Addition Funnel

Addition funnel is a kind of common laboratory apparatus. Addition funnels can be divided into glass addition funnels and plastic addition funnels depending on the making material. Their main purpose is to add solid powders and liquids to volumetric bottles.

The additional funnel is a kind of funnel that prevents leakage and solves the problem of outside discharge of liquid or powder. It includes a hopper body and a pilot neck. The bottom end of the conical hopper body is connected to the upper end of the diversion neck; the outer wall of the neck is provided with an air guide channel extending from the lower end of the diversion neck down to the largemouth end of the hopper body. It is characterized in that the upper side of the said hopper is provided with an inward-facing flap, and the exhaust port of the air guide passage extends upward to the inner side of the flap. The air guide passage is formed by a gap between a convex rib set on the lead neck wall or on the hopper wall and the outer wall. The air guide passage is also formed by the interlayer set in the wall of the lead neck or the wall of the hopper body.

Usually, the upper side of the hopper body is equipped with an inward-facing flap, and the exhaust port of the air guide channel is located on the inner side of the flap to effectively prevent the material from splashing outward.

There are two main types of additional funnels, simple addition funnels, and pressure-equalizing addition funnels.

The addition funnel consists of a (usually) graduated cylindrical tube or, in some models, a pear-shaped sphere. It has a female ground glass fitting at the top, where a PP or glass stopper is used. The lower part of the funnel has a stopper, glass, or Teflon, which controls the flow. The dropper is separated from the ground glass fitting and extends a little below the fitting. The dropper funnel is similar in construction to the separating funnel, although the main difference is that the separating funnel does not have a male ground glass fitting.

The equal-pressure addition funnel consists of a graduated cylindrical tube or pear-shaped bulb. There is an additional narrow-bore glass tube in it. Starting at the top of the bulb, there is usually a small deformation upward to the bottom of the funnel, where it connects to the lower tube, below the stopper, and in the space above the male ground glass fitting. The function of this tube is to replace the volume of liquid lost in the bulb with an equivalent amount of gas from the flask into which the reagents flow. This allows the liquid in the funnel to drip smoothly without having to remove the stopper, which is necessary when precise amounts of liquid need to be added from the dropping funnel and when handling air-sensitive reagents in a sealed inert gas environment. Without this tube, or some other means to equalize the pressure between the sealed receiving flask and the sphere of the funnel, the flow of liquid from the sphere will quickly stop.

An addition funnel is suitable for the slow addition of reagents, which means dropwise addition. This may be desirable when the rapid addition of reagents may lead to side reactions, or when the reaction is too violent.

In most cases, addition funnels are made of borosilicate glass, while PP dropping funnels are rarely used.

a. Check whether the stopper is working properly or not.

b. If the stopper is not working properly, you should apply grease to the ground glass fitting.

c. Pour the liquid from the funnel through the upper female fitting and make sure that the liquid level remains below the upper opening of the horizontal glass tube where the pressure is balanced.

d. Use the stopper to close the funnel, or use the snap clips if needed.

e. Place the addition funnel in the corresponding socket of the flask.

f. Once in place, you will need to slowly open the stopper to release the liquid from the funnel.

a. If you are working in an inert gas environment, you must replace the air in the funnel with vacuum and inert gas.

b. To do this, you will need to attach the funnel to the flask and perform air removal with the funnel secured to the flask.

c. As soon as you remove it from the funnel, place the internally threaded glass stopper into the bottom of the funnel and close the funnel, moving it quickly to limit the amount of inert gas leaving the funnel.

d. Connect the dropping funnel to the inert gas solvent distillation unit by attaching the male connector of said unit to the female glass connector at the top and securing it with a clip.

e. Make sure the pressure balance tube is located above the funnel, not below, as any solvent dripping into the funnel could flow into the lateral tube and ruin your setup.

f. When you have collected enough solvent, you should close the stopcock and allow the solvent to cool to ambient temperature.

g. Remove the clip and immediately place the stopper on the funnel, then close the male connector of the installation with its female stopper.

h. Reattach the addition funnel to the flask, remove the stopper from the flask, then quickly remove the inner stopper of the funnel, attach the dropping funnel to the flask, and secure it with a keck clip.

a. If you collect a large amount of solvent in the addition funnel, a good idea is to support the end of the funnel slightly with a jack to prevent the funnel from becoming heavier and breaking the solvent drip fitting at the male end.

b. When dripping liquids, it is better to avoid using the stopper hole as a reference for drip rate and instead just open the stopper very slowly and adjust the drip rate by the time period between drops.

a. When filtering, the funnel should be placed on a funnel holder. The lower end of the funnel handle should be purple against the inner wall of the receiving vessel, and the filter paper should be tight against the inner wall of the funnel, with the edge of the filter paper about 5 mm below the edge of the funnel. Moisten it with distilled water beforehand so that no air bubbles remain.

b. When pouring in the separated material, it should flow into the funnel along the glass rod leading into the funnel, and the glass rod should be close to the filter paper at three layers. The liquid level of the separation should be lower than the edge of the filter paper.

c. The precipitate in the funnel must not exceed the height of the filter paper to facilitate the washing of the precipitate after filtration.

d. The funnel should not be heated by direct fire. If you need to filter while hot, the funnel should be placed in a metal heating jacket. If there is no metal jacket, the funnel can be preheated by soaking it in hot water before use.

a. The operator should add the solids directly to the reaction mixture, all at once or in parts. If the reaction is carried out in an inert atmosphere, take care to avoid excessive exposure to air.

b. The operator should dissolve the solid in a small amount of reaction solvent and add it via a syringe. This is a valuable method for small-scale reactions.

a. If the liquid is a solution in a solvent, add it only via syringe.

b. For highly exothermic reactions or other reactions requiring slow addition, the operator should dilute the pure liquid with the reaction solvent before adding via a syringe or addition funnel.

c. For slow reactions (several hours to completion), pure liquid can be added via syringe.

Additions are accomplished by replacing the atmosphere of the reaction mixture with gas using a balloon. First, bubble the gas through the solution (via pipette/tube or needle/Luer lock/tube) for a few minutes to saturate. Then, during the reaction, the balloon is connected to the flask to provide about 1 atmosphere (aka "positive pressure") of gas.

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