208 METALLOIDS. 



5 12. CRYSTALLIZATION. Dissolve 



Howmaycrys- ir i r i ^ 



ta^s of alum be hall a pound oi alum in a pint of 

 obtained? boiling water, and hang a cotton cord 

 in the vial. As the water cools, crystals will form 

 on the thread. Bonnet wire may be bent into the 

 shape of baskets, miniature ships, &c., and cov- 

 ered, by this means, with a beautiful crystalliza- 

 tion. 



Explain the 513. EXPLANATION. Hot water has for 



process. most substances greater solvent power 



than cold water. In the case of alum, for example, water 

 slightly warmed, will dissolve twice as much as cold 

 water. It follows, that as the hot water becomes cold, 

 part of the alum must become solid again. In so 

 doing, the particles, in obedience to their mutual at- 

 traction, arrange themselves in crystals, as described 

 in the first Chapter III. 



514. SNOW CRYSTALS. Snow flakes are 



What is said 1-1 



of snow crys- always either grouped or single crystals, 

 and their form may often be distinctly seen 

 with the naked eye. They 

 are best observed by catching 

 them upon a hat, or other 

 dark object, and inspecting them in the open air. 



515. CHEMICAL COMBINATIONS. Water 



What is said 



of the combi- unites with both bases and acids, to form 



nations of wa- hydrate ^ Thus? ^^ lim ^ ^ formg hy _ 



drate of lime ; with sulphuric acid, hy- 

 drated sulphuric acid. Most of. the oxygen acids, in 

 the form in which we employ them, contain water in 

 a state of combination, and are therefore hydrated 



