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TRANG CHỦ Sản phẩm Parr Sample Preparation Acid Digestion

Parr’s Acid Digestion Vessels are designed specifically for preparing laboratory samples for chemical analysis. Parr offers both general purpose and microwave acid digestion vessels for dissolving or digesting inorganic or organic samples in strong acids or alkalis in pressure vessels at elevated temperatures and pressures, with complete containment and recovery.

  Acid Digestion Vessels

Parr acid digestion vessels offer an alternative to the task of preparing analytical samples for analysis. By combining the unique chemical inertness of PTFE with the advantages of a sealed pressure vessel, these convenient vessels offer a rapid procedure for sample dissolution or digestion that has several important advantages over more traditional methods of sample preparation. By providing a convenient means for holding strong mineral acids or alkalis at temperatures well above normal boiling points, these sturdy digestion vessels will:

  • Accelerate digestions which otherwise would proceed slowly if conducted in an open container at atmospheric pressure.
  • Permit the use of strong acids, such as HF or aqua regia, which will attack most other conventional containers.
  • Dissolve analytical samples without losing trace elements and without adding unwanted contaminants from the container itself.
  • Generate a vigorous chemical action that is a great time saver in analytical procedures.
  • Obtain complete digestion or dissolution of samples that react slowly or incompletely when treated by other methods.

Chemists who have worked with sealed glass tubes and other cumbersome digestion devices will recognize the attractiveness of these convenient digestion vessels.

 

  Microwave Acid Digestion Vessels

 

In addition to unique acid digestion vessels, Parr offers a line of chemically-inert vessels in which microwave heating can be used for rapid sample dissolution in a sealed vessel. These vessels can be placed directly in a microwave oven for specific, high speed heating to drastically reduce the time required to dissolve or digest an analytical sample. They are made in two sizes that can be heated in any of the commercial microwave ovens regularly offered for household use. Specially constructed and/or vented ovens are not required.

Metal Jacketed and Microwave Styles

 

 

Parr PTFE lined acid digestion vessels are made in two different styles: There is a line of metal-jacketed vessels that can be heated in an oven, sand bath, oil or water bath and in other conventional ways, and a line of digestion vessels developed specifically for rapid heating in a microwave oven. Both styles are made in several sizes, offering a broad selection of vessels ranging from economical models for routine tests to massive styles for procedures involving extreme conditions or potentially hazardous samples. Each of these vessels has a thick walled PTFE liner that completely isolates the charge from the supporting body. These liners are removable and can be charged or emptied while outside of the vessel to eliminate any possible contamination from acid contact with metal parts. They can be replaced if they become damaged or contaminated.

The Nature of PTFE

 

  Unique Closures

Several designs are used to keep Parr acid digestion vessels tightly sealed during consecutive heating and cooling cycles when conventional seals might leak. One of these designs uses a tapered closure between the PTFE cup and cover with an unusually long sealing face that tends to become self-sealing. This long path also minimizes the tendency for acid migration through the joint. vessels using this design can be sealed by simply turning down a knurled cap by hand without using a wrench or spanner. For applications requiring higher temperatures and pressures, the PTFE liners are made with a broad, flanged closure and sealed by tightening the vessel cap with a spanner or, in a larger design, by using cap screws to develop the sealing force. Tight closures for the PTFE cup in Parr microwave vessels are developed and maintained with self-sealing PTFE O-rings.

 

  Spring-Loaded Seals

Since PTFE has a much larger coefficient of thermal expansion than the materials within which a liner is enclosed, a PTFE liner will expand and contract more than its enclosure when these vessels are heated and cooled. To compensate for this difference and to maintain a constant loading on the PTFE seal, all Parr acid digestion vessels have spring-loaded closures which will continue to maintain pressure on the liner seal throughout the operating cycle, and particularly during cooling when PTFE parts would otherwise relax and leak.

 

  Safety Blow-Off Discs

Safety blow-off assemblies are provided on most Parr Acid Digestion Vessels to protect the vessel and the operator from the hazards of unexpected or dangerously high internal pressures. The blow-off feature consists of an area with an intentionally weakened structure allowing the vessel to fail in a predictable and reasonably safe manner in the event it becomes over pressurized.  The burst pressure in each installation is established by a frangible metal disc installed as a sandwich with a matching inner disc which serves as a corrosion barrier to protect the main disc from corrosive vapor.

 

 

Acid Digestion Vessel Selection Guide