Pasteur apparatus

Fig. 1.2 Pasteur s apparatus if the oven is not switched on, the microorganisms in the air enter the sterile culture solution and multiply. If the oven is switched on, they are killed by the heat. After Conaut (1953)...

Follow the procedure described above using 1 g portions in 10 , 10 , 10 , 10 " and 10 M CTAB solutions. Addition of CTAB may cause extensive frothing. Since the powder will be retained in this foam it must be broken up either mechanically using a Pasteur pipette or by the addition of a small amount of ethanol. The powder may also stick to the walls of the apparatus above the collection tube. This powder should be dislodged by gentle tapping on the walls of the apparatus. Calculate the mean flotation efficiency at each concentration and graph the results. 

When set (about 30 min.) remove the tape from the bottom of the gel, remove the slot former and clamp the gel plates vertically into the electrophoresis apparatus. Fill the reservoirs with 1 x TBE and flush out the wells with a pasteur pipette to wash out unpolymerised acrylamide. 

Low-viscosity liquids can be transferred to the hermetic DSC pan using a Pasteur-pipette or similar apparatus. Dipping one end of an opened paper clip into viscous liquids and then placing it onto the base of the sample pan may transfer higher viscosity samples. Care should be taken not to contaminate the lip of the pan with any liquid as this will result in a poor seal. 

In animal tissues (e.g. calf liver) X.o. is in the Golgi apparatus it is also a secretory enzyme present in milk, where its activity can be used to differentiate between fresh and heated or pasteurized milk. 

Caffeine can be purified by sublimation (Technique 17, Section 17.5). Assemble a sublimation apparatus as shown in Figure 17.2A. Add approximately 0.5 mL of methylene chloride to the Erlenmeyer flask and transfer the solution to a clean, 5-mL, thin-walled, conical vial, using a clean and dry Pasteur pipette. Add a few more drops of methylene chloride to the flask in order to rinse the caffeine out completely. Transfer this liquid to the conical vial. Evaporate the methylene chloride from the conical vial by gentle heating in a warm water bath imder a stream of dry air or nitrogen. 

As distillate condenses in the Hickman head, transfer the liquid from the reservoir to a preweighed 3-mL conical vial. If your Hickman head does not have a side port, it will be necessary to use a 9-inch Pasteur pipette. In the latter case, it is helpful to bend the tip of the pipette slightly by heating it in a flame. The distillate can then be removed without removing the thermometer. Be sure to cap the conical vial used for storage each time after you transfer the distillate. Continue to distill the mixture, and transfer the distillate to the vial until the temperature in the Hickman head increases above 78°C or until the temperature in the Hickman head drops several degrees below 78°C and remains at this lower temperature for 10 minutes or more. You should collect about 0.4 mL of distillate. The distillation should then be interrupted by removing the apparatus from the heat source. 

Set up a sublimation apparatus as shown in Technique 17, Figure 17.2A. Dissolve the camphor in about 4 mL of methylene chloride (dichloromethane), and dry the solution over anhydrous granular sodium sulfate (see Technique 12, Section 12.9). Transfer the solution in 1 to 2 mL portions with a Pasteur pipette to the 5-mL thin-walled reaction vial, leaving the anhydrous sodium sulfate behind. Use a beaker of warm water (about 40°C) to remove the solvent while carefully directing a stream of air into the vial. As the solvent evaporates, add further portions of the methylene chloride solution. As the evaporation continues, a solid will form in the vial. Be patient, as it may take a while to remove the solvent completely. You may find it useful to rotate the vial in the air stream to remove the last traces of solvent. 

Turn off the microburner and allow the apparatus to cool. Carefully remove the water from the central tube with a long-stemmed Pasteur pipette so that no water overflows from the tube. Turn off the vacuum and disconnect the vacuum pressure tubing from the apparatus. 

Detach the air condenser when the apparatus is cool enough to handle. Transfer the reaction mixture, which may contain some solid, with a Pasteur pipette into a 10-mL beaker. Allow the mixture to cool to room temperature and then cool in an ice-water bath for about 15 minutes until crystallization is complete. It may be necessary to scratch the inside of the beaker with a glass stirring rod to induce crystallization. Crystallization is complete when virtually the entire mixture has solidified. Collect the crystals on a Hirsch funnel by vacuum filtration and wash the crystals thoroughly with three 1-mL portions of ice-cold 95% ethanol. The solvent should remove most of the color from the crystals. 

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