BS 4695-1980 Method for determination of melting point of petroleum wax (cooling curve)《石油蜡熔点(冷却曲线)的测定方法》.pdf

1、BRITISH STANDARD BS 4695:1980 ISO 3841:1977 Method for Determination of melting point of petroleum wax (cooling curve) ISO title: Petroleum waxes Determination of melting point (cooling curve) Technically equivalent to method ASTM D 87-74:IP 55/77 UDC 665.772:536.421.1BS4695:1980 This British Standa

2、rd, having been prepared under the directionof the Petroleum Standards Committee, was published under the authority ofthe Executive Board and comesinto effect on 30 April 1980 BSI 11-1999 First published August 1971 First revision April 1980 The following BSI references relate to the work on this st

3、andard: Committee reference PTC/- Draft for comment 79/53232 DC ISBN 0 580 11383 3 Cooperating organizations The Petroleum Standards Committee, under whose direction this British Standard was prepared, consists of representation from the following Government departments and scientific and industrial

4、 organizations: Chemical Industries Association British Lubricants Federation Limited British National Oil Corporation Department of Industry (National Engineering Laboratory) Hydrocarbon Solvents Association Institute of Petroleum* London Transport Executive Ministry of Defence* Society of Motor Ma

5、nufacturers and Traders Limited The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Liquefied Petroleum Gas Industry Technical Association (UK) Amendments issued

6、since publication Amd. No. Date of issue CommentsBS4695:1980 BSI 11-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii 1 Scope and field of application 1 2 Principle 1 3 Definition 1 4 Apparatus 1 5 Procedure 2 6 Expression of results 2 7 Precision 2 8 Test Report

7、 2 Figure Apparatus for determination of melting point (cooling curve) ofpetroleum wax 1 Publications referred to Inside back coverBS4695:1980 ii BSI 11-1999 National foreword This British Standard, which is published under the direction of the Petroleum Standards Committee, was first published in 1

8、971, as a result of an agreement between the British Standards Institution and the Institute of Petroleum, and was identical with ASTM D 87-66:IP 55/67. The present revision is identical with ISO 3841:1977 and technically equivalent to ASTM D 87-74:IP 55/77. ISO 3841 was prepared by Technical Commit

9、tee 28, Petroleum products, of the International Organization for Standardization (ISO) as the result of discussions in which the United Kingdom participated. Terminology and conventions. The text of the International Standard has been approved as suitable for publication, without deviation, as a Br

10、itish Standard. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as

11、the decimal marker. Wherever the words “International Standard” appear, relating to this standard, they should be read as “British Standard”. Cross-references. With reference to the note in 1.2, it is intended to publish in this series a British Standard identical with ISO 2207, when the latter is p

12、ublished, as a revision of BS 5088 “Method for the determination of congealing point of petroleum waxes, including petrolatum” (ASTM D938-70:IP 76/70). Consideration will also be given, when ISO . . . . “Petroleum waxes Determination of drop melting point” has been published, to its implementation a

13、s a dual-numbered British Standard. Additional information. With reference to 4.4, thermometer number ASTM 14C/IP 17C described in “IP Standards for Petroleum and its Products”, 1980, has similar dimensions and is likely to be suitable for use in connection with this British Standard. CAUTION. Atten

14、tion is drawn to the Health and Safety at Work etc. Act, 1974, and the need for ensuring that the method of test specified in this standard is carried out with suitable precautions. The procedure described in this standard method is intended to be carried out by qualified chemists or other suitably

15、trained and/or supervised personnel. Normal safety precautions should be observed throughout the use of the method. 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. Compliance with a B

16、ritish Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 and 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments

17、 incorporated. This will be indicated in the amendment table on the inside front cover.BS4695:1980 BSI 11-1999 1 1 Scope and field of application 1.1 This International Standard specifies a method for the determination of the melting point (cooling curve) of petroleum wax. It is unsuitable for waxes

18、 of the petrolatum group, the microcrystalline waxes, or blends of such waxes with paraffin wax or scale wax. 1.2 Melting point (cooling curve) is a test that is widely used by wax suppliers and consumers. It is particularly applicable to petroleum waxes that are rather highly paraffinic or crystall

19、ine in nature. Aplateau occurs with specimens containing appreciable amounts of hydrocarbons that crystallize at the same temperature, giving up heat of fusion, thus temporarily retarding the cooling rate. In general, petroleum waxes with large amounts of non-normal hydrocarbons or with amorphous so

20、lid forms will not show the plateau. NOTEFor additional methods used for testing petroleum waxes, see ISO 2207, Petroleum waxes Determination of congealing point, and ISO . . ., Petroleum waxes Determination of drop-melting point. 1)Results may differ, depending on the method used. For pharmaceutica

21、l petrolatum, ISO . . . is usually used. 2 Principle A specimen of molten wax in a test tube fitted with a thermometer is placed in an air bath, which in turn is surrounded by a water bath maintained at16 to 28 C. As the molten wax cools, periodic readings of its temperature are taken. When solidifi

