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1、BRITISH STANDARD BS 734-1:1973 Incorporating Amendment No. 1 Measurement of the Density of milk using a hydrometer Part 1: Specification for hydrometers for use in milk UDC 637.127:531.756 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:53:00 GMT+00:00 2006,
2、Uncontrolled Copy, (c) BSI BS 734-1:1973 This British Standard, having been approved by the Dairying Industry Standards Committee, was published under the authority of the Executive Board on 29 October 1973 BSI 11-1999 First published May 1937 First revision March 1955 Second revision as Part I Sept
3、ember 1960 Third revision October 1973 The following BSI references relate to the work on this standard: Committee reference DAFA/3 Draft for comment 69/29084 ISBN 0 580 07074 3 Co-operating organizations The Dairying Industry Standards Committee, under whose supervision this British Standard was pr
4、epared, consists of representatives from the following Government departments and scientific and industrial organizations: Chemical SocietyNational Farmers Union Commonwealth Bureau of Dairy Science andNational Institute for Research in Dairying* TechnologyOffice of the High Commissioner for Austral
5、ia* Dairy Trade Federation*Office of the High Commissioner for Department of Health and Social SecurityNew Zealand* Department of Trade and Industry, LaboratoryProcess Plant Association of the Government Chemist*Royal Association of British Dairy Farmers* Institute of Food Science and TechnologyRoya
6、l Institute of Public Health and Hygiene Milk Marketing Board*Royal Society of Health Milk Marketing Board for Northern Ireland*Scottish Milk Trade Federation Milking Machine Manufacturers AssociationSociety of Chemical Industry Ministry of Agriculture, Fisheries and Food*Society of Dairy Technology
7、* National Association of Creamery ProprietorsUnited Kingdom Dairy Association* and Wholesale DairymenWest of Scotland Agricultural College The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly rep
8、resented on the committee entrusted with the preparation of this standard: Association of British and DominionHannah Research Institute Condensed Milk ManufacturersIce Cream Alliance Ltd. Association of British Manufacturers ofIce Cream Federation Ltd. Milk PowderJoint Committee of the Milk Marketin
9、g Board Association of Butter Makers, Blenders andand the Dairy Trade Federation PackersLondon Provision Exchange Association of Public AnalystsMinistry of Agriculture, Government of Association of Public Health InspectorsNorthern Ireland British Food Manufacturing IndustriesSociety for Analytical C
10、hemistry Research AssociationUniversity of Reading British Paper and Board Makers Association Amendments issued since publication Amd. No.Date of issueComments 1963May 1976Indicated by a sideline in the margin Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:5
11、3:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 734-1:1973 BSI 11-1999i Contents Page Co-operating organizationsInside front cover Forewordii 1Scope1 2Scale ranges, subdivision of scales and tolerances1 3Adjustment1 4Materials and construction1 5Form2 6Scales2 7Principal dimensions2 8Inscriptions
12、3 Appendix A Suitable hydrometer cylinders4 Appendix B Thermometer4 Appendix C Notes on verification of hydrometers4 Appendix D Testing of British Standard hydrometers for use in milk6 Figure 1 British Standard density hydrometers for use in milk7 Figure 2 Hydrometer scales8 Figure 3 Cylinder for No
13、s. 1 and 1A hydrometers9 Figure 4 Cylinder for Nos. 2 and 2A hydrometers10 Table 1 Principal dimensions3 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:53:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 734-1:1973 ii BSI 11-1999 Foreword BS 734 was first pu
14、blished, under the authority of the Dairying Industry Standards Committee, in 1937 and a revised edition was published in 1955. In 1959 the standard was again revised; Part 2 “Methods” was published in that year, and in 1960, Part 1, “Apparatus”. Part 1 of this British Standard specifies hydrometers
15、 of two sizes to meet the need of the dairying industry to deal with milk samples of differing volumes. Two scale ranges are provided for each size. This revision has been based on draft International Standard ISO 2449, “Milk and Liquid milk products density hydrometers for use in products with a su
16、rface tension of approximately 45 mN/m”, to which the Nos. 1 and 1A hydrometers strictly conform. The smaller, less precise Nos. 2 and 2A hydrometers, which do not appear in the ISO document, have been retained in a modified form as their use is widespread in the United Kingdom. The Nos. 3 and 3A hy
