Abstract: A closure vessel assembly for use in laboratory work within a range of temperature from -196.degree. C. to 100.degree. C. above zero includes a vessel made of a plastic material and having a wall defining the vessel mouth, and a closure for closing the vessel. The closure has an annular sealing lip which depends from the top wall of the closure and extends into the vessel mouth when the closure is locked on the vessel. The sealing surface of the sealing lip engages the sealing surface of the vessel wall, in the locked position of the closure with the vessel, to provide a seal therebetween. The respective radii of the sealing surfaces of the sealing lip and the wall are selected so as to provide for minimum surface pressure yet sufficient sealing between the sealing surfaces, despite any deformation of the materials of the sealing surfaces during the required closing time of the vessel.

Abstract: A cover receptacle assembly of plastics for use in laboratories, in particular for the polymerase chain reaction technique, comprising a tubular receptacle having a receptacle botton at one end and a receptacle opening at an opposite end, a cover for sealingly closing said receptacle opening, strap hinge means integrally and pivotally connecting said receptacle and cover with each other, and holding means for holding said cover in an intermediate position between an initial position wherein said cover is pivoted away from said receptacle opening for 180.degree. and a closing position wherein said cover closes said receptacle opening.

Abstract: A cell for mixing operations and for optical examinations of liquids has a measuring region which has a small cubic capacity and a relatively large height. In a horizontal cross-section that measuring region has curved transitional wall portions between parallel end wall portions for receiving incident radiation and side walls. In the measuring region, the side walls have inwardly curved portions, which protrude inwardly to such an extent that in a transverse sectional view a tangent to the apex of each inwardly curved portion intersects the parallel end wall portions at an edge thereof or at a point which is inwardly spaced from said edge so that a double-tapered beam of measuring radiation will be closely approached by the inwardly curved side wall portion. At least one side wall portion may constitute a positive lens.