Four samples of various phosphorites were treated with H2SO4, in a lab. batch reactor under industrial plant conditions. The content of phosphates in phosphorite and in obtained phosphoric acid were detd. by weighing and in phospho gypsum by a spectrometric method. For each grade of phosphorite, the ratio of mass of the resulting phosphogypsum to the mass of phosphorite, the degree of conversion of phosphorite and phosphate efficiency were 1.36-1.52; 97.6-99.9% and 92.5-95.5%, resp. No significant differences between the chem. anal. results of products from lab. tests and industrial plant were obsd.