1、BRITISH STANDARD BS733-2:1987 Pyknometers Part2: Methods for calibration and use of pyknometers UDC531.754.4:542.3BS733-2:1987 This British Standard, having been prepared under the directionof the Laboratory Apparatus Standards Committee,was published underthe authority of the BoardofBSI and comesin
2、to effect on 31July1987 BSI07-1999 The following BSI references relate to the work on this standard: Committee reference LBC/27 Draft for comment86/50278DC ISBN 0 580 15941 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Laboratory App
3、aratus Standards Committee (LBC/-) to Technical Committee LBC/27 upon which the following bodies were represented: Association of Clinical Biochemists British Laboratory Ware Association Department of Health and Social Security Department of Trade and Industry (Laboratory of the Government Chemist)
4、Department of Trade and Industry (National Weights and Measures Laboratory) Glass Manufacturers Federation Institute of Medical Laboratory Sciences Medical Sterile Products Association Ministry of Defence Scientific Glassware Association Society of Chemical Industry South Western Regional Health Aut
5、hority Amendments issued since publication Amd. No. Date of issue CommentsBS733-2:1987 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii Section 1. General 1 Scope 1 2 Definitions 1 3 Symbols 1 4 Principle of use 1 5 Apparatus and materials 2 6 Cleanliness of the glas
6、s surface of the pyknometer 3 Section 2. Calibration of pyknometer 7 Calibration of type3 and type5 pyknometers (not using a water-bath) 4 8 Calibration of type1 pyknometer 4 9 Calibration of type2 pyknometer 4 10 Calibration of type3 and type5 pyknometers 5 11 Calibration of type4 pyknometer 5 12 R
7、ecalibration 6 Section 3. Procedure for use of pyknometer 13 Procedure for type3and type5pyknometers (not using a water-bath) 7 14 Procedure for type1pyknometer 7 15 Procedure for type2pyknometer 7 16 Procedure for type3and type5pyknometers 7 17 Procedure for type4pyknometer 7 18 Procedure for type5
8、pyknometer for solid and semi-solid samples 7 Section 4. Calculation of sample density 19 Correction for the thermal expansion of the pyknometer 8 20 Calculation of the density of a sample liquid 8 21 Calculation of the density of a solid or semi-solid sample 9 Section 5. Measurement of the apparent
9、 mass in air of liquid in bulk 22 Procedure 10 Table 1 Buoyancy corrections for density determinations 8 Table 2 Correction for buoyancy and change in volume of pyknometers made of borosilicate glass 9 Table 3 Correction for buoyancy and change in volume of pyknometers made of soda glass 9 Table 4 C
10、orrection for change in volume between t c C andt t C for pyknometers made of borosilicate glass 10 Table 5 Correction for change in volume between t c C andt t C for pyknometers made of soda-lime glass 10 Publications referred to Inside back coverBS733-2:1987 ii BSI 07-1999 Foreword This Part of BS
11、733 has been prepared under the direction of the Laboratory Apparatus Standards Committee. BS733 was first published in1937, as a single publication, under the title “Density bottles” and was revised in1952 and 1965. The 1965 edition specified the requirements for a range of Gay-Lussac density bottl
12、es, and contained a number of appendices which described how capacity could be determined, density calculated and liquid in bulk measured. To facilitate alignment with corresponding international standards, BS733 has been published in two Parts. Part1, which is identical with ISO3507:1976 “Pyknomete
13、rs”, published by the International Organization for Standardization (ISO), was published in1983, when BS733:1965 was withdrawn. Part1 specifies requirements for ranges for five types of pyknometer. This Part incorporates the material previously given in the appendices of the1965 edition, expanded t
14、o cover the five types of pyknometers specified in Part1, and to describe the method of use of each of the five types. In this Part of BS733, in order to avoid any ambiguity, the symbol “C” is used to denote actual temperatures, and the words “degrees Celsius” to denote temperature intervals. A Brit
15、ish Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a fron
16、t cover, an inside front cover, pagesi andii, pages1to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS733-2:1987 BSI 07-1999 1 Section 1.
