44 



CHEMISTRY. 



it is a hydrate. The hydrate is very fusible, and on cooling it con- 

 denses into a transparent brittle solid, called glacial phosphoric acid, 

 which is very deliquescent. It contains one eq. of basic water. It 

 forms an insoluble compound with albumen. 



BORON. 



Is the basis of boracic acid ;— may be procured from boracic acid 

 by heating it with potassium ; the oxygen of the acid, uniting with the 

 potassium, sets the boron free. 



Pro;;.— A dark olive-coloured substance; insoluble; a non-con- 

 ductor of electricity ; when burned in the open air or oxygen, it 

 generates boracic acid, Eq.=IO. Symb. B. It forms only one 

 compound with oxygen, namely, boracic or boric acid. This can 

 be procured by decomposing biborate of soda (borax) by means of 

 sulphuric acid ; the sulphate of soda remains in solution, and the 

 boracic acid is deposited in the form of crystals. 



It is sparingly soluble in cold water, more so in hot water, and 

 very soluble in boiling alcohol. The alcoholic solution when set on 

 fire, burns with a beautiful green flame, a good test of its presence. 

 When boracic acid is heated, it melts into a glassy mass. 



The most important salt of boracic acid is borax — a biborate of 

 soda. 



SILICON. 



The basis of silex or silicic acid; — procured by heating the double 

 fluoride of silicon and potassium ; the latter combines with the fluo- 

 rine, liberating the silicon. 



Prop. — A dark brown powder, a non-conductor of electricity, and 

 without the metallic lustre; heated in the air, it burns, and is con- 

 verted into silicic acid ; — forms only one compound with oxygen. 

 Eq.=22-5. Symb. Si. 



Silicic acid, SiOg, — known also as silex or siliceous earth — exists 

 abundantly in nature in the form of quartz and sand. Rock crystal 

 is a very pure form of it. — Prepared by igniting transparent rock 

 crystal, throwing it when red hot into water, and then reducing to 

 powder ; or by heating together powdered quartz or sand and car- 

 bonate of soda : a silicate of soda is formed, which is to be boiled 

 in water ; hydrochloric acid is then added, which combines with the 

 soda, precipitating the silicic acid in the form of a gelatinous mass. 



Prop. — A white powder, insoluble, tasteless; sp. gr. 2-69; very 

 infusible; has no action on test paper on account of its insolubility; 

 but it is a powerful acid, since it forms salts with the alkalies. Com- 

 mon glass is a silicate of potash. The best varieties of glass are 

 made out of a pure alkali and very fine sand, free from iron: flint- 

 glass contains some litharge, or red lead, also. If the proportion be 



