s which should never
be used for boiler feed purposes and which no treatment can render
suitable for such purpose. In such cases, the only remedy is the
securing of other feed supply or the employment of evaporators for
distilling the feed water as in marine service.

TABLE 14

APPROXIMATE CLASSIFICATION OF IMPURITIES FOUND IN FEED WATERS
THEIR EFFECT AND ORDINARY METHODS OF RELIEF

+-----------------------+--------------+-----------------------------+
| Difficulty Resulting | Nature of | Ordinary Method of |
| from Presence of | Difficulty | Overcoming or Relieving |
+-----------------------+--------------+-----------------------------+
| Sediment, Mud, etc. | Incrustation | Settling tanks, filtration, |
| | | blowing down. |
| | | |
| Readily Soluble Salts | Incrustation | Blowing down. |
| | | |
| Bicarbonates of Lime, | Incrustation | Heating feed. Treatment by |
| Magnesia, etc. | | addition of lime or of lime |
| | | and soda. Barium carbonate. |
| | | |
| Sulphate of Lime | Incrustation | Treatment by addition of |
| | | soda. Barium carbonate. |
| | | |
| Chloride and Sulphate | Corrosion | Treatment by addition of |
| of Magnesium | | carbonate of soda. |
| | | |
| Acid | Corrosion | Alkali. |
| | | |
| Dissolved Carbonic | Corrosion | Heating feed. Keeping air |
| Acid and Oxygen | | from feed. Addition of |
| | | caustic soda or slacked |
| | | lime. |
| | | |
| Grease | Corrosion | Filter. Iron alum as |
| | | coagulent. Neutralization |
| |