Pipette measuring

Bottles made of plastic materials are better avoided for storage, since the solvent is capable of leaching a plasticizer out from the bottle. For rapid transfer, however, polyethylene or -propylene pipettes, measuring cylinders, etc. can be used with apparently no detrimental effects. 

Determine the Strength of the Solution. With a pipette measure 10 cc. of the preparation into a 300-cc. Erlenmeyer flask, add 100 cc. of distilled water, and titrate against standard HC1 using phenolphthalein as the indicator. (See Experiment 6, page 75.) Carry out a duplicate titration with a second 10-cc. sample, and take the average of the results to give the normality of the solution. Label the bottle with the number of cubic centimeters of the solution, with its normality, and with the actual amount in grams of the hydroxide. 

To quantify luciferase reporter gene expression in cell lysates, transfer 50 pi cell lysate from each well into a 96-well black flat-bottom microplate. Add 100 pi luciferase buffer per well, and optionally mix with a pipette. Measure the chemiluminescence intensity (count time 0.20 min with background correction) using a luminometer, e.g., a Microplate Scintillation Luminescence Counter (Canberra Packard) or a Wallac Victor 2 Multi-label Counter (PerkinElmer). 

Narrow-necked polythene bottles (50 or 100-mL), piezoelectric spark generator, sparking plug attached to base plate, gas inlet tubes, 1-L beaker, dropping pipette, measuring cylinder, safety glasses, protective gloves. 

Material Beakers, test tubes, plastic pipettes, measuring cylinders (100 ml), scales copper sulfate hydrate, 2-M hydrochloric acid, ammonia solution (25% solution, diluted 1 50). 

Material 8 small beakers, plastic pipettes, measuring cylinders, scales, photometer 0.1 -M solutions of copper sulfate and ammonia, ammonium nitrate. 

Robots efficiently pipette measured volumes of liquids. One cannot nearly as efficiently quantitate and transfer a neat (solid) compound. When a compound in DMSO solution is added to an aqueous medium, it is being delivered in a very high energy state relative to the thermodynamically most stable polymorph.The compound is in DMSO solution, so there is no compound crystal lattice to disrupt as part of the aqueous solubilization process. The effect is that the compounds initial apparent aqueous solubil-... 

Cuvettes, Erlenmeyer flasks, transfer pipettes, measuring flasks Nitrate calibrating solution ... 

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. 

The classical method for DO determination is the Winkler titration method, which is still frequently used as a reference procedure for calibration of DO meters. It is inexpensive in capital cost outlay, requiring only common laboratory glassware (burettes, pipettes, measuring cylinders, conical flasks, volumetric flasks), burette stands, wash bottles, and chemicals. The principal reactions involved are... 

Classical techniques for measuring the sedimentation behavior include taking samples with a pipette, measurement of height of sediment layer at the bottom, and use of balance pan to measure the weight of settled particles. Modern sedimentometers make use of the diffraction pattern of a light beam, the power loss of an x-ray, or a Doppler shift of a laser beam. The... 

Pasteur pipette measuring cylinders graduated pipette... 

This method relies on the simple principle that the flow of ions into an electrolyte-filled micropipette as it nears a surface is dependent on the distance between the sample and the mouth of the pipette [211] (figure B 1.19.40). The probe height can then be used to maintain a constant current flow (of ions) into the micropipette, and the technique fiinctions as a non-contact imaging method. Alternatively, the height can be held constant and the measured ion current used to generate the image. This latter approach has, for example, been used to probe ion flows tlirough chaimels in membranes. The lateral resolution obtainable by this method depends on the diameter of the micropipette. Values of 200 nm have been reported. 

The transference of a liquid from one vessel to another is best carried out by means of a dropping pipette A (Fig. 30). For measuring out a definite volume of liquid it is obviously an advantage to have a calibrated pipette B (Fig. 30) of i or 5 ml. total capacity. Alternatively, semi-micro burettes reading to 0 02 ml. are particularly convenient for class work. 

