ISO-6618-1997.pdf
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1、INTERNATIONAL STANDARD IS0 6618 Second edition 1997-02-01 Petroleum products and lubricants - Determination of acid or base number - Colour-indicator titration method Produits p6 troliers et lubrifian ts - DGtermina tion de Iindice d acide ou de Iindice de base - M extremely weak acids or bases whos
2、e dissociation constants are less than IO-9 do not interfere. Salts react if their hydrolysis constants are greater than 10-g. NOTE 1 In new and used oils, the constituents considered to have acidic characteristics include organic and inorganic acids, esters, phenolic compounds, lactones, resins, sa
3、lts of heavy metals, and additives such as inhibitors and detergents. Similarly, constituents considered to have basic properties include organic and inorganic bases, amino compounds, salts of weak acids (soaps), basic salts of polyacidic bases, salts of heavy metals, and additives such as inhibitor
4、s and detergents. The method is not suitable for measuring the basic constituents of many basic additive-type lubricating oils, for which IS0 3771 can be used. This International Standard indicates relative changes that occur in an oil during use under oxidizing conditions. Although the titration is
5、 made under definite equilibrium conditions, the method does not measure an absolute acidic or basic property that can be used to predict performance of an oil under service conditions. NOTES 2 No general relationship between bearing corrosion and acid or base number is known. 3 Oils, such as many c
6、utting oils, rustproofing oils, and similar compounded oils, or excessively dark-coloured oils, that cannot be analysed by this method owing to obscurity of the colour-indicator end-point, can be analysed in accordance with IS0 6619. The acid or base numbers obtained by this colour-indicator method
7、may or may not be numerically the same as those obtained by IS0 6619, but they are generally of the same order of magnitude. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of p
8、ublication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain re
9、gisters of currently valid International Standards. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 02:49:21 MDTNo reproduction or networking permitted without license from IHS -
10、,-,- IS0 6618:1997(E) 0 IS0 IS0 3696: 1987, Water for analytical laboratory use - Specification and test methods. IS0 3771:1994, Petroleum products - Determination of base number - Perchloric acid po ten tiome tric titration method. IS0 6619:1988, Petroleum products and lubricants - Neutralization n
11、umber - Po ten tiome tric titration method. NOTES 1 IS0 3771 employs the use of chlorobenzene as a solvent. Alternatives to this solvent are being sought. 2 IS0 6619 is under review, and the scope will be restricted to acid number. 3 Definitions For the purposes of this International Standard, the f
12、ollowing definitions apply. 3.1 acid number: Quantity of base, expressed in milligrams of potassium hydroxide (KOH) per gram of sample, that is required to titrate the acid constituents present in 1 g of sample when titrated under prescribed conditions. 3.2 strong acid number: Quantity of basel expr
13、essed in milligrams of potassium hydroxide (KOH) per gram of sample, that is required to titrate the strong acid constituents present in 1 g of sample when titrated under - prescribed conditions. 3.3 base number: Quantity of acid, expressed in terms of the equivalent number of milligrams of potassiu
14、m hydroxide (KOH) per gram of sample, that is required to titrate the base constituents present in 1 g of sample when titrated under prescribed conditions. 4 Principle To determine the acid number or base number, the test portion is dissolved in a mixture of toluene and propan-Z-01 containing a smal
15、l amount of water, and the resulting single-phase solution is titrated at room temperature with standard alcoholic base or alcoholic acid solution, respectively, to the end-point indicated by the colour change of added pnaphtholbenzein solution (orange in acid and green-brown in base). To determine
16、the strong acid number, a separate portion of the sample is extracted with boiling water and the aqueous extract is titrated with potassium hydroxide solution using methyl orange as indicator. 5 Reagents and materials During the analysis, use only reagents of recognized analytical grade, and only wa
17、ter in accordance with Grade 3 of IS0 3696. 5.1 Propan-Z-01, anhydrous, maximum water content 0,9 %(V/v) (volume fraction 0,9 %). 5.2 Toluene. 5.3 Titration solvent. Add 500 ml of toluene (5.2) and 5 ml of water to 495 ml of propan-2-01 (5.1). 5.4 Hydrochloric acid, c(HCI) = 0,l mol/l standard volum
18、etric alcoholic solution. Prepare in accordance with 5.4.1 or use commercially available solution. Standardize in accordance with 5.4.2. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/2
19、1/2007 02:49:21 MDTNo reproduction or networking permitted without license from IHS -,-,- 0 IS0 IS0 6618:1997(E) 5.4.1 Preparation Mix 9 ml of concentrated HCI 35,4 %( avoid unnecessary exposure to carb on d ioxide during filtration. Store the solution in a chemically resistant dispensing bottle out
20、 of contact with cork, rubber or saponifiable stopcock lubricant and protected by a guard tube containing soda lime or nonfibrous soda silicate absorbentl). Glass bottles are not recommended for storage. 5.52 Standardization Standardize frequently enough to detect changes of 0,000 5 mol/l, preferabl
21、y against 0,l g to 0,15 g of pure potassium acid phthalate (5.9) weighed with an accuracy of 0,000 2 g and dissolved in approximately 100 ml of carbon dioxide-free water, using phenolphthalein (5.8) to detect the end-point. NOTES 1 To simplify calculations, both the standard potassium hydroxide and
22、hydrochloric acid solutions may be adjusted so that 1 ml is equivalent to 5 mg of KOH. 2 Because of the relatively large coefficient of cubic expansion of organic liquids such as propan-2-01, the standard alcoholic solutions should be standardized at temperatures close to those employed in the titra
23、tions of sample, and close to 20 “C. 56 . Methyl orange, indicator solution. Dissolve 0,l g of methyl orange in 100 ml of water. 5.7 p-naphtholbenzein indicator solution, meeting the specifications given in annexes A and B. Dissolve I,0 g of pnaphtholbenzein in 100 ml of titration solvent (5.3). NOT
24、E- In a study in 1992, only one co mmercially available sou Careful adhe rence to this requirem ent is t herefore recommended. rce of this indicator met the s pecif ica tion given in annex A*). 1) Ascarite, Carbosorb and lnde carb are examples of suitable products available commercially. T the conve
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