VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. 13 



solved 2 oz. and 1 dr. of mercury ; the quantity of air obtained during the solu- 

 tion was igo cubic inches French (= 202.55 English). This air was all nitrous. 

 There remained a white mercurial salt, which, being distilled, afforded 12 cubic 

 inches (= 12.785 English) of air mixed with red vapours, and which differed 

 little from common air. There afterwards arose 224 cubic inches (= 238.56 

 English) of dephlogisticated air, during the production of which, the mercury 

 was almost revivified, there remaining but a few grains of a yellow sublimate. 

 The 12 inches of air mixed with red vapours arose, he says, from a mixture of 

 36 cubic inches of nitrous air (=38.34 English) and 14 of dephlogisticated 

 air (M.91 English) ; and as the mercury was almost wholly revived, he concludes, 

 that these airs arose from the nitrous acid, and formed it; and hence infers, that 

 16 oz. of this spirit of nitre (= 7560 gr. troy) contained 13 oz. 7 dr. 36fgr. 

 (that is, 6589 gr. troy) of water, and consequently only Q7 1 gr. troy of real 

 acid, and therefore 2oz. of this spirit of nitre contained but 120 gr. troy of real 

 acid: but, by my calculation, 2oz. of this spirit of nitre contained 213 gr. acid; 

 for its mathematical specific gravity is I.265. The same weight of acid will 

 also be found in it by computing the weight of the volumes of the different airs 

 he himself found it consist of, or at least to afford by its decomposition ; for 

 202.55 cubic inches of nitrous air weigh, by Mr. Fontana's experiment, 80.8174 

 gr. troy, and 238.56 inches of dephlogisticated air weigh 100.ig52gr. troy, and 

 adding to these the weight of 38.34 inches of nitrous air, and of 14.91 of 

 dephlogisticated air, which made the 12 cubic inches of air mixed with red 

 vapours, we shall find the whole weight of these airs to be 202.181 gr. the few 

 grains wanting of 213 gr. may be accounted for from the absorption of the water 

 in which he received the airs, and by allowing for that still remaining in the 

 yellow sublimate. 



Of oil of vitriol. — The oil of vitriol I made use of was not perfectly dephlo- 

 gisticated; but though pale, yet a little inclined to red. It contained some 

 whitish matter, as I perceived by its becoming milky on the affusion of pure 

 distilled water. How far this may alter the result of the following experiments 

 1 have not tried; but believe it to be as pure as that which is commonly used in 

 experiments, and therefore the fittest for my purpose. 



To 2519.75 gr. of this oil of vitriol, whose specific gravity was 1.81Q, I 

 gradually added lSOgr. of distilled water, and 6 hours after found its specific 

 gravity to be 1.77 1. To this mixture I again added 1 78.75 gr. of water, and 

 found its specific gravity, when cooled to the temperature of the atmosphere, 

 to be I.719: it was then milky, t then saturated the same quantity of the oil 

 of tartar abovementioned, with each of these sorts of oil of vitriol in the manner 

 already mentioned, and found the saturation to be effected (taking the medium 

 of 5 experiments) by 6.5 gr. of that whose specific gravity was 1.819; by 6.96 



