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THE ALUMNI JOURNAL. 



INFLUENCE OF THE CHEMICAL NATURE 

 OF SUBSTANCES AND THEIR PERME= 

 ABILITY BY THE ROENTGEN RAYS. 



BY MADP-ICE MKSLANS. 



Numerous experiments have demon- 

 strated that certain bodies are transparent 

 to the radiations emitted by the Crookes 

 tube, while others present as regards 

 these rays a relative opacity. I have un- 

 dertaken to examine vi^hat is the relation 

 which may exist between the transpar- 

 ency of these substances and their chem- 

 ical nature, and if the Roentgen rays may 

 not furnish a new means of investigation 

 in the domain of chemistry. I will here 

 merely indicate the most striking of the 

 results which I have obtained ; they are 

 manifest on an examination of the photo- 

 graphic proofs which I submit to the 

 Academy, and which refer to about fifty 

 substances, simple and compound. These 

 results, though incomplete, seem to me 

 to offer some very definite conclusions, 

 and determine me to pursue this study 

 further. 



The transparency or opacity of bodies 

 to the "X" rays is not absolute; the influ- 

 ence of thickness has been already dem- 

 onstrated, and the role of density has 

 been examined. The specific chemical 

 nature appears to me to present a very 

 considerable influence. I have compared 

 together the various nonmetallic bodies 

 as well as their acid derivatives, and the 

 salts, metallic or organic, which they 

 yield. My experiments have related 

 chiefly to organic bodies, and to their es- 

 sential element, carbon. 



I have been hitherto able to establish 

 the extreme transparency not merely of 

 carbon in its different states, compared 

 to those ot other nonmetals. The slight 

 opacity of organic compounds when along 

 with carbon they contain merely the gas- 

 eous elements, hydrogen, oxygen and 

 nitrogen. Still this transparence is far 



from being uniform, and presents very 

 various degrees which appear connected 

 with the chemical function of these bodies. 



The photographic proofs which accom- 

 pany this memoir have been obtained by 

 shutting up a photographic plate in a 

 frame for negatives, and arranging upon 

 the little board which covers the plate 

 the substances whose transparence it was 

 desired to study, lighting up the whole 

 with a Crookes tube, placed at a distance 

 of 20 cm. After an exposure of thirty 

 minutes, the plate and development gave 

 silhouettes of the bodies experimented 

 upon, the relative intensities of which 

 measured their transparence. 



Diamond, graphite, anthracite, sugar 

 charcoal give a faint tinge of tonality sim- 

 ilar to that of wood or of paraffin of an 

 equal thickness, while sulphur, selenium, 

 phosphorus, iodine, afford very strong 

 images of great opacity. 



The organic substances, ethers, acids, 

 nitrogenous substances were easily trav- 

 ersed by the "X" rays, and gave images 

 scarcely perceptible; but the introduction 

 into the organic molecule of a mineral 

 element, such as iodine, chlorine, fluo- 

 rine, sulphur, phosphorus, etc., gives to 

 the molecule a great opacity. 



The sulphates of the alkaloids are in | 



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this case. In like manner iodoform is j 

 very opaque, while the alkaloids, picric j 

 acid, magenta and urea are very trans- 

 parent. Phthalyl fluoride is much more 

 opaque than phthalic acid, although the ' 

 molecular weights of the two bodies ap- j 

 proximate very closely. The metallic i 

 salts possess a great opacity, but which 

 varies with the metal and the acid. 



These results are corroborated by the \ 

 photography of hands and of small entire ! 

 animals executed by Prof. Roentgen and i 

 others. In these proofs the muscles re- 

 main transparent. They are, in fact, 

 substances formed entirely of carbon, hy- ; 

 drogen, oxygen and nitrogen. The bones 



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