Abstract 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 redhot. 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.
An improved closing and observing device, specifically for use with graphite tube sample cells for flameless atomic absorption, wherein an opening is provided in the housing surrounding the cell through which the sample under analysis is introduced, said opening being provided with a closing and observing device through which the graphite tube may be observed while in a state of incandescence, the improvement in which: said closing and observing device comprises a pinhole camera of a generally known type, said device comprising an elongated tubular member supporting a ground-glass for observation of the incandescent graphite tube adjacent one end of said member which is remote from said incandescent tube, and an apertured stop positioned a substantial distance from said one end of said member so as to act as the pinhole of the system, said device further comprising a field stop means intermediate and spaced from said apertured stop and said ground-glass for limiting the field angle of those rays which pass through said apertured stop and reach said ground-glass, so as to reduce glare by non-image-forming rays.
Claim 2
Dependent Claim
178 words
An improved closing and observing device, specifically for use with graphite tube sample cells for flameless atomic absorption, wherein an opening is provided in the housing surrounding the cell through which the sample under analysis is introduced, said opening being provided with a closing and observing device through which the graphite tube may be observed while in a state of incandescence, the improvement in which: said closing and observing device comprises a pinhole camera of a generally known type, said device comprising an elongated tubular member supporting a ground-glass for observation of the incandescent graphite tube adjacent one end of said member which is remote from said incandescent tube, and an apertured stop positioned a substantial distance from said one end of said member so as to act as the pinhole of the system, said device further comprising a field stop means intermediate and spaced from said apertured stop and said ground-glass for limiting the field angle of those rays which pass through said apertured stop and reach said ground-glass, so as to reduce glare by non-image-forming rays.
Claim 3
Dependent Claim
48 words
An improved closing and observing device as claimed in the claim 1, in which: the aperture diameter of said apertured stop is of a size sufficient for the formation on said ground-glass of an image of the average-heated graphite tube cell of sufficient brightness to be readily visible.
Claim 4
Dependent Claim
58 words
An improved closing and observing device as claimed in the claim 1, in which: the surface of said apertured stop remote from said one end and therefore on the side facing the graphite tube and the inner surfaces of the supporting structure of said apertured stop on the side thereof closer to the graphite tube are specularly reflecting.