Hjdrometetermetoden

Abstract

Hydrometer Analysis. The hydrometer test has found a widespread use for size analysis. To make the method more rapid the Geological Division of the Swedish State Road Institute has worked out a timesaving apparatus, nomogram and way of analysis. Apparatus (standardized for ten analyses). Hydrometer, streamlined and graded in gram particles (specific gravity = 2,65) per litre of soil suspension. Fig. 1. Ten sedimentation cylinders of equal interior diameter. Fig. 8. Apparatus to make the ten cylinders disperse their contents. Fig. 8. Nomogram. Lines of concentrations on a log-log paper, ordinate particle diameter, abscissa time of sedimentation. The nomogram is based on Stokes' law, and it is possible to get the particle diameters for every value of the hydrometer readings and at any time from 0,2 to 2 000 minutes. Fig. 7 a. Corrections. Corrections for temperature are avoided (constant temperature) and corrections for spec. gravity are easily to get from the particle size nomogram (particle size corrections) and from a special correction nomogram, fig. 5, (correction of hydrometer readings). Stages of analysis. 1. If necessary, purifying from salts and humus. 2. Dispersion by aid of a solution of sodiumpyrophosphate in the shaker apparatus, ten cylinders at the same time (during a quarter of an hour). 3. After shaking, hydrometer readings in the same cylinders (during day). 4. Construction of the grain size accumulation curve by means of the particle size nomogram. Time of analysis. If no other preparations of the soil are necessary except dispersion, one man is able to do ten analyses per day and will besides have time to spare, and twice that amount with some help of an assistent.