.THE ASH OF PLANTS. 149 



thab occur in very small proportion in the ashes of plants 

 and in soils, but are important ingredients of some 

 fertilizers. 



The Chloeides are all characterized by their ready 

 solubility in water. The Chlorides of Calcium and Mag- 

 nesium are deliquescent, i. e., they liquefy by absorbing 

 moisture from the air. The Chlorides of Potassium and 

 Sodium alone need to be described. 



Potassium Chloride, or Muriate of Potash, 

 KUl, 74.5. — This bodyja^y be produced either by expos- 

 ing metallic potassium to chlorine gas, in which case the 

 two elements unite together directly ; or by dissolving 

 caustic potash in hydrochloric acid. In the latter case 

 water is also formed, as is expressed by the equation 

 KHO + HCl = KCl + WO. 



Potassium chloride closely resembles common salt in 

 appearance, solubility in water, taste, etc. It is now an 

 important article of commerce and largely consumed as 

 a fertilizer. It is also often present in the ash and in 

 the juices of plants, especially of sea-weeds, and is like- 

 wise found in most fertile soils. 



Chloride of Sodium, NaCl, 58.5. — This substance is 

 common or culinary salt. It was formerly termed muri- 

 ate of soda. It is scarcely necessary to speak of its oc- 

 currence in immense quantities in the water of the ocean, 

 in saline springs, and in the solid form as rock-salt, in 

 the earth. Its properties are so familiar as to require no 

 description. It is rarely absent from the ash of plants. 



Besides the salts and compounds just described, there 

 occur in the living plant other substances, most of which 

 have been indeed already alluded to, but may be noticed 

 again connectedly in this .place. 



These compounds, being destructible by heat, do not 

 appear in the analysis of the ash of a plant. 



Nitrates. — Nitric acid (the compound by which ni- 

 trogen is chiefly furnished to plants for the elaboration 



