VOL. XLIII.] PHILOSOPHICAL TRANSACTIONS. 3 



it gives a much larger quantity of the acid of sulphur. (2.) That it gives a very 

 volatile acid; whereas his is fixed, so as scarcely to differ from oil of vitriol. 

 (3.) That it is obtained in a much easier and cheaper manner. (4.) That this 

 spirit has probably much greater medicinal virtues. (5.) That it is a much more 

 powerful menstruum; especially with regard to metals, and particularly their 

 crystallization. (6.) That the caput mortuum is a medicine of great use; and 

 may defray the expence of the whole operation ; being perhaps the best way of 

 making the tartarus vitriolatus perfectly pure and neutral for medicinal purposes ; 

 its expected virtues greatly depending on its being clean and neutral. 



7. His method has also several advantages over Dr. Stahl's; though his indeed 

 affords a volatile acid. But then, (1.) Stahl's method bums the sulphur, and 

 consequently destroys its texture, and throws off part of the spirit or gas ; where- 

 as this gently dissolves the sulphur, and only divides it, so as to leave the acid 

 afterwards separable by a stronger or more ponderous acid ; and no-way consumes 

 or destroys the inflammable part, as burning does. (2.) This method is more 

 neat or elegant than his, and affords a larger produce, at a cheaper rate, and in 

 greater perfection, both as a medicine, and as a menstruum; leaving also the 

 tartarus vitriolatus cleaner, and fitter for use as a medicine. 



8. Persons but little versed in chemical philosophy, and its operations, might 

 be apt to suspect, that this spirit is not a pure spirit, or acid of sulphur; but 

 mixed with the oil of vitriol, here used as the medium to separate the spirit from 

 the sulphur and fixed alkali : but the Society very well knows it to be a universal 

 law, that a heavier or stronger acid, used in a suitable proportion, constantly in 

 these cases separates a weaker, and leaves it free to rise by itself in distillation, as 

 it remarkably does in the present operation; where all the oil of vitriol employed 

 unites with the fixed alkali, so as to make the true tartarus vitriolatus, and leaves 

 the lighter spirit quite detached and free to rise, and come over the helm in 

 distillation. So that this volatile spirit and the fixed oil of vitriol are by no 

 means the same thing; nor should the one b« used for the other, especially in 

 physic. 



Q. But though the oil of vitriol be allowed to differ from the volatile acid of 

 sulphur, some may imagine that there is no difference between this volatile acid and 

 the volatile spirit of vitriol, as it comes over in the rectification of oil of vitriol ; 

 or between our spirit and the gas sulphuris, which is extremely pungent and 

 volatile: but whoever attentively examines and compares the volatile spirit of 

 vitriol, or the gas sulphuris, with our spirit, will soon be convinced of a great 

 difference; though indeed they agree in the point of gassy volatility: for the 

 volatile spirit of vitriol is only an impure phlegm of vitriol, containing very little 

 acid, and is chiefly impregnated with the wild fumes of the vitriol ; so as, by 

 standing a while, to quit die liquor, and leave it nauseous, vapid, and gross; 



B 2 



