472 



Popular Science Monthly 



Making a Practical Fluoroscope 

 at Home 



M 



ANY electrical experimenters pos- 

 apparatus such as Tesla, 



sess 



or high frequency apparatus, a large 

 spark-coil, or a static machine, which 

 may be used very well for X-ray ex- 

 periments with only a few accessories. 

 The high cost of the most important 

 of these accessories, the X-ray tube 

 and the fluoroscope, has caused many 

 amateurs to defer, not without reluct- 

 ance, work in this most interesting and 

 instructive field. 



It is impossible to make an X-ray 

 tube in the ordi- 

 nary shop or labo- 

 ratory, but it may 

 now be purchased 

 at a very reason- 

 able price. In or- 

 der to secure the 

 best results, care 

 should be taken 

 to select a tube 

 designed especial- 

 ly for use with the 

 particular type of 

 apparatus to be 

 used. There is 

 considerable dif- 

 ference in the de- 

 sign of tubes for 

 the diff'erent types 

 of apparatus. A 

 tube made for use 

 upon a static ma- 

 chine may give 



Frame and pyramid for cutting out the 

 side lights from the fluorescent screen 



very poor results upon a coil or for other 

 purposes, and last only a short time. 

 It is best to get a tube with some form 

 of vacuum-regulating device, as it great- 

 ly increases its usefulness and life. 



A fluorescent screen or fluoroscope 

 may be constructed in the laboratory, 

 and may be used equally well with any 

 form of apparatus or tube. To make 

 the fluorescent screen, the fluorescent 

 substance is mounted upon any suit- 

 able supporting surface, such as card- 

 board, in an even continuous layer, 

 so that the rays act through the support 

 and excite the active substance. 



A great deal of experimenting has 

 been done in order to ascertain just 

 what substances are fluorescent, and 

 which possess this property in the 

 highest degree. Perhaps the substance 

 best suited for the use of the average 



experimenter is calcium tungstate. This 

 is sometimes found in a sufficiently 

 pure state for use in the natural mineral 

 scheelite, or it may be purchased from 

 a reliable chemist, or made in the lab- 

 oratory. Great care should be taken in 

 order to secure a good crystalline 

 variety. 



In order to prepare calcium tung- 

 state (CaW04), in the laboratory, 294 

 parts, by weight, of sodium tungstate, 

 (Naa WO4) ; III parts-of calcium chlor- 

 ide, (CaCl2); and 59 parts of common 

 salt, sodium chloride, (NaCl) are thor- 

 oughly mixed. The commercial, chem- 

 ically pure sodium 

 tungstate should 

 first be pulverized 

 and heated in an 

 air bath to about 

 110° C. or 225° F. 

 until the water of 

 crystallization has 

 been driven off", 

 and the salt is 

 thoroughly dry. 

 The calcium chlor- 

 ide and salt should 

 also be pulverized 

 and dried at about 

 the same tempera- 

 ture. This should 

 be done before 

 weighing the 

 chemicals. 



The mixture is 

 placed in a cruci- 

 ble and heated in 

 a blast lamp until 

 The crucible 

 cooled, and 

 extracted by 



a furnace or with 



it is thoroughly fused. 



is then very gradually 



when cold, the mass is 



dissolving out the sodium chloride with 



water, which leaves a mass of calcium 



tungstate crystals. These are separated 



from the liquid by filtering, washed 



well with water to remove any trace 



of the chloride, and thoroughly dried. 



These crystals should be sifted through 



a sieve with a mesh of about 30 to 



the linear inch, and preserved for use 



in a well stoppered bottle. 



Another method of preparing this 

 salt is to precipitate the calcium tung- 

 state from a solution of sodium tung- 

 state in water, with calcium chloride 

 or nitrate. The precipitate is removed 

 by filtering, thoroughly washed, dried 

 and mixed with about twice its 



