Preparative flow meters

A solution of -1 mol of ethylmagnesium bromide (prepared from 1.10 mol of C2H5Br and Mg as described in ref. 4) in -1000 ml of THF (note 1) is heated to 50 C. Acetylene (note 2) is then introduced at a rate of 300-400 mVmin (flow meter) with vigorous stirring, while keeping the temperature between 50 and 55 C (note 3). The introduction of gas is stopped when the temperature has dropped to between 40 and 45 C (without external cooling). The jelly-like suspension is then heated for an additional 30 min at 50 C with introduction of N2 (300-500 m]/min, note 4)... 

Figure 7.5 Product preparation using flow meters.

Other applications for water meters, besides the water line where the fluoride is injected as discussed above, are on supply lines for solution makeup water. Additionally, a flow meter is a necessity when a sodium fluoride saturator is used to prepare the fluoride solution, (see Section 5.) Because the water usage rate in a saturator installation is minimal, the meter must be the smallest available (usually 1/2 in 1 in. = 2.54 cm). A propeller type is commonly used here. 

Bubble flow meters are the simplest laboratory flow meters, suitable particularly for the calibration of the other instruments at very low flow rates. They are based on the determination of the velocity of the motion of soap bubbles driven by the gas measured, in a calibrated tube. They can be easily prepared from commonly used pipettes. An advantage is that... 

Fig. 179. Preparation of large quantities of anhydrous hydrazine. a) Tap /i) high-efficiency condensation trap /a) condensation trap m ) flow meter r) reaction tube s j) air cooling coll ...

Fig. 340. Preparation of active metal oxides by oxidation of metal vapor, a funnel for addition of metal b observation port c side port d circular nozzle for air intake e first chamber with lateral observation ports (these are not shown) f illuminating device g glass tubes (the remaining parts of the apparatus are made from sheet iron) h carbon electrodes i flow meter activated by differential pressure n precipitation cell s movable carbon electrode.

The more complex part is the preparation system that gathers the different flow meters and the different control instruments. 

At the same time that Jacobson was doing the work just described, he and two other colleagues prepared a dog with a Heidenhain pouch supplied by a single artery around which they placed an electromagnetic flow meter and a hydraulic occluder. Flow rose under histamine stimulation and fell under pitressin inhibition. Using aminopyrine clearance as a measure of mucosal flow, Jacobson found that with increasing doses of histamine both secretion and aminopyrine clearance rose, but that there was no correlation between mucosal flow as measured by aminopyrine clearance and total flow. During brisk secretion, mucosal flow was 25 times the secretory rate. ... 

Solutions of the complexes were prepared in spectral grade benzene or carbon tetrachloride solvents, which were deaerated with prepurified nitrogen before use in order to minimize oxidation of the chromium complexes. The flow rate for the SCOT column was determined by injecting 40 to 50y 1 of methane and measuring the time of elution. The resultant linear gas velocity in ft/sec was then converted to volume flow rate in ml/min by the appropriate conversion factors. Flow rates for the packed column were determined by use of a soap-film flow meter. 

Reactor System. A general purpose reactor system shown in Figure 1 was used in this work to study catalytic oxidation reactions over supported platinum catalyst pellets. This equipment allowed up to six precise gas mixtures to be prepared and made available for feed to the reactor. The switching valve directed a desired gas mixture flow to the reactor while another gas mixture flow was precisely measured by the bubble flow meter. 

Thin film composite membranes were prepared on in-house fabricated porous supporting membranes made of either polyetherimide (Ultem ) or polyacrylonitrile (PAN). Gas fluxes of composite membranes were measured at 1-5 bar feed pressure (pure gases) and room temperature using a soap-film bubble flow meter. In this case, the permeate pressure was the ambient atmospheric pressure. 

If we are not limited in column-base holdup and can design for reasonably well-damped control, then we can treat reboiler dynamics as ne gible. This says that steam flow responds to the flow controller set point immediately, and that boilup follows steam flow without lag. We may Aen prepare the signal flow diagram of Figure 16.7. Note that = steam flow-meter gain = 12/(Wsr)max- This may be partially reduced to the form of Figure 16.8. From this last illustration we can see some of the loop s characteristics as they ate afiected by reboiler swell and inverse response. 

Li et al. prepared a kind of acid-base PEM membrane by introducing polypyrrole (Ppy) into sulfonated poly(ether ether ketone) (SPEEK) membranes by polymerization in SPEEK solutions, thus improving their methanol resistance. Cell performance was evaluated by using a DMFC unit cell, and the catalysts used at the anode and the cathode were Pt-Ru/C and Pt/C, respectively. The catalyst loading was 2.5 mg cm at both the anode and the cathode. A 2 M methanol solution was fed to the anode at a flow rate of 82 mL min , while the cathode was fed with dry O2 at a rate of 2000 mL min via a flow meter. The cell temperature was kept at 70°C. The cell performance of the SPEEK membrane was a little better than its composite membranes with a power of 115 mW. The highest power of the composite membranes was about 95 mW. But after the fuel cell performance experiment, SPEEK membranes show much more serious swelling than the composite membranes, despite the fact that they have a little better performance. 

The permeation experiments were carried out with pure CO2, CH4, O2 and N2 gases by using a gas permeation system under conditions of constant pressure. Two coupon samples were prepared and tested for each membrane batch. The active area of the coupons was 9.24 cm. The membranes were conditioned for individual feed at 120 psig for a required time to obtain a steady permeation rate. All permeation experiments were carried out at 100 psig. The cell was open to the atmosphere on the permeate side and the flow rate from this side was measured by a bubble flow meter. The permeation experiments were carried out at ambient temperature and the permeation results were corrected to standard temperature and pressure. 

On preparative chromatographs it is usual to install flow meters even on those systems utilizing diaphragm or piston positive displacement pumps. The reason being that the accuracy of these pumps is less than their anal3dical counterparts, coupled with the fact they are often operated at their flow rate extremes, where the flow inaccuracy is even greater. 

In static runs gas is supplied to the ion source only at a rate sufficient to compensate the outflow through the leak (0.5 cc./sec. for air, equal to conductance of leak). The gas mixtures were prepared in two 2-liter storage flasks of the gas handling system. Flow runs can be made by passing gas through the ion source. Different flow rates were obtained by interposing capillary tubes in series with the flow system. Flow rates with an average linear velocity of up to 10 meters sec.-1 could be obtained. Since the distance from the foil window to the leak is about 3 cm., the contact time for irradiation at this velocity is some 3 msec. 

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