Chemical Properties attributed to Light. 91 



On shaking the phial before it had been exposed to 

 the heat, and mixing its contents, and then suffering it 

 to stand quiet, the oil of turpentine, on taking its place 

 at the top of the aqueous solution, was not found to 

 have acquired any colour; nor was the bright gold 

 colour of the solution found to be at all impaired. 

 When sulphuric ether was used instead of the oil of 

 turpentine, the effect was in this respect very different. 



To find out whether the oil of turpentine used in 

 this experiment, and which had acquired a deep yellow 

 colour, had lost that property by which it effected the 

 reduction of the metallic oxide, I now poured an ad- 

 ditional quantity of the aqueous solution of the oxide 

 into the phial, and shaking the phial exposed it, with 

 its contents, to the heat of boiling water. 



After it had been exposed to this heat about two 

 hours, I examined it, and found that though a consid- 

 erable quantity of gold had been revived, yet the aque- 

 ous liquid still retained a faint yellow colour. 



The oil of turpentine had acquired a deeper and 

 richer gold colour, approaching to orange. 



To the contents of the phial I now added about 

 half as much distilled water, and mixing the whole by 

 shaking I exposed the phial again, during two hours, 

 to the heat of boiling water ; when the remainder of 

 the oxide was reduced, and the aqueous • liquid left 

 perfectly colourless. 



On repeating this experiment with oil of turpentine, 

 and varying it by using a solution of the oxide of 

 silver (an aqueous solution of nitrate of silver) instead 

 of that of gold, the result was nearly the same. The 

 metal was revived, and the oil of turpentine acquired a 

 faint greenish yellow colour. 



