and attraSlive' Powers of various J aline Subfances. 31 
The fpecific gravity of the moft concentrated oil of vitriol 
yet made is, according to Mr. baume and bergman, 2,125, 
I afcertained the proportion of acid water and fixed alkali in 
tartar vitriolate, as before, in nitre and digeftive fait. I found 
the faits, refulting from the faturation of the fame oil of tar- 
tar, with portions of oil of vitriol of different fpecific gravi- 
ties, to weigh, at a medium, 12,45 g r - Of 7 this weight only 
1 1 , 85 gr. were alkali and acid, the remainder therefore was 
water, viz. 0,6 of a grain ; confequently 100 gr. of perfedly 
dry tartar vitriolate contain 28,51 gr. acid, 4,82 of water, and< 
66,67 of fixed vegetable alkali. Note, in drying this fait I 
ufed a heat of 240° to expel the adhering acid more thoroughly^ 
I kept it in that heat a quarter of an hour. 
According to Mr. fiomberg,, i French oz. (or 472,5 gr„ 
Troy) of dry fait of tartar required 297,5 gr. Troy of oil of 
vitriol, whofe fpecific gravity was 1,674, to faturate it ; but, 
by my calculation, this quantity of fixed alkali would require 
325 gr. : a difference which, confidering our different methods 
of determining the fpecific gravity of liquids (his method, 
viz. that by menfuration, giving it always lefs than mine) the 
different deficcation of our alkalies, &c. may pafs for incon- 
fiderable. 
The refulting fait weighed, according to Mr. homberg, 
182 gr. Troy above the original weight of the fixed alkali ; 
but by my experiment it fhould weigh but 87,7 gr. more ; for 
K 10,5 . 12,45 :: 4 72,5 • 560,2. It is hard to fay how Mr.. 
homberg could find this great excefs of weight both in nitre 
and tartar vitriolate, unlefs he meant by the original weight of 
the fait of tartar the weight of the mere alkaline part, diftind 
from the fixed air it contained: and indeed one would be 
tempted to think, he did make this difliadion ; for in that 
6 cafe 
