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EXPERIMENT 29. ORGANIC MATTER IN WATER 



Pour some water into an evaporating dish and put the 

 dish on a sand bath, allowing the water to evaporate slowly. 

 After the evaporation of the water, some solid material 

 will probably remain in the dish. If a lighted match is 

 applied to this residue and the material blackens, organic 

 matter is present. 



All organic matter blackens when burned slowly by a 

 weak fire ; charred wood is a good illustration. 



The presence of organic matter in water is always dan- 

 gerous. Decayed animal and vegetable matter, as well as 

 small living organisms, frequently produce widespread dis- 

 ease, and it is principally through drinking water that many 

 diseases, such as typhoid fever, are spread. 



EXPERIMENT 30. FILTRATION 



Fold a piece of filter paper so that it fits into a glass fun- 

 nel. Then put some powdered bone black into the fun- 

 nel and pour muddy water, or water slightly colored with 

 red ink, upon the charcoal. Collect in a beaker the water 

 which filters through the charcoal and the filter paper, and 

 runs out of the funnel. Test the water for organic matter 

 as in the preceding experiment. 



Repeat this experiment, omitting the charcoal and using 

 filter paper alone. In which case does the water contain 

 less organic matter ? 



Describe the appearance of the filter paper after a pint 

 of water has passed through it. 



Give two household illustrations of filtration. 



