SOLUTION AND CRYSTALLIZATION 95 



Solution and Crystallization. 



The solvent action of water is such an important agent in the 

 world of nature, both the living and non-living, that it becomes a 

 good subject for nature study work. 



The substances which plants take from the soil must be in a 

 state of solution. The various forms of the foods that animals 

 use must be reduced to a liquid form to be absorbed and they are 

 in the blood in solution. The solution of one or more of the 

 ingredients of a rock which act as a cement to hold the rest 

 together, allows the rock to fall to pieces and to become soil. The 

 solution of certain substances from the soil permits them to be 

 carried great distances to be deposited as minerals in veins or in 

 masses of crystals, or, as in salt, in great salt lakes or in beds of 

 salt. In some situations immense quantities of rock are entirely 

 dissolved out and carried away, as in the caves in limestone strata, 

 of which the Mammoth and Wyandotte Caves are notable examples. 

 The beautiful cave formations are the result of regaining dissolved 

 substances from their solutions. Most of the wonderful things to 

 be seen in the Yellowstone Park are the result of solution and the 

 regaining of substances from solution. Thus by solution and a re- 

 gaining of substances from solution the character of the crust of 

 the earth may be constantly undergoing changes. 



To illustrate the facts of solution have the pupils make solu- 

 tions of some common substances such as table salt, sal ammoniac, 

 alum, sugar, copper sulphate and bichromate of potash. This 

 selection contains substances of different colors and all readily 

 obtainable. They all make clear solutions. Have comparisons 

 made with attempts to dissolve powdered sulphur or powdered 

 chalk, which will not dissolve in water. 



Have the pupils by experimenting learn that some substances 

 like sal ammoniac, dissolve readily in water, the water taking in 

 a large amount, while others, like bichromate of potash, dissolve 



