Assuming a tube volume of 4.9 ml, a CsCl solution with \(\rho\) = 1.89 and a desired density of 1.725 g ml-1 then \(V_{CsCl}\) should be 3980 µl and the rest (920 µl) should be a mixture of GB and DNA. It is recommended to prepare a volume larger by about 2--3% than needed to account for volume differences between tubes and for pipetting errors.