1 4 Mr, ktr wan’s Experiments , &e, fpecific Gravities 
Common fpirit of fait is always adulterated with vitriolic 
acid, and therefore not fit for thefe trials. 
Intending to determine by this experiment the proportion of 
acid, water, and fixed alkali in digefdive fait, as it is called, I 
took ioo gr, of a folution of a tolerably pure vegetable alkali 
that had been three times calcined to whitenefs, the fpecific' 
gravity of which folution was 1,097. I alfo diluted the fpirit of 
fait with different portions of water ; the fpecific gravity of one 
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 faturation 2 7 gr. of that fpirit of 
fait whofe fpecific gravity was 1,098, and 23,35 gr. of that 
fpirit of fait whofe fpecific gravity was 1,115. Now, 27 gr. of 
fpirit of fait, 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 fubflances 
in .alloy is found, may not be generally known, I fhall here 
mention them in the words of Mr. cotes. 
44 The data requifite are the fpecific gravities of the mixture 
44 and of the two ingredients. .... Then, as the difference 
44 of the fpecific gravities of the mixture and the lighter ingre- 
44 dient is to the difference of the fpecific gravities of the mix- 
44 ture and the heavier ingredient, fo is the magnitude of the 
44 heavier to the magnitude of the lighter ingredient. Then, 
44 as the magnitude of the heavier multiplied into its fpecific 
44 gravity is to the magnitude of the lighter multiplied into its 
44 fpecific gravity, fo is the weight of the heavier to the weight 
64 of the lighter .... Then, as the fum of thefe weights 
44 is to the given weight of either ingredient, fo is the weight 
44 given to the weight of the ingredient fought.’ 5 
Thus, 
