CHEMICAL SCIENCE. 



THE DIVISIBILITY OF MATTER. 



The divisibility of matter is a subject which has been frequently 

 treated of and reasoned upon ; indeed, in most works on physics or 

 chemistry, illustrations are given of the extraordinary degree of sub- 

 division to which bodies may be brought by mechanical means. All 

 these illustrations have, however, stopped far short of the limit attain- 

 able by mechanical means, and indeed have been merely given to 

 illustrate extreme subdivisions without pushing the subject to its legit- 

 imate extent. The following experimental illustration shows what 

 infinitesimally minute quantities the natural philosopher is capable of 

 working with and rendering evident to the senses (or rather sense, for 

 sight alone can appreciate them), and will also show how conventional 

 are the ordinary ideas of magnitude. 



We will start with a sheet of gold leaf. This consists of metallic 

 gold beaten out into a film of about -j-g-oVoTj 1 ^ an mcn i Q thickness, 

 measuring 3.375 inches square, and weighing about i of a grain. A 

 single square inch therefore weighs -^ of a grain. Now, Faraday, in 

 his beautiful researches on the relations of gold to light, has shown 

 that it is possible by chemical means to reduce this thickness very 

 considerably, still preserving the metallic continuity of the film. This 

 is readily effected by breathing on a clean plate of glass and then 

 gently placing on it a piece of gold leaf; the latter will adhere to it, 

 and if distilled water be immediately applied at the edge of the leaf, 

 it will pass between the glass and gold, and the latter will be perfectly 

 stretched. Upon now draining the water out, the gold leaf will be 

 left well extended, smooth, and adhering to the glass. If, after the 

 water is poured off, a weak solution of cyanide of potassium be intro- 

 duced beneath the gold, the latter will be gradually dissolved away, 

 becoming thinner and thinner ; but at any moment the process may 

 be stopped, the cyanide washed away by water, and the attenuated 

 gold film left on the glass. If, towards the end, a washing be made 

 with alcohol, and then with alcohol containing a little varnish, the 

 gold film will be left cemented to the glass. By this means the thick- 

 ness will have become reduced to about -fa part of what it was origi- 

 nally, weighing, in round numbers, about g^ of a grain to the square 

 inch, and being only about 3 ^ O -Q of an i ncu in thickness. The 

 film in this condition, although consisting of pure gold, presents none 

 of the ordinary appearances of the metal, being perfectly transparent, 

 and resembling a delicate film of pale green varnish more than a 

 dense metallic body. 



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