This Bureau of Mines report describes the preparation of phosphoric acid directly from phosphate ore, without prior beneficiation, in a small-scale continuous process research unit, as part of an effort to improve minerals and metals recovery from domestic resources while minimizing environmental effects. Three phosphate-matrix samples, ranging in grade from 18.2 pct p2o5 to 11.9 pct p2o5, were dry-fed at a rate of 1.82 Kg/hr (4 lb/hr) to a continuous-circuit, 12-liter, single-tank digester to yield phosphoric acid and byproduct gypsum filter cake. Comparison with earlier data shows that a significantly improved filtration rate was attained in a single-tank reactor compared with that attained in a five-tank reactor train processing the same ore. Iron and aluminum impurities in the product phosphoric acid averaged about 60 pct higher than amounts reported in commercially prepared, concentrate-derived acid. All gypsum filter cakes prepared had a firm, sandy texture, rendering them physically suitable for stacking or landfill use. Introduction of dry attritioning and air classification approximately doubled the attainable filtration rate when the dry- beneficiated product was digested. In air classification, there was a 12- to 14-pct p2o5 loss. Depending on the technique used and the matrix grade, overall p2o5 recovery ranged from about 72 to 89 pct.