AGRICULTURAL CHEMISTRY. Vd 



dients are entirely changed ; in the last, they remain 

 unaltered. Thus, if you bring chlorine and sodium 

 together, a substance totally unlike either is produced ; 

 from two virulent poisons a wholesome condiment is 

 formed — common salt : this is a compound. But if 

 you put water with milk, no new substance is formed 

 — the properties of the ingredients remain unaltered ; 

 they are water and milk still, and nothing more. This 

 is a mere mixture, 



9. A substance that can be dissolved in a liquid is 

 said to be soluble ; one that cannot, to be insoluble^ as 

 sugar, for instance, is soluble in water, and sand inso- 

 luble. When a substance is dissolved, it is called a 

 solution, as a solution of sugar, salt, or nitre, in water. 

 A distinction is also to be made between a solution and 

 a mixture. If you put cider into water, this is nothing 

 more than a mixture ; a color is in this case communi- 

 cated, whereas, if the cider were perfectly dissolved, 

 it would leave the water transparent. If now you 

 add a spoonful of salt to a pint of water, the water 

 will remain as transparent as before. This is a solu- 

 tion. Any liquid which dissolves other substances is 

 called a solvent. Water is the great solvent of those 

 salts which feed growing plants. These salts enter the 

 roots of plants in the state of transparent, colorless 

 solutions in water. 



10. There are different degrees of solubility. Water 

 will hold in solution but -^^-^ of its own weight of 

 quicklime; it will hold in solution ji^ of its own 

 weight of gypsum ; j\ of its weight of common 



