284. WATER HYGIENE 
The following reagents are required: 
1. Sodium or Potassrum Hydroxide Solution. Dissolve 250 gms. of 
hydroxide in 1.25 liters of distilled water. Add several strips of alumi- 
num foil and allow the evolution of hydrogen to continue over night. 
Concentrate to a liter by boiling. 
2. Aluminum Foil. Strips of pure aluminum about 10 cm. long, 
6 mm. wide and weighing about 0.5 gm. should be used. 
Nitrates represent the end products of nitrification. They repre- 
sent stable forms of nitrogen and are desired in the various methods of 
sewage treatment. They indicate that there was originally in the 
water a relative amount of organic matter which has been changed by 
ammonification and nitrification to completely oxidized forms. 
Nitrites give indication that nitrogen is being oxidized. This in 
turn represents great bacterial activity on organic matter. All deter- 
minations of nitrogen represent the various stages in the oxidation and 
reduction of nitrogenous compounds. 
Oxygen Consumed. Place 100 c.c. of the sample in a flask. Add 
10 c.c. of the sulphuric acid solution and 10 c.c. of the standard per- 
manganate solution and digest the solution for thirty minutes on a 
water bath. The flasks should be placed in the water bath so that the 
level of the water is kept above the level of the water in the flask. If 
the amount of permanganate is not sufficient for the oxidation of the 
sample, repeat the digestion with a larger sample. At least 5 c.c. excess 
of permanganate should be present when the oxalate is added. Remove 
the flask and add 10 c.c. ammonium oxalate solution, and titrate until a 
faint pink color appears and remains with the permanganate solution. 
If 100 c.c. of water is used the number of cubic centimeters of potassium 
permanganate solution in excess of the number of cubic centimeters of 
ammonium oxalate solution is equal to the parts per million of oxygen 
consumed. 
Reagents. 1. Dilute Sulphuric Acid. Dilute 1 part of concentrated 
sulphuric acid with three parts of distilled water and free the solution 
of oxidizable matter by adding potassium permanganate until a faint 
pink color persists after the solution has stood for several hours. 
2. Standard Ammonium Oxalate. Dissolve 0.888 gm. of the pure 
salt in a liter of distilled water. One c.c. is equivalent to 0.1 mg. of 
oxygen. An equivalent quantity of oxalic acid may be used. 
3. Standard Potasstum Permanganate. Dissolve 0.4 gm. of crys- 
tallized salt in a liter of distilled water. Add 10 c.c. of the dilute sul- 
phuric acid and 10 c.c. of this solution of potassium permanganate to 
100 ¢c.c. of distilled water, and digest thirty minutes. Add 10 e.c. of 
