ISO-6293-1-1996.pdf

INTERNATIONAL STANDARD IS0 6293-l First edition 1996-12-01 Petroleum products - Determination of saponification number - Part 1: Colour-indicator titration method Prod the mushroom-type condenser shall fit loosely to permit venting of the flask. All glasswa re shall be chemically cl ean. The flasks should be cle cleanliness obtaine d by the use of chromosulfuric acid (see wa aned by nona ). For co Ikaline cle Impartson ani ng agents to match the of cleaning efficiency, the 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6293=1:1996(E) IS0 visual appearance and loss in mass on heating may be used. Detergent cleaning, or the use of other strong oxidizing agents, avoids the specific hazards related to chromosulfuric acid, and is preferred for routine analysis. Flasks of borosilicate glass are preferred. New flasks may give high values, and old flasks that have become etched by long use should not be used. Blank tests should be run concurrently on both used and new flasks. WARNING - Chromosulfuric acid is a health hazard. It is toxic, a recognized carcinogen as it contains Cr(VI) compounds, highly corrosive and potentially hazardous in contact with organic materials. When using chromosulfuric acid cleaning solution, eye protection and protective clothing are essential. Never pipette the cleaning solution by mouth. After use, do not pour cleaning solution down the drain, but neutralize it with great care owing to the concentrated sulfuric acid present, and dispose of it in accordance with standard procedures for toxic laboratory waste (chromium is highly dangerous to the environment). Non-chromium-containing, strongly oxidizing acid cleaning solutions are also highly corrosive and potentially hazardous in contact with organic materials, but do not contain chromium which has special disposal problems. 6.2 Hotplate, heated by either electricity or steam. 6.3 Titration burette, of capacity 50 ml, graduated in 0,l ml subdivisions, or of capacity 10 ml, graduated in 0,05 ml subdivisions. 6.4 Balance, capable of weighing to the nearest 0,2 mg. 7 Blank run 7.1 Carry out one or more blank determinations concurrently with each set of samples in the manner described in 7.2 and 7.3. Blank determ nations should be run in dupl icate on samp les requiring t he high est act based on dup icate blank determinat ions. A single blank is su fficient for routine work. uracy. The precision data are 7.2 Measure from a burette or pipette into the conical flask (6.1) 25 ml + 0,03 ml of the alcoholic potassium hydroxide solution (5.2) and 25 ml + 1 ml of the butan-Z-one (5.4). If a volumetric pipette is used, wait 30 s after delivery for complete drainage. Connect the condenser to the flask, and heat for 30 min after refluxing begins. NOTE 1 It is known that some fats are readily saponified and complete saponification takes place within 10 min after refluxing begins. On the other hand, some materials are saponifiable only with difficulty, and are known to require more than 2 h in some cases. Neither the shortened period nor the longer period should be used except by mutual consent of the interested parties. The reflux time of the blank should be the same as that of the sample in all cases. Turn off the heat source and immediately add 50 ml of the petroleum spirit (5.5) by cautiously pouring it down the condenser (disconnect the condenser if a mushroom-type is used). NOTE 2 Pouring 50 ml of petroleum spirit down the condenser at the end of the saponification not only rinses the condenser but also cools the reaction mixture. However, in the case of insulating oils, the addition of petroleum spirit is not necessary. 7.3 Titrate the blank while hot, without reheating, with the hydrochloric acid solution (5.3) using three drops of the phenolphthalein indicator solution (5.6). When the indicator colour has disappeared, add, drop by drop, more indicator solution. If this addition of indicator restores the colour, continue the titration, making further drop-by-drop additions of indicator, if necessary, until the 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 IS0 6293=1:1996(E) end-point is reached. The end-point is reached when the indicator colour has completely disappeared and does not immediately reappear upon further drop-by-drop addition of the indicator solution. To avoid emulsification of the titration mixture, but assure phase contact, swirl the flask vigorously as the end-point is approached. 8 Test procedure 8.1 Test portion Estimate the saponification number and select a test portion mass from table 1. NOTE - The mass is based on an anticipated back-titration of between 40 % and 80 % of the blank, with a maximum test portion of 20 g. Table 1 - Mass of test portion I Estimated saponification number mg/g KOH Mass of test portion g 181 to 400 111 to180 71to110 31to 70 16to 30 Oto 15 1 2 3 5 10 20 8.2 Determination 8.2.1 Weigh the test portion, to the nearest 0,Ol g, into the conical flask (6.1). Add 25 ml + 1 ml of the butan-Z-one (5.4) followed by 25 ml + 0,03 ml of the alcoholic potassium hydroxide solution (5.2), measured from a burette or pipette (see 7.2). Connect the condenser to the flask and heat for 30 min after refluxing begins (see 7.2). Turn off the heat source and immediately add 50 ml of the petroleum spirit (5.5) by cautiously pouring it down the condenser (disconnect the condenser if a mushroom-type is used). 8.2.2 Titrate while hot with the hydrochloric acid solution (5.3) as specified in 7.3. NOTE - When testing waxes, it may be necessary to reheat the solution during titration to prevent solidification of the sample. 9 Calculation Calculate the saponification number, SN, in milligrams of KOH per gram of sample, from equation (1). SN (V. - VI) cHC, x 563 - - . . . (1) m where V, is the volume, in millilitres, of hydrochloric acid solution required for titration of the test portion; V. is the volume, in millilitres, of hydrochloric acid solution required for titration of the blank solution; CHcI is the concentration, in moles per litre, of the standard volumetric hydrochloric acid solution; m is the mass, in grams, of the test portion. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6293=1:1996(E) IS0 10 Expression of results Report the results, calculated in clause 9, as saponification number (milligrams KOH per gram sample), as follows. For electrical insulating oils: to the nearest 0,l; for saponification numbers below 50: to the nearest 0,s; for saponification numbers of 50 and above: to the nearest 1. 11 Precision The precision of the method, as obtained by statistical examination of interlaboratory test results, is given in 11 .I and 11.2, and is illustrated in figure 1. NOTE - No precision can be given for highly-coloured new or used oils, or for oils which produce dark-coloured solutions upon saponification, as colour may interfere with the detection of the end-point of the titration. 11 .I Repeatability, r The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the normal and correct operation of the test method, exceed the value below in only one case in 20. - 0,26 b) the type and complete identification of the product tested; c) the results of the test (see clause 10); d) any deviation, by agreement or otherwise, from the standard procedures specified; e) the date of the test. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6293=1:1996(E) c- : 5 c c 0 .- + m u ;I .- c E G 100 90 80 70 60 50 40 30 20 IO 9 8 6 2 3 4 5 6 7 8 Difference, saponification number 9 10 11 12 Figure 1 - Precision data 7 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,- This page intentionally left blank Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,- This page intentionally left blank Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6293=1:1996(E) ICS 75.080 Descriptors: petroleum products, chemical analysis, determination, saponification number, volumetric analysis. Price based on 7 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 20:40:58 MDTNo reproduction or networking permitted without license from IHS -,-,-