days 198 16 days 975 330 195 33020 days 1095 365 210 365______________________________________ sup a gum precipitated sup b boiling point 82 u00b0 c sup c methylethylketone boiling point 80 u00b0 c sup d boiling point 84 u00b0 c air flow started several additional materials were evaluated according to the procedure of example i except that flow times were measured only at the beginning and the end of the test period and flowing air was not introduced during the test the control precipitated gum but the stabilized test mixtures did not results are shown in table iii table iii______________________________________time dependent flow times t sec of fuel band fuel b 10 additive mixturesadditive sup a b p u00b0 c t sub o sup b t sub t sup c______________________________________none 460 sup 511 sup dt butanol 83 177 255t butanol 5 cyclohexanol 5 198 202diphenylmethanol 297 435 458triethylamine 88 74 83diphenylamine 302 303 339methylphenylketone 202 180 210benzophenone 305 367 446______________________________________ sup a no gum deposition in the presence of additives sup b time 0 sup c time 12 days sup d gum deposited stabilization of coal liquid fraction b by additives in the presence of drum material the experiment of example i was repeated with drum material typically 1 2 g cut in narrow strips present for eleven days no test with air was included untreated fuel b precipitated gum during the test but stabilized test mixtures did not results are shown in table iv and fig2 as found in the tests of example.