nitric acid concentration and was found to have a nitric acid concentration of 11 5 percent the remaining solids amounting to 65 5 grams were exhaustively extracted at ambient temperature and pressure with methanol the extract was subjected to a vacuum of 28 inches of mercury and about 13 u00b0 c to remove methanol therefrom the amount of solvent insoluble coal derivative amounted to 20 3 grams while the amount of solvent soluble coal derivative amounted to 40 9 grams this example is similar to example i except that the coal was added to the reaction zone in two separate stages in the first stage the slurry added to the nitric acid in the flask contained 42 0 grams of coal on a moisture free and ash free basis and 90 grams of water this time the holding period after the addition of the slurry was one half hour at the end of the one half hour holding period there was added to the reactor contents a second slurry containing nine grams of coal on a moisture free basis and 25 grams of water over a ten minute period while the temperature was maintained at 55 u00b0 c as in the first stage addition the contents of the reactor were held at one hour at 55 u00b0 c the product was then worked up as in example i whereas some foaming occurred during the course of the slurry addition period and during the evaporation stage of example i which required constant attention no foaming problems were noticeable herein example iii below was carried out following the procedure described in u s pat no 4 052 448 referred to hereinabove the reaction stage described in example i was repeated instead of subjecting the reactor contents to.