17、drometers specified in the 1960 edition have not, however, been retained. The basis of adjustment of the hydrometers adopted in 1937 was density in grams (mass) per millilitre at 20 C in a liquid with a surface tension of 46 dyn/cm. In this revision, however, the internationally accepted value of 45
18、 mN/m (see 3.3, Note) for the average surface tension at 20 C of freshly formed surfaces of milk has been adopted as the basis of adjustment. NOTEThe system of units known as the International System of units (SI), and adopted by ISO see BS 3763, “The International System of units (SI)”, has been us
19、ed in this British Standard as follows. 1) Instead of the surface tension unit “dyne per centimetre” (dyn/cm) used in ISO R 387, “Principles of construction and adjustment of hydrometers”, the unit adopted is the “millinewton per metre” (mN/m), the appropriate decimal multiple of the SI unit of surf
20、ace tension “newton per metre” (N/m), where the newton (N), the SI unit of force, is defined as that force which, when applied to a body having a mass of 1 kg gives it an acceleration of 1 m/s2. (1 mN/m = 1 dyn/cm.) 2) The SI unit of density, i.e. mass per unit volume, is the “kilogram per cubic met
21、re” (kg/m3), an appropriate decimal multiple being the “gram per cubic centimetre” (g/cm3). As a convenient synonym for the latter unit, the SI system allows the use of “gram per millilitre” (g/ml), and this method of expressing density, accepted in ISO R387, has been adopted. It should be noted tha
22、t “density (g/ml)”, means “gram (mass) per millilitre” and not “gram (observed weight) per millilitre.” (1 g/ml = 1 g/cm3.) Details of cylinders in which the hydrometers may be used are given in Appendix A, and suitable thermometers for use with them are described in Appendix B. Notes on the verific
23、ation of hydrometers are given in Appendix C, with two recommended procedures for comparison with similar reference hydrometers in order to determine corrections for hydrometer errors. For the benefit of users, these methods will also be included in the revision of the 1959 edition of Part 2 of this
24、 British Standard BS 734, “Measurement of the density of milk using a hydrometer”, Part 21), “Method for the determination of milk density”. Details of the facilities available for verification of the hydrometers are given in Appendix D. 1) In course of preparation Licensed Copy: London South Bank U
25、niversity, London South Bank University, Fri Dec 08 10:53:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 734-1:1973 BSI 11-1999iii A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Co
26、mpliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may
27、have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:53:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: London South Bank University, L
28、ondon South Bank University, Fri Dec 08 10:53:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 734-1:1973 BSI 11-19991 1 Scope This Part of this British Standard specifies requirements for glass hydrometers of constant mass, for use in milk having a surface tension of approximately 45 mN/m, which in
29、dicate density in grams per millilitre and which comply with ISO 387, “Principles of construction and adjustment of hydrometers”. Two sizes of hydrometer are specified, with two scale ranges for each size. The larger hydrometers, designated No. 1 and No. 1A to distinguish between the scale ranges, c
30、orrespond to the precision types specified in draft International Standard ISO 2449, “Milk and liquid milk products Density hydrometers for use in products with a surface tension of approximately 45 mN/m”. The smaller hydrometers, designated No. 2 and No. 2A to distinguish between the scale ranges,
31、are more robust instruments intended to permit the density of smaller samples to be determined. 2 Scale ranges, subdivision of scales and tolerances 2.1 Scale ranges. The scale ranges shall be as follows: 1) 1.025 g/ml to 1.035 g/ml for the Nos. 1 and 2 hydrometers, for use in milks of normal densit
32、y; 2) 1.015 g/ml to 1.025 g/ml for the Nos. 1A and 2A hydrometers, for use in milks of low density. 2.2 Sub division of scales. The scales for the hydrometers shall be sub divided at each 0.000 2 g/ml for the Nos. 1 and 1A hydrometers and at each 0.000 5 g/ml for the Nos 2 and 2A hydrometers. 2.3 To
33、lerances. The density indication of the hydrometers shall not be in error at any point on the scale by more than 0.000 2 g/ml for the Nos. 1 and 1A hydrometers, or by more than 0.000 3 g/ml for the Nos. 2 and 2A hydrometers. 3 Adjustment 3.1 Reading level. The hydrometers shall be adjusted to be rea
34、d at the top of the liquid meniscus, i.e. where the meniscus appears to meet the stem see 3.4 and 8 2). 3.2 Immersion. The hydrometers shall be adjusted to give correct readings when the emergent stem is wetted by the liquid to a level not more than 3 mm above the top of the meniscus. 3.3 Temperatur
