PHILOSOPHICAL TRANSACTIONS. [ANNO 1781. 



The specific gravity of the strongest spirit of 

 salt, made in the usual way, is, according to 

 Mr. Baume, 1.18', and according to Mr. Berg- 

 man, I.19O ; but we read in the Paris Memoirs 

 for the year 1700, p. 19 1, that Mr. Homberg 

 passed a spirit whose specific gravity was 1.300 ; 

 and that made by Dr. Priestley (vol. 3, p. 275) 

 must have been about 1.500. Hence we see 

 that spirit of salt, whose specific gravity is I.261 

 or less, has little or no attraction with water, and 

 therefore attracts none from air, and on that ac- 

 count does not heat a thermometer whose ball is 

 dipped in it as spirit of vitriol and spirit of nitre 

 do, as has lately been observed by the Friendly 

 Society of Berlin. 



This table is not exactly accurate, as I had 

 not in this first experiment found the point of 

 saturation so nicely as was requisite. However 

 I have not corrected it, as the error is but 

 small, and the proportion may at any time be 

 found by calculation ; at least when the specific 

 gravity of this spirit does not exceed 1.253. 

 Whether the mathematical specific gravity and 

 that by observation differ in the higher degrees 

 of specific gravity, I have not examined ; but 

 the table is formed on the supposition that they 

 do not. 



Common spirit of salt is always adulterated with vitriolic acid, and therefore 

 not fit for these trials. Intending to determine by this experiment the propor- 

 tion of acid, water, and fixed alkali in digestive salt, as it is called, I took 100 

 gr. of a solution of a tolerably pure vegetable alkali that had been 3 times cal- 

 cined to whiteness, the specific gravity of which solution was I.O97. I also 

 diluted the spirit of salt with different portions of water ; the specific gravity of 

 one sort was 1.1 15, and of another I.O98. I then found that the above quan- 

 tity of the solution of a vegetable alkali required for its saturation 27 gr. of that 

 spirit of salt whose specific gravity was I.O98, and 23.35 gr. of that spirit of 

 salt whose specific gravity was 1.115. Now, 27 gr. of spirit of salt, whose 

 specific gravity is I.098, contain 3.55 gr. of marine acid, as appears by calcula- 

 tion. As the principle on which this calculation, by which the proportion of 