Amount of material required. It is convenient to employ an arbitrary ratio of 0 10 g. of solid or 0 20 ml. of liquid for 3 0 ml. of solvent. Weigh out 0 10 g. of the finely-powdered solid to the nearest 0 01 g. after some experience, subsequent tests with the same compound may be estimated by eye. Measure out 0-20 ml. of the liquid either with a calibrated dropper (Fig. 11,27, 1) or a small graduated pipette. Use either a calibrated dropper or a graduated pipette to deliver 3 0 ml. of solvent. Rinse the delivery pipette with alcohol, followed by ether each time that it is used. 

A liquid may be transferred from one vessel to another with a dropper pipette (Fig. XII, 1, 2, a or b). If the dropper pipette is calibrated, it may be employed for measuring out a definite volume of liquid. 

Calibration of apparatus and application of corrections. All instruments (weights, flasks, burettes, pipettes, etc.) should be calibrated, and the appropriate corrections applied to the original measurements. In some cases where an error cannot be eliminated, it is possible to apply a correction for the effect that it produces thus an impurity in a weighed precipitate may be determined and its weight deducted. 

The above procedure may be adapted to the determination of molybdenum in steel. Dissolve a 1.00 g sample of the steel (accurately weighed) in 5 mL of 1 1 hydrochloric acid and 15 mL of 70 per cent perchloric acid. Heat the solution until dense fumes are evolved and then for 6-7 minutes longer. Cool, add 20 mL of water, and warm to dissolve all salts. Dilute the resulting cooled solution to volume in a 1 L flask. Pipette 10.0 mL of the diluted solution into a 50 mL separatory funnel, add 3 mL of the tin(II) chloride solution, and continue as detailed above. Measure the absorbance of the extract at 465 rnn with a spectrophotometer, and compare this value with that obtained with known amounts of molybdenum. Use the calibration curve prepared with equal amounts of iron and varying quantities of molybdenum. If preferred, a mixture of 3-methylbutanol and carbon tetrachloride, which is heavier than water, can be used as extractant. 

Procedure. Weigh out accurately about 4 g of the pure organic acid, dissolve it in the minimum volume of water (Note 1), or 1 1 (v/v)ethanol/water mixture, and transfer the solution to a 250 mL graduated flask. Ensure the solution is homogeneous and make up to the required volume. Use a pipette to measure out accurately a 25 mL aliquot and transfer to a 250 mL conical flask. Using two drops of phenolphthalein solution as indicator, titrate with standard 0.2M (approx.) sodium hydroxide solution (Note 2) until the colourless solution becomes faintly pink. Repeat with further 25 mL volumes of the acid solution until two results in agreement are obtained. 

Notes. (1) For elementary students, it is sufficient to weigh out accurately about 1.25 g of arsenic(III) oxide, dissolve this in 50 mL of a cool 20 per cent solution of sodium hydroxide, and make up to 250 mL in a graduated flask. Shake well. Measure 25.0 mL of this solution by means of a burette and not with a pipette (caution — the solution is highly poisonous) into a 500 mL conical flask, add 100 mL water, 10 mL pure concentrated hydrochloric acid, one drop potassium iodide solution, and titrate with the permanganate solution to the first permanent pink colour as detailed above. Repeat with two other 25 mL portions of the solution. Successive titrations should agree within 0.1 mL. 

Using a burette or a pipette with a safety pump (this is necessary owing to the poisonous properties of the solution) measure out 25.0 mL of the arsenite solution into a 250 mL conical flask, add 25-50 mL of water, 5g of sodium hydrogencarbonate, and 2 mL of starch solution. Swirl the solution carefully until the hydrogencarbonate has dissolved. Then titrate slowly with the iodine solution, contained in a burette, to the first blue colour. 

Measure out a 100 mL portion of the solution with a pipette and titrate the iodine with approximately Mj80 standard sodium thiosulphate solution adding 2mL of starch solution as indicator as the titration proceeds and after the titration liquid has become pale yellow in colour. 

---