Floatation in Clerici solution for density measuring is one of the most effective methods in the determination of the specific gravity of small mineral grains. It is only necessary to mix with water to succeed in getting a set of liquids of lower specific gravity decreased one after another by degrees than the concentrated Clerici solution at regular intervals. Experimental data show that a straight line relationship exists between the refractive index and specific gravity of Clerici solution. Both will decreases with increased temperature. The value of dN/dT(the change in index of refraction for each degree centigrade change in the temperature) is -X0.0004 and that of dD/dT (the change in density for each degree centigrade change in the temperature) is 士0 .001. For very accurate work a correction factor is necessary if the obtai- ring temperature is other than 19℃. A correction of specific gravity of plus or minus 0.001 per degree above or below 190C should be made. This method gives results reliable to the nearest士0.005-0.01 in specific gravity. The error of the specific gravity determination is to a certain extent relative to the size of the mineral and the skilled level of the operator. In this paper, the opera- tion sequence, the author's experience, the requirements, the matters needing attention etc. are related.