478 Intelligence and Miscellaneous Articles. 



Analysis gave — 



Experiment. Calculation. (C^OR^) 



Carbon 88-1 81-24 



Hydrogen ITS 11-76 



99-9 100-00 



Oil of turpentine acts exactly in the same way with anhydrous phos- 

 phoric acid as the hydrates, being like them converted into tereben 

 and colophen. — Ann. de Ch. et de Phys,, Septembre 1849. 



ON THE INFLUENCE OF BORACIC ACID ON VITRIFICATION. 



M. Maes, manufacturer of flint-glass^ has, conjointly with M. Cle- 

 mandot, long paid attention to the above-named subject. The prin- 

 cipal results hitherto obtained are : — 1st, borosilicate of potash and 

 lime ; 2ndly, borosilicate of potash and zinc ; 3rdly, borosilicate of 

 potash and barytes ; 4thly, borosilicate of soda and zinc. 



The borosilicate of potash and lime was formed with the intention 

 of producing in close vessels with coal furnaces, the best imitations 

 of Bohemian glass. In the Compte Rendu de V Exposition AutricM- 

 enne, 1845, published by M. Peligot, it appears, that in order to 

 make the purest and most durable glass in 13ohemia, they use with 

 100 parts of silica, 12 parts of unslaked lime, and only 28 parts of 

 carbonate of potash. From this we must conclude that the glass is 

 better the less potash and the more lime it contains. 



The above proportions yield a glass which is infusible in the fur- 

 naces employed by M, Maes. The addition of a few hundredths 

 of boracic acid is sufficient to occasion fusion, and the resulting pro- 

 duct possesses all the limpidity, splendour and hardness which can 

 be desired. 



This first experiment naturally suggested the advantage which 

 might be derived from the solvent power of boracic acid so as to in- 

 troduce bases into glass which had not hitherto been employed, as 

 borosilicate of potash and zinc, and that of potash and barytes. The 

 borosilicate of potash and zinc appeared to impart all the qualities of 

 a pure and durable glass. As to the borosilicate of potash and ba- 

 rytes, it was prepared from native carbonate of barytes, contaminated 

 with sulphate of barytes and a ferruginous gangue. If then it be less 

 colourless than the zinc glass, the colour is certainly accidental : on 

 again making it with pure carbonate, this imperfection would un- 

 questionably disappear. 



The beauty of borosilicate of potash and zinc led to the compara- 

 tive trial of borosihcate of soda and zinc : this, although inferior to 

 the potash, incontestably excelled all the soda glasses compared 

 with it. 



To recapitulate : the borosilicates are chiefly remarkable for their 

 transparency and hardness. They derive these important qualities 

 from reducing considerably the potash and soda which almost always 

 are in excess in common glass; and every one knows that glass 

 "which is too alkaline, is cloudy, soft and hygrometric. 



