This paper exhibits a third-order Newton process for approximating

, the general fractional capacitor, for any integer

> 1. The approximation is based on predistortion of the algebraic expression

. The resulting approximation in real variables (resistive networks) has the unique property of preserving upper and lower approximations to the

th root of the real number

. Any Newton process which possesses this property is regular. The real variable theory of regular Newton processes is presented because motivation lies in the real variable domain. Realizations of 1/3 and 1/4 order fractional capacitor approximations are presented.