D94

ISO-6293
Saponification Number of Petroleum Products

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 through 13), and Method B-Potentiometric Titration (Sections 14 through 22).

1.2 Because compounds of sulfur, phosphorus, the halogens, and certain other elements which 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 crank-case 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, etc. 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 D-128 or IP Method 284/86 can be used to determine fatty acids gravimetrically.

Also see: D-94

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