32 



LABORATORY EXERCISES 



What is a definition of distillation? What is the taste of dis- 

 tilled water? 



If you have not the apparatus of Fig. 16, you can get some 

 distilled water by inverting a small, clean pail over the nozzle 



of a tea kettle in which water is 

 boiling. Catch the water that 

 drops from the lower edge of the 

 pail. 



c. Evaporate about 5 cu. cm. 

 of distilled water on a watch glass 

 placed over a cup or beaker of 

 boiling water. If you have no 

 watch glass, use a piece of clean 

 sheet glass. Lay it perfectly hori- 

 zontal, and put the water to be 

 evaporated, a few drops at a time, 

 upon the center of its upper sur- 

 face. 



In the same way evaporate about 5 cu. cm. of hydrant water 

 or well water. Which water leaves the greater residue? Why 

 does distilled water leave any residue at all? 



FIG. 16. 



EXERCISE 30 

 WATER TESTS 



Apparatus and Materials. Beakers or bottles (3), graduated cylin- 

 der, cardboard or glass covers, dilute sulphuric acid, potassium per- 

 manganate solution, distilled water, natural water, powdered calcium 

 sulphate (gypsum or plaster of Paris), soap. 



a. Organic Matter in Water. Measure out 50 cu. cm. of 

 distilled water, and put it into a clean glass vessel, such as a 

 beaker. Add to it 2 cu. cm. of dilute sulphuric acid and one 

 drop of potassium permanganate solution. 



