A manual of practical medical electricity : the Röntgen rays and Finsen light . machine is that, unless amotor be employed, an assistant is required to rotate it ;its working is also affected by the weather, its behaviourbeing capricious in this respect, so that, on the whole, it RoNTGEN X Rays 323 is not nearly so efficient or convenient an instrument forproducing the X radiation as a good induction coil. The vacuum tube should be a focus one ; this is a bulbof glass, into either end of which platinum wires are the extremity of one of the wires, the anode, a smallflat piece of plati
A manual of practical medical electricity : the Röntgen rays and Finsen light . machine is that, unless amotor be employed, an assistant is required to rotate it ;its working is also affected by the weather, its behaviourbeing capricious in this respect, so that, on the whole, it RoNTGEN X Rays 323 is not nearly so efficient or convenient an instrument forproducing the X radiation as a good induction coil. The vacuum tube should be a focus one ; this is a bulbof glass, into either end of which platinum wires are the extremity of one of the wires, the anode, a smallflat piece of platinum is attached, inclined at an angle of45° ; to the extremit^^ of the other, the kathode, a concavedisc of aluminium is fastened, at such a distance fromthe anode that the kathode rays are focussed upon wires are chosen to pass through the glass,because platinum and glass have nearly the same co-efficient of expansion under alterations of temperature,and aluminium wires may be used to connect the platinumwires to the internal electrodes. The glass of which the. Fig. 140.—Diagram of Focus Tube. tube is made must be quite free from lead, because leadis very opaque to X radiation. The tube must now beexhausted, first by an ordinary air-pump, and afterwardsby some form of mercurial pump ; nothing but a goodmercurial pump will suffice to produce the high vacuumrequired, the best mechanical pump being quite ineffi-cacious. The tube should be warmed during the pumping pro-cess, and a bulb of phosphoric anhydride should be in-serted between the tube and the pump to remove theaqueous vapour. The degree of exhaustion can be esti-mated by the character of the discharges, which shouldfrom time to time be passed through the tube, and by theresistance offered to the passage of the electricity. Atthe proper degree of exhaustion, that part of the wall ofthe tube which is opposite the free surface of the anodewill be bathed with a greenish-yellow phosphorescence, 21—2 324 A M
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectelectro, bookyear1902
