of the treated water is used for this
test, one cubic centimeter of the soap solution corresponding to one
degree of hardness. The soap solution is added a very little at a time
and the whole violently shaken. Enough of the solution must be added to
make a permanent lather or foam, that is, the soap bubbles must not
disappear after the shaking is stopped.

Excess of lime as determined by nitrate of silver: If there is an excess
of lime used in the treatment, a sample will become a dark brown by the
addition of a small quantity of silver nitrate, otherwise a milky white
solution will be formed.

Combined Heat and Chemical Treatment: Heat is used in many systems of
feed treatment apparatus as an adjunct to the chemical process. Heat
alone will remove temporary hardness by the precipitation of carbonates
of lime and magnesia and, when used in connection with the chemical
process, leaves only the permanent hardness or the sulphates of lime to
be taken care of by chemical treatment.

TABLE 16

REAGENTS REQUIRED IN LIME AND SODA PROCESS
FOR TREATING 1000 U. S. GALLONS OF WATER
PER GRAIN PER GALLON OF CONTAINED IMPURITIES[16]

+-----------------------+-----------+-----------+
| | Lime[17] | Soda[18] |
| | Pounds | Pounds |
+-----------------------+-----------+-----------+
| Calcium Carbonate | 0.098 | ... |
| Calcium Sulphate | ... | 0.124 |
| Calcium Chloride | ... | 0.151 |
| Calcium Nitrate | ... | 0.104 |
| Magnesium Carbonate | 0.234 | ... |
| Magnesium Sulphate | 0.079 | 0.141 |
| Magnesium Chloride | 0.103 | 0.177 |
| Magnesium Nitrate | 0.067 | 0.115 |
| Ferrous Carbonate | 0.169 | ... |
| Ferrous Sulphate | 0.070 | 0.110 |
| Ferric Sulphate | 0.074 | 0.126 |
| Aluminum Sulphate | 0.087 | 0.147 |
| Free Sulphuric Acid | 0.100 | 0.171 |
| Sodium Carbonate | 0.093 | ... |
| Free Carbon Dioxide | 0.223 | ... |
| Hydrogen Sulphite | 0.288 | ... |
+-----------------------+-----------+-----------+

The chemicals used in the ordinary lime and soda process of feed water
treatment are common lime and soda. The efficiency of such apparatus
will depend wholly upon the amount and character of the impurities in
the water to be tre