A sample vial [24] is disclosed, having a generally tubular body [32]. The vial [24] has a generally round lip [34] defining an opening [36] at the top of the body [32]. The vial [24] has a foot [38] at the base of the body [32], having asymmetric first and second sides [40, 42]. A rack [28] is disclosed for supporting such a sample vial [24]. The rack [28] supports the sample vial [24] in a generally upright position in a single orientation. The rack [28] has an asymmetric recess [50] adapted to receive the asymmetric foot [38] in a single orientation. The rack [28] also has an orientation abutment [82] adapted to interfere with a projecting abutment [46] of a vial [24] to prevent insertion of a vial [24] into the asymmetric recess [50] in an orientation other than the single orientation. The orientation abutment [82] also allows insertion of a vial [24] into the asymmetric recess [50] in the single orientation.