BORACIC ACID, 493 



Lussae prefers the muriatic, and the boracic acid must be afterwards 

 ignited in a platinum crucible, to expel any excess of the decompos- 

 ing acid. 



4. PROPERTIES. 



(a.) The form is that ofkexahedral scales, white and brilliant. 



(b.) Feel, a little unctuous, like spermaceti, which it somewhat re- 

 sembles. The sublimed boracic acid is much more light and volu- 

 minous than the precipitated. 



!c.) Taste, cool, bitterish, and slightly sour; inodorous, 

 d.) Reddens blue vegetable colors, effervesces with the alkaline 

 carbonates, but turns turmeric brown, like the alkalies. Its sp. gr. 

 1 .48 after fusion, 1.803. 



(e.) " When sulphuric acid is poured upon it, a transient odor of 

 musk is produced." 



(/.) This acid a hydrate, for by ignition it loses about 43 per cent, 

 which is the water of crystallization; if heat be suddenly applied, a 

 large quantity of acid rises with the water of crystallization, and in 

 either case we obtain boracic acid, fused, and becoming when 

 cold, a hard transparent glass, not deliquescent, but partly opaque ; 

 if dissolved in hot water, it crystallizes again on cooling. Authors 

 are exceedingly at variance as regards the solubility of this acid ; 

 but they agree that it is much more soluble in hot than in cold 

 water, the general statement being 12 parts of cold, and 3 or 4 of 

 boiling water.* 



(g.) When a saturated solution of this acid, in water, is distilled, 

 a part of the acid passes over, and crystallizes in the receiver ; when 

 solid, it will melt into glass, rather than sublime. 



(h.) Soluble in 5 parts of boiling alcohol, which will then burn 

 with a beautiful green flame ; it is best exhibited by dipping a paper 

 in the solution, and setting it on fire, or by burning it from a watch 

 or wine glass ; but sponge does not shew it well, as the yellow color 

 produced by the salt with which it is impregnated, overpowers the 

 green. If the paper which has been dipped in the alcoholic solution 

 be dried first, it then burns with a yellow flame ; other substances, 

 which burn with a blue flame, as sulphur, burn green when mixed 

 with boracic acid.f 



5. COMPOSITION AND POLARITY. In the next article, the de- 

 composition of this acid will be mentioned ; we may now say that it 

 has a combustible base, called boron, which by union with oxygen, 

 forms boracic acid. 



* According to Murray it requires 5 parts of boiling water, and 2& of cold ; but 

 Davy asserts that it requires 50 parts, even of boiling water, 

 t Aikin'sDict. 



