Cooling preparation

While the sodium ethoxide solution is cooling, prepare a solution of 7 7 g. of finely powdered iodine in 60 ml. of ether. When this solution is ready, add 9 ml. (9 6 g.) of ethyl malonate to the ethanolic sodium ethoxide solution, mix w ell and then allow to stand for 30-60 seconds not longer) then cautiously add the ethereal solution of the iodine, mixing thoroughly during the addition in order to avoid local overheating by the heat of the reaction. (If, after the ethyl malonate has been added to the sodium ethoxide, a considerable delay occurs before the iodine is added, the yield of the final product is markedly decreased.)... 

For each solution With constant mixing, add casein and PVP to warm (65°C) TTBS. Stir for 5 min, then cool. Prepare each solution just before use. 

While the sample is cooling, prepare a chromatographic column. Take a 25-mL buret. Add a small piece of glass wool. With the aid of a glass rod, push it down near the stopcock. Add 15-16 mL of petroleum ether to the buret. Open the stopcock slowly, and allow the solvent to fill the tip of the buret. Close the stopcock. You should have 12-13 mL of petroleum ether above the glass wool. Weigh about 20 g of alkaline aluminum oxide (alumina) in a 100-mL beaker. Place a small funnel on top of your buret. Pour the alumina slowly, in small increments, into the buret. Allow it to settle to form a 20-cm column. Drain the solvent but do not allow the column to run dry. 

Transfer a 50.0-mL aliquot of this solution into a 150-mL beaker, and add 1.0 mL of 1 5 sulfuric acid and 1.0 mL of a filtered solution of 1 25 potassium permanganate. Heat the solution just to boiling, simmer for about 5 min, and cool. Prepare a reagent blank in the same manner. 

Dissolve the sodium hydroxide (40 g) in water (150 mL) and pour this mixture through a funnel into the round-bottomed flask. Allow it to cool to 0°C. While this solution is cooling, prepare a solution of tetraethylene glycol, 14 (68.3 g, 0.35 mmol) in THF (200 mL) and water (50 mL) and pour this solution into the round-bottomed flask. 

Dissolved substances may recrystallise in large crystals when kept too cool. Preparations should thus not be stored in the fridge unnecessarily. 

Isolation While the reaotion mixture is cooling, prepare an apparatus for steam distillation with internal steam generation. Add about 35-40 ml of water to the reaction flask. Heat the flask and steam-distill the product until about 30-35 ml of... 

Because of its antispasmodic, carminative, choleretic, and cholagogic effects it is traditionally used for treating gastrointestinal disorders and also in mucusdissolving and broncholytic preparations. In pharmaceuticals it is a compound in antipruritic, antiseptic, and cooling preparations [40]. 

PVAl-PVAc gels form upon cooling prepared by fieeze/thaw cycling [552, 553] the gel-sol transition for physically crosslinked PVA hydrogels is 55-7(fC [554]... 

Boron trioxide is not particularly soluble in water but it slowly dissolves to form both dioxo(HB02)(meta) and trioxo(H3B03) (ortho) boric acids. It is a dimorphous oxide and exists as either a glassy or a crystalline solid. Boron trioxide is an acidic oxide and combines with metal oxides and hydroxides to form borates, some of which have characteristic colours—a fact utilised in analysis as the "borax bead test , cf alumina p. 150. Boric acid. H3BO3. properly called trioxoboric acid, may be prepared by adding excess hydrochloric or sulphuric acid to a hot saturated solution of borax, sodium heptaoxotetraborate, Na2B407, when the only moderately soluble boric acid separates as white flaky crystals on cooling. Boric acid is a very weak monobasic acid it is, in fact, a Lewis acid since its acidity is due to an initial acceptance of a lone pair of electrons from water rather than direct proton donation as in the case of Lowry-Bronsted acids, i.e. 

This chloride is prepared by dissolving tin in concentrated hydrochloric acid on cooling, the solution deposits crystals of hydrated tin(II) chloride. SnClj. 2H2O ("tin salt ). The anhydrous chloride is prepared by heating tin in a current of hydrogen chloride ... 

