14 PHILOSOPHICAL TRANSACTIONS. [aNN0 1781. 



gr. of that whose specific gravity was 1-77 I ; and by 7.41 of that whose specific 

 gravity was 1 .7 J 9. 



I was obliged to add a certain proportion of water to each of these sorts of 

 oil of vitriol; for when they were not diluted, I perceived that part of the acid 

 was phlogisticated, and went off with the fixed air; but knowing the quantity of 

 water that was added, it was easy to find, by the rule of proportion, the quantity 

 of each sort of oil of vitriol that was taken up by the alkali. Hence I supposed that 

 each of these quantities of oil of vitriol, of different densities, contained 3.55 

 gr. of acid, as they saturated the same quantity of vegetable fixed alkali as 1 1 gr. 

 of spirit of nitre, which contained that quantity of acid. 



I then endeavoured to find the specific gravity of the pure vitriolic acid, in 

 the same manner as I before had that of the nitrous, as it cannot be had in the 

 shape of air unless united to such a quantity of phlogiston as quite alters its 

 properties. The loss of 6.5 gr. of oil of vitriol, whose specific gravity is 1.81 9, 



is — '- — = 3.572; but as these 6.5 gr. contained, besides 3.55 gr. acid, 2.Q5 of 



1.819 

 water, the loss of this must be subtracted from the entire loss, and then the 



remainder 0.622 is the loss of the pure acid part, in that state of density to 



which it is reduced by its union with water. The specific gravity therefore of the 



3 55 



pure vitriolic acid, in this state of density, is -^.- = 5.707. But to find its 

 natural specific gravity, we must find how much its density is increased by its 

 anion with this quantity of water: and in order to observe this, I proceeded as 

 before with the nitrous acid. Thus, 6.96 gr. of oil of vitriol, whose specific 

 gravity was 1-771, contained 3.55 gr. acid, and 3.41 of water; then its specific 

 gravity by calculation should be I.726, for the loss of 3.55 gr. acid is — '— - = 

 .0622; the loss of 3.41 gr. water is 3.41 ; the sum of the losses 4.032. Then 

 ~-s= 17.261 ; therefore the accrued density is I.771 — I.726 = .045. 

 Taking this therefore from 1.81 9, its mathematical specific gravity will be 

 1.774; then the loss of 6.5 gr. of oil of vitriol, whose specific gravity, 



by observation, is 1.819, will be found to be — —^ = 3.664; but of this, 



* 1.7/4? 



2.95 gr. are the loss of the water it contains, and the remainder 0.7 14* the loss 



3 55 

 of the mere acid part. Then — '— = 4.9649 is nearly the true specific gravity 



of the pure vitriolic acid. I then found the true increase of density arising from 

 the union of the vitriolic acid and water in the foregoing mixtures, and observed, 

 that in oil of vitriol, whose specific gravity was 1.77 1 3 it was 0.84, and in that 

 whose specific gravity was 1 .7 19, it was 0.100. 



* By mistake, the following calculations were made on the supposition dial the loss was 0.715; 

 the difference being immaterial, die calculations were not repeated. — Orig. 



