230 WALL'S MANUAL 



This acid condenses into solid white flakes of snowy 

 appearance, and possesses a powerful affinity for 

 water, hissing like red-hot iron when brought in 

 contact with it. 



Phosphoric acid is of the highest importance in 

 agriculture. It is principally from its presence in 

 bones that they are useful as a manure. There are 

 three other compounds of phosphorus and oxygen, 

 but they are of interest only to the scientific chemist. 



Nitric Acid or Aquafortis. This acid is the most 

 powerful of the chemical compounds of oxygen and 

 nitrogen. It is prepared by distilling equal weights 

 of sulphuric acid and saltpetre. Pure nitric acid is a 

 colorless liquid, one -and- a- half times heavier than 

 water. It smokes when exposed to the air, and is 

 partially decomposed by the action of light, nitrous 

 acid being formed, which gives it a yellow color. It 

 has an intensely acid taste, and reddens vegetable 

 blues. It is used for etching on copper, for assaying 

 or testing metals, and as a solvent for tin by dyers 

 and calico printers. It is also used as a medicine, as 

 a caustic to cleanse and purify foul ulcers. In conse- 

 quence of its large proportion of oxygen, it corrodes 

 or rusts metals with great energy, and hence it is a 

 most powerful oxydizing agent. 



Nitric acid occurs in small quantity in rainwater, 

 especially after thunder-storms, and is thought to be 

 produced in the air by lightnings, which combines 

 the gaseous nitrogen and oxygen, and also by the 

 oxydation of ammonia in the air. It is found in 

 nature in combination with the alkalies and earths. 

 Combined with potash or soda, nitric acid is a valuable 

 fertilizer. It hastens and increases the growth of 



