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1、INTERNATIONAL STANDARD 384 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION 4iElYHAPOAHAR OPrAHM3ALWl II0 CTAH - the lower grade shall be designated “class B”. 4.2 Limits of volumetric error shall be specified for each type of article having regard to the method and purpose of use and the class of acc
2、uracy. 4.3 The numerical values of limits of volumetric error for articles of volumetric glassware for general purposes shall be chosen from the series 10 - 12 - 15 - 20 - 25 - 30 - 40 - 50 - 60 - 80, or a suitable decimal multiple thereof.2) 4.4 The limits of volumetric error specified for a series
3、 of sizes of an article should provide a reasonably uniform progression in relation to capacity when plotted on a logarithmic graph as shown in annex A. Such a graph should be included as an annex to all specifications in which a series of three or more sizes of an article is specified. 4.5 Where tw
4、o classes of accuracy are specified, then the limits of volumetric error permitted for class 8 should, in general, be approximately twice those permitted for class A. 4.6 For all articles having a scale, the maximum permitted volumetric error for either class of accuracy shall not exceed the volume
5、equivalent of the smallest scale division. 2) This is the R” 10 series of preferred numbers and has been adopted because decimal sub-multiples of some of the unrounded numbers, for example 31,5, would appear to imply a degree of precision which is not intended and which could not be measured in prac
6、tice. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:20:53 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 384-1978 (E) 4.7 Where two classes
7、of accuracy are specified, the class A limit of volumetric error specified for any article shall not be smaller than that calculated from the maximum permitted diameter at the relevant graduation line by the formulae detailed in annex B; the corresponding class B limit shall be derived in accordance
8、 with 4.5. Where only one class of accuracy is specified, the limit of volumetric error specified for any article shall be similarly determined, on the basis of a preliminary decision as to whether class A or class B accuracy is appropriate to the article in question. A nomograph, plotted on a logar
9、ithmic scale as shown in annex B, should be included, as an annex, in all specifi- cations for articles of volumetric glassware. 4.8 The limit of volumetric error specified for any article designed for delivery shall also be not less than four times the standard deviation (RMS) determined experiment
10、ally by an experienced operative from a series of at least twenty replicable determinations of delivered capacity on the same article, carried out strictly in accordance with the method specified for that article, 5 METHODS OF VERIFICATION AND USE 5.1 The method of verification should be clearly spe
11、cified for each article of volumetric glassware. Ii,2 Any difference between the method of verification and the method of use shall be clearly indicated, 5.3 Delivery times and, where applicable, waiting times for all articles intended for delivery of a liquid shall be specified. ) 5.4 Setting of th
12、e meniscus shall be performed by one of the two methods detailed below. Wherever practicable, the meniscus should descend to the position of setting. a) The meniscus is set so that the plane of the upper edge of the graduation line is horizontally tangential to the lowest point of the meniscus, the
13、line of sight being in the same plane, In the case of a mercury meniscus, however, the highest point of the meniscus is set to the lower edge of the graduation line. b) The meniscus is set so that the plane of the centre of the graduation line is horizontally tangential to the lowest point of the me
14、niscus. The eye is raised towards the plane and observes the front and back portions of the line apparently meeting the lowest point simultaneously. In the case of a mercury meniscus, the eye is lowered towards the plane of the centre of the graduation line. NOTE - The difference between meniscus po
15、sitions resulting from the alternative methods of setting is the volume equivalent to one-half the thickness of the graduation line. In the case of articles where the capacity is read as the difference between two meniscus readings (for example on a burette) then no error results if the article is m
16、anufactured using one method and is later used by the other method. Even in most unfevourable cases of single- mark articles (for example large flasks), when working to the highest attainable accuracy, the difference resulting from use of the two methods is unlikely to exceed 30 % of the class A lim
17、it of error, and a correction can be calculated where necessary. 5.5 When the article is used with opaque wetting liquids, the horizontal line of sight shall be taken through the upper edge of the meniscus, and where necessary an appropriate correction shall be applied. 6 CONSTRUCTION 6.1 Material V
