ASTM D3279 – n-Heptane Insolubles
Heptane-insoluble substances include asphaltenes (waxes, heavy oils, resins), wear debris, and other compounds. This test has two important uses:
(1) In refining, the level of heptane insolubles may be an indication of the degree of refinement – more refined oils typically have fewer heptane insoluble compounds than less refined ones.
(2) In end use applications, heptane insolubles may precipitate in pipelines, tubing, valves and process control equipment impeding lubricant flow and potentially damaging system components. Since solvents such as heptane are often used to clean these systems, heptane insoluble compounds are difficult to remove.
This test determines the mass percent of heptane-insoluble substances in lubricating oils, gas oils, heavy fuel oils and crude petroleum.
The sample is weighed into a flask, heptane is added and the mixture is refluxed to dissolve the soluble components of the oil. The mixture is filtered, the sediment is rinsed with heptane, dried and weighed. Reported is the mass % of heptane insolubles.