Screw clamp

The screw clamp may be adjusted so that there will be a spattering on the upper, cool part of the flask, while the pressure is still maintained below 30 mm. Under these conditions, the initiation of crystallization is speeded. 

Schraub-verschluss, tn. screw cap screw plug, -zwinge, /. screw clamp. 

In the meantime, a mixture of 79 g. (0.55 mole) of cuprous bromide (Note 3) and 80 ml. (0.6 mole) of 48% hydrobromic acid (Note 1) is heated to boiling in a 5-1. round-bottomed thrcc-necked flask, equipped with a condenser set for distillation and provided with a 2-1. receiving flask, a steam inlet tube closed by a screw clamp, and a separatory funnel. About one-fourth of the diazonium solution is transferred to the separatory funnel, without filtration, and immediately run into the cuprous bro-mide-hydrobromic acid solution, which is kept boiling over a free flame, at such a rate that boiling is continuous. When the separatory funnel is nearly empty a further portion of the cold... 

So, for your own protection, make up a water trap from some stoppers, rubber tubing, a thick-walled Erlenmeyer or filter flask, and a screw clamp (Fig. 48). Do not use garden variety Erlenmeyers they may implode without warning. Two versions are shown. I think the setup using the filter flask is more flexible. The screw clamp allows you to let air into your setup at a controlled rate. You might clamp the water trap to a ringstand when you use it. The connecting hoses have been known to flip unsecured flasks, two out of three times. 

The powder is spread on cotton muslin stretched over wooden frames and placed on the shelves. The drier is then closed and the vacuum pump set in motion. The pump usually operates a pressure of 100-150 mm Hg. When the pressure becomes steady, the screws clamping the lids are released, but the lids continue to adhere hermetically to the drier, owing to the reduced pressure created inside. As a safety precaution the driers work in this manner until drying has been completed. Thus should ignition occur the lids are freely detached. This prevents thepowder from burning in a confined space, and exploding, and so destroying the drier. The capacity of the... 

A liter of commercial absolute alcohol is dried by means of sodium and ethyl phthalate 1 in a 2-1. distilling flask equipped with a reflux condenser. A short section of rubber tubing closed by a screw clamp is attached to the side arm of the flask. In the next step the condenser is set for downward distillation. 

With the screw clamp open, the pyrites is gently heated with a wing burner in a slow stream of air drawn in by the aspirator. The clamp is then partially closed so that air also passes through the capillary into the nitric add. The pyrites may now be heated more strongly the current of air through the nitric add is adjusted by means of the clamp so that red fumes of nitrogen oxides are always present in the bottle or chamber, If not enough vapor of nitric acid is provided, colorless crystals of nitrosyl sulfuric acid ( chamber crystals ) will form on the walls of the bottle. 

Sephadex G-50 has been prepared for your use. The dry beads have been preswollen in water for several hours, fine particles that may slow column flow have been removed, and the gel has been equilibrated in Tris buffer. If chromatography columns are not available, one can easily be constructed from a glass tube (2.5 X 40 cm), cork stoppers, Tygon tubing, a screw clamp, and small glass tubing as shown in Figure E4.4. With the screw clamp closed, add 10 to 15 mL of Tris buffer and insert a small piece of... 

The stopper in the top of the column must be airtight. Adjust the screw clamp so that the flow rate of the column is about 5 to 10 mL/hr. Collect... 

The apparatus shown in Fig. 3 has been found convenient for such evaporations under reduced pressure. The distillation is started with 3.5-4 1. in the 12-I. flask, and the level of liquid is maintained by controlling the rate of addition by means of a screw clamp. A 2-1. flask has been found satisfactory for the condensing intermediate receiver, provided the outside be completely wetted by the cold water. 

B. 2,2 -Bipyridine. With the apparatus set as described above, 100 ml. of pure pyridine (Note 7) is poured into the dropping funnel, and the screw clamps are completely closed. Immediately afterward about 80 ml. of the pyridine is run slowly onto the catalyst from the dropping funnel. Under no circumstances is any air allowed to enter the flask. The flask is then shaken carefully in order to wet the catalyst as much as possible with pyridine. Another 80 ml. of pyridine is added in the same way, and the flask is shaken again. Finally 40 ml. of pyridine is added, and air is allowed to enter the flask. The connections to the Buchner flask are removed, and a reflux condenser is fitted. The reaction mixture is then boiled gently under reflux (Note 8). After about 48 hours the flask is allowed to cool to about 60°, and most of the liquid is decanted (Hoodt) and filtered through a sintered-glass funnel (Note 9) into a 500-ml. round-bottomed flask. Then 50 ml. of fresh pyridine is added to the catalyst in the reaction flask, and the mixture is heated to reflux... 

The average time required for the complete removal of the water from the catalyst varies from 4 to 12 hours. It is essential to evaporate the water slowly since much nickel may be lost if the water boils too vigorously. If the temperature of the bath should rise too high, the screw clamps are closed far enough to increase the pressure slightly in the apparatus. As soon as the bath has cooled to the required temperature, the clamps are reopened fully. The maximum practical temperature for the removal of the water was found to be 25-30° at pressures between 17 and 20 mm. 

Fig. 8.3. Cross-section of a Urry type glass O-ring joint and two types of screw clamps, (u) An O-ring. b) Cross section of a Urry-typc O-joint. Note the ridge which is tooled into the groove, (c) Two types of joint clamps. The upper one is manufactured by A. H. Thomas Co., Philadelphia, PA 19105.

Fig. 8.1. Standard taper ( ) and spherical joint ( ). When the joints are lubricated with grease, they must generally be held together. Springs or rubber bands arc frequently employed on standard taper joints, while a spring-loaded clamp (illustrated here) or a screw clamp (illustrated in Fig. 8.3) is used with ball joints. The method used for specifying joint sizes in the United States is illustrated, and it is described in detail in National Bureau of Standards, Commercial Standard CS 21-39.

To cause adsorption of the glucose-1-phosphate by the IR-45, gently pour the acidic solution treated with Dowex 50 (steps 13 and 14 of the protocol for Day 2) onto the column, avoiding the introduction of air bubbles into the resin bed. Open the screw clamp and adjust the flow rate to about 15 ml/min. Pass the entire solution through the IR-45 resin without permitting air to enter the column. 

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