VOL. LXXX.] PHILOSOPHICAL TRANSACTIONS. 701 



but also on several others. It forms with iron a beautiful rose-coloured solution, 

 without application of any artificial heat; and in time a rose-coloured saline pre- 

 cipitate is deposited, which is soluble in water with considerable effervescence. It 

 dissolves copper, and acquires from this metal, and also from regulus of cobalt, 

 zinc, and lead, pretty deep violet tinges. Bismuth and regulus of antimony were 

 also attacked by tiiis phlogisticated acid. To ascertain more exactly the effects 

 of this phlogisticated acid on some metals, I made the following experiments, 

 with a liquor prepared by making nitrous gass pass through oil of vitriol during 

 a considerable time. 



22. To 200 grain-measures of the oil of vitriol impregnated with nitrous 

 gas, put into a retort with a long neck, the capacity of which, including the 

 neck, was 1 1 50 grain-measures, I added 144 grs. of standard silver, and im- 

 mersed the mouth of the retort in water, under an inverted jar filled with water, 

 to catch the gas which might be extricated. The acid began to dissolve the 

 silver with effervescence without application of heat; the solution became of a 

 violet colour, and the quantity of nitrous gas received in the inverted jar was 

 14700 grain-measures. On weighing the silver remaining, the quantity which 

 had been dissolved was found to be 70 grs. When water was added to the solu- 

 tion, an effervescence appeared, but only a very small quantity of gas was ex- 

 tricated. By means of the water, a white saline powder of silver, soluble in a 

 larger quantity of water, was precipitated from the solution. The solution of 

 silver, when saturated and undiluted, congeals readily in cool temperatures, and, 

 when diluted to a certain degree with water, gives foliated crystals. 



23. In the same apparatus, and in the same manner, 100 grain-measures of 

 this impregnated oil of vitriol were applied to iron. An effervescence appeared 

 without application of heat, the surface of the iron acquired a beautiful rose 

 colour or redness mixed with purple: and this colour gradually pervaded the 

 whole liquor, but disappeared on keeping the retort some time in hot water. 

 Notwithstanding a considerable apparent effervescence, the quantity of air ex- 

 pelled in the inverted jar was only 400 grain-measures, of which 4- was nitrous, 

 and the rest phlogisticated. The solution was then poured out of the retort, 

 and the iron was found to have lost only 2 grs. in weight. The solution was re- 

 turned into the retort, without the iron, and 200 grs. of water were added to it; 

 on which a white powder was immediately precipitated, which re-dissolved with 

 great effervescence. When 2000 grain-measures of nitrous gas had been ex- 

 pelled in the inverted jar, without application of heat, the retort was placed in 

 the water-bath, the heat of which rendered the effervescence so strong, that the 

 liquor boiled over the neck of the retort, so that the quantity of gas extricated 

 could not be ascertained. 



.24. In the same manner 11 grs. of copper were dissolved in 100 grain- 



