VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 331 



of it. And the solution of it affords 20 cubic inches of nitrous air ; whereas 

 lOOgrs. of silver, revived from luna cornea, afford about 14. 



Silver in the marine acid. — I have not been able to dissolve silver, in its 

 metallic state, in spirit of salt, yet I believe it may be effected, if sufficient time 

 be allowed, as Mr. Bayen, in his Treatise on Tin, p. 201, says, he dissolved 

 3xgrs. of silver by digesting it for some days in 2 ounces of strong spirit of salt. 

 Leaf silver is also said to be corroded by strong spirit of salt, l Newm. 70. The 

 dephlogisticated marine acid also dissolves it, according to the observations of 

 Messrs. Scheele and Bergman: and so does the phlogisticated in a vaporous 

 state. 100 grs. of horn silver contain 75 of silver, nearly 18 of acid, and 7 of 

 water. 



Gold in aqua regia. — I made several experiments with aqua regia, in which 

 the nitrous and marine acids were mixed in different proportions, and found that 

 to succeed best, in which the quantity of real marine acid was to that of the 

 nitrous as 3 to 1, and both as concentrated as possible; though if both be very 

 concentrated, it is hard to mix them so as to prevent a great quantity from 

 escaping, as they effervesce very violently some time after mixture. 100 grs. of 

 gold require 246 grs. real acid for their solution, the 2 acids being in the above- 

 mentioned proportion. The specific gravity of the nitrous acid used was I.465, 

 and that of the marine KI78. The solution is better promoted by allowing it 

 sufficient time than by applying heat. The heat used did not exceed 90 or 100°. 

 Very little air is produced, and the solution is very slow. A.qua regia made with 

 common salt or sal ammoniac and spirit of nitre is much less aqueous, than that 

 resulting from an immediate combination of both acids; and hence is the fittest 

 for the production of crystals of gold. Gold is also soluble in the dephlogisti- 

 cated marine acid, but in very small quantity, unless this acid be in a vaporous 

 state, for in a liquid state it is too aqueous. In vitriolic and nitrous acids it is 

 also insoluble; but the calces of gold are easily soluble in the marine acid, very 

 slightly in the nitrous, and scarce at all in the vitriolic. Gold in its metallic 

 state may be diffused through, but not dissolved, by the concentrated nitrous 

 acid. 



Mercury in vitriolic acid. — 100 grs. of quicksilver require, for their solution, 

 230 grs. of real vitriolic acid, whose proportion to that of water is at least as 1 

 to -jSg-, and also a strong heat. The air produced is vitriolic. Precipitate per se 

 is still less soluble. 100 grs. of vitriol of mercury, produced by precipitation, 

 contain 77 of mercury, 10 of acid, and 4 of water. 



Mercury in nitrous acid. — 100 grs. of mercury are dissolved by 28 grs. of real 

 nitrous acid, whose proportion to that of water is as 1 to 1 and -j^u-j and without 

 the assistance of heat. Mercury is also soluble, but in smaller quantity, in a 

 much more dilute acid, with the assistance of heat. The product of air is about 



u u 2 



