Heating mantles

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... 

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-fltting electric heating mantle) if gentle suction is applied to the Alter flask, hot (or warm) air will pass over the crystalline solid. 

Place 3 3oz packets of Mildewcide into a 1L flask with an electric heating mantle and cork in the neck connected to a gas bubbler immersed in at least 550mL of distilled water. Heat the paraformaldehyde (what is in the Mildewcide) to between 180-200C (a temp, regulator is absolutely necessary for this step or use a silicone oil bath). The paraformaldehyde will depolymerize making formaldehyde gas in about 91% yield. Alternatively, the gas can be bubbled through the Ammonia solution directly (only for the brave ). If the Formaldehyde solution will not be used immedi-... 

A dry 1-L, three-necked, round-bottomed flask, fitted with a reflux condenser, mechanical stirrer, and ground-glass stopper, is charged with 111.0 g (0.25 mol) of phosphorus sulfide, P4S10 (Note 1) and 270 g (2.5 mol) of anisole (Note 1). Stirring Is commenced and the mixture is heated at reflux temperature by use of a heating mantle. After 1 hr, the solution Is... 

C. Thiete 1,1-dioxide. A sample of 3-chlorothietane l,l-d1ox1de (8.0 g, 0.057 mol) Is dissolved In dry toluene (300 ml) (Note 7) In a 500-mL, twonecked, round-bottomed flask equipped with a reflux condenser, magnetic stirrer, heating mantle (or silicone oil bath), and thermometer. The reaction Is heated to 60° C and tri ethyl amine (28.7 g, 0.28 mol, 39,5 ml) Is added through the condenser. The reaction mixture Is stirred for 4 hr and triethyl-amine hydrochloride is removed by filtration and washed with toluene (100 mL), Toluene is removed on a rotary evaporator and the residue is recrystallized from diethyl ether-ethanol (Note 8) to give a white solid (4.5-4.8 g, 75-81 ) mp 49-50°C (llt mp 52-54°C). 

Chlovothiete 1,1-dioxide. A solution of 3,3-d1chloroth1etane 1,1-dioxide (4.0 g, 0.023 mol) in toluene (150 mL) Is placed In a 250-mL, round-bottomed, two-necked flask equipped with a heating mantle (or silicone oil... 

Preparation and Standardisation of Alumina. The activity of alumina depends inversely on its water content, and a sample of poorly active material can be rendered more active by leaving for some time in a round bottomed flask heated up to about 200° in an oil bath or a heating mantle while a slow stream of a dry inert gas is passed through it. Alternatively, it is heated to red heat (380-400°) in an open vessel for 4-6h with... 

In a 500-ml. round-bottomed flask fitted with a reflux condenser are placed 16.2 g. (0.08 mole) of dry a-naphthylthiourea (Note 1) and 180 ml. of redistilled chlorobenzene. The flask is heated at the reflux temperature by means of an electric heating mantle. Evolution of ammonia begins almost at once, and all of the solid dissolves after 30-45 minutes. The solution is maintained at reflux for 8 hours (Note 2) and then evaporated on a steam bath at water-pump pressure to remove all of the chlorobenzene. The residue crystallizes on cooling and is extracted with four 30-ml. portions of boUing hexane (Note 3). Removal of solvent from the combined hexane extracts affords pale yellow crystals of naphthyl isothiocyanate, m.p. 58-59°. The yield is 12.7-13.0 g. (86-88%). Recrystallization from hexane (9 ml. of hexane for 1 g. of solute) gives colorless needles, melting point unchanged (Note 4). 

The ice bath is replaced, and 250 ml, of ethylene dichloride is added to the mixture. When the internal temperature has been lowered to 5°, a solution of 67 g. (1.0 mole) of freshly distilled pyrrole in 250 ml. of ethylene dichloride is added through a clean dropping funnel to the stirred, cooled mixture over a period of 1 hour. After the addition is complete, the ice bath is replaced with a heating mantle, and the mixture is stirred at the reflux temperature for 15 minutes, during which time there is copious evolution of hydrogen chloride. 

Usually a small amount of material remains undissolved. This material does not affect the melting point significantly but can be removed if desired by forcing the solution, kept hot by an electric heating mantle, through the filter arrangement described above into a dry flask protected from moisture by a calcium chloride tube. 

The submitters used an electric heating mantle as a source of heat. 

A 250-ml round-bottom flask is fitted with a condenser (drying tube), a magnetic stirrer, and a heating mantle. The flask is charged with 8.2 g (0.1 mole) of cyclohexene, 14 g (0,079 mole) of NBS, 0.1 g of benzoyl peroxide, and 50 ml of dry carbon tetrachloride. The flask is flushed with nitrogen and then refluxed for 40 minutes with... 

A solution of 3 g of the nitrile, water (5 moles per mole of nitrile), and 20 g of boron trifluoride-acetic acid complex is heated (mantle or oil bath) at 115-120° for 10 minutes. The solution is cooled in an ice bath with stirring and is carefully made alkaline by the slow addition of 6 A sodium hydroxide (about 100 ml). The mixture is then extracted three times with 100-ml portions of 1 1 ether-ethyl acetate, the extracts are dried over anhydrous sodium sulfate, and the solvent is evaporated on a rotary evaporator to yield the desired amide. The product may be recrystallized from water or aqueous methanol. Examples are given in Table 7.1. 

---