Chemistry and Physics, 271 



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evaj^oration of a solution of that substance in snlphid of carbon, in tlae 

 course of a few hours the solution becomes colored of a ruby tint ; and 

 the effect goes on increasing, sometimes for two or three days. At times 

 the liquid appears clear, at other times turbid. As far as Mr. Faraday 

 has proceeded, he believes this fluid to be a mixture of a colorless trans- 

 parent liquid, with fine particles of gold. By transmitted light, it is of 

 a fine ruby tint ; by reflected light, it has more or less of a brown yellow 

 color. That it is merely a diffusion of fine particles is shown by two 

 results ; the first is, that the fluid being left long enough the particles 

 settle to the bottom : the second is, that whilst it is colored or turbid, if a 

 cone of the sun's rays (or that from a lamp or candle in a dark room) be 

 thrown across the fluid by a lens, the particles are illuminated, reflect 

 yellow light, and become visible, not as independent particles, but as a 

 cloud. Sometimes a liquid which has deposited much of its gold, re- 

 mains of a faint ruby tint, and to the ordinary observation, transparent; 

 but when illuminated by a cone of rays the suspended particles show 

 their presence by the opalescence, which is the result of their united ac- 

 tion. The settling particles, if in a flast, appear at the bottom, like a 

 lens of deep colored fluid, opaque at the middle, but deep ruby at the 

 edges ; when agitated they may be again diff^used through the liquid. 

 These particles tend to aggregate into larger particles, and produce other 

 efiects of color. It is found that boiling gives a certain degree of perma- 



j nencc to the ruby state. Many saline and other substances affect this 



ruby fluid ; thus, a few drops of solution of common salt being added, 



' the whole gradually becomes of a violet color ; still the particles are only 



in suspension, and when illuminated by a lens arc a golden yellow by 

 reflected light : they separate now much more rapidly and perfectly by 

 deposition from the fluid than before. Some specimens, however, of the 

 fluid, of a weak purple or violet color, remain for months without any 

 appearance of settling, so that the particles must be exceedingly divided ; 

 still the rays of the sun or even of a candle in a dark room, when col- 

 lected by a lens, will manifest their presence. The highest powers of the 

 microscope have not as yet rendered visible either the ruby or the violet 

 particles in any of these fluids. 



Glass is occasionally colored of a ruby tint by gold ; such glass, when 

 examined by a ray of light and a lens, gives the opalescent effect de- 

 scribed above, which indicate the existence of separate particles; at 

 least such has been the case with all the specimens Mr. Faraday has ex- 

 amined. It becomes a question whether the constitution of the glass 

 and the ruby fluids described is not, as regards color, alike. At present, 

 he believes they arc ; but whether the gold is in the state of pure metal, 

 or of a compound, he has yet to decide. It would be a point of consid- 

 erable optical importance if they should prove to be metallic gold ; from 

 the effects presented when gold wires are deflagrated by the Leydcn dis- 

 charge over glass, quartz, mica, and vclUira, and the deposits subjected to 



heat, pressure, Arc, he inclines to believe they are pure metal 



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