The Mk 4 Sulfinert™ Treated Cryogenic Distillation Unit (Mk 4 Cryogenic Unit) is a mobile piece of equipment designed to allow the distillation of a pressurised single phase hydrocarbon reservoir fluid into a gas phase and a liquid phase, which are in a state suitable for direct chromatographic composition analysis. The Cryogenic Distillation unit is better for the distillation of volatile oils, condensates & gas systems. The Cryogenic unit can often isolate a residual liquid from a rich gas system, which aids characterisation of the heavy-end of the composition. This is because, instead of the heavy-ends being a small portion of the tail of an extended gas analysis, it can be separately chromatographically, analysed as a liquid alongside the extended gas analysis of the gas phase.