08 TECHNICAL INFORMATION | PRODUCT-SPECIFIC SECTION
Recommendations • Glass filters should always be cleaned immediately after use. • Do not use sharp objects to remove the filtrate to prevent damage to the filter surface.
Chemical cleaning
If some of the pores on the filter disk still remain clogged after mechanical cleaning or if it is desirable to make sure that no residue from previous work remains before filtering a new substance, then thorough chemical cleaning is necessary. The choice of solvent used depends on the nature of the contamination (see example in the following overview).
Barium sulfate Silver chloride Red copper oxide Mercury residue Mercury sulfide
hot conc. sulfuric acid hot ammonia liquor
hot hydrochloric acid and potassium chlorate
hot conc. nitric acid
hot aqua regia
Albumen Grease, oil
hot ammonia liquor or hydrochloric acid
acetone, isopropanol
Other organic substances
hot conc. sulfuric acid with addition of nitric acid, sodium nitrate or potassium dichromate
When chemical cleaning is completed, it should be followed by thorough rinsing with copious amounts of water. Use of hot concentrated phosphoric acid and hot alkali solutions is not recommended, as these may attack the glass surface.
Screwfilters with interchangeable filter disks
With 3 filter sizes, each having 4 filter disks of varying porosity, 12 different filter rates are available. DURAN® screwfilters have a range of benefits compared with conventional filter apparatus: • Interchangeable filter disks • Safe and simple removal of the filtered material • Disks have longer service life, as no damage is caused by scraping off the fiItered material • Filter disks are easy to clean from both sides • Slit sieve (Cat. No. 213403108) can be used in the medium sized screwfilter to support membrane and paper filters • Space saving • Cost-effective; filter disks and apparatus can be ordered individually, as required.
Recommendations The filter disk should be located between 2 FKM gaskets.
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