BORATES. 497 



(d.) Sp. gr. 1.74 after fusion, flies and cracks to pieces in 

 cooling. 



(e.) Action of the acids as already mentioned under boracic acid, 

 and the general characters of the borates. 



(/.) If only the excess of soda be neutralized by an acid, the whole, 

 by evaporation becomes a confusedly crystallized mass, containing all 

 the ingredients. 



(g.) The excess of alkali can also be saturated by boracic acid; the 

 salt takes up nearly half its weight, and ceases to affect the blue col- 

 ors, to effloresce, to taste alkaline, and to crystallize in the same form 

 as borax. 



(h.) Baryta, strontia, lime, and magnesia, decompose borax. 



(i.) Potash also decomposes it, but there is no precipitate, because 

 soda dissolves borate of potash. 



(j.) Borax fluxes silica into a transparent, and alumina into an 

 opake glass ; the ingredients being in equal proportions, the com- 

 pound is insoluble in the mineral acids, but a great excess of borax 

 makes it soluble. 



(k.) The borax of the shops exhibits an imperfect crystallization, 

 with a figure approaching to the hexahedral prism. The crystals 

 are slightly efflorescent. 



3. COMPOSITION AND REPRESENTATIVE NUMBER. 



Gmelin, acid, 35.60, base, 17.80, water, 46.6 = 100 ) , 



Thomson, 31.51, 20.42, 48.0=100 j n< 



The representative number of boracic acid has already been stated 

 as being 24. According to Dr. Thomson, this salt is composed of 

 2 proportions of boracic acid, =48 



1 " soda, - - =32 



8 " water, - - - =72 



Its equivalent, 152 

 In the 100 parts, acid 31.58, soda 21.05, water 47.37. 



4. MISCELLANEOUS. The natural and commercial- history of this 

 salt has been already given under boracic acid. In addition to the 

 localities already named, it is found in China, in Peru, in Transyl- 

 vania and Saxony.* 



The crude borax brought from the East Indies and the Levant, is al- 

 ways enveloped in an oleaginous matter ; which Vauquelin found to be 

 a soap with soda for its base. It is believed that the natives cover it 

 with a film of oil to prevent its efflorescence, and it is said to be mois- 

 tened by sour milk for the same purpose. 



It is purified by repeated solutions and crystallizations, in vessels of 

 lead ; they obtain from the tincal .80 of borax, and they expose it 



* Thenard, III, 90. 

 63 



