The colorimetric single channel system Autolab is described. The precision of volume delivery by the syringes and the precision and linearity of the photometer have been investigated. The carry-over and cross-contamination effects have been studied in general and measured for the sampler, the stirrers, and the photometer cell. The effectiveness of the incubation module has been studied and a sampling technique which makes it possible to adapt the system to water analysis with an essentially better sample/reagent ratio is described.