3 JO BORON. 



during summer. But the most considerable of the present 

 sources of boracic acid are the hot lagoons of a district in Tus- 

 cany, which are charged with the free acid, from the condensa- 

 tion in them of vapours of a volcanic origin. Boracic acid is 

 likewise found in the hot springs of Lipari. It is a constituent 

 also of several minerals, of which datolite and boracite are the 

 most remarkable. Boron was first discovered by Sir H. Davy 

 in 1 807, by exposing boracic acid to the action of a powerful 

 voltaic battery, and was afterwards obtained by Gay-Lussac and 

 Thenard in greater quantity, by heating boracic acid with potas- 

 sium. 



Preparation. Boron is prepared with greatest advantage 

 from a combination of fluoride of boron and fluoride of potas- 

 sium, which is obtained on saturating hydrofluoric acid with 

 boracic acid, and adding to it drop by drop, the fluoride of po- 

 tassium. This compound which is of slight solubility, is col- 

 lected on a filter, and dried at an elevated temperature, but 

 which should not reach a red heat. Equal weights of this com- 

 pound and potassium are mixed together in a cylinder or tube 

 of iron, closed at one end, which is gently heated, and the mix- 

 ture stirred with an iron rod, till the potassium is melted. 

 Heated more strongly by a spirit lamp, the mass evolves heat 

 and becomes red-hot ; the potassium combines with the fluorine, 

 and a mixture is obtained of boron and the fluoride of potassium. 

 On treating this with water, the fluoride of potassium dissolves, 

 and the boron remains insulated. In washing it farther, instead 

 of pure water, which acts upon boron, a solution of sal ammo- 

 niac should be employed, which does not dissolve that body, 

 and the sal ammoniac remaining in the boron may be taken up 

 by alcohol. 



Properties. Thus prepared, boron is obtained in the form 

 of a greenish brown powder, without the metallic lustre, which 

 becomes hard and assumes a deeper colour, when ignited in 

 vacuo, or in gases which do not combine with it, but undergoes 

 no farther change. Heated in atmospheric air or oxygen it 

 burns with a vivid light, scintillating powerfully, and forms 

 boracic acid. Nitric acid and many other substances also oxi- 

 date it easily, and always produce that compound. Fused 

 with carbonate of potash, it decomposes the carbonic acid, and 

 gives borate of potash, carbon being liberated. Boron is not 

 known to possess any other degree of oxidation. Boron com- 