22、cation of the wax occurs, the rate of temperature change decreases, yielding a plateau in the cooling curve. 3 Definition For the purpose of this International Standard, the following definition applies. melting point (cooling curve) of petroleum wax the temperature at which a melted petroleum wax f

23、irst shows a specified plateau in its cooling curve when allowed to cool under prescribed conditions 4 Apparatus 4.1 Test tube, of soda-lime glass type, of outside diameter 25 mm and length 100 mm. It may be marked with a filling line, 50 mm above the bottom, and a reference line for positioning the

24、 bottom of the thermometer at 10 mm above the bottom. 4.2 Air bath, comprising a cylinder of inside diameter 51 mm and depth 113 mm, provided with a tightly fitting cork having a central opening for holding the test tube (4.1) firmly in a vertical position in the centre of the air bath. 4.3 Water ba

25、th, comprising a suitable cylindrical vessel, of inside diameter 130 mm and depth 150 mm, provided with a fitted cover equipped to support the air bath (4.2) vertically so that the sides and bottom of the air bath are surrounded by a layer of water about 38 mm thick. The cover shall have an opening

26、through which the bath thermometer may be suspended 20 mm from the outside wall of the water bath. NOTEThe air bath, water bath, and water bath cover may be made in one assembly as shown in the Figure. 1) In preparation. Figure Apparatus for determination of melting point (cooling curve) of petroleu

27、m waxBS4695:1980 2 BSI 11-1999 4.4 Melting-point thermometer, partial immersion type, conforming to the following specification: 4.5 Bath thermometer, of suitable partial immersion type, accurate to 1 C throughout the required range. 4.6 Oven or water bath, capable of being controlled at temperature

28、s up to 93 C. 5 Procedure 5.1 Support the air bath (4.2) in its proper position in the water bath (4.3). Fill the water bath to within15 mm of the top with water at a temperature of 16 to 28 C. The bath temperature shall be kept within these limits throughout the test. 5.2 Heat the wax sample to at

29、least 8 C above its expected melting point (see note). To heat the wax sample, use a suitable container in the oven or water bath (4.6) which is controlled at a temperature not exceeding 93 C. Avoid direct heat such as a flame or hot-plate. Do not keep the sample in the molten state longer than 1 h.

30、 NOTEIf no estimate of the melting point is available, heat the wax sample to 10 C above the temperature at which the wax is completely molten, or to a temperature of 90 to 93 C, before proceeding to the next step. 5.3 Fill the test tube (4.1) to a height of 50 mm with the melted sample. Insert the

31、melting-point thermometer (4.4) through the centre of a cork so that the 79 mm immersion line is at the lower surface of the cork. Insert the cork into the test tube so that the bottom of the thermometer bulb is 10 mm from the bottom of the test tube. Support the test tube assembly in the air bath a

32、s shown in the Figure while the temperature of the molten wax is still atleast 8 C above its expected melting point (seenote to 5.2). 5.4 Read the melting point thermometer every 15s. Record each reading to the nearest estimated 0,05 C. Observe the progress of these sequential readings to determine

33、the appearance of the plateau. Identify the plateau as the first five consecutive readings all of which agree within 0,1 C. Discontinue the test after obtaining these five plateau readings. NOTEIf no plateau appears as defined above, continue the reading procedure until either the temperature reache

34、s 38 C, or the temperature reaches a point 8 C below a temperature at which the wax has solidified (as may be observed through a transparent bath). In either of these cases, the test shall be discontinued and the method judged NOT APPLICABLE to the sample. In such cases, other methods may be selecte

35、d (see note to 1.2). 6 Expression of results Average the first five consecutive thermometer readings of the identified plateau, which agree within 0,1 C. Correct this average for uncertainty (error) in the thermometer scale where necessary. 7 Precision The precision of the method, as obtained by sta

36、tistical examination of inter-laboratory test results, is as follows. 7.1 Repeatability The difference between two test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct oper

37、ation of the test method, exceed the following value only in one case in twenty: 0,1 C 7.2 Reproducibility The difference between two single and independent results obtained by different operators working in different laboratories on identical test material, would in the long run, in the normal and

38、correct operation of the test method, exceed the following value only in one case in twenty: 0,5 C 8 Test report Report the result to the nearest 0,05 C as the melting point (cooling curve) and make reference to this International Standard. Range 38 to 82 C Immersion 79 mm Graduation at each 0,1 C L

39、onger line at each 0,5 C Figured at each 1,0 C Maximum scale uncertainty 0,1 C Expansion chamber permitting heating to 100 C Overall length 377 5 mm Stem diameter 6,0 to 7,0 mm Bulb length 18 to 28 mm Bulb diameter 5,0 to 6,0 mm Distance from bottom of bulbto40 C line 116 to 125 mm Distance from bot

40、tom of bulbto80 C line 315 to 335 mm Distance from bottom of bulb totop of contraction chamber 41 mm max.BS4695:1980 BSI 11-1999 Publications referred to See national foreword.BS 4695:1980 ISO 3841:1977 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent na

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