324 
Sulphat of Lime. 
Smithson Tenant obtained 39 grains of calcined sulphat of lime 
by means of vitriolic acid, from 30 grains of carbonat of lime. 
This agrees with my own observation from repeated experiment. 
Vauquelin, Berthier, and Thompson, compute the lime in cal- 
cined sulphat of lime at 42 per cent. Klaproth and Henry at 4 1 
per cent. Chevenix 56,3 per cent. 
Hence, according to Tenant, 77 parts of limestone will make 
100 parts of calcined gyfisum. 
According to Vauquelin, Berthier, and Thompson, it will require 
75,6 7 parts of limestone. 
According to Klaproth and Henry, 73,87 parts of limestone will 
suffice for 100 of gypsum. 
According to Chevenix it will require 101,4 parts of limestone. 
(2 Nich. Jour. 196.) 
Hence also, taking the average of the experiments of Vauque- 
lin, Berthier, Thompson, Klaproth and Henry, and considering 
the lime to be 4 If per cent, in anhydrous gyps, 100 grains of lime- 
stone ought to produce 135 grains of sulphat of lime ; which ac- 
cording to Henry, 26 Nich. Journ. 278, it does produce at a low 
red heat. 
Bucholz and Thompson make the common gyps to contain 24 
per cent, of water of chrystallization : Bergman and Henry 22 ; 
taking 23 as the average, then the analysis of common gyps will 
be acid 44: lime 33 : water 23 per cent. For my own part I 
never could expel more than 21i parts of water, from 100 parts 
of gypsum. 
The experiment of Mr. Chevenix cannot be reconciled with any 
of the rest. 
Hence it is manifest that there is no accurate agreement among 
Chemists, either as to the proportion of lime in gypsum, or the 
proportion of water in that substance. This diversity is owing 
entirely to the varieties of temperature in which the gypsum when 
obtained by their experiments was dried. 
On entering on the course of experiments to ascertain the com- 
ponent parts of the limestones sent to me by judge Peters, I found 
it convenient to institute a set of experiments on gypsum for my- 
self. 
Klaproth from 100 grains of pure carbonat of lime, procured 
1 60 grains of chrystallized gypsum. 
Henry and others at alow red heat procured 135 grains. 
T enant at a higher heat 1 30 grains. 
