386 PHILOSOPHICAL TRANSACTIONS. [ANNO 1798. 



of ether, I conceived it might be possible to perform that chemical process, in 

 the moist way, by means of essential oils ; and this conjecture proved to be well 

 founded. 



Exper. 14. On a quantity of diluted aqueous solution of nitro-muriate of gold, 

 in a small pear-like phial, about 1-f inch in diameter at its bulb, was poured a small 

 quantity of etherial oil of turpentine, just as much as was sufficient to cover the 

 aqueous solution to the height of T V of an inch ; and the phial, being well closed 

 with a good cork, well secured, was exposed one hour to the heat of boiling water 

 in a steam-vessel. The gold was revived, appearing in the form of a splendid pel- 

 licle, of a bright gold colour, which floated on the surface of the aqueous liquid. 

 The oil of turpentine, which, at the beginning of the experiment, was as pale and 

 colourless as pure water, had taken a bright yellow hue ; and the aqueous fluid, on 

 which it reposed, had entirely lost its yellow colour. On shaking the phial, its 

 contents were intimately mixed ; but, on suffering it to stand quiet, the oil of tur- 

 pentine soon separated from the aqueous liquid, retaining its bright yellow hue, and 

 leaving the aqueous liquid colourless. 



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 co- 

 lour ; 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 additional 

 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 1 hours, I examined it, and found, that though a con- 

 siderable quantity of gold had been revived, yet the aqueous 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 2 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. I also revived the oxides of gold and silver with oil of olives, by 

 a similar process, with the heat of boiling water. The oil of olives used in these 

 experiments lost its transparency, and became deeply coloured ; that used in the 

 reduction of the oxide of silver, taking a very deep dirty brown colour, approach- 

 ing to black ; and that employed in reducing the oxide of gold, being changed to 



