Optical high-pressure transmission cell

An optical high-pressure transmission cell, preferably a measuring cell for SFC-FTIR, comprising a pressure-resistant housing part which is passed by two bores of different diameter extending perpendicularly relative to, and intersecting, each other, a thinner bore forming a passage for a highly compressed solvent containing a substance under examination, whereas a thicker bore forms a transmission path for light of an IR spectrometer, further fittings for connection of lines to ends of the thinner bore and IR-permeable windows closing off the thicker bore on both sides at points of opening to the thinner bore, each of said windows being arranged in a recess provided in the housing part at the end of the thicker bore and being held in said recess by a clamping body resting against an outer surface of the window and fixed to the housing part by screwing, and being sealed off relative to the housing part by means of an O-ring arranged between the housing part and an inner window surface adjoining the housing part, so that the thicker bore delimited by the windows arranged opposite each other defines a high-pressure resistant, tight chamber for the substance passed therethrough by means of the thinner bore, wherein:

• said windows (4) are stepped in an axial direction of said thicker bore and comprise each an outer portion and an inner cylindrical neck portion (5) of smaller diameter, arranged concentrically with said outer portion, said cylindrical neck portion positioned in said thicker bore (3) and having an axial length corresponding to a desired length of a light path through said chamber so that said chamber is defined by end faces (22) of said neck portions (5), wherein each end of said thicker bore (3) is connected with an adjoining recess (6) by a concentrical portion (9) widening towards the outside, and said O-ring (32) is arranged in an annular space (11) defined by a circumferential surface of said cylindrical neck portion (5), a surface of said widening portion 9 and an inner surface (7) of the outer portion of said stepped window (4) facing the chamber.