Funnels: filter electrically heated

If crystallisation commences as soon as the solvent cools or if large quantities of hot solution are to be filtered, the funnel (and fluted filter paper) should be warmed externally during the filtration (hot water funnel). Three types of hot water funnel are illustrated in Fig. 11,1, 6 no flames should be present whilst inflammable solvents are being filtered through the funnel of Fig. 11, 1, 6, a. Alternatively, the funnel may be surrounded by an electric heating mantle (see Section 11,57) the heat input may be controlled by a variable transformer. When dealing with considerable volumes of aqueous or other solutions which do not deposit crystals rapidly on cooling, a Buchner funnel may be used for filtration (see detailed account in Section 11,1 and Fig. 11 1, 7, c). The filter paper... 

In a 1 litre round-bottomed flask provided with an efficient double surface condenser, place 40 g. (39 ml.) of aniline, 50 g. (40 ml.) of carbon sulphide CAUTION inflammable) (1), and 50 g. (63-5 ml.) of absolute ethyl alcohol (2). Set up the apparatus in the fume cupboard or attach an absorption device to the top of the condenser (see Fig. 11, 8, 1) to absorb the hydrogen sulphide which is evolved. Heat upon an electrically-heated water bath or upon a steam bath for 8 hours or until the contents of the flask sohdify. When the reaction is complete, arrange the condenser for downward distillation (Fig. 11, 13, 3), and remove the excess of carbon disulphide and alcohol (CA UTION inflammable there must be no flame near the receiver). Shake the residue in the flask with excess of dilute hydrochloric acid (1 10) to remove any aniline present, filter at the pump, wash with water, and drain well. Dry in the steam oven. The yield of crude product, which is quite satisfactory for the preparation of phenyl iao-thiocyanute (Section IV.95), is 40-45 g. Recrystalhse the crude thiocarbanihde by dissolving it, under reflux, in boiling rectified spirit (filter through a hot water funnel if the solution is not clear), and add hot water until the solution just becomes cloudy and allow to cool. Pure sj/m.-diphenylthiourea separates in colourless needles, m.p, 154°,... 

For solids which melt above 100° and are stable at this temperature, drying may be carried out in a steam oven. The crystals from the Buchner funnel should then be placed on a clock glass or in an open dish. The substance may sometimes be dried in the Buchner funnel itself by utilising the device illustrated in Fig. 77,33,1. An ordinary Pyrex funnel is inverted over the Buchner funnel and the neck of the funnel heated by means of a broad flame (alternatively, the funnel may be heated by a closely-fitting electric heating mantle) if gentle suction is applied to the filter flask, hot (or warm) air will pass over the crystalline solid. 

The precipitate is separated by suction filtration, pressed on the funnel, and washed successively with three 100-ml. portions of water and two 100-ml. portions of 95% ethanol. The product is transferred to a 1-1. Erlenmeyer flask, boiled for 10 minutes with 400 ml. of 60% ethanol with occasional stirring, filtered hot, washed twice with 50-ml. portions of 95% ethanol, and then dried in an oven at 90-100° for 6-12 hours. The crude a-phthalimido-o-toluic acid, which weighs 140-155 g., is divided into two equal portions, and each portion is dissolved in boiling propionic acid (Note 5). Each solution is treated with 1 tablespoon of Norit and filtered through an electrically heated gravity funnel. The filtrates are allowed to cool slowly to room temperature and are then refrigerated overnight. The crystals from the two portions are collected by suction filtration in one funnel and washed on the funnel with 400 ml. of 95% ethanol. The product is dried over potassium hydroxide in a vacuum desiccator. The yield of nearly white crystals of a-phthalimido-o-toluic acid is 126-141 g. (60-67% based on phthalide), m.p. 265.0-266.5°. 

A three neck round bottomed flask was equipped with a dropping funnel, water cooled condenser, argon purge, electric heating mantle and magnetic stirrer. The flask was charged with 1,2 di (p-n-butylphenyl)ethane 1,2 dione(1.8 g, 3.6 mmol), phosphorous pentasulfide (1.2 g 5., 5 mmol) and 30 dioxane. The mixture was refluxed for 5 hours. The reaction mixture was filtered hot to remove the unreacted phosphorous pentasulfide and the residue was washed with hot dioxane several times. The filtrate was returned to the cleaned round bottom flask, and nickel (ll)chloride hexahydrate (0.48 g, 2.0 mmol) in 10 ml of water was... 

The experimental procedure employed a capillary viscometer made of quartz as shown in Fig. 26. A solid sample was put in the filtration chamber and the top of the chamber was sealed under a vacuum. Then the sample was heated to melting and filtered into the viscometer and the connecting tube sealed at the middle. The viscometer was settled inside a transparent electric furnace and after the temperature of the melt was stabilized, the furnace containing the viscometer was turned upside down, which transferred the melt into the funnel. Then the tube was turned... 

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