ABSTRACT
Laboratory solvents may be classified according to their polarity into three groups: apolar aprotic solvents, dipolar aprotic solvents and protic solvents. Many solids may be purified by recrystallisation by dissolving the substance in a minimum quantity of hot solvent, filtering the solution and then cooling the solution so that crystals of the desired substance form while the impurities remain in solution. This chapter provides a list of some solvents suitable for the extraction of aqueous solutions. It provides a list of some freezing mixtures and their approximate temperatures. Experimental work with cooling baths and Dewar flasks containing freezing mixtures requires the use of efficient fume hoods and personal protection equipment. The silicona (SI) units for derived physical quantities are those coherently derived from the SI base units by multiplication and division. The chapter also provides some of the SI-derived units that have special names and symbols.