Nitric acid is prepared in the laboratory by distilling equal weights of potassium nitrate and concentrated sulphuric acid using an air condenser, the stem of which dips into a flask cooled by tap water. The reaction is ... 

Phosphorus pentachloride is prepared by the action of chlorine on phosphorus trichloride. To push the equilibrium over to the right, the temperature must be kept low and excess chlorine must be present. Hence the liquid phosphorus trichloride is run dropwise into a flask cooled in ice through which a steady stream of dry chlorine is passed the solid pentachloride deposits at the bottom of the flask. 

To prepare the potassium salt, the mixture of ethanol and sulphuric acid is boiled under reflux, cooled, and treated with an excess of calcium carbonate. 

Place 0 5 ml. of acetone, 20 ml. of 10% aqueous potassium iodide solution and 8 ml. of 10% aqueous sodium hydroxide solution in a 50 ml. conical flask, and then add 20 ml. of a freshly prepared molar solution of sodium hypochlorite. Well mix the contents of the flask, when the yellow iodoform will begin to separate almost immediately allow the mixture to stand at room temperature for 10 minutes, and then filter at the pump, wash with cold w ater, and drain thoroughly. Yield of Crude material, 1 4 g. Recrystallise the crude iodoform from methylated spirit. For this purpose, place the crude material in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, add a small quantity of methylated spirit, and heat to boiling on a water-bath then add more methylated spirit cautiously down the condenser until all the iodoform has dissolved. Filter the hot solution through a fluted filter-paper directly into a small beaker or conical flask, and then cool in ice-water. The iodoform rapidly crystallises. Filter at the pump, drain thoroughly and dry. 

Prepare a solution of 12 5 g. of hydroxylamine hydrochloride in 20 ml. of water contained in a too ml. conical flask. Dissolve 7 g. of powdered sodium hydroxide in 20 ml. of water, cool the solution in ice-water, and then add it to that of the hydroxylamine hydrochloride. Place a thermometer in the mixed solution, and chill the flask in ice-water until the temperature of the solution is between 5 and 10 . Now add 12 ml. (9 5 gO of dry acetone (preferably from a burette to ensure... 

For this preparation, it is particularly necessary that the sodium acetate should be free from traces of water. The anhydrous material can be prepared by gently heating the hydrated salt (CHsCOONa,3HjO) in an esaporating-basin over a small Bunsen flame. The salt dissolves in its water of ciystallisation and resolidifies as this water is driven off further heating then causes the anhydrous material to melt. Stir the molten anhydrous material to avoid charring, and then allow it to cool in a desiccator. Powder the cold material rapidly in a mortar, and bottle without delay. 

When the ij hours boiling is complete, preheat a Buchner funnel and flask by pouring some boiling water through the funnel with the filter-paper already in position, and then quickly filter the boiling solution. Transfer the filtrate to a beaker to cool, and then wash the insoluble residue of diphenylurea on the filter twice with hot water, and drain thoroughly. Cool the filtrate in ice-water the monophenylurea separates as colourless needles. Filter at the pump and drain well. Recrystallise the crude product from boiling water, as in the previous preparation. Yield of monophenylurea, 2 5-3 g. m.p. 147°. 

For these experiments, prepare two solutions (A) A solution of 2 5 g. of sodium metaperiodate in 50 ml. of water. A clear solution can be readily prepared by gentle warming, and then cooled. 

Place 8 0 g. of magnesium turnings or ribbon and 80 ml. of the dry benzene in the flask. Prepare a solution of 9-0 g. of mercuric chloride in 50 ml. of the dry acetone, transfer it to the dropping-funnel, and then allow it to enter the flask slowly at first, and then more rapidly, so that the addition takes about 3-5 minutes. The reaction usually starts shortly after the initial addition of the mercuric chloride solution if it is delayed, it may then start vigorously, and the flask may have to be cooled in water to prevent escape of acetone through the condenser. 

The benzene used in this preparation should be reasonably free from toluene therefore use a sample of benzene supplied by dealers as crystalUsable benzene, i.e.y one which crystallises readily when cooled in ice-water. It should preferably be dried over calcium chloride and, immediately before use, filtered through a fluted filter-paper. The pyridine should also preferably be dried over solid potassium hydroxide and redistilled. 

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