18、olumetric glassware shall be constructed of glass of suitable chemical and thermal properties. It shall be as free as possible from visible defects and shall be reasonably free from internal stress. 6.2 Shape All articles shall be of a shape which will facilitate emptying and drainage, and should pr
19、eferably be of circular cross-section. 6.3 Capacity 6.3.1 The numerical values of capacity of articles of volumetric glassware for general purposes should preferably be chosen from the series 10 - 20 - 25 - 50, or a decimal multiple or submultiple thereof. 6.3.2 The numerical value of the volume equ
20、ivalents of the smallest division on articles having a scale shall be chosen from the series 1 - 2 - 5, or a decimal multiple or submultiple thereof. 6.3.3 In the case of a special purpose article of volumetric glassware which is to be graduated for direct reading of capacity when used with a specif
21、ic liquid other than water, the specification should also indicate the corresponding capacity when used with pure water so that the latter can be used for verification. 1 I See definitions given in IS0 4791/ll. 2 Copyright International Organization for Standardization Provided by IHS under license
22、with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:20:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO384-1978 (E) 6.4 Stability Vessels provided with a fiat base shall stand firmly thereon without rocking when placed on a level surf
23、ace and, unless specified otherwise, the axis of the graduated portion of the vessel should be vertical. Wherever practicable, vessels shall not topple when placed empty on a surface inclined at an angle to the horizontal to be specified for each article. Vessels provided with a base which is not ci
24、rcular shall meet this requirement in alI directions. 6.5 Delivery jets 6.5.1 Delivery jets smooth and gradual at the orifice. ) should be strongly constructed with a taper without any sudden constriction 6.5.2 The end of the jet shall be finished by one of the methods listed below in order of prefe
25、rence : a) smoothly ground square with the axis, slightly bevelled on the outside and fire-polished; b! smoothly ground square with the axis and slightly bevelled on the outside; c) cut square with the axis and fire-polished. A fire-polished finish reduces the danger of chipping in use, but should n
26、ot result in constriction, as indicated in 6.5.1, or in undue stress. 6.5.3 The jet should form an integral part of an article intended for class A and should preferably form an integral part of an article intended for class B. 6.6 Stoppers 6.6.1 Glass stoppers should preferably be ground so as to b
27、e interchangeable, in which case the ground portions shall comply with IS0 383. If individually fitted, they shall be well ground so as to prevent leakage, preferably with a taper of approximately l/l 0. 6.6.2 Stoppers of a suitably inert plastics material may be permitted as an alternative to glass
28、. In such cases, the glass socket into which the stopper fits should preferably comply with IS0 383. 6.7 Stopcocks or similar devices 6.7.1 Stopcocks and similar devices shall be designed to permit smooth and precise control of outflow and to prevent a rate of leakage greater than that allowed in th
29、e specification for the article. 6.7.2 Stopcocks and similar devices shall be made from glass or from suitable inert plastics material. 6.7.3 All-glass stopcocks shall have the key and barrel finely ground preferably to a taper of l/10 and shall comply with appropriate national or international spec
30、ifications. 6.7.4 Glass stopcock barrels to receive plastics keys shall be polished internally. 6.7.5 Stopcock components may be fitted with suitable retaining devices. 7 LINEAR DIMENSIONS 7.1 Linear dimensional requirements shall be specified for all articles of volumetric glassware in such a way a
31、s to ensure that : a) the article is convenient and satisfactory for its intended use; b) in a series of sizes of an article, unnecessary inconsistencies in shape and proportions can be avoided; c) a limitation is placed on the maximum internal diameter at the graduation line or lines (see 4.7 and a
32、nnex 8); this limitation may be a direct limitation on diameter or an indirect one by a minimum limitation on scale length; d) the requirement for spacing of graduation lines specified in 9.1.2 is achieved; e) the stability requirements of 6.4 can be achieved.2) Linear dimensions shall be specified
33、in millimetres. 7.2 Dimensional requirements should not be more restrictive than is necessary to achieve the aims listed in 7.1, 7.3 In order to permit maximum freedom in manufacture within the restrictions imposed by 7.1, dimensions may be divided into two categories of importance and classified as
