Stirrers reciprocating

When the curvature of the reaction vessel is too great for the efficient operation of the bar type magnetic stirrer, a miniature solenoid-operated reciprocating stirrer may be employed (Fig. XII, 2, 19). This stirrer may be easilj constructed from a telephone relay or electric bell. It is advisable to have a control for adjusting the stroke while running. 

Figure 4. ABCOR drum ultrafilter with high-speed reciprocating stirrer (1)...

A typical arrangement of components in a tensimetric titration is presented in Fig. 9.5, which shows the previously discussed tensimeter and a calibrated bulb attached to a vacuum line.2 The sample container on the tensimeter is fitted with a small reciprocating stirrer which consists of a thin glass rod connected to a glass-encased headless nail or glass-encased bundle of soft iron wire. This stirrer is driven by an external solenoid, the field of which is switched on and off by a current-interrupting device, the details of which are laid out in Fig 9.6. The size of the calibrated bulb is chosen so that it will contain the desired amount of gas for each addition at a pressure which is convenient and accurately measured (e.g., 100-500 torr). The calibration procedure and steps used dispensing gas from such a bulb are described in Section 5.3.G. 

Self aspirating devices (hollow stirrers, ejectors, funnel-shaped nozzles) have to overcome the hydrostatic pressure Aphydr = pg H. This is taken into account by the combination Fr = Fr (d/H ). By the way, this extended Froude number, Fr, represents the reciprocal value of the Euler number, Eu ... 

For the determination of equilibrium data a high-pressure reactor with a total volume of 530 ml was used. This reactor can be operated at a maximum pressure of 325 bar at 473 K and is equipped with a reciprocating stirrer for better phase contact. Samples can be taken as well from the liquid phase at the bottom as from the CO2 phase at the top of the reactor. In this work a defined volume of the liquid phase was withdrawn for analytical purpose and the amount of substances dissolved in the CO2 phase was calculated via mass balance. 

Since the hollow stirrer operates in accordance with the principle of jet suction, it should be pointed out here that the process number Fr d/H in the gas throughput characteristic is the reciprocal value of the Euler number Eu. If the tip speed of the stirrer u = d is regarded as a characteristic velocity, it follows that ... 

To maintain equilibrium between the solid and liquid phases it is necessary to maintain efficient stirring. The appropriate type of stirrer will depend on the physical properties of the mixture to be stirred. The majority of organic solid/liquid mixtures are viscous. For a viscous mixture of components of comparable density a reciprocating stirrer is more effective than a rotary propeller type in a cylindrical container. With the latter there is a tendency for concentric laminar flow currents to be set up around the stirrer and mixing between these currents is relatively slow. The stroke of the stirrer should traverse the whole... 

The apparatus (Fig. 5) consists of a bell-mouthed glass test-tube, to contain the sample, inside a larger test-tube which acts as an air-jacket. The sample tube is fitted with a cork through which pass a central thin-walled thermometer pocket and a reciprocating hand stirrer which serves also as a gas inlet tube. The stirrer, made of capillary tubing of 0 5 mm... 

The stirrer was made to reciprocate at 3 to 4 cycles/sec by alternately energizing two solenoid coils of double glass-insulated aluminum wire wrapped around the autoclave body. The timing unit consisted of a multivibrator circuit whose frequency of oscillation and cycle time division could be controlled by varying resistances in the circuit. The timer unit, in turn, controlled the grids of two pairs of thyratrons which furnished power to the solenoids. Stirrer operation was monitored by a tickler coil connected to an oscilloscope. 

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