Page 106 - The Veterinary Laboratory and Field Manual 3rd Edition

The selection, use, maintenance and quality control of laboratory equipment and supplies 75

Figure 2.38 Deionizer. Photo: Dr Ziay Ghulam, Dr Figure 2.39 Manesty water distillation apparatus.
Wahidullah Bahaer, Central Veterinary Diagnostic Photo: Dr Ziay Ghulam, Dr Wahidullah Bahaer, Central
and Research Laboratory, Kabul, Afghanistan. Veterinary Diagnostic and Research Laboratory,
Kabul, Afghanistan.

water supply, which remains fully open (thereby • After cleaning/descaling/rinsing, switch on
providing at least the required minimum pres- the still and rinse it with the first 5 l of dis-
sure), and another to further control water flow tilled water production. Then, the pH value
to the still. Cooling water should be adjusted so of the distilled water should be around pH
that residual water has a temperature of about 6.0.
70°C. This way, the amount of cooling water
used is minimal.
Deionizers
uSE, carE and MaIntEnancE: Deionized water is produced by using a unit
• Make sure there is enough supply of cool run- containing a cation – anion exchange resin in a
ning water to feed the still. cartridge which can be refilled or exchanged. A
• Check the boiling chamber regularly for built-in mains or battery-operated conductivity
build-up of scale. meter monitors the water quality and will indi-
• Cleaning and descaling: the day before the cate when resin cartridges should be refilled/
cleaning and descaling is planned one has to replaced/regenerated. Sometimes charcoal is
pour about 60 ml of concentrated acetic acid included, which removes contaminants other
in the (warmed up) boiling chamber of about than mineral salts. Water from ion exchange is
5 l. not sterile and may contain pyrogens. Deionizers

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