1 6 Mr. kir wan’s Experiments , Sic. on the fpecific Gravities 
of the compound. When this difference amounted to 2,2 g t. 
then I judged the whole of the fixed air expelled, and found it to 
be lo, as 100 gr. of this alkaline folution, being evaporated to 
drynefs in a heat of 300°, left a refiduum which amounted to 
1 of gr. ; which io§ gr, contained 2,2 gr. of fixed air, as will 
hereafter be feen. 
Hence 8,3 gr. of pure vegetable fixed alkali, free from fixed 
air and water, or 10,5 of .mild fixed alkali, were faturated by 
3,55 gr. of pure marine acid, and confequently the refulting 
neutral fait fhould, if it contained no water, weigh 11,85 gr. ; 
but the falts refulting from this union (the folution being eva- 
porated to perfect drynefs in a heat of 160 0 kept up for four 
hours) weighed at a medium 12,66 gr. Of this weight 11,85 
gr. were acid and alkali ; therefor^ the remainder, viz. 0,81 of 
gr. were water; therefore 100 gr. of perfectly dry, digeftive 
fait contain 28 gr. acid, 6,55 water, 65,4 of fixed alkali. 
I was then curious to compare my experiments with thole 
made by others-, but could not find any made with fufficient 
precifion but thole of Mr. homberg in the Paris Memoirs for 
2699. However, as to fpirit of fait 1 did not think proper to 
compare them, as he mentions that his could diffolve gold, and 
therefore was probably impure. 
OF SPIRIT OF NITRE.' 
The common reddifh brown or greenilh fpirit of nitre con- 
taining, befides acid and water, a certain portion of phlogiflon, 
and being alfo mixed with fome portion of the acid of fea, fait, 
I judged unfit for thefe trials, and therefore ufed only the.de- 
phlogifticated fort, which is quite colourlefs, and refemblespure 
water in its appearance. This pure acid cannot be made to exifh 
111 