34、 “essential dimensions” and “guidance dimensions”. 1) A reason for not permitting a sudden constriction at the orifice is that such a shape could conceal the fact that the jet had been damaged, cut back and refired. Following such treatment the volume delivered by the article could have been altered
35、 beyond the specified limits of volumetric error without any visible evidence of this fact. 2) The stability requirement is controlled by the angle of displacement from the vertical at which the centre of gravity comes vertically above the edge of the base. The height of the centre of gravity is not
36、 only a function of the specified dimensions but is also affected by the distribution of mass in the various parts of the article. It is, however, important to ensure that the specified dimensions do not make it difficult or impossible to achieve the required stability. 3 Copyright International Org
37、anization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:20:53 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 384.1978 (E) 7.4 In a specification where these two categories of dime
38、nsions are used, the requirements of 7.1 c) and d) shall be included as essential dimensions. 7.5 The requirements of 7.1 b) can in many cases be ensured sufficiently by guidance dimensions. 7.6 Essential dimensions shall be expressed in one of the following ways, whichever is the most suitable or c
39、onvenient ) : a) a median figure with 1: tolerance; 6) a maximum and minimum figure; c) a maximum or a minimum figure, if the other limit is unimportant or is controlled by other factors in the specification. 7.7 A dual limitation on dimensional tolerances should be avoided wherever possible; for ex
40、ample, if an overall length is limited by the methods shown in 7.6 a) or 7.6 b) and there are two or more additive components of this length to be specified, then - either the tolerance on overall length should be sufficient to accommodate the additive tolerance of all the components, - or the least
41、 important component should be left undimensioned so that it is controlled only by the difference between overall length and the total length of the other components. 7.8 Guidance dimensions shall be expressed as median figures without tolerance, or as minima or maxima, If both limits are considered
42、 necessary, then the dimension in question shall be classed as an essential dimension. 8 GRADUATION LINES 8.1 Graduation lines shall be clean, permanent lines of uniform thickness. 8.2 A maximum thickness of graduation line shall be specified appropriate to the particular article and its class of ac
43、curacy. This thickness shall not exceed one-half of the linear equivalent of the limit of volumetric error (see annex C). 8.3 On articles having a scale, the specified maximum thickness of lines shall not exceed one-quarter of the minimum distance between centres of adjacent lines (see also annex C)
44、. 8.4 All graduation lines shall lie in planes at right angles to the longitudinal axis of the graduated portion of the article. On articles provided with a flat base, the graduation lines shall therefore lie in planes parallel to the base. 8.5 In general, graduation lines should be confined to cyli
45、ndrical portions of an article s cross-section and should preferably be situated not less than IO mm from any change in diameter. In special circumstances, preferably for class B articles only, graduation lines may be provided on a parallel side portion of non-circular cross-section or on a conical
46、or tapered portion of the article. 8.6 On articles not having a scale, all graduation lines should extend completely round the circumference of the article, except that a gap, not exceeding 10 % of the circumference, may be permitted. In the case of an article which is restricted as to the normal di
47、rection of viewing in use, this gap should be at the right or left of the normal direction of view. 9 SCALES 9.1 Spacing of graduation lines 9.1.1 There should be no evident irregularity in the spacing of graduation lines (except in special cases where the scale is on a conical or tapered portion of
48、 the article and a change of subdivision takes place). 9.1.2 The minimum distance between the centres of adjacent graduation lines shall be not less, in relation to diameter, than that calculated from the formula (0,8 + 0,02 D) mm where D is the maximum permitted internal diameter of the tube in mil
49、limetres (see also annex C). 9.2 Length of graduation lines (see figure 2) 9.2.1 On articles of circular cross-section having a scale, the length of the graduation lines shall be varied so as to be clearly distinguishable and shall be in accordance with the provisions of 9.2.2, 9.2.3 or 9.2.4. 9.2.2 Graduation pattern I a) The length of the short lines should be approx. imately, but not less than, 50 % of the circumference of the article. b) The length of t