BORATS. 
Sp. 4. Borat of Magnesia. 
BERGMAN formed this salt by dissolving magnesia in 
boracic acid. The solution proceeded slowly; and on 
evaporation, the salt was precipitated in small irregular 
crystals. It is soluble in acetous and formic acids. Al 
cohol decomposes it. It melts easily in the fire without. 
being decomposed *. 
Sp. 5. Borat of Lime-and-magnesia. 
THIS salt, which is found native in the mountain of 
Kalkberg near Luneburg in Germany, was first analy 
sed by Westrum in 1788. 
It is in the form of transparent or opaque white cry 
stals, consisting of cubes, having their edges and four of 
their angles truncated. It is so hard as to scratch glass, 
and to strike fire with steel. Its specific gravity is 
2.566. When heated, it becomes electric; and what is 
singular, the truncated angles are always positively e 
lectric, while the opposite entire ones are negative j. 
These crystals are insoluble in water, and not altered 
by exposure to the air. When heated, they decrepitate: 
in a red heat they lose their lustre, but do not sensibly 
diminish in weight. In a white heat they lose 0.005 
of their weight. When exposed to the action of a very 
violent heat, they melt into a yellow-coloured glass. 
According to Westrum, they are composed of 
73.5 acid 
14.6 magnesia 
11.9 lime 
100.0 
* Bergman, i. 386. 
Hauy, Ann. de Chim. ix. 59. 
Aa2 
371 
Chap. III. 
Properties, 
Tompesde 
tion.