WATER STILLS AND DEIONISERS

In performing various laboratory tests, basically in clinical chemistry, pure water is the requirement for use. These pure form of water are sourced/gotten either by distillation or deionisation processes respectively.

Distillation

This is a process of subjecting water to high temperature resulting to the formation of steam which is then condensed on a surface which is usually cold to give a pristine state of water. The instrument used for this process is referred to as a ‘STILL’. The mechanism behind the method by which it works is as follow; the sample (water) is introduced into the equipment, electrically it is heated by a heating coil and when the boiling point is reached and the formation of steam proceeds, the steam is then condensed in the condenser and cooled by circulating water from the tap. The cooled steam is then collected as distilled water. The pure distilled water must have qualities such as it being free from dissolved salts, clarity, free from smell and colour, and has no taste. It can be made free from origin of bacteria substances if only it contains condensed steam and is collected in clean, sterile container.

Water stills; the following characteristics/devices are found in most water stills which are electrically heated.

1. Splash guard: this device stops water which are not yet treated from splashing/entering into the distillate
2. Cut out device: in emergencies such as power failure and reduction of water supply, the device switches off the power causing the equipment to stop.

Some version of these equipment are provided with the cut out devices that switches off the power when the container for collection are at maximum. These also provide a sense of safety as the still can be functioning without supervision.

3. Easy cleaning: due to the presence of deposited salt on the boilers, regular cleaning is required and as such the still should be designed in such that it can be dismantled and assembled back easily in its right position.

The strength of the still components determines the production rate of distilled water. An average sized still is capable of producing up to 4-5 litres per hour of distilled water.

Testing distilled water

There are two easy tests carried out to determine the quality of distilled water, they include:

1. Test for Chlorides: few drops of 10% silver nitrate is added to quantity of the distilled water in test. No form of CLOUDINESS is observed in good distilled water
2. Test for Sulphates: few drops of 10% barium chloride is added to a small volume of water under test. Presence of PRECIPITATES indicates that the distilled water is not free of sulphates hence the quality has been breached.