300 PHILOSOPHICAL TKAN8ACTIONS, [aNNO I766. 



Tin was found to dissolve scarcely at all in oil of vitriol diluted with an equal 

 weight of water, while cold; with the assistance of a moderate heat it dissolved 

 slowly, and generated air, which was inflammable; the quantity was not ascer- 

 tained. Tin dissolves slowly in strong spirit of salt while cold: with the assist- 

 ance of heat it dissolves moderately fast. One ounce of tinfoil yields 202 ounce 

 measures of inflammable air. These experiments were made when the thermo- 

 meter was at 50° and the barometer at 30 inches. 



All these three metallic substances dissolve readily in the nitrous acid, and ge- 

 nerate air, but the air is not at all inflammable. They also unite readily, with 

 the assistance of heat, to the undiluted acid of vitriol; but very little of the salt, 

 formed by their union with the acid, dissolves in the fluid. They all unite to the 

 acid with a considerable effervescence, and discharge plenty of vapours, which 

 smell strongly of the volatile sulphureous acid, and which are not at all inflam- 

 mable. Iron is not sensibly acted on by this acid, without the assistance of heat, 

 but zinc and tin are in some measure acted on by it, while cold. Hence it seems 

 likely, that when either of the above-mentioned metallic substances are dissolved 

 in spirit of salt, or the diluted vitriolic acid, their phlogiston flies off", without 

 having its nature changed by the acid, and forms the inflammable air; but that 

 when they are dissolved in the nitrous acid, or united by heat to the vitriolic acid, 

 their phlogiston unites to part of the acid used for their solution, and flies off" 

 with it in fumes, the phlogiston losing its inflammable property by the union. 

 The volatile sulphureous fumes, produced by uniting these metallic substances by 

 heat to the undiluted vitriolic acid, show plainly that in this case their phlogiston 

 unites to the acid; for it is well known, that the vitriolic sulphureous acid consists 

 of the plain vitriolic acid united to phlogiston.* It is highly probable too, that 

 the same thing happens in dissolving these metallic substances in the nitrous acid; 

 as the fumes produced during the solution appear plainly to consist in great mea- 

 sure of the nitrous acid, and yet it appears, from their more penetrating smell 

 and other reasons, that the acid must have undergone some change in its nature, 

 which can hardly be attributed to any thing else than its union with the phlo- 

 giston. As to the inflammable air, produced by dissolving these substances in 

 spirit of salt or the diluted vitriolic acid, there is great reason to think that it 

 does not contain any of the acid in its composition ; not only because it seems 

 to be just the same whichever of these acids it is produced by ; but also because 

 there is an inflammable air, seemingly much of the same kind as this, produced 



* Sulphur is allowed by chemists^ to consist of the plain vitriolic acid united to phlogiston. The 

 volatile sulphureous acid appears to consist of the same acid united to a less proportion of phlogistoa 

 than what is required to form sulphur. A circumstance which I think shows the truth of this, i« 

 that if oil of vitriol be distilled from sulphur, the liquor which comes over will be the volatile sul- 

 phureous acid. — Orig. 



