198 WALL'S MANUAL 



bago, sulphuret of iron or iron pyrites, and the 

 sulphuret of potassium, or the liver of sulphur. 



2. They chemically combine with each other. 

 Thus are formed sulphuret of carbon, sulphuret of 

 silicon, etc. 



3. They all form acids by combining with oxygen. 

 Thus are formed carbonic, sulphuric, phosphoric, and 

 silicic acids. 



NAMING ACIDS. 



The rule followed in naming acids is, that each is 

 called after the substance forming it, the metalloids 

 having ous added, to denote the weaker, and ic to 

 designate the stronger acids, thus : 



1 sulphur 16x2 of oxygen =16x1 6 ==22 sulphurous 

 acid. 1 sulphur 16x3 of oxygen = 16x24 = 40 sul- 

 phuric acid. In the same way carbonic and phosphoric 

 acids are formed. Silica or sand forms but one acid, 

 silicic. 



Silicon, from which silicic acid or silica is formed, 

 requires a more extended notice. Silicon, when united 

 with oxygen, forms pure rock crystal, quartz, agate, 

 cornelian. It is this that forms the glazed coating to 

 the rush and the grasses. Wheat, rye, oats, cornstalks, 

 and barley owe their support to this covering of 

 silicon or sand. It cases the bamboo and rattan with 

 an armor of flint, from which, when dry, may be 

 struck sparks of fire. 



Silicon in the purest state yet obtained, is a dull 

 brown powder, soiling the fingers. It dissolves in 

 hydro -fluoric acid and in caustic potash. When heated 

 with dry potash, it is converted into silicic acid. Silicic 

 acid exists in two states, soluble and insoluble in 



