Funnel clogging

Allow the reddish-yellow solution to cool to about 40° and then filter off at the pump the polyene which has separated this filtration should be performed as rapidly as possible to avoid contamination with lead acetate, and a Buchner funnel of not less than 6 cm. diameter should therefore be used to avoid clogging the filter. Wash the crude production the filter with... 

The funnel should be previously heated and have fairly large holes so as not to be clogged by the mandelic acid that begins to crystallize as soon as the solution cools slightly. Only a slight suction should be applied during filtration. 

To prevent clogging of the Buchner funnel during filtration it is necessary to preheat the funnel and keep it hot during filtration. 

The addition of 2,4-pentanedione to liquid ammonia is a highly exothermic process. Also, ammonia vapor reacts with the /3-diketone to produce an insoluble ammonium salt, which tends to clog the tip of the addition funnel. Cooling the reaction mixture in dry ice-acetone reduces the vigor of the reaction and minimizes the dogging of the addition funnel. The 2,4-pentanedione should be added in spurts which fall on the surface of the reaction mixture rather than on the wall of the flask... 

About 75 ml. of ethanol is used for every gram of butenolide to be dissolved. Clarification of the solution with charcoal should be avoided because the butenolide tends to separate from solution during filtration and clogs the steam-jacketed funnel. The crystallized butenolide melts at 150-152°. 

If you decide to add salt to a sep funnel, don t add so much that it clogs up the stopcock For the same reason, keep drying agents out of sep funnels. 

Aspirator filtration through a pad of Celite was beneficial to prevent small particulate matter from clogging the fritted funnel. However, it was necessary to break up the pad of Celite to allow for effective filtration. 

After cooling slightly, the reaction mixture is transferred to a large flask and treated with 3.5 1. of water. Part of this is used to rinse out the reaction flask. The mixture is boiled with 30 g. of Norite for about ten minutes and is filtered while still hot with suction, using a preheated Buchner funnel. Furylacrylic acid tends to separate quickly and sometimes offers trouble in clogging the funnel. The filtrate is acidified to Congo red by the addition of a 1 1 solution of concentrated hydrochloric acid in water. 

If, however, an excess of the reducing agent is to be avoided and a solution of the hydride is to be added to the compound to be reduced (by means of the so-called inverse technique ) special care must be taken to prevent clogging of the stopcock of a separatory funnel with undissolved particles. 

At this point the checkers filtered the mixture through a pad of 30 g of Cellte to remove the green precipitate. This filtration reduces the problem of emulsions and clogging of the separatory funnel during subsequent extractions. 

This prevents clogging of the funnel during the subsequent addition of methyllithium solution. 

The addition of 2,4-pentanedione to liquid ammonia is a highly exothermic process. Also, ammonia vapor reacts with the fi diketone to produce an insoluble ammonium salt, which tends to clog the tip of the addition funnel. Cooling the reaction... 

A heated Buchner funnel is preferably used to prevent clogging by crystallization. 

Usually the pores oU the zfilter paper become partially clogged after about hal f of the mixture has been filtered so that the rate of filtration is cut cdown considerably. In this event a fresh funnel and filter should be employed. 

A rather large suction funnel (125 mm. or more) should be used in the filtration as the sulfonyl chloride has a tendency to clog the filter. 

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