Graduated apparatus

In 1964 the Conference Generate des Poids et des Mesures (CGPM) decided to accept the term litre as a special name for the cubic decimetre, and to discard the original definition. With this new meaning of the term litre (L), the millilitre (mL) and the cubic centimetre (cm3) are identical. 

The most commonly used pieces of apparatus in titrimetric (volumetric) analysis are graduated flasks, burettes, and pipettes. Graduated cylinders and weight pipettes are less widely employed. Each of these will be described in turn. 

Many commercially available detergents are suitable for this purpose, and some manufacturers market special formulations for cleaning laboratory glassware some of these, e.g. Decon 90 made by Decon Laboratories of Portslade, are claimed to be specially effective in removing contamination due to radioactive materials. 

A method which is frequently used consists in filling the apparatus with chromic acid cleaning mixture (CARE), a nearly saturated solution of powdered sodium dichromate or potassium dichromate in concentrated sulphuric acid, and allowing it to stand for several hours, preferably overnight the acid is then poured off, the apparatus thoroughly rinsed with distilled water, and allowed to drain until dry. [It may be mentioned that potassium dichromate is not very soluble in concentrated sulphuric acid (about 5 g per litre), whereas 

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British Standards for graduated apparatus (with International Standardisation Organisation equivalents ) ... 

Volumetric analysis essentially comprises of the most precise and accurate measurement of interacting solutions or reagents. It makes use of a number of graduated apparatus, such as graduated (volumetric) flasks, burettes, pipettes and measuring cylinder of different capacities (volumes). 

A volume corresponding to about I gram is delivered into a round flask (200 c.c.) by attaching a piece of lubber tubing to the wide end of the apparatus and blowing until the liquid descends to the required graduation on the wide limb. Twenty-five c.c. of the standard alcoholic potash solution is added, and the mixture boiled on the water-bath wuth reflux condenser for twenty minutes. 

About 60 c.c. of a cold saturated solution of sodium bicarbonate and neutral sodium sulphite. After shaking vigorously for half a minute, the Apparatus is almost filled with the sulphite solution, the whole again sh en for a few minutes, and the apparatus inverted when the unabsorbed oil rises cleanly into the graduated tube, and its volume may be read ofif. 

A clear solution can be obtained more quickly, and incidentally the transfer can be made more satisfactorily, by rapidly filtering the solution through a sintered glass funnel with exclusion of carbon dioxide with the aid of the apparatus shown in Fig. 10.9. It is advisable to calibrate the test-tube in approximately 5 mL intervals and to put the graduations on a thin slip of paper gummed to the outside of the tube. 

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... 

Titrimetric apparatus see Graduated glassware Toluene-3,4-dithiol see Dithiol Tongs for crucibles and beakers, 98 Transmittance 648 conversion to absorbance, 709 Triangulation 245 Triethanolamine 317 Tri-n-butyl phosphate 171 Triethyl phosphate in homogeneous pptn. 425 Triethylenetetramine-fV,fV,fV, yV",fV", fV "-hexa acetic acid (TTHA) 57 Trifluoroacetylacetone 170, 237 Trimethyl phosphate in homogeneous pptn., 425... 

Volumetric analysis see Titrimetric analysis Volumetric apparatus see Graduated glassware Volumetry 7 Vycor apparatus 92... 

Photo 11 Graduate student Lawrence D. Brockway (SP 59, SP 60, SP 61) operating electron-diffraction apparatus in the mid 1930 s. 

Other apparatus includes a Waring Blendor, 1-quart mixing cup 24 or more 125-ml. Erlenmeyer flasks two 10-ml. graduated cylinders a 50-ml. glass-stoppered volumetric flask and 10-ml. volumetric and 5-ml. serological-type pipets. 

Material required Dry plant material, ethylacetate, methanol, anhydrous Na2C03 and 2N HC1 (HPLC grade), N2, distilled water, graduated tube, glass flasks of 100 ml, funnels, separatory funnels, Soxlet apparatus, rotary evaporator, filter paper, shaker, mill, sieve of 0.5 mm in diameter, water bath, pipette of 1,2 and 10 ml, test tubes of 20 ml. 

Determination of the accuracy of graduation marks on volumetric apparatus by weighing measured volumes of water, or determinations of the accuracy of weights by comparison with weights whose value is known with a high degree of accuracy. 

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