OBSERVING DEVICE FOR HEATED SAMPLE CELLS

An opening in the housing surrounding a graphite tube sample cell of the type used for heating an atomic absorption sample may be used for introducing the sample and later (when the graphite cell is heated during sample measurement) must be closed to avoid escaping of the non-oxidizing gas introduced within the housing for protection of the graphite cell. It has already been proposed to construct such a closing device so as to allow observation of the graphite cell but existing devices do not allow observation of the graphite cell during sample measurement when it is red-hot. An improved combined observing and closure device utilizing the known principles of a pin-hole camera includes an apertured stop (preferably a field stop) and a ground-glass screen for receiving the image, all in a supporting tubular member which may be utilized as the closure. Preferably the parts of the device nearest the graphite tube cell (e.g., one surface of the aperture stop and its supporting structure) are made specularly reflecting.