and attractive Powers of various f aline Subjlances . 41 
Gr. of the 
; folution. 
Gr. of 
alkali. 
Gr. of 
water. 
Accrued 
denfity. 
Mathema- 
tical fpecific 
gravity. 
3 j 
Specific 
gravity by 
obfervation 
274 , 7 s 
- 
- 
248,83 
*015 
1,079 
1,092 
280^46 
- 
- 
254*51 
,012 
1,077 
1,089 
286,14 
- 
- 
260,19 
,on 
1,076 
1,087 
291,82 
- 
- 
265,87 
,010 
1,074 
1,084 
297*50 
- 
- 
271,5s 
*009 
1,070 
5 ? 0 79 
3 ° 3 ' lS 
- 
- 
277,23 
,008 
1,069 
1,077 
308,86 
26, 
25 
282,91 
,007 
1,068 
x >° 75 
3 ;I 4>54 
- 
- 
2-88,59 
,006 
1,066 
1,072 
3^,22 
- 
- 
294,27 
5°°5 
1,065 
1,070 
324 > 9 o 
- 
- 
3°°,45 
,004 
1,064 
1,068 
33 °, 5 s 
- 
- 
306,13 
*003 
1,063 
1,066 
1 33 M 6 
- 
- 
311,81 
-,002 
1,062 
1,064 
1 34 i ,94 
- 
- 
317,49 
,OOI 
I,06l 
1,062 
Impure vegetable fixed alkalies fuch as pearl' aft, pot aftes, &c. 
contain more fixed air, as appears by the experiments of Dr* 
lewis. Pearl aft, according to Mr. cavendish, contains 28,4 
or 28,7 per cent . of fixed air. Hence in lyes of equal fpecific 
gravity with thofe of a purer alkali, the quantity of faline mat- 
ter will be more probably in the ratio of 28,4 or 28,7 to 21 ; 
but this furplus weight is only fixed air ; and hence even in thefe 
lyes the quantity of depurated fait they will afford will be found 
by the above table. Much alfo depends on their age, the oldeft 
containing mod fixed air. 
Vol. LXXI. 
G 
