Abstract: In an acid digestion reaction performed in a vessel, an elastic lid or septum can be mounted to the mouth of the vessel with a flanged band. In response to determining that a predetermined pressure has been reached in the vessel, a closing force being applied to the lid or septum can be reduced to initiate venting from the vessel. One or more parameters, including the closing force, can be monitored during the venting, and the closing force can be responsively adjusted to optimize the venting. The closing force can be provided by a clamping apparatus that may or may not include a hydraulic system. The clamping apparatus can be configured to increase the closing force in response to increased hydraulic pressure in the hydraulic system. The clamping apparatus can include an engager having an upwardly extending recess extending at least partially around a downwardly protruding portion of the engager.

Abstract: A pressure-measuring vessel system for microwave assisted chemical processes is disclosed. The vessel system includes a pressure resistant vessel that is otherwise transparent to microwave radiation, a pressure-resistant closure for the mouth of the vessel, with portions of the closure including a pressure resistant synthetic membrane, a pressure transducer external to the vessel, and a tube extending from the transducer, through the membrane and into the vessel for permitting the pressure inside the vessel to be applied against the transducer while the closure and membrane otherwise maintain the pressure resistant characteristics of the vessel.

Abstract: A pressure-measuring vessel system for microwave assisted chemical processes is disclosed. The vessel system includes a pressure resistant vessel that is otherwise transparent to microwave radiation, a pressure-resistant closure for the mouth of the vessel, with portions of the closure including a pressure resistant synthetic membrane, a pressure transducer external to the vessel, and a tube extending from the transducer, through the membrane and into the vessel for permitting the pressure inside the vessel to be applied against the transducer while the closure and membrane otherwise maintain the pressure resistant characteristics of the vessel.

Abstract: A pressure-measuring vessel system for microwave assisted chemical processes is disclosed. The vessel system includes a pressure resistant vessel that is otherwise transparent to microwave radiation, a pressure-resistant closure for the mouth of the vessel, with portions of the closure including a pressure resistant synthetic membrane, a pressure transducer external to the vessel, and a tube extending from the transducer, through the membrane and into the vessel for permitting the pressure inside the vessel to be applied against the transducer while the closure and membrane otherwise maintain the pressure resistant characteristics of the vessel.

Abstract: A pressure-measuring vessel system for microwave assisted chemical processes is disclosed. The vessel system includes a pressure resistant vessel that is otherwise transparent to microwave radiation, a pressure-resistant closure for the mouth of the vessel, with portions of the closure including a pressure resistant synthetic membrane, a pressure transducer external to the vessel, and a tube extending from the transducer, through the membrane and into the vessel for permitting the pressure inside the vessel to be applied against the transducer while the closure and membrane otherwise maintain the pressure resistant characteristics of the vessel.

Abstract: An instrument is disclosed for microwave-assisted chemical processes that avoids tuning discrepancies that otherwise result based upon the materials being heated. The instrument includes a source of microwave radiation, a waveguide in communication with the source, with at least a portion of the waveguide forming a cylindrical arc, a cylindrical cavity immediately surrounded by the cylindrical arc portions of the waveguide, and at least three slotted openings in the circumference of the circular waveguide that provide microwave communication between the waveguide and the cavity.

Abstract: A pressure-sealing, pressure-monitoring closure for non-invasively sealing a reaction vessel to a defined release pressure in microwave-assisted chemistry is disclosed. The closure includes a pressure-resistant, microwave-transparent reaction vessel, one portion of which defines a mouth, a flexible pressure-transmitting releasable cover assembly on the mouth of the vessel, a pressure transducer on the cover and external to the vessel for monitoring the pressure in the vessel as exerted against the flexible cover, and a clamp for urging the vessel, the cover and the transducer together under a defined force so that when the pressure in the vessel exceeds the defined force, the cover can flex and release the pressure from the vessel.

Abstract: An instrument is disclosed for microwave-assisted chemical processes that avoids tuning discrepancies that otherwise result based upon the materials being heated. The instrument includes a source of microwave radiation, a waveguide in communication with the source, with at least a portion of the waveguide forming a cylindrical arc, a cylindrical cavity immediately surrounded by the cylindrical arc portions of the waveguide, and at least three slotted openings in the circumference of the circular waveguide that provide microwave communication between the waveguide and the cavity.

Abstract: A method is disclosed for carrying out microwave-assisted chemical reactions. The method includes the steps of adding reagents to a pressure-resistant microwave-transparent vessel, securing the vessel against pressure release with a penetrable septum made of a material that can be penetrated by a needle while surrounding and sealing against the needle even after penetration to thereby maintaining the pressure integrity of the vessel, thereafter inserting a needle through the penetrable septum and into the pressure-secured vessel to provide fluid communication to the interior of the scaled pressure-resistant vessel through the needle, applying mechanical pressure against the septum while the needle is inserted therethrough, and irradiating the vessel and its contents with microwaves with the needle inserted therein.

Abstract: A pressure-measuring vessel system for microwave assisted chemical processes is disclosed. The vessel system includes a pressure resistant vessel that is otherwise transparent to microwave radiation, a pressure-resistant closure for the mouth of the vessel, with portions of the closure including a pressure resistant synthetic membrane, a pressure transducer external to the vessel, and a tube extending from the transducer, through the membrane and into the vessel for permitting the pressure inside the vessel to be applied against the transducer while the closure and membrane otherwise maintain the pressure resistant characteristics of the vessel.

Abstract: An instrument for microwave-assisted chemical processes is disclosed that provides greater flexibility in carrying out microwave-assisted chemistry under varying conditions. The instrument includes a source of microwave radiation, and a cavity in communication with the source, with the cavity including at least one wall formed of two engaged portions that form a barrier to the transmission of microwaves when so engaged. The engaged portions are disengagable from one another, and one of the portions includes a microwave-attenuating opening.

Abstract: A volatiles analyzer is disclosed that includes a source of microwave radiation that can selectively produce at least one predetermined frequency of microwave radiation. A cavity is in communication with the source. The walls of the cavity form a twelve faced polyhedron in which eight faces form a regular octagon and having two faces that are both non-parallel and non-perpendicular to the eight faces of the regular octagon. The polyhedron focuses microwave energy of the predetermined frequency on a balance pan while supporting a plurality of TM and TE modes in the cavity.

Abstract: An instrument is disclosed for microwave-assisted chemical processes that avoids tuning discrepancies that otherwise result based upon the materials being heated. The instrument includes a source of microwave radiation, a waveguide in communication with the source, with at least a portion of the waveguide forming a cylindrical arc, a cylindrical cavity immediately surrounded by the cylindrical arc portions of the waveguide, