Flasks pressure

Nitrogen oxide sampling is simpler. This gas is drawn into an evacuated sample flask containing dilute sulfuric acid and hydrogen peroxide. The flask is shaken and allowed to stand for 16 h before the flask pressure is measured. Then the solution is made alkaline, and the nitrogen oxides are deterrnined by the phenoldisulfonic colorimetric test. 

Once the actual reaction begins, a defoamer can be used, but it is simpler not to overfill the reaction flask. Pressure vessels allow the use of higher temperatures and result in much shorter reaction times, simultaneously overcoming the foaming problems. After the reaction is complete and the GPC/SEC gel has been cleaned it is important not to dry the gel above 85°C as self-ignition can occur. 

L three-necked round-bottomed flask 500 mL round-bottomed flask 150 mL round-bottomed flask Pressure-equalized dropping funnel X3 Separating funnel X2 Sinter funnel X2... 

Dry all glassware for at least 2 h in an oven at 150°C, and assemble flask, pressure-equalising addition funnel, condenser and nitrogen bubbler on top of condenser while still warm, passing nitrogen through the bubbler whilst apparatus cools, and stopper the third neck. 

Dry all glassware in an oven. Assemble the two-necked flask, pressure-equalising addition funnel, condenser, gas line adaptor, stirrer bar and stopper on the hot plate stirrer while warm and allow to cool under nitrogen. 

This example of high and low pressure also shows the ambiguities of these tenns in science. All these pressures are essentially constant in tenns of tire range of pressures encountered in nature. From negative pressures in solids under tension (e.g., on the wall of flask confining a fluid), pressure in nature increases... 

It has already been pointed out that a liquid even when subjected to simple atmospheric distillation may become superheated and then bump violently in consequence this danger is greatly increased during distillation under reduced pressure and therefore a specially designed flask, known as a Claisen flask, is used to decrease the risk of superheating. In Fig. i2(a) a Claisen flask D is shown, fitted up as part of one of the simplest types of vacuum-distillation apparatus. ... 

Fractional Distillation under Reduced Pressure. One great disadvantage of the simple vacuum-distillation apparatus shown in Fig. 12(a) is that, if more than one fraction distils, the whole process has to be stopped after collecting each consecutive fraction, in order to change the receiver F. This may be overcome by replacing the simple receiving flask F by a pig (Fig. 13) which collects consecutive... 

Add 15 g, of chloroacetic acid to 300 ml. of aqueous ammonia solution d, o-88o) contained in a 750 ml. conical flask. (The manipulation of the concentrated ammonia should preferably be carried out in a fume-cupboard, and great care taken to avoid ammonia fumes.) Cork the flask loosely and set aside overnight at room temperature. Now concentrate the solution to about 30 ml. by distillation under reduced pressure. For this purpose, place the solution in a suitable distilling-flask with some fragments of unglazed porcelain, fit a capillary tube to the neck of the flask, and connect the flask through a water-condenser and receiver to a water-pump then heat the flask carefully on a water-bath. Make the concentrated solution up to 40 ml. by the addition of water, filter, and then add 250 ml. of methanol. Cool the solution in ice-water, stir well, and set aside for ca. I hour, when the precipitation of the glycine will be complete. 

Place 80 g, of hydroxylamine sulphate (or 68-5 g. of the hydrochloride), 25 g. of hydrated sodium acetate, and 100 ml. of water in a 500 ml. flask fitted with a stirrer and a reflux water-condenser, and heat the stirred solution to 55-60°. Run in 35 g (42 nil,) of -hexyl methyl ketone, and continue the heating and vigorous stirring for ij hours. (The mixture can conveniently be set aside overnight after this stage.) Extract the oily oxime from the cold mixture twice with ether. Wash the united ethereal extract once with a small quantity of water, and dry it with sodium sulphate. Then distil off the ether from the filtered extract, preferably using a distillation flask of type shown in Fig. 41 (p. 65) and of ca, 50 ml, capacity, the extract being run in as fast as the ether distils, and then fractionally distil the oxime at water-pump pressure. Collect the liquid ketoxime, b.p. 110-111713 mm. Yield, 30-32 g. 

Chill the concentrated solution of the amine hydrochloride in ice-water, and then cautiously with stirring add an excess of 20% aqueous sodium hydroxide solution to liberate the amine. Pour the mixture into a separating-funnel, and rinse out the flask or basin with ether into the funnel. Extract the mixture twice with ether (2 X25 ml.). Dry the united ether extracts over flake or powdered sodium hydroxide, preferably overnight. Distil the dry filtered extract from an apparatus similar to that used for the oxime when the ether has been removed, distil the amine slowly under water-pump pressure, using a capillary tube having a soda-lime guard - tube to ensure that only dry air free from carbon dioxide passes through the liquid. Collect the amine, b.p. 59-61°/12 mm. at atmospheric pressure it has b.p. 163-164°. Yield, 18 g. 

Cool the solution thoroughly in ice-water, and then make it alkaline by the cautious addition (with stirring or shaking) of a solution of 80 g. of sodium hydroxide in ca, 150 ml. of water. Now isolate the free tertiary amine by steam-distillation into hydrochloric acid, etc., precisely as for the primary amine in Stage (D), but preferably using a smaller flask for the final distillation. Collect the 2-dimethylamino- -octane, b.p. 76-78715 mm. Yield, 13-14 g. At atmospheric pressure the amine has b.p. 187-188°. 

Dissolve I ml. of benzaldehyde and 0-4 ml. of pure acetone in 10 ml. of methylated spirit contained in a conical flask or widemouthed bottle of about 50 ml. capacity. Dilute 2 ml. of 10% aqueous sodium hydroxide solution with 8 ml. of water, and add this dilute alkali solution to the former solution. Shake the mixture vigorously in the securely corked flask for about 10 minutes (releasing the pressure from time to time if necessary) and then allow to stand for 30 minutes, with occasional shaking finally cool in ice-water for a few minutes. During the shaking, the dibenzal -acetone separates at first as a fine emulsion which then rapidly forms pale yellow crystals. Filter at the pump, wash well with water to eliminate traces of alkali, and then drain thoroughly. Recrystallise from hot methylated or rectified spirit. The dibenzal-acetone is obtained as pale yellow crystals, m.p. 112 yield, o 6 g. 

Assemble in a fume-cupboard the apparatus shown in Fig. 67(A). Place 15 g. of 3,5-dinitrobenzoic acid and 17 g. of phosphorus pentachloride in the flask C, and heat the mixture in an oil-bath for hours. Then reverse the condenser as shown in Fig. 67(B), but replace the calcium chloride tube by a tube leading to a water-pump, the neck of the reaction-flask C being closed with a rubber stopper. Now distil off the phosphorus oxychloride under reduced pressure by heating the flask C in an oil-bath initially at 25-30, increasing this temperature ultimately to 110°. Then cool the flask, when the crude 3,5-dinitro-benzoyl chloride will solidify to a brown crystalline mass. Yield, 16 g., i.e,y almost theoretical. Recrystallise from caibon tetrachloride. The chloride is obtained as colourless crystals, m.p. 66-68°, Yield, 13 g Further recrystallisation of small quantities can be performed using petrol (b.p. 40-60°). The chloride is stable almost indefinitely if kept in a calcium chloride desiccator. 

The pure quinaldine can now be isolated by either of the following methods, (a) Transfer the acetylated mixture to a Claisen flask (preferably having a short fractionating column below the side-arm) and distil the mixture slowly at water-pump pressure by heating the flask in an oil or silicone bath. The first fraction, of b.p. ca. 50715 mm., contains acetic acid and... 

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