Wea ae 
experiment it appears that 84 parts tartar vitriolate are in that 
refpeat equal to 100 of gypfum. 
Of Epfom Salk. 
Ir is generally agreed that common aerated magnefia lofes 
above + its weight by calcination in a red heat, which expels 
all the water and fixed air that inheres in it. Dr. Black, whofe 
fortunate inquiries concerning the nature of this eatth, laid the 
foundation of the greater part of the modern improvements in 
chemiftry, found it to lofe about 51 per cent. Mr. Butini of 
Geneva 59 per cent. Mr. Wenzel 58 per cent. Mr. Bilhabar 65 
per cent. and Mr. Bergman 55 per cent. As magnefia lofes a 
{mall part of its earth when calcined in an open veffel, as was 
difcovered by Mr. Tingry, perhaps we may acquiefce in Mr. 
Bergman’s determination, as approaching to a mean among thofe of 
other chemifts. 
A souurion of 100 grs. ‘cryftallized Epfom in 926 of water 
had its fpecific gravity in the temperature of 56°=1,0448; the 
weight of the falt was therefore of the whole weight of 
I 
10,26 
the folution. 
50 grs. of oil vitriol, whofe {pecific gravity was 1,5654, and 
which by the table contained 0,61 of its weight of ftandard, 
were diluted with 599 of water. This dilute acid was faturated 
by 35 gts. of common magnefia, and when 278 gts. more of 
; ; water 