17、 General 1 Scope This Part of BS733describes the methods for calibrating each of the five types of pyknometer specified in BS733-1. It also describes the general procedure for using the pyknometers, and methods for the calculation of sample densities and measurement of the apparent mass in air of li
18、quid in bulk. NOTE 1The type5 (Hubbard) pyknometer flask is the only type covered by this standard, which is suitable for use with solids and semi-solids. NOTE 2The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Par
19、t of BS733, the definitions given in BS733-1apply together with the following. density the mass of the sample divided by its volume NOTEWhen reporting the density, the unit of density used, together with the temperature, should be explicitly stated, for example grams per millilitre or kilograms per
20、cubic metre, att C. 3 Symbols For the purposes of this Part of BS733the following symbols apply. 3.1 Temperatures (inC) 3.2 Apparent mass of the pyknometer in air (in g) 3.3 Capacity of pyknometer (in mL) 3.4 Densities (in g/mL) 3.5 Coefficient of cubical expansion (inC 1 ) 3.6 Corrections for densi
21、ty calculations 4 Principle of use 4.1 General In each case, the capacity is first calculated from precise measurements using water, followed by measurement of the mass of sample required to fill that capacity, all measurements being made at known temperatures. Thermal equilibrium of the pyknometer,
22、 whether filled or empty, with the surroundings is regarded as having been achieved when three successive weighings at1min intervals are within 0.5mg of their mean value. In general a constant-temperature water-bath is used to give an accurately known temperature for measurements both with water and
23、 the sample under test. NOTEThese temperatures are not necessarily the same. However, a simpler alternative method, not requiring a water-bath, is given for those two pyknometers (types3and5) into which a thermometer can be inserted at appropriate stages in the method. Corrections are given for air
24、buoyancy and for thermal expansion of the glass of the pyknometer when the weighings with water and the sample are not performed at the same temperature. NOTEIt should be recognized that, if the atmospheric pressure and humidity are significantly different from accepted standard values, care should
25、be shown when applying the corrections given, since these are strictly accurate only at standard pressure and humidity. t c at which the pyknometer is calibrated using water. t r at which the pyknometer will have the precise capacity specified. NOTEThe preferred reference value is20C, or27C for work
26、 in tropical countries. The standard reference temperature for international trade in petroleum and its products is15C. t t at which the pyknometer is filled with the sample under test. m 0 when measured empty after cleaning and drying. m c when filled with water at t c . m t when filled with the sa
27、mple under test at t t . m 1 when part filled with sample (see18.2). m 2 when filled with sample and water at t t(see18.5). V c the volume of water contained at t c . V r the volume of water contained at t r . c of the sample at t c . r of the sample at t r . t of the sample at t t . * for the glass
28、 of the pyknometer. A buoyancy correction given in Table 1. B combined correction for buoyancy and for the change in volume of the pyknometer between t cand t tobtained from Table 2 or Table 3 depending on the glass from which the pyknometer is made. coefficient of change in density of the sample in
29、 g/mL for each1C change in temperature.BS733-2:1987 2 BSI 07-1999 4.2 Type1: bicapillary pyknometer tube (Lipkin) A type1 pyknometer has two capillary arms having identical graduated scales, seeFigure1of BS733-1:1983. It is suitable for volatile liquids, particularly when only a small amount of samp
30、le is available. Its use is limited to liquids with vapour pressures up to130kPa (1.3bar) 1)and having a kinematic viscosity less than50mm 2 /s(50cSt 2) ) at the test temperature. The pyknometer has to be supported with its capillary arms approximately vertical for weighing. It does not have to be f
31、illed to any specific volume, but the volume used has to be within the range of the graduated scale length of the capillary arms. The initial calibration with water is repeated with several volumes within this range, so that an interpolation can be made to determine the actual volume of sample used.
