Water in the Laboratory

 
 
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Distillation


Distillation is probably the oldest method of water purification. Water is first heated to the boiling point. The water vapor rises to a condenser where cooling water lowers the temperature so the vapor is condensed, collected and stored.

Merck:/Freestyle/LW-Lab-Water/water-lab/LW-Distillation-Water-353x318.jpg

Benefits & Limitations
Benefits
  • Removes a broad range of contaminants and therefore useful as a first purification step.
  • Reusable.
Limitations
  • Contaminants are carried to some extent into the condensate.
  • Requires careful maintenance to ensure purity.
  • Consumes large amounts of tap water (for cooling) and electrical energy (for heating).
  • Not environment-friendly.

Many contaminants remain behind in the boiling vessel. However, the process has several limitations:
  • Inorganic contaminants are able to migrate along the thin water film that forms on the inner walls of the still. This explains why ions can be found in the distillate, whose resistivity is therefore usually between 0.5 and 1 MΩ•cm @ 25 °C (i.e., about 500 ppb total ionic contamination in water). Contaminants are also extracted from the glass or metal boiling pot used to heat the water (silica, sodium, tin, copper).
     
  • Organics with boiling points lower than 100 °C will automatically be transferred to the distillate, and even organics with a boiling point superior to 100 °C can dissolve in the water vapor and also pass into the distillate. In addition, new organochlorine compounds may be generated during the distillation process, which provides the energy required for chlorine in the tap water (added for sanitization purposes) to react with the natural organic substances also present in this water. This explains why the TOC level of distilled water is typically around 100 ppb.
     
  • Distillation is a slow process that requires storage of water for long periods. During this time, recontamination occurs from the ambient air (inorganic and organic volatile substances, bacteria, particulates and algae) and the container (organics from plastic tanks or ions from glass reservoirs).
     
  • Distillation requires large amounts of energy and water, and therefore is expensive to operate. In addition, a still requires regular cleaning of the boiling pot with HCl, a brush and sand paper to remove the contaminants accumulated during the process.


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Eventos

abr 23
04/23/18 - 04/25/18
Lab Design Conference
Sheraton Philadelphia
Philadelphia, PA, USA
Purificación de agua Norteamérica 20180423
jul 08
07/08/18 - 07/11/18
2018 IAFP Annual Meeting
Salt Palace Convention Center
Salt Lake City, UT, USA
Purificación de agua, Investigación en ciencias de la vida ,Microbiología industrial Norteamérica 20180708
oct 16
10/16/18 - 10/17/18
Gulf Coast Conference 2018
Moody Gardens Convention Center
Galveston, TX, USA
Purificación de agua,Medicamentos de molécula pequeña,Reactivos, compuestos químicos y material de laboratorio, Investigación en ciencias de la vida ,Fabricación biofarmcéutica ,Analítica y preparación de la muestra Norteamérica 20181016