist glass plug at the top of the funnel, the piston part of the funnel, with his left hand index finger pressure piston, gently lift up and down shaking funnel, and every few seconds will funnel inversion cock up, carefully open the cock, to balance the internal and external pressure, repeat for 2 to 3 times, and then boost the considerable time, Make the two insoluble liquid fully contact, improve the extraction efficiency; However, if emulsification occurs due to strong shaking, the operation method should be changed and the funnel should be leveled before and after shaking

(4) can not use the hand to hold the liquid funnel to separate liquid

(5) The piston can only be opened after the upper port plug is opened

(6) The separation funnel should be placed in the iron ring, and the liquid can be released from the lower port after the solution is stratified

The upper liquid needs to be poured out from the upper port, not released from the lower port

The liquid funnel should be cleaned immediately after use

2. solid-liquid extraction

Solid-liquid extraction is also common in daily life, such as making tea, cooking Chinese medicine and so on.

In the laboratory, the extraction of solid substances usually with the help of Soxhelt (Soxhelt) extractor, is the use of solvent reflux and siphon principle, so that solid organic matter is continuously extracted by pure solvent for many times, it has the characteristics of higher extraction efficiency and saving solvent (reference from tea extraction of caffeine). The material that is easy to decompose or change color by heat should not be selected.

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