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Apparatus and Supplies
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If your use of distilled water is minimal (e.g., a few gallons per month) then simply purchase the distilled water at your local supermarket.
If you use a sufficient amount to justify the purchase of a water treatment device, then the following information will prove helpful. A definition of terms will assist you as you review the process chart at right.
Dissolved Ionized Solids—Solids that cannot be removed by filtration. Major examples are iron, calcium, magnesium, chlorine, carbonates and sodium.
Dissolved Gases—Examples are oxygen, nitrogen and carbon dioxide. Dissolved Organics—Sediments, microorganisms and other organic
material.
Bacteria—Single-celled microorganisms, some of which are the cause of disease.
Pyrogens—Toxic, fever-producing substances formed by various microorganisms.
Particulates—Matter in a fine state of subdivision.
If the water produced will be used by both the biology and chemistry departments, then distilled water is your best choice. In fact, if you examine the chart, you will quickly conclude that, except for dissolved gases, a still produces the best overall water quality. Deionizing is usually good enough for water needed in general chemistry laboratory activity.
Other factors to consider:
• Water stills require regular cleaning and maintenance.
• Water stills are expensive to operate.
• Water stills take up a lot of space.
• A water still (if properly maintained) can give you decades of service. • Deionizers (demineralizers) do not provide biological quality water.
• Deionizers require repeated expenditures for cartridge replacement.
• Deionizers require little if any maintenance.
Water Purification Process Comparison
Distill, Deionize or Buy H2O?
MAJOR CLASSES OF CONTAMINANTS
E = Excellent (capable of complete or near total removal)
G = Good (capable of removing large percentages)
P = Poor (little or no removal) PURIFICATION PROCESS
DISTILLATION
E
P
G
E
E
E
DEIONIZATION
E
E
P
P
P
P
Demineralizer Accessories, continued
Water Hardness Testing Paper
Easy way to determine water hardness in seconds. Two test papers are packaged in one convenient plastic dispenser. The first test paper allows you to measure water hardness between 0–20 grains per gallon. The second measures water hardness between 10–50 grains per gallon. Both test papers are 4.5 meters in length, enough for over 100 tests.
Desiccators
Desiccator, Scheibler
Heavy flint glass with wide ground glass rim (flange) to provide an air- tight seal. Height 91⁄4". Diameter at widest point 81⁄8". Inside diameter of chamber 6". Use porcelain desiccator plate Catalog No. AP8252 for hot objects or plastic desiccator plate Catalog No. AP1046 for room temperature objects (see page 427). You will need stopcock grease to lubricate and seal the flange ground glass surfaces. See page 427 for stopcock grease. Remember: Never lift a desiccator lid, always slide it from side to side.
DESICCATORS continued on next page.
Water Hardness Testing Paper AB1161
Catalog No.
Description
Price/Each
AB1161
Water Hardness Testing Paper
$12.55
Desiccator, Scheibler AP8250
Catalog No.
Description
Price/Each
AP8250
Desiccator, Scheibler
$76.80
Use a Desiccator
A desiccator will provide an atmosphere with low humidity for the storage of samples, precipitates, crucibles and other equipment.
Desiccants have a limited capacity to absorb moisture from the atmosphere. Learn how to tell when your desiccant is no longer effective.
Do not place hot items in a desiccator. As the items cool, they can create a partial vacuum in the desiccator and may spill when the desic- cator is opened and air rushes in.
Lubricate lip of desiccator and lid with stopcock grease to ensure a good seal.
Desiccator Plate
Dry desiccant like Drierite® or anhydrous calcium chloride
Dissolved Ionized Solids Dissolved Gases Dissolved Organics Particulates
Bacteria Pyrogens