WATER SUPPLY 277 



Test of Impurities in Water. Water may be contaminated by: 



1. Organic matter. 



2. Leaf mold. 



3. Vegetable matter. 



4. Animal matter. (Sewer contamination.) 



Heating Test. Heat a little water in a corked flask. Do not bring it to 

 boiling point. Shake, remove the stopper, and smell the contents. Pure water 

 is free from odor. 



Test for Organic Matter, Animal or Vegetable Matter. Add to a small 

 amount of water in a test tube a few drops of sulphuric acid. To this add a 

 small amount of potassium permanganate until the water takes on a decided 

 color. Boil. If the water remains the same color, no organic contamination 

 has taken place, but if the water changes to brown, or becomes colorless, there 

 is organic contamination, either animal or vegetable. 



Ammonia Test. To a small amount of water in a test tube add a little 

 Nessler's reagent. A faint yellow tinge only should be visible. A turbid 

 appearance indicates animal contamination and that the water is dangerous to 

 use. All natural water contains a very small amount of ammonia but not 

 enough to cause more than a slight coloration with the above test. 



Rain water, although practically pure, contains a considerable 

 amounto^rmmonia dissolved from the atmosphere. 



Lead in Water. Sometimes water standing for some time in 

 the pipes dissolves the lead from lead pipes. We should always 

 allow the water to run from the faucet or drinking fountain for a 

 short time in the morning to be sure that all the water which has 

 stood in the pipes overnight is removed. 



Test for Lead. Place 100 cubic centimeters of water in a flask, and evaporate 

 water until only J of the original volume remains. Add a few drops of potassium 

 bichromate. A yellow precipitate shows the presence of lead. Other metals, 

 such as iron and copper, may be dissolved in spring water. This may be 

 detected by boiling 2 grams of stearic acid in 30 cubic centimeters of water for 

 five minutes. After the water has cooled, examine it before a white background. 

 Iron salts cause the water to have a yellow color. Copper salts will give a 

 bluish appearance. 



Hot water from kitchen boilers should never be used for drinking 

 water, since hot water dissolves both the lead and the copper and 

 some of the brass from the boiler and pipes, 



