Calibration of liquids

Fig. 2.30 The principle features of the solid-stem liquid-in-glass thermometer. From Figure 3 from the NBS Monograph 90, Calibration of Liquid-in-Glass Thermometers," by James F. Swindells, reprinted courtesy of the National Institute of Standards and Technology, Technology Adminstration, U.S. Department of Commerce. Not copyrightable in the United States.

A2.2.3 Procedure for Ice-point Re-calibration of Liquid-in-glass Thermometers. 

ISO/DIS 4548-12 Methods of Test for Full-Flow Lubricating Oil Filters for Internal Combustion Engines - Part 12 Particle Retention Ability and Contaminant Holding Capacity Using Particle Counting ISO/DIS 11171 Hydraulic Fluid Power - Calibration of Liquid Automatic Particle Counters... 

ASTM F1226-89(1994)el Standard Test Method for Calibration of Liquid-... 

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. 

In addition to the orthodox method, just described, for the determination of the boiling points of liquids, the student should determine the boiling points of small volumes (ca. 0 5 ml.) by Siwolobofifs method. Full details are given iri Section 11,12. Determine the boiling points of the pure liquids listed in the previous paragraph. Observe the atmospheric pressure and if this differs by more than 5 mm. from 760 mm., correct the boiling point with the aid of Table II,9,B. Compare the observed boiling points with the accepted values, and draw a calibration curve for the thermometer. 

Phenylacetylene. Support a 5-litre glass Dewar flask in a wooden case. Equip the flask with a lid of clear Perspex, provided with suitable apertures for a mechanical stirrer, introducing solids (e.g., sodium) or hquids, a calibrated dip stick for measuring the volume of liquid in the Dewar vessel, a gas mlet tube and an ammonia inlet arrange for an electric light to shine downwards into the flask. 

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. 

Three important precautions are needed when working with pipets and volumetric flasks. First, the volume delivered by a pipet or contained by a volumetric flask assumes that the glassware is clean. Dirt and grease on the inner glass surface prevents liquids from draining evenly, leaving droplets of the liquid on the container s walls. For a pipet this means that the delivered volume is less than the calibrated volume, whereas drops of liquid above the calibration mark mean that a volumetric flask contains more than its calibrated volume. Commercially available cleaning solutions can be used to clean pipets and volumetric flasks. 

With liquids at low velocities, the effect of the Reynolds number upon the coefficient is important. The coefficients are appreciably less than unity for Reynolds numbers less than 500 for pitot tubes and for Reynolds numbers less than 2300 for pitot-static tubes [see Folsom, Trans. Am. Soc. Mech. Eng., 78, 1447-1460 (1956)]. Reynolds numbers here are based on the probe outside diameter. Operation at low Reynolds numbers requires prior calibration of the probe. 

Calibration of Gauges Simple liquid-column manometers... 

When a tank volume cannot be calculated or when greater precision is required, calibration may be necessaiy. This is done by draining (or filling) the tank and measuring the volume of liquid. The... 

Set up the calibration apparatus, replacing the cassette with the impinger/bubbler lined with the amount of liquid reagent specified in the sampling method. 

The device most commonly used to measure volume in general chemistry is the graduated cylinder. A pipet or buret (Figure 1.8) is used when greater accuracy is required. A pipet is calibrated to deliver a fixed volume of liquid—for example, 25.00 mL—when filled to the mark and allowed to drain. Variable volumes can be delivered accurately by a buret, perhaps to 0.01 mL. 

Use of a refractometer to make measurements of the refractive index of liquids. This will often provide a means of identifying a pure compound, and can also be used (in conjunction with a calibration curve) to analyse a mixture of two liquids. 

By calibration against solutions containing known activities of the ion being determined, measurement of the current can be used to ascertain the activity of the ion in the test solution. Such measurements can be carried out with very small volumes of liquid, and find application in biochemical analyses.36 37 However, the simpler ion-selective electrodes discussed above can be readily adapted for dealing with small volumes, and even for intracellular measurements. 

FIGURE G.9 A buret is calibrated so that the volume of liquid delivered can be measured. 

There are two steps in the calculation. First, calibrate the calorimeter by calculating its heat capacity from the information on the first reaction, Cca) = qc, /AT. Second, use that value of Cc-1 to find the energy change of the neutralization reaction. For the second step, use the same equation rearranged to gcal = Cca AT, but with AT now the change in temperature observed during the reaction. Note that the calorimeter contains the same volume of liquid in both cases. Because dilute aqueous solutions have approximately the same heat capacities as pure water, assume that the heat capacity is the... 

Protocols must specify calibration of application equipment before and after application to determine the rate of product delivery when application equipment was traveling at a constant ground speed. Liquid or emulsion samples should be collected from spray nozzles and granule collection should occur as the test substance exits the application equipment. Once the correct ground speed has been determined for a given application system, that speed is maintained throughout the application process. 

Russell, D. J., Calibration of high performance size exclusion chromatography for small epoxy molecules, /. Liquid Chromatogr., 11, 383, 1988. 

Dunsmore, H. S. Midgley, D., The calibration of glass electrodes in cells with liquid junction, Anal. Chim. Acta 61, 115-122 (1972). 

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