1 8 Acid of Borax. [Book VL 



ilate of great purity in mineral waters, and fmce real 

 borax may be formed by adding this fcaly fait to the 

 mineral alkali. The acid of borax requires about 

 fifty times its weight of water for its folution. In a 

 moderate heat it melts with lefs intumefcence than 

 borax itfelf ; and the glafly fubflance, thus formed, is 

 again foluble in water, having only loft its water of 

 cryftailizadon. 



The acid of borax is ufed to fufe the flinty earths, 

 with which it forms clear and almoft colourlefs glaf- 

 fcs ; by the affiftance of heat it difiblves the earth 

 precipitated from what is called the liquor of flints, 

 or " flint diffolved in fparry acid. It unites with 

 ponderous earth, magnefia, lime, and alkalis, and 

 forms with thefe fubftances faline compounds. All 

 thefe properties, and more efpecially its tafte, the red 

 colour it communicates to the tinctures of violets and 

 turnfole, and its neutral combinations with alkalies, 

 fufficiently indicate its acid nature ; but it is the moft 

 feeble of all the acids, and is difengaged from its com- 

 binations even by the carbonic acid. The acid of 

 borax is the fubftance called by Homberg fedative 

 ialt, from its fuppofed e(icc~!s on the human body. It 

 effervefces with a boiling hot alkaline folution, but 

 not \vith metals or abforbenc earths, though it may be 

 united with them. It has a weak attraction for in- 

 flammable fubftances, particularly fpirits of wine, the 

 flame of which it tinges green. From this circumftance 

 it has been fuppofed, but without iufficient proof, to 

 contain copper. 



" PHOSPHORIC acid is .obtained by the combuftion of 

 the bones of adult animals, which are afterwards 

 pounded, and pafied through a fine filk fieve? a quan- 

 tity of weak vitriolic acid is then poured upon the 

 powder, but lefs than is fufrkient for diffolving the 

 whole. This acid unites with the calcareous earth of 



the. 



