VOL. LXXX.] PHILOSOPHICAL TRANSACTIONS. 6qJ 



or gas which might be extricated. — The silver began to dissolve, and the solution 

 became of a purple or violet colour. No air was thrown into the inverted jar, 

 excepting a little of the common air of the retort, by means of the expansion 

 which it suffered from the heat of the water-bath, and from some nitrous fumes 

 which appeared in the retort, and which having afterwards condensed, occasioned 

 the water to rise along the neck, of the retort, and mix with the solution. The 

 remaining silver was then separated and weighed, and it was found that 39 grains 

 had been dissolved; but probably more would have been dissolved if the operation 

 had not been interrupted by the water rushing into the retort. 



6. In the same apparatus 200 grs. of standard silver were added to a mixture 

 of 100 grs. of nitre, previously dissolved in 200 grain-measures of oil of vitriol; 

 and in this solvent 92 grs. of the silver were dissolved, without any production 

 of air'or gas. The solution, which was of a violet colour, having been poured 

 out of the retort while warm (for with so large a proportion of nitre, such mix- 

 tures, especially after having dissolved silver, are apt to congeal with small de- 

 grees of cold,) in order to separate the undissolved silver from it, and having 

 been returned into the retort without this silver, I poured 200 grs. of water into 

 the retort, on which a strong effervescence took place between the solution and 

 the water, and 3100 grain-measures of nitrous gas were thrown into the inverted 

 jar. On pouring 200 grs. more of water into the retort, 600 grain-measures of 

 the same gas were expelled. Further additions of water yielded no more gas; 

 neither did the silver, when afterwards added to this diluted solution, give any 

 sensible effervescence, or suffer a greater loss of weight than 2 grains. 



7. In the same apparatus 100 grs. of standard silver were exposed to a mixture 

 of 30 grs. of nitre dissolved in 200 grain-measures of oil of vitriol; and in this 

 operation, 80 grs. of silver were dissolved, while at the same time 4500 grain- 

 measures of nitrous gas were thrown into the inverted jar. When the un- 

 dissolved silver was removed, 200 grs. of water were added to the solution, which 

 was of a violet colour, and on the mixture of the 2 fluids an effervescence hap- 

 pened; but only a few bubbles of nitrous gas were then expelled. 



8. In the same apparatus 100 grs. of standard silver were exposed to a mixture 

 of 200 grain-measures of oil of vitriol, 200 grs. of nitre, and 200 grs. of water; 

 and in this operation 20 grs. of the silver were dissolved without any sensible 

 emission of air or gas. 



9. In these experiments, the copper contained in the standard silver gave a 

 reddish colour to the saline mass which was formed in the solution, and 

 seemed to be a calx of copper interspersed through the salt of silver. I per- 

 ceived no other difference between the effects of pure and standard silver dissolved 

 in this acid. 



10. I then exposed tin to the same mixture of oil of vitriol and nitre, in the 



VOL. XVI. 4 U 



