1857.] of Gold (and other Metals) to Light. 405 



agate pressureTappeared to change this brown towards blue. 

 Zinc : the reflexion bright white and metallic ; the transmission 

 a dark smoky colour with portions of blue-grey, brown-grey 

 and pale brown ; agate pressure tended to change the blue-grey 

 to brown. Palladium: the reflexion fine metallic and dark 

 grey ; the transmitted light, where most abundant, sepia-brown ; 

 agate pressure converted the tint in the thinner places from 

 brown towards blue-grey. Platinum : the reflexion white, 

 bright and metallic ; the transmission brown or warm grey with 

 no other colours ; agate pressure increased the reflexion and 

 diminished the transmission as with tin. Aluminium: the 

 reflexion metallic and white, very beautiful ; the transmitted 

 light was dark brown, bluish brown, and occasionally in the 

 thinner parts orange ; agate pressure caused but little change. 



Films of Gold (and other metals) by Phosphorus, Hydrogen, 

 Sfc. effect of heat pressure. 



The reduction of gold from its solution by phosphorus is 

 well known. If fifteen or twenty drops of a strong solution of 

 gold, equal to about 1J grain of metal, be added to two or 

 three pints of water, contained in a large capsule or dish, if 

 four or five minute particles of phosphorus be scattered over 

 the surface, and the whole be covered and left in quietness for 

 twenty-four or thirty-six hours, then the surface will be found 

 covered with a pellicle of gold, thicker at the parts near the 

 pieces of phosphorus, and possessing there the full metallic 

 golden reflective power of the metal ; but passing by gradation 

 into parts, further from the phosphorus, where the film will 

 be scarcely sensible except upon close inspection. If plates 

 of glass be introduced into the fluid under the pellicle, and 

 raised gradually, the pellicle will be raised on them ; it may 

 then be deposited on the surface of pure distilled water to 

 wash it ; may be raised again on the glass ; the water allowed 

 to drain away, and the whole suffered to dry. In this way the 

 pellicle remains attached to the glass, and is in a very convenient 

 condition for preservation and examination. 



If phosphorus be dissolved in two or three times its bulk of 

 sulphide of carbon, and a few drops of the fluid be placed on 

 the bottom of a dry basin, vapour of the phosphorus will soon 

 rise up and bring the atmosphere in the basin to a reducing 



