A. M. Mayer — Researches on the Rontgen Rays. 467 



Art. LIV. — Researches on the Rontgen Rays; by Alfred 



M. Mayer. 



Contents : 1. The Rontgen rays cannot be polarized by passing through 

 herapathite. 2. The density of herapathite. 3. The formulae of transmis- 

 sion of the Rontgen rays through crown glass, aluminum, platinum, green 

 tourmaline and herapathite. 4- The actinic action of the Rontgen rays varies 

 inversely as the square of the distance of the sensitive plate from the source of 

 the rays. 



1. The Rontgen rays cannot be polarized by passing through 



herapathite. 



Herapathite is an iodo-sulphate of quinine, discovered by 

 W. B. Herapath in 1852,* and named herapathite by Haidinger. 

 Herapath gives several formula for its production. The one 

 which succeeded the best with me in giving crystal plates of 

 large area is contained in Phil. Mag., Nov. 1853. It is as 

 follows : 



JBisulphate of quinine _ _ 3*24 grams. 



Pyroligneous acid 56 cc 



Alcohol (95 per cent) 56 cc 



Solution of iodine (1 grm. in ll cc alcohol) 50 drops. 



The bisulphate of quinine is added to the mixture of pyro- 

 ligneous acid and alcohol and heated to 55° C, and then the 

 iodine is added drop by drop while constantly stirring the solu- 

 tion. The vessel containing the solution is then placed on 

 several layers of thick felt resting on a iirm support to prevent 

 vibration, and it thus remains about 18 hours at a temperature 

 of 8° C. At the expiration of that time large crystals will 

 generally be seen floating on the surface of the liquid, the 

 majority being at the bottom of the vessel. The solution 

 gives, of herapathite, only -^ of the weight of bisulphate of 

 quinine. 



As suggested by Herapath, a microscope cover glass is 

 cemented to the end of a glass rod, with its plane at right 

 angles to the rod, and is carefully brought under the floating 

 crystal, very slowly brought up to it and the crystal is thus se- 

 cured on the surface of the glass. The mother liquid is then 

 absorbed from the glass by blotting paper. If several crystals 

 are desired on a cover glass, a glass tube closed by the finger is 

 brought over the crystals at the bottom of the vessel, the finger 

 removed, then replaced and the tube taken out of the liquid. 

 The crystals are allowed to sink into the drop at the end of the 

 tube by holding the latter for some time in a vertical position ; 



*Phil. Mag., Mar 1852 



