The dual wavelength spectrophotometer, noted for its high sensitivity and accuracy in the recording of oxidation-reduction and other reactions of membrane bound components in turbid suspensions of biological materials, has now been modified to scan the spectrum of these components over a reasonable wavelength range (40 nm) and in a short time (rates as rapid as 20 nm/sec). The baseline precision is not remarkable (approximately 1% error) but the method retains the intrinsic noise rejection properties of the dual wavelength technique. Two forms of the apparatus are discussed, one a simple modification involving a previously described time sharing compensating circuit, and the other incorporating a tapped potentiometer for more precisely correcting the baseline, and a comparator and error detector for correcting wavelength dependent sensitivity error.