32、 4.3 Type2: bicapillary pyknometer tube (Sprengel) A type2pyknometer has two capillary arms with a single graduation line on one arm, seeFigure2of BS733-1:1983. It is suitable for low viscosity liquids and is suitable for use for volatile liquids providing the alternative version supplied with caps
33、is used. Equal volumes of water and sample are ensured by filling in each case to the rated capacity, that is between the tip of the jet on one capillary arm, to the graduation line on the other, before supporting the pyknometer with the axis of its bulb vertical for weighing. 4.4 Type3: capillary-s
34、toppered pyknometer flask (Gay-Lussac) A type3pyknometer, seeFigure3of BS733-1:1983, is most commonly used for general purposes and is suitable for non-volatile liquids, except those of high viscosity. Equal volumes of water and sample are ensured by the pyknometer being filled so as to overflow, be
35、fore drying externally and weighing. 4.5 Type4: stoppered pyknometer flask (Reischauer) A type4pyknometer has a graduated scale on its extended neck, seeFigure4of BS733-1:1983. It is suitable for use with volatile liquids with vapour pressures up to30kPa(0.3bar) and having a kinematic viscosity less
36、 than20mm 2 /s (20cSt) at the test temperature. The capacity used is determined by the zero mark of the graduated scale, accurate filling and adjustment of the liquid level being achieved using a draw-off needle and a filling needle shown in Figures6and7of BS733-1:1983. 4.6 Type5: capillary-stoppere
37、d pyknometer flask (Hubbard) A type5pyknometer, see Figure5of BS733-1:1983, is a wide-mouth version of the type3pyknometer. It is particularly useful for very viscous liquids. It is used in the same way as the type3pyknometer. The wide mouth of this type also enables it to be used for the measuremen
38、t of density of solids and semi-solids. 5 Apparatus and materials 5.1 Balance, capable of weighing to the nearest0.1mg. 5.2 Thermometer, having a limit of error of0.1C. 5.3 Water-bath, being a constant-temperature bath having a depth greater than that of the pyknometer to be used, and capable of bei
39、ng maintained within0.05C of the desired temperature. 5.4 Barometer, with a limit of error of100Pa(1mbar). NOTEThis may be required for atmospheric pressure measurements. 5.5 Gloves or cloth, of lint-free cotton, always to be used for holding the pyknometer to avoid contamination from the hand. 5.6
40、Water, for calibrating the pyknometer, shall be freshly distilled or deionized, complying with BS3978. 5.7 Clean lint-free cotton cloth (or filter paper), for drying the surface of the pyknometer. 5.8 Surfactant cleaning fluid 5.9 Ethanol 5.10 Acetone. 5.11 Light petroleum 5.12 Beaker 5.13 Pipette-f
41、illing device/aspirator 5.14 Hypodermic syringe or a vacuum suction system, using the draw-off needle shown inFigure6of BS733-1:1983. 1) 1bar = 100KN/m 2= 100 Pa. 2) 1cSt = 1m 2 /s.BS733-2:1987 BSI 07-1999 3 6 Cleanliness of the glass surface of the pyknometer Thoroughly clean the pyknometer, its st
42、opper or caps and any counterpoise vessels used during the weighing process with surfactant cleaning fluid(5.8). Then rinse well, first with water(5.6), then with ethanol(5.9) and/or with acetone(5.10). Ensure that all traces of water and solvent are removed, if necessary by means of a current of dr
43、y filtered air. Carry out cleaning in this way whenever the pyknometer is to be calibrated, or whenever liquid fails to drain evenly from the internal walls of the pyknometer or the capillary of the stopper. Normally clean the pyknometer between determinations by washing with a suitable light petrol
44、eum(5.11), such as40C to60C light petroleum, followed by vacuum drying. Do not touch the glass surface by hand after cleaning except when detailed in the calibration or procedure for use (see sections 2 and 3), since this could introduce contamination or, in low humidity conditions, produce an elect
45、rostatic charge on the surface. Gloves or cloth should always be used. NOTEif additional precautions against electrostatic charge are thought to be desirable, the ambient relative humidity in the weighing room may be maintained at60% or higher, or the surface of the pyknometer (and any counterpoise
46、vessel) may be wiped gently with a damp cloth before being placed on the balance. In the latter case the film of water left on the surface will then evaporate quickly with the desired result. Alternatively one of the accepted techniques for electrostatic discharge can be employed.BS 733-2:1987 4 BSI
47、 07-1999 Section 2. Calibration of pyknometer NOTEWhile the determination of density requires the accurate knowledge of sample temperature, which normally involves the use of a constant-temperature water-bath, it is possible when using type3and type5pyknometers to carry out a simplified procedure no
48、t requiring a water-bath. This is described in clause7 in this section, followed by the more accurate method for each type of pyknometer using a water-bath(see clauses8 to11). 7 Calibration of type3and type5pyknometers (not using a water-bath) 7.1 Place the clean and dry pyknometer and its stopper s
49、eparately on one pan of the balance(5.1) and, after reaching thermal equilibrium with the surroundings(see4.1), weigh to the nearest0.1mg to obtain the value ofm 0 . 7.2 Lift the pyknometer clear of the balance and fill it with water(5.6) to within a short distance of the bottom of the neck. Immediately measure the water temperature to0.1C, or better, by inserting a thermometer(5.2) and using it to stir the water gently before noting the temperature. 7.3 Remove the thermometer and quickly fill the pyknometer with water. Then insert the sto
