For preparing a CsCl density gradient one typically mixes a high-density solution of CsCl (7.163 M) with an aqueous buffer solution to reach a target density. For DNA separation in SIP studies this is typically 1.725 g ml-1. Despite the simplicity of the problem, different formulae appeared in the literature, leading to slightly different end values. Most notably, the famous publication by \citealp{Neufeld_2007} uses a constant---1.52---instead of a variable that would represent the density of the mixture. The source of this constant appears to be from the classical book Centrifugal Separations: Molecular and Cell Biology by \citealp{1985}, where it is used for a specific case only.
While the practical implications are small so long as one tries to create a solution with a density of 1.725 g ml-1 (although the resulting value is still wrong), the deviations become significant the further the target density deviates from this value.