Henry's function

Henry's function (related to electrophoretic mobility) is given by (Eq. 2 in ):

$f(\kappa a)=1+{\frac {1}{16}}(\kappa a)^{2}-{\frac {5}{48}}(\kappa a)^{3}-{\frac {1}{8}}(\kappa a)^{4}\left[{\frac {1}{12}}(1-\kappa a)-\left(1-{\frac {1}{12}}(\kappa a)^{2}\right)e^{\kappa a}E_{1}(\kappa a)\right]$

where Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle a} is the radius of the particle, Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \kappa } is the Debye length and Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle E_1(\kappa a )} is the first order exponential integral.