We review, the recent work done in the Leiden Observatory Laboratory on measuring the IR band strengths of CO and CO2 diluted in various binary ice mixtures. These measurements were performed with a novel technique in Which the component gases are deposited simultaneously through separate tubes; avoiding a number of pitfalls intrinsic in previous methods where the components were pre-mixed in a gas container before deposition. The error in the new method is in general only a few percent. We also review the results on the UV photolysis of solid methanol at t0 K. By starting the IR spectroscopic monitoring after very small UV doses (i.e. 6 s). we clearly distinguish the first order photolysis products. i.e. H2CO, CH4, HCO and H2. from the higher order products. i.e. CO and CO2. © 1995.