84 NON-METALS AND THEIR COMBINATIONS. 



rocks, such as granite, porphyry, basalt, feldspar, mica, etc., are 

 such silicates, or a mixture of them. Small quantities of silica 

 are found in spring waters, and also enter into vegetable and 

 animal bodies. 



Boron is found in but few localities, either as boric or boracic 

 acid, H 3 B0 3 , or borate of sodium (borax). Formerly the total 

 supply of boron was derived from Italy; lately large quantities 

 of borax have been discovered in California. 



Boracic acid is a white, solid substance, which is sparingly 

 soluble in water, and has but weak acid properties. 



Tests for silicic and boracic acid or their salts. 



1. Silicic acid and most silicates are insoluble in water and 

 acids. By fusion with a mixture of the carbonates of sodium 

 and potassium, the silicate of these metals (known as soluble 

 glass) is formed. By dissolving this salt in water, neutralizing 

 the solution with hydrochloric acid, and supersaturating with 

 ammonia, a portion of the silica separates as the gelatinous 

 hydrate. Complete separation of the silica is accomplished by 

 evaporation to dryness of the acidified solution. ' 



2. Boracic acid and borates color the flame green, especially 

 when moistened with sulphuric acid; their solution, when acidi- 

 fied by hydrochloric acid, turns turmeric paper brown (after 

 being dried), and when neutral gives, with barium and silver 

 salts, white precipitates of the borates of barium or silver. 



QUESTIONS. 



121. How is carbon found in nature ? 



122. State the physical and chemical properties of carbon in its three 

 allotropic modifications. 



123. Mention three different processes by which carbon dioxide is 

 generated in nature, and some processes by which it is generated by 

 artificial means. 



124. State the physical and chemical properties of carbon dioxide. 



125. Explain the process of respiration from a chemical point of view. 



126. What is the percentage of carbon dioxide in the atmospheric 

 air, and why does its amount not increase ? 



127. State the composition of carbonic acid and of a carbonate. How 

 can they be recognized by analytical methods ? 



