702 PHILOSOPHICAL TRANSACTIONS, [aNNO I79O. 



measures of impregnated oil of vitriol. The solution was of a deep violet colour, 

 and at last was turbid. The quantity of nitrous gas expelled into the inverted jar 

 during the operation was 4700 grain-measures. When the copper was removed, 

 and 200 grs. of water were added to the solution, an effervescence took place, 

 1700 grain-measures of nitrous gas were expelled, and the solution then acquired 

 a blue colour. 



25. In the same apparatus and manner, 100 grain-measures of the impreg- 

 nated oil of vitriol were applied to tin, which was thence diminished in weight 

 id grs., while the liquor acquired a violet colour, became turbid by the suspen- 

 sion of the calx of tin, and a quantity of nitrous gas was thrown into the in- 

 verted receiver equal to 4100 grain-measures, without application of heat, and 

 another quantity equal to 4900 grain-measures, after the retort was put into the 

 water- bath. 



26. Mercury added to the impregnated oil of vitriol formed a thick white 

 turbid liquor, which was rendered clear by addition of unimpregnated oil of 

 vitriol. In a little time this mixture continuing to act on the remaining mer- 

 cury acquired a purple colour. The mercury acted on sunk to the bottom of 

 the glass in the form of a white powder, and the purple liquor, when mixed 

 with a solution of common salt in water, gave no appearance of its containing 

 any mercury in a dissolved state. 



27. The nitrous gas with which the oil of vitriol is impregnated shows no 

 disposition to quit the acid by exposure to air; but, on adding water to the im- 

 pregnated acid, the gas is expelled suddenly with great effervescence, and with 

 red fumes, in consequence of its mixture with the atmospherical air. On adding 

 240 grs. of water to 60 grain-measures of impregnated oil of vitriol, 2300 grs. 

 of nitrous gas were thrown into the receiver; but as the action of the 2 liquors 

 is instantaneous, the quantity of gas expelled from the retort before its neck 

 could be immersed in water, and placed under the receiver, must have been con- 

 siderable. The whole of the gas however was not extricated by means of the 

 water, for the remaining liquor dissolved 5 grs. of copper, while 800 measures 

 of nitrous gas were thrown into the retort. 



28. The following facts principally are established by the preceding experi- 

 ments. 1. That a mixture of the vitriolic and nitrous acids'in a concentrated 

 state has a peculiar faculty of dissolving silver copiously. 2. That it acts on, and 

 principally calcines, tin, mercury, and nickel; the latter of which however it 

 dissolves in small quantity: and that it has little or no action on other metals. 

 3. That the quantity of gas produced while the metal is dissolving is greater, re- 

 latively to the quantity of metal dissolved, when the proportion of nitre to the 

 vitriolic acid is small, than when it is large; and that when the metals are dis- 

 solved by mixtures containing much nitre, and with a small production of gas, 



