372 
Book II. 
Division II. 
History. 
SALTS. 
Sp. 6. Borat of Potass. 
THIs salt, which was first formed by Baron, is very 
little known. It may be prepared by calcining a mix 
ture of boracic acid and nitre. The heat drives off the 
nitric acid, and leaves a white saline mass, which, when 
dissolved in water, yields crystals of borat of potass. It 
is capable of combining with an excess of base, and 
forming a sub-borat of potass. 
Sp. 7. Borat of Soda. 
THIs salt, which may be formed by saturating bo 
rax with boracic acid, has never been examined. Berg 
man informs us, that about half its weight of boracic 
acid is necessary to saturate borax*. Its specific gra 
vity is 1.351f. 
Sp. 8. Sub-borat of Soda or Boras. 
THIs salt, the only one of the borats which has been 
accurately examined, is supposed to have been known 
to the ancients, and to be the substance denominated 
chrysocolla by Pliny. At any rate, it is mentioned by 
Geber as early as the ninth century under the name of 
borax. Its composition was first pointed out by Geof 
froy in 1732, and Baron in 1748. Bergman was the 
first who demonstrated that it has an excess of base, and 
is therefore in the state of a sub-borat. 
This salt is brought from the East Indies in an im 
pure state under the name of tinkal, enveloped in a kind 
* Bergman, iii. 325. According to Withering, twice its weight is 
necessary.—Bergman’s Sciagraphia, p. 26. Engl. Trans. 
Hassenfratz, Ann. de Chim. xxviii. 12.