Burettes, calibration

Burettes calibration of, 88 manipulation of, 85 standardised, 84 stopcock lubricant, 85 tolerances of, 84... 

Burettes calibrated at 20°C and 25°C deliver different weights of water for each 10 ml, when weighed with standard brass weights in air at 50% relative humidity (RH) at standard atmospheric pressure, as given below ... 

No/e.-These temp corrections are applied to burettes calibrated at 20°. The corrections for TiClj and Fe(NH4)(S04)2 soins are different from those applicable to aq soins generally due chiefly to the large amt of HC1 present. The cubic coeff of expansion of the soins is on the average 0.000254 ml per degree per ml becw 18° and 25°C. If all calibrations are Hone at the same temp, no temp corrections are necessary... 

Burette Calibrations See under Calibration of Laboratory Glassware... 

Note.-These temp corrections are applied to burettes calibrated at 20°. The corrections for TiCl,... 

Bubble burette calibration of personal sampler pump. 

Phenolphthalein, 104-109 Phenylalanine, 60 pH-logC diagrams, 1 Phosphoric acid, 79, 90 Pipettes/burettes, calibration, 103 Potassium benozoate, 83... 

The errors resulting from the addition of distilled water to reach the various concentrations should be negli-bible if done with care. For example, to reach a concentration of exactly 10% by volume, 1.022 mL of water should be added. In order to avoid the errors resulting from attempting to extrapolate between divisions, a volume of 1.05 itiL is used which results in a true concentration of 10.22% by volume. This is designated at the 10% sample. Since exactly the same volume is used on the tritiated water as on the comparable tritiated toluene sample, the final concentrations are the same in each vial and the errors cancel. Adding quantities of water that are measurable exactly on burette calibration marks tremendously improves the ability to add equal amounts to comparable vials. 

Accurate burette For example Metrohm piston burette, calibrated, with subdivisions of 0.005 mL. 

Accurate burette For example, a Metrohm piston burette, calibrated in subdivisions of 0.005 mL, needed only if the titration curve is performed by conventional procedure (e.g., as described under 5a of this section). 

Accurate burette (For example a piston burette), calibrated with subdivisions of 0.01 mL. 

The diluted extracts are injected via the alar vein from a burette calibrated to 0-05 ml, infusing 1 ml per kg body weight within a few seconds at five-minute intervals until the pigeon dies of cardiac arrest. If the number of doses required to produce this is less than 13 or exceeds 19 or if the larger average in one test exceeds the lower by more than 4 doses the data are regarded as preliminary. Not less than 6 pigeons are used for standard and not less than 6 for the assay preparation. 

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. 

The air may be collected directly into a Hempel gas-burette (Fig. 76) and there measured. This burette consists of a glass tube H calibrated in ml. from the tap E downwards, and connected by a piece of rubber tubing to the reservoir R, the height of which can be adjusted. The tap E is a 3-way tap. by which the tube H can be connected directly through to the capillary tube above, or either tube can be connected through the left- hand end of the tap to the atmosphere. 

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. 

To construct the calibration curve, run 5-50 mL of the standard boron solution by means of a burette into 100 mL graduated flasks, add 30 mL of dilute sulphuric acid, and make up to volume. These solutions contain 1 — 10 /ig of B per 3 mL. Use 3 mL of each solution and of a boron-free comparison solution and proceed as above. Plot a calibration curve relating absorbance and boron content. 

With the aid of a calibrated burette, run 10.0, 17.0, 24.0, 31.0, 38.0, 45.0, 52.0, and 62.0 mL of the above dilute standard solution into separate lOOmL graduated flasks and dilute each to the mark with 0.05M sulphuric acid. 

Calcium, D. of - continued in limestone or dolomite, (fl) 813 in presence of barium, (ti) 333 with CDTA, (ti) 333 with lead by EDTA, (ti) 333 with magnesium by EDTA, 328 by EGTA, (ti) 331 by flame emission, (aa) 804 Calcium oxalate, thermal analysis 498 Calcon 318 Calculators 133 Calibration of apparatus, 87 of burettes, 88 of graduated flasks, 88 of pipettes, 88 of weights, 74... 

In a similar manner, the calibration of glassware, such as volumetric flasks, pipettes, burettes, measuring cylindres are duly carried out by specific methods recommended by Indian Standards Institution (ISI), British Standards Institution (BSI), National Physical Laboratory (NPL), United States Pharmacopoeia (USP) at specified temperatures (See Chapter 2). 

Titration is the process of adding and then actually measuring the volume of titrant consumed in the assay. This volume is usually measured by the help of a calibrated burette. 

Outlet Tip From a practical point of view the outlet tip of either types of burette, i. e., having Teflon or glass stopcocks, must be of such diameter and taper as to allow the delivery of a single drop whose volume is significantly less than that which can be held between any two finest graduations of the scale with which the burette is calibrated. 

Most of the instruments, commonly used in an analytical laboratory, such as UV-Spectrophoto-meter, IR-Spectrophotometer, single—pan electric balance, pH-meter, turbidimeter and nephelometer, polarimeter, refractometer and the like must be calibrated duly, before use so as to eliminate any possible errors. In the same manner all apparatus, namely pipettes, burettes, volumetric flasks, thermometers, weights etc., must be calibrated duly, and the necessary corrections incorporated to the original measurements. 

In this case a preset equivalence point potentiometer is applied at the two electrodes with the aid of a calibrated potentiometer (I). It will give rise to an error signal (C) provided a difference is caused between this potential and that of the electrodes. The feeble signal thus generated is duly amplified (D) and closes an electronic switch (E) which allows the electricity to flow through the solenoid operated value (B) of the burette (J). As the titration proceeds, the error signal (C) starts approaching a zero value, subsequently the... 

Computer-controlled motorized syringe-type precision burettes are generally employed nowadays for addition of titrant. The burettes are calibrated by weighing the amounts of distilled water they deliver over various time intervals. The delivery rate in units of volume per unit time is determined from the mass rate delivery using the density of water at the calibration temperature. 

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