CHAPTER II 



SOLUTIONS 



We have seen that living beings are transformers of energy 

 and of matter, evolutionary in form and liquid in consistency ; 

 that they are solutions of colloids and crystalloids separated 

 by osmotic membranes to form microscopic cells, or consisting 

 merely of a gelatinous mass of protoplasm, with a nucleus 

 of slightly differentiated material. The elementary pheno- 

 menon of life is the contact of two different solutions. This 

 is the initial physical phenomenon from which proceed all 

 the other phenomena of life in accordance with the ordinary 

 chemical and physical laws. Thus the basis of biological 

 science is the study of solution and of the phenomena which 

 occur between two different solutions, either in immediate 

 contact or when separated by a membrane. 



A solution is a homogeneous mixture of one or more solutes 

 in a liquid solvent. Before solution the solute or dissolved 

 substance may he solid, liquid, or gaseous. 



Solutes, or substances capable of solution, may he divided 

 into two classes — substances which are capable of crystal- 

 lization, or crystalloids ; and those which are incapable of 

 crystallization, the colloids. Crystalloids may be divided 

 again into two classes, those whose solutions are ionizable and 

 therefore conduct electricity, chiefly salts, acids, and bases; 

 and those whose solutions are non-ioni/ahle and are there- 

 fore non-conductors. These latter are for the most part 

 crystallizable substances of organic origin, such as sugars, 

 urea, etc. 



Avogadro's law asserts that under similar conditions of 



temperature and pressure, equal volumes of various gases 



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