. Radiography, X-ray therapeutics and radium therapy . -rays in measured doses. standards for the unexposed pastille and for -| and ^ B require the additionaluse of neutral-tint glasses if the colours are to be matched exactly, otherwisethey are brighter than standard, due to the white light reflected. Thisbrightness is dulled by the interposition of a standard neutral-tint grade of neutral-tint varies very slightly with the amount of varnishon the pastille. On an average the neutral-tints required are 1-5 forthe unexposed pastille, 04 for £ B, and 0-2 for % B. For higher dosesno neu
. Radiography, X-ray therapeutics and radium therapy . -rays in measured doses. standards for the unexposed pastille and for -| and ^ B require the additionaluse of neutral-tint glasses if the colours are to be matched exactly, otherwisethey are brighter than standard, due to the white light reflected. Thisbrightness is dulled by the interposition of a standard neutral-tint grade of neutral-tint varies very slightly with the amount of varnishon the pastille. On an average the neutral-tints required are 1-5 forthe unexposed pastille, 04 for £ B, and 0-2 for % B. For higher dosesno neutral tints are necessary. When measuring by electric light a neutraltint is only required for the unexposed pastille standard, and this is usuallyabout 50. Hampsons Radiometer.—This is a new radiometer designed for thepurpose of reducing the length of time which is necessary before the full dosemay be given when employing the Sabouraud-Noire pastilles. It consists of a series of twenty-five very carefully graded tints, which HAMPSON RADIOMETER 291. Fig. 212.—Hampson and Wright.) represent the colour assumed by a pastille of barium platino cyanide underthe action of X-rays. The initial or zero tint is thecolour of the unexposed salt, andthe sixteenth change represents thebrown shade of colour equivalentto the maximum or B tint of apastille as employed by Dr. Sabou-raud. The radiometer consists of thesetints arranged upon a circular card,the latter being enclosed in an outercase. This has a small aperture cutin it, through which the tints can besuccessively viewed one at a time,and the aperture is so shaped thatthe sensitive pastille can be placedin close proximity to the tint, thelatter being rotated by the thumbuntil an exact match in colour hasbeen obtained. Another small opening exposesto view a series of numbers, ranging from 0 to 24, whereby the tints can be identified. The whole is coveredin black cloth. Tints are so arranged that for exact matching
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