remarkable Properties of Iodine, S^-c. 209 



This will be understoocl when I state, that an engraving exposed 

 to the vapour of niercuryor sulphur no longer takes the iodine; 

 the same occurs when it is immersed in nitrate of mercury 

 diluted with water, nitrate of silver, the sulphates of zinc, 

 copper, &c. ; oxide of copper, minium, ultramarine, cinnabar, 

 orpiment, white lead, gelatine, albumen, and gum produce 

 the same effects. However, drawings made with these sub- 

 stances may be copied, by subjecting them, with some modi- 

 fications, to the pieparation previously described. I may say 

 that I have not found any drawings which could not be copied, 

 except those made with the iodide of starch. 



I shall now speak of a second property which I have dis- 

 covered in iodine,and which is quite independent of the former; 

 it is that of being attracted by designs in relief, and by all 

 bodies which present ridges, of whatever colour or composition. 

 Thus all embossed impressions on white paper are copied 

 perfectly. 



The edges of a strip of glass or marble produce also an 

 impression. The same effects occur with other elastic fluids, 

 gases or vapours, as the fumes of phosphorus exposed to the 

 air, and the vapour of nitric acid. But iodine also exerts the 

 property of which I spoke at the commencement, as I obtained 

 the following results. 



I joined a piece of white wood to a piece of ebony ; after 

 having glued them I planed them both, by which means I 

 obtained a perfectly flat black and white block : this was next 

 exposed to the vapour of iodine and then placed upon a plate 

 of copper; the black portion only was copied. I made similar 

 combinations with chalk and a black stone, white and black 

 silk, and always obtained the same results. 



All these phsenomena are manifested both in the most per- 

 fect darkness as also in vacuo. I may repeat here, that if the 

 objects are exposed for too long a time to the vapour of the 

 iodine, the white portions ultimately become impregnated, but 

 the black parts are always strikingly distinct upon the plate 

 of metal. 



On making the same experiments with chlorine and bro- 

 mine, the same results were obtained with the former as with 

 iodine ; but the impression is so indistinct, that it is requisite 

 to blow upon the metal to perceive it, or rather to expose the 

 plate of copper to the vapour of ammonia, and the plate of 

 silver to the vapour of mercury, to render it distinctly visible. 



The results with bromine were unsuccessful ; all my expe- 

 riments were made with either plates of silver or copper. 

 There is one experiment which I think worthy of mention, as 

 being of theoretical interest; it is this: after having put a 



Phil. Mas. S. S. Vol. 32. No. 2 14-. March 1848. P 



