Distribution in gravitational field

To detennine Avogadro s number from the distribution of an emulsion in a gravitational field. 

Perrin (Ann. Chim. Phys. 1909,18.55,63) measured the distribution in the earth s gravitational fidd of an aqueous emulsion of rubber latex. Partides of uniform size were obtained by fractional centrifuging. Their size was determined by dialdng some emulsion containing a known total mass of latex with sli tly addified water and then putting a drop of known volume on to a microscope slide. The latex partides then adhere to the surface of the glass and can be counted through a microscope. 

The density of the latex partides exceeded that of the surrounding aqueous liquid by 0.2067 g cm at 20 °C. 

The mean radius of the partides was found by the method outlined above to be 2.12 x 10- cm. 

Hie number of partides visible over a certain constant cross-section of the fidd at various heights above the slide was observed at intervals of 15 s and the average number calculated. These averages, obtained by observations on altogether 13000 particles, were found to be in the ratios diown in table 1 

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