46 
LABORATORY EXERCISES 
color, odor, and general appearance. Explain the differences 
which you find in any sample after it has stood in the oven, as 
compared with its former characteristics. 
II. Place 4 cc. of distilled water in each of two clean test tubes. 
To one add a small amount of organic matter. Next add a drop of 
potassium permanganate solution to each tube. (This may be 
made by adding a crystal of potassium permanganate to sufficient 
water to make a bright purple solution.) Gently heat the tubes. 
Note any change in color. How did the contents of the two tubes 
differ before adding the solution? What then has caused the 
difference in results? State clearly the test for organic matter as 
shown by this experiment. 
III. Test each of the samples in Part I for organic matter. In 
which is the most present? Has this organic matter any relation 
to the odor and appearance of the sample? Is there any relation 
between the amount of organic matter and the results which you 
observed after allowing the samples to stand for two days? Is 
organic matter itself likely to be very injurious to those who drink 
the water which contains it? What does its presence indicate as 
to the source of the water which contains it? Why then is water 
containing organic matter objectionable? 
IV. What is organic matter? What is its source? 
EXERCISE 49 
THE REMOVAL OF SEDIMENT IN 
DRINKING WATER 
I. Settling. Allow water from five sources — a well, a cistern, 
a faucet, a pond, and a muddy pool — to stand over night in well 
cleaned deep glass vessels. At the end of this period, compare the 
amounts of sediment. Is the water in all the vessels equally clear? 
Explain the differences which you observe. What is the nature 
of the sediment in each? Examine some which has been mounted 
under a microscope. 
