PARR Acid Digestion Bombs

PARR Acid Digestion Bombs

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 its 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 bombs 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

The Nature of Teflon

Unique Closures

Several designs are used to keep Parr acid digestion bombs 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. Bombs 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 bomb 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 bombs 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 bombs are heated and cooled. To compensate for this difference and to maintain a constant loading on the PTFE seal, all Parr acid digestion bombs 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 Rupture Discs

Safety rupture discs are provided in most Parr acid digestion bombs to protect the bomb and the operator from the hazards of unexpected or dangerously high internal pressures. 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 rupture disc from corrosive vapor.

Acid Digestion Bomb Selection Guide

Acid Digestion & Microwave Digestion Vessels
Model Number 4744 4745 4746 4747 4748 4749 4781 4782
Size, mL 45 23 23 23 125 23 23 45
Maximum Charge, grams
Inorganic Sample 2.0 1.0 1.0 1.0 5.0 1.0 1.0 2.0
Organic Sample 0.2 0.1 0.1 0.1 0.5 0.1 0.1 0.2
Recommended Maximum Temperature, °C 250 150 275 275 250 250 250 250
Absolute Maximum Temperature, °C 250 250 275 275 250 250
Absolute Maximum pressure, psig 1800 1200 5000 3300 1900 1800 1200 1200
Body Material Stainless Steel Stainless Steel Stainless Steel Nickel Stainless Steel Stainless Steel High Strength Polymer High Strength Polymer
Cup Seal Flanged Tapered Tapered Tapered Flanged Flanged Teflon O-ring Teflon O-ring
Overpressure Protection Rupture Disc Rupture Disc Rupture Disc Rupture Disc Rupture Disc Rupture Disc Compressible Relief Disc Compressible Relief Disc
Closure Style Spanner Wrench Hand Tighten Spanner Wrench Spanner Wrench Six Cap Screws Spanner Wrench Hand Tighten Hand Tighten
Vessel Dimensions, cm
Overall Height 13.41 8.56 12.57 12.57 15.21 8.33 11.2 14.3
Maximum O.D. 6.35 5.99 8.41 8.41 9.45 6.35 7.8 7.8
Cup Dimensions, cm
Inside Diameter 2.64 3.10 3.10 3.10 4.45 2.64 3.1 3.1
Inside Depth 9.47 3.09 3.18 3.18 8.26 4.39 3.07 6.12
Vessel Weight, grams 1430 965 3700 3700 3750 1020 515 625
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