Scientific apparatus, namely, gas-containing vessels used to establish desired heat flux to provide for temperature control with respect to an outside source to test or react a sample contained therein, to test for the viscosity of a fluid sample, and for use as a stator to test for the viscosity of a fluid sample; viscometers using gas-containing vessels as stators to establish desired heat flux to test for the viscosity of a fluid sample; viscometer parts, namely, stators and rotors, rotors and spindles matched with gas-containing vessels used to establish desired heat flux to test for the viscosity of a fluid sample, spindle supports, spindle clips, and connectors; other components for use with such vessels, stators, viscometers, rotors and spindles, namely, viscometer heads, baths, for containing fluids to set and control temperature of a sample contained in such vessels and stators immersed in the baths, instrument consoles, computers and computer programs for use in database management in viscometry and assemblies with such vessels, stators, rotors and spindles, or other components, namely, unprogrammed, partially programmed, and completely, programmed viscometer units, matched spindle-stator pairs, and test cell assemblies having a stator, a spindle and one or more of further test cell assembly components, namely, a spindle support, a spindle clip, and a connector