IT has been reported elsewhere1 that organic nitrogen in plant materials, soil organic matter and extracted proteins undergoes partial oxidation to nitrate on treatment with a mixture of sulphuric and chromic acids. It has since been found that the proportion of total nitrogen recovered as ammonia is constant for each substance, provided the oxidation is completed under conditions of reduced pressure and moderate temperature1, and sufficient of the substance be taken to contain more than 20 mgm. of nitrogen. Of the fraction not recovered as ammonia, a portion is oxidised to nitrate and the rest is lost in gaseous form, probably as nitrogen or nitrous oxide. The oxidation constants bear definite relationship to the structure of the compound.