35、e and surface tension. The hydrometers shall be adjusted to indicate density in grams per millilitre at 20 C when floating in a liquid at 20 C with a surface tension of 45 mN/m. NOTEThe value 45 mN/m is taken as the average surface tension at 20 C of freshly formed surfaces of cows milk, i.e. the su
36、rface obtained by pouring milk into a vessel until some has overflowed. 3.4 Adjustment Level. A No. 1 (or 1A) hydrometer or a No. 2 (or 2A) hydrometer shall be regarded as being correctly adjusted when its reading at the level of the flat surface of a transparent liquid at 20 C and with a surface te
37、nsion of 45 mN/m (see Note 1), exceeds the density of the liquid by 0.000 3 g/ml or 0.000 4 g/ml, respectively, values that correspond to the height of each meniscus (see Note 2). NOTE 1It is not essential for the transparent liquid used for adjustment to have a temperature of 20 C and a surface ten
38、sion of 45 mN/m provided that appropriate corrections are applied. NOTE 2The quoted values of 0.000 3 g/ml and 0.000 4 g/ml were derived from a modification of Langbergs formula for meniscus height (see below), and also from experimental observations, for hydrometers whose scales and dimensions comp
39、ly with the requirements of this British Standard. 4 Materials and construction 4.1 The bulb and stem of the hydrometer shall be made of transparent glass, and shall be as free as possible from strain and visible defects. In particular, the external surface shall be smooth and free from irregulariti
40、es. The base of the bulb may be strengthened by internal thickening of the wall. 4.2 The loading material shall be lead shot securely embedded in a suitable cementing material in the bottom of the bulb. The loading material shall be such that, if the hydrometer is kept in a horizontal position for o
41、ne hour at 40 C, it shall subsequently float with its axis within 1.5 of the vertical (see 5.3). 4.3 There shall be no loose material in the hydrometer. 4.4 The scale paper shall preferably be white, shall be of high quality and shall have a smooth surface that permits the graduation lines, numbers
42、and inscriptions to be marked finely and clearly on it. All scale markings shall be permanent. Where h is the meniscus height in terms of “grams per millilitre”, is the surface tension of liquid (mN/m), i is the scale range (g/ml) (i.e. 0.01 for No. 1, 1A, 2, or 2A hydrometers), d is the external di
43、ameter of the stem (mm), is the density of the liquid (g/ml), and s is the mean scale length (mm) (e.g. 64 for a No. 1 or No. 1A hydrometer). Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:53:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 734-1:1973 2 BSI
44、11-1999 NOTEIt is recommended that the paper should be an esparto paper (65 % to 75 % esparto is suitable) and that the scale strips should be cut with their length in the machine direction of the paper. The scale paper in a hydrometer shall show no evidence of charting and when exposed to a tempera
45、ture of 80 C for 24 h shall not become discoloured or distorted. 4.5 The scale paper shall be securely fastened in place. The scale paper shall have a scale mark, a few millimetres above the top graduation line, consisting of a short horizontal line with a “V” at each end (thus: ). A fine reference
46、line of uniform thickness shall be cleanly etched on the hydrometer stem at a position coincident with the horizontal portion of the scale mark so that the ends of the etched line project into the “V” at each end of the scale mark. A hydrometer shall be deemed not to comply with the requirements of
47、this British Standard if there is any displacement of the scale paper, i.e. if the scale mark and the reference line do not exactly coincide. 5 Form 5.1 The outer surface of the hydrometer shall be symmetrical about its axis and there shall be a smooth transition between the bulb and the stem and no
48、 other abrupt changes in cross-section. 5.2 The tapered designs shown in Figure 1 are preferred, but any similar design that does not permit air bubbles to be trapped is acceptable. 5.3 The hydrometer shall float so that its axis does not deviate by more than 1.5 from the vertical position. 6 Scales
49、 Figure 2 shows the sequence and numbering of graduation lines which shall be followed, and illustrates acceptable scales. 6.1 General 6.1.1 The scale shall be straight and without twist. 6.1.2 There shall be no irregularities in the spacing of the graduation lines. 6.1.3 The graduation lines shall be at right angles to the axis of the hydrometer. 6.1.4 The graduation lines shall be of uniform thickness not exceeding 0.2 mm. 6.1.5 The scale shall extend at both ends beyond its nominal limits by at least two graduation lines. 6.1.6 All n
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