(1) A new method for the analytical determination of the diffusion constant
of a virus is described.
(2) This method is based upon the amount of virus which diffuses across
the interface formed between an infective emulsion and the dispersion
medium and the method of calculation is detailed.
(3) From the experimental data collected the diffusion constant is
calculated as 0.87 x 10-7 cm²/sec.
(4) From the diffusion constant the size is calculated as 48.8 m.µ, a
figure which corresponds closely to that obtained from ultrafiltration and
(5) By combining the diffusion constant with the sedimentation and
partial specific volume data the molecular weight is calculated to be of the
order or 41,000,000.
(6) From the above data it is shown that horsesickness virus particles
are essentially globular in shape and not threadlike or elongated.