Pipette bulbs

FIG. 1 Representation of a reversed micelle ( surfactant molecules are obtained by combining rubber pipette bulbs and magnetic stir bars). 

Pipette 2 mL of blue dye stock solution from the beaker into test tube 1, 4 mL into test tube 2, 6 mL into test tube 3, and 8 mL into test tube 4. CAUTION Always pipette using a pipette bulb. 

Do not use mouth suction to pipette chemicals or to start as siphon a pipette bulb or an aspirator should be used. 

Break a craft stick in two. Place one half of the stick on either side of the pipette bulb. Tighten a small C-clamp around the bulb of the pipette so that the clamp just holds the bulb snugly (see the diagram). 

Squeezing the pipette bulb, draw enough water into the pipette to form a small plug. The rest of the pipette should contain air. 

Draw buffer from each bottle up the glass tubing past the two-way tap using a pipette bulb filler, then close the tap. Ensure that no air bubbles are present in the tubing. 

By suction with a pipette bulb through a rubber tube, draw the solution up to a point well above the upper fiducial mark. Release the suction and measure the flow time between the upper and lower marks with a stopwatch or timer. Obtain two or more additional runs with the same filling of the viscosimeter. Three runs agreeing within about 1 percent should suffice. 

Many chlorinated hydrocarbons are toxic to some degree. Thus the mixed solvent of dichloroacetic acid and ethylene dichloride should be handled with care. This solvent is also very corrosive. If it is necessary to prepare the PEG solutions, gloves should be worn. Use a pipette bulb do not pipette by mouth. Dispose of waste chemicals as instructed. 

Capacitance cell as shown in Fig. 1 oscillator as described in the text and Fig. 2 frequency counter (range at least 0.5 to 5 MHz) shielded coaxial cables with connectors five 50- or 100-mL volumetric flasks a 5-mL Mohr pipette acetone wash bottle rubber pipette bulb. 

Into the bottom of a 25-mL filter flask place 50 mg of an impure unknown taken from the list in Table 3. These substances can be sublimed at atmospheric pressure although some will sublime more rapidly at reduced pressure. Close the flask with a rubber pipette bulb, and then place ice water in the centrifuge tube. Cautiously warm the flask until sublimation starts... 

FIG. 1 Calcium chloride drying tube fitted with a rubber stopper. Store for future use with cork in top, pipette bulb on bottom. 

FIG. 1 Balloon technique of oxygenation. About 10 1b oxygen pressure are needed to inflate the pipette bulbs. 

The reaction vessel is a 125-mL filter flask with a white rubber pipette bulb wired onto the side arm (Fig. 1). Introduce 10 mL of water, 1 mL of platinum(IV) chloride solution, and 0.5 g of decolorizing charcoal and swirl during addition of 3 mL of stabilized 1 M sodium borohydride solu-... 

Turn the generating pipette bulb-end down and submerge the bulb in the beaker of hot water. Cover the tip of the generating pipette with the collecting pipette, as shown in Figure A. 

After collecting ammonia gas for 3 min, remove the collecting pipette from the generating pipette. Set the generating pipette bulb down in the 100-mL beaker. 

Aquariums, capacity 10 litres Graduated pipettes Bulb pipettes Measuring flasks Measuring cylinders Erlenmeyer flasks 230 ml Glass beakers 230 ml Aeration stones Thermometers Oxygen meter pH meter with electrodes De-ionized water. 

Never draw liquids into the pipettes using mouth suction. A pipette bulb or a pipette piunp, not a rubber dropper bulb, must be used to fill pipettes. We recommend the use of a pipette pump. A pipette fits snugly into the pipette pump, and the pump can be controlled to deliver precise volumes of liquids. Control of the pipette pump is accomplished by rotating a knob on the pump. Suction created when the knob is turned draws the liquid into the pipette. Liquid is expelled from the pipette by turning the knob in the opposite direction. The pump works satisfactorily with organic, as well as aqueous, solutions. 

An alternative, and less expensive, approach is to use a rubber pipette bulb. Use of the pipette bulb is made more convenient by inserting a plastic automatic pipette tip into a rubber pipette bulb. The tapered end of the pipette tip fits snugly into the end of a pipette. Drawing the liquid into the pipette is made easy, and it is also convenient to remove the pipette bulb and place a finger over the pipette opening to control the flow of liquid. 

The two liquid layers are separated by withdrawing the lower layer using a disposable Pasteur pipette. This separation technique is illustrated in Figure 9. Take care not to disturb the liquid layers by allowing bubbles to issue from the pipette. Squeeze the pipette bulb to the required amount before introducing the pipette into the vial. Also take care not to allow any of the upper liquid layer to enter the pipette. The pointed shape of the interior of the conical vial makes it easy to remove all the lower layer without allowing it be contaminated by some of the upper liquid layer. More precise control in the separation can be achieved by using a filter-tip pipette (see Technique 8, Section 8.6). 

Pipettes The Pasteur pipette is shown in Figure 5.5A with a 2-mL rubber bulb attached. There are two sizes of pipettes a long one (9 inch) and a short one (5% inch). It is important that the pipette bulb fit securely. You should not use a medicine dropper bulb, because of its small capacity. A Pasteur pipette is an indispensable piece of equipment for the routine transfer of liquids. It is also used for separations (Technique 12). Pasteur pipettes may be packed with cotton for use in gravity filtration (Technique 8) or packed with an adsorbent for small-scale column chromatography (Technique 19). Although they are considered disposable, you should be able to clean them for reuse as long as the tip remains unchipped. 

To use a filter-tip pipette as a filter, the mixture is drawn up into the Pasteur pipette using a pipette bulb and then expelled. With this procedure, a small amoimt of solid will be captured by the cotton. However, very fine particles, such as activated charcoal, cannot be removed efficiently with a filter-tip pipette, and this technique is not effective in removing more than a trace amount of solid from a liquid. 

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