This should be carried out at regular intervals, preferably once or twice a day, and the results entered in a log book ; this log will enable us to ascertain if the chemical process is being properly carried out, and to rectify any errors that may have been made.

Tests should be made as follows :

Test " A."-Fill one of the glasses up to the 80 c.c. mark and add 3 drops of Alkalinity Indicator (phenolphthalein). The water should turn red. If the water does not turn red the discharge of the chemical valve should be increased.

If the water does turn red, drops of Hydrochloric Acid should be added (stirring well after the addition of each drop) until the colour disappears.

Call the correct number of drops required x. If it takes more than this quantity to decolour the water the discharge of the chemical valve must be decreased. If it takes less than the above-mentioned number of drops to decolour the water the discharge of the chemical valve must be increased. The actual number of drops of acid added must be entered up in the log book in the Test " A " Column.

Test " B."-Test " B " should now be made : A measuring glass is again filled with 80 c.c. of water and 3 drops of Alkalinity Indicator (phenolphthalein) added. The water will turn red as before. Then add a spoonful of Barium Chloride and stir well-the colour should not entirely disappear on adding the Barium chloride.

If the colour does disappear, the lime must be increased by, say, 10 per cent., and the soda decreased by the same amount. If the colour does not disappear, the water should be filtered into the other glass by means of the funnel and filter papers supplied, and drops of Hydrochloric Acid added, stirring well.

If more than x drops decolour the water the lime must be decreased, say, by 10 per cent., and the soda ash increased, say, by the same amount.

If less than x drops decolour the water the lime must be increased by, say, 10 per cent., and the soda ash decreased by the same amount.

Testing The Hardness Of Water

(The Testing Set comprises one Pipette, one 40 c.c. Shaking Bottle, and one Bottle of Soap Solution.) Fill the Shaking Bottle with a sample of the water to be tested up to the 40 c.c. mark.

Fill the Pipette with Soap Solution to the mark above zero.

Add Soap Solution from the Pipette to the water sample \° at a time, until a permanent lather is obtained. The lather to be satisfactory should last 5 minutes.

At this point the reading on the Pipette gives direct the number of English degrees of hardness (grains of CaCO3 per gallon of water).

For waters over 20° hardness use only 20 c.c. of the sample, and make up to the 40 c.c. mark with distilled water. The reading on the Pipette multiplied by 2 will then give the hardness.

The flow of the Soap Solution from the Pipette can be regulated by opening or closing the orifice by which the Pipette is filled with the finger.

" Zero-Hardness " Water from "Permutit " Brand Water Softeners. -By employing the "Permutit " zeolite water softening system, it is now possible to produce from any water supply, however hard, a completely softened water, free from every trace of hardness, the softening being automatically effected.

The "Permutit " process is simplicity itself. It consists in passing the water through a filter filled with "Permutit," which possesses the property of chemically extracting all the Lime and Magnesia from hard water, and of afterwards giving up these impurities again when acted upon by a solution of ordinary salt. A similar faculty of chemical " exchange " has long been known to be characteristic of certain natural minerals which have in combination various metallic bases and silicic acid. "Permutit " is, in fact, a synthetic product having greater capacity and readier exchange than the natural product.

All Hardness Removed

By the power of "base-exchange " which Permutit" possesses, both calcium and magnesium are totally removed from water which has passed through a "Permutit " softener. Every trace of hardness disappears.

No Moving Parts

" Permutit" softeners have no moving parts, the entire process consisting of the simple filtration of the hard water through a bed of " Permutit."

No Regulation Needed

The softening power of a " Permutit " plant is drawn upon by the water itself in exact accordance with its hardness and its rate of flow, and it follows that " Permutit " absolutely prevents all possibility of either under-treatment or over-treatment. The precise amount of treatment required to eliminate every particle of hardness is given automatically by " Permutit "' to any hard water brought into contact with it. Variation in the quality or quantity of the water within the limits of the capacity of the plant makes no difference to " Permutit."

Working Under Pressure

The " Permutit" system is the only system of water purification which functions equally well whether operated under pressure or by gravity ; and a " Permutit " softener can in consequence be fixed to the water service at any convenient level.

How " Permutit " Removes Hardness

The " hardness " of water is classified as " temporary" or " permanent " according to the behaviour of the salts which constitute it. The" temporary " hardness is caused by the presence of the bicarbonates of calcium and magnesium, held in solution by carbonic acid, which precipitate when the water is boiled, as insoluble carbonates. The " permanent " hardness is, on the other hand, due to the sulphates, nitrates and chlorides of calcium and magnesium. These salts are not precipitated on boiling the water, and require to be chemically removed.

" Base- Exchange."-When sodium " Permutit " is brought into contact with hard water, it eliminates the whole of the permanent and temporary hardness, the lime and magnesia contained in the latter being exchanged for the sodium of the " Permutit."

This " base-exchange " softening action continues until the sodium in the " Permutit " molecule has been entirely replaced by calcium and magnesium. When this point has been reached the material becomes exhausted and then requires regeneration to restore its original activity. Regeneration is effected by passing a solution of sodium chloride (common salt) slowly through the filter ; by this means the calcium and magnesium are expelled from the " Permutit," their place being taken by sodium from the salt solution, thus reconstituting the original sodium " Permutit," which is as fresh and active as when first put to work.

The alternating cycle of softening and regeneration is perfectly regular and automatic. " Permutit " filters have been in uninterrupted use for several years and are still delivering water of zero degrees of hardness containing not the slightest trace of lime or magnesia.

Rapid-Regenerating " Permutit."

-The makers have introduced another type of " Permutit " for industrial use, which will be found in many cases to offer special advantages in respect of installation and operation.

" Permutit " 1" B."-The new material (named " Permutit" " B ") differs from the synthetic product both in physical characteristics and molecular constitution, these differences causing a radical change in the timing of the periodic cycle of softening and regeneration, and enabling day and night continuous duty to be performed by one unit only, instead of two as heretofore.

Previously a single unit was usually designed to soften continuously for a maximum period of 10 or 12 hours, and it then required an equal length of time for regeneration. Where day and night working was the rule, this, of course, involved the employment of two units.