14 AC> ’::av: .vf i E *ijic C 
Common fpirit of fait is always adulterated with vitriolic 
acid, and therefore not fit for thcle trials. 
Intending to determine by this experiment the proportion of 
acid, water, and fixed alkali in digeilive fait, as it is celled, I 
took ioo gr, of a lolution of a tolerably pure vegetable alkali 
that had been three times calcined to whitenefs, the fp-jcific 
gravity of which lolution was 1,097. I alio diluted the fpirit of 
fait with dijfterent portions of water ; the fpecific gravity of 011c 
fort was 1,115, and of another 1,098. 
I then found that the above quantity of the folution of a ve- 
getable alkali required for its figuration 27 gr. of thatfpiritof 
lalt whofe fpecific gravity was 1,098, and 23,35 gr. of that 
fpirit of lalt whale fpecific gravity was 1,115. Now, 27 gr. of 
fpirit of lalt, whofe fpecific gravity is 1,098, contain 3,55 gr. 
of marine acid, as appears by calculation. As the principle on 
which this calculation, by which the proportion of fubftances 
in alloy is found, may not be generally known, I fliall here 
mention them in the words of Mr. cotes. 
66 The data requifite are the fpecific gravities of the mixture 
“ and of the two ingredients Then, as the difference 
“ of the fpecific gravities of the mixture and the lighter ingre- 
“ dient is to the difference of the fpecific gravities of the mix-* 
ture and the heavier ingredient, fo is the magnitude of the 
“ heavier to the magnitude of the lighter ingredient. Then, 
46 as the magnitude of the heavier multiplied into its fpecific 
gravity is to the magnitude of the lighter multiplied into its 
fpecific gravity, fo is the weight of the heavier to the weight 
46 of the lighter .... Then, as the fum of thefe weigiits 
46 is to the given weight of either ingredient, fo is the weight 
“ given to the weight of the ingredient fought.” 
Thus, 
