ASTM D94 standard test method for saponification number of petroleum products
1. Scope
1.1 These test methods cover the determination of the amount of constituents in petroleum products such as lubricants, additives, and transmission fluids that will saponify under the conditions of the test.
1.1.1 Two test methods are described: Method A - Color Indicator Titration (Sections 6-13), and Method B - Potentiometric Titration (Sections 14-23).
1.2 Because compounds of sulfur, phosphorus, the halogens, and certain other elements that are sometimes added to petroleum products also consume alkali and acids, the results obtained indicate the effect of these extraneous materials in addition to the saponifiable material present. Results on products containing such materials, on used internal-combustion-engine crankcase oils, and on used turbine oils must be interpreted with caution.
NOTE 1 - The materials referred to above, which are not normally considered saponifiable matter, include inorganic or certain organic acids, most nonalkali soaps, and so forth. The presence of such materials increases the saponification number above that of fatty saponifiable materials for which the test method is primarily intended. The odor of hydrogen sulfide near the end of the back-titration in the saponification test is an indication that certain types of reactive sulfur compounds are present in the sample. In the case of other reactive sulfur, chlorine, and phosphorus compounds and other interfering materials, no simple indication is given during the test. A gravimetric determination of the actual amount of fatty acids is probably the most reliable method for such compounds. Test Methods D128 or IP Method 284/86 can be used to determine fatty acids gravimetrically.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Sections 6, 7, 8, 10, 15, 16, 17, and 19.
2. Referenced Documents
2.1 ASTM Standards:
D117 Guide to Test Methods, Specifications, and Guides for Electrical Insulating Oils of Petroleum Origin
D128 Test Methods for Analysis of Lubricating Grease
D1193 Specification for Reagent Water
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance Techniques to Evaluate Analytical Measurement System Performance
2.2 Institute of Petroleum Standards:
IP 136 Method of Test for Saponification Number of Petroleum Products
IP 284 Method of Test for Fatty Acids
3. Terminology
3.1 Definitions:
3.1.1 saponification number, n - the number of milligrams of potassium hydroxide consumed by 1 g of a sample under the conditions of the test.
3.1.1.1 Discussion - The value of the saponification number in these test methods can be affected by the presence of other alkali-reactive species, as described in Note 1.
3.1.2 saponify, v - to hydrolyze a fat with alkali to form an alcohol and the salt of a fatty acid.
