45(J On the Chemical Properties attributed to Light. 



In the experiment with the oxide of fiiver, the infide of the phial, in the region where 

 the oil repofed on the aqueous folution, was beautifully filvtred, the revived metal form- 

 ing a narrow metallic ring, extending quite round the phial ; and, in both experiments, 

 fmall detached pellicles of revived metal were vifible in the oil, and adhered in feveral 

 places to the infide of the phial, forming bright fpots, in which the colour of the metal 

 aiid its peculiar fplendoar were perfedliy confpicuous. 



Experiment No. 15. As carbon \s one of the Gonflituerit principles of fpirit of wine, aj 

 well as of eflcntial oils and fulphuric ether, I thought it poffible that I might fucceed in 

 the rediiftion of the oxide of gold, by mixing alcohol with an aqueous folutioti of nitro- 

 muriate of gold, and expofing the mixture in a phial well clofed to the heat of boihng 

 water ; but the experiment did not fucceed. 



By pouring upon this mixture a fmall quantity of oil of olives, and expofmg it again to 

 the heat of boiling water, the gold was revived. 



Is it not probable that the reafon why the oxide was not reduced by alcohol, is the mo- 

 bility of thofe elements, which ought to acl on each other, in order that the cfFed in 

 queftion may be produced ? I have no doubt but the oxide would be reduced, could 

 the alcohol be made to reft on the furfacc of the aqueous folution without mixing 

 with it. 



I wiflied to have been able to have collcfled and examined the elaftic fluids, which 

 probably were formed in pioft of the preceding experiments ; but my time was fo 

 much taken up with other matters that 1 had not leifure to purfue thefe inveftigatlons 

 farther. 



In order to fee what effe£ls would be produced by the heat generated at the furface of 

 an opaque body, of a nature different from thofe hitherto ufed in the redu£lion of th« 

 metallic oxides, and one that is little difpofed to form a chemical union with oxygen, 

 [magnefta alba) wten, being immerfed in an aqueous folution of the oxide of gold, 

 the rays of the fun were made to impinge on it, 1 contrived the following experi- 

 ment. 



Experiment No. \6. I took four fmall thin phials, A, B, C, and D, of very fine glafs, 

 arid putting into each of them about five grains of dry magnefui alba, I filled the phial Aj 

 nearly full, with a faturated aqueous folution of the oxide of gold. 



I filled the phial B, in like manner, with fome of the fame folution, diluted with an 

 equal quantity of dillilled water; and the phials C and D were fiiled with the folution 

 ftill farther diluted. 



Thefe phials, open or without (loppers, were expofed one whole day to the action of the 

 direct rays of a bright fun, their contents being often well mixed together during that 

 lime by fliakirjg. 



The contents of all thefe phials changed colour more or lefs, but they acquired very difir 

 ferent hues. The contents of the phial A became of a very deep rich gold colour, ap- 

 proaching to orange, the earthy fediment being throughout of the fame tint. 



The contents of the phial B, which were at firft of a light ftraw colour, firft changec^ 

 to a light green, and then to a greenifh blue. The phial having been fuftered to (land 

 quiet feveral days, in an' uninhabited room in a retired part of the houfe, the folution bc^ 

 came nearly colourlefs, and the fediment was found to be of a dirty olive colour. 



The 



