VOL. LXXIX.] PHILOSOPHICAL TRANSACTIONS. 603 



over, and found it to be the same thing with water impregnated with vitriolic acid 

 air. The smell of it was exceedingly pungent; and it was evident, that more of 

 this air had escaped than could be retained by that quantity of water. The oil 

 of vitriol used in this process was 1 oz. Q dw. 18 gr. and the liquor collected was 

 6 dw. 12gr. When he collected the air that was produced in this manner, it 

 appeared to be very pure, about the standard of 0.3 with 2 equal measures of 

 nitrous air. At another time, expending 1 oz. 11 dw. 18 gr. of oil of vitriol, of 

 the specific gravity of 1856, that of water being 1000, he collected ig dw. 6gr. 

 of the volatile acid, of the specific gravity of 1340, and 130 oz. measures of 

 dephlogisticated air of the purest kind, viz. of the standard of 0.13. Going 

 through the same process with spirit of nitre, the result was in all respects simi- 

 lar, but much more striking, the production of both dephlogisticated air and 

 phlogisticated acid vapour being prodigiously quicker, and more abundant. Ex- 

 pending 5 oz. 8 dw. 6 gr. of spirit of nitre, he collected 600 oz. measures of 

 very pure dephlogisticated air, being of the standard of 0.2. He also collected 

 1 oz. 7 dw. 14 gr. of a greenish acid of nitre, which emitted copious red fumes. 

 All the apparatus beyond the hot tube was filled with the densest red vapour, and 

 the water of the trough in which the air was received was so much impregnated 

 with it, that the smell was very strong; and it spontaneously yielded nitrous air 

 several days, just as water does when impregnated with nitrous vapour. Perceiv- 

 ing the emission of air from the water, after it had stood some time, he filled a 

 jar containing 30, oz. measures with it, and without any heat it yielded 2 oz. 

 measures of the strongest nitrous air. 



To try whether the acid, thus supersaturated with phlogiston, was convertible 

 into pure air by this process. Dr. P. heated the liquor collected after the dis- 

 tillation of the oil of vitriol, that is, water impregnated with vitriolic acid air, 

 and made the vapour pass through the hot tube, but no air came from it; and 

 when collected a 2d time, it was not at all different from what it had been before. 

 The specific gravity was also the same. It is evident however, though this pro- 

 cess does not show it, that the volatile vitriolic acid contains the proper element 

 of dephlogisticated air; since by melting iron into vitriolic acid air, a quantity of 

 fixed air, which is composed of inflammable and dephlogisticated air, is produ- 

 ced. Melting iron in Q oz. measures of vitriolic acid air, it was reduced to 0.3 oz. 

 measures, and of this 0.1/ oz. measures was fixed air. He repeated the ex- 

 periment with the same result, and putting the residuums together, found the 

 air to be inflammable. 



Though, in the process with spirit of salt, the result be difTerent from that of 

 those with oil of vitriol and spirit of nitre, yet there is an analogy among all 

 these 3 acids in this respect, viz. that the marine and both the volatile acids of 

 vitriol and nitre are made by impregnating water with the acid vapour; so that in 



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