The chloroform anion in liquid methylcyclohexane (MCH) fragments during the time scale of geminate ion recombination (143 K less than or equal to T less than or equal to 193 K). Its lifetime can only be determined if the geminate ion kinetics can be calculated. The t(-0.6) semiempirical law is used. Because CHCl3 quenches M+*, the precursor of the solvent radical cation MCH+, much less effectively than N2O, the fragmentation of M+* to produce the methylcyclohexene cation (MCHene(+)) has to be considered by theory. The t(-0.6) simulation therefore was modified to include the two parallel reactions of the M+* decay, which are forming mixed ion pairs (MCNene(+), MCH+/X-). It is found that mixed pairs are still describable by the t(-0.6) linearity, yet the mobility factor delta (slope of t(-0.6)) is now lambda-dependent. Complete simulation of the ionic mechanism yields the following results: (1) The fragmentation rate constant for CHCl3- is k(1)(143 K) = (3.6 +/- 0.3) x 10(6) s(-1) with E-act = 4.6 +/- 0.5 kJ/mol and logA = 8.2 +/- 0.2. The lifetime of 280 ns is substantially larger than expected from gas phase data. (2) By applying the known G(fi) values to the free ion spectra at 143 K, 153 K, and 173 K, the absorption coefficients of the CHCl3- band were determined and a Lorentzian line shape fitted: lambda(max) = 470 nm, epsilon(max) = 1900 +/- 30 M-1 s(-1) and a width of hwhm = 28 +/- 2 nm. (3) Assuming that the M+* fragmentation (k(frag)) and the natural relaxation to MCH+ (k(0)) are the same as in N2O-saturated MCH, the quenching rate constant at 143 K may be derived: k(2)(M+* + CHCl3 --> MCH+) = (7.7 +/-2.6) x 10(6) M-1 s(-1). Quenching by CHCl3 therefore is about. four times slower than by N2O; the yield of the olefinic cation (MCHene(+)) is strongly increased relative to the MCH+ yield. Furthermore, the ratio quenching/fragmentation with chloroform as solute is found to increase with temperature, suggesting that fragmentation at room temperature might have much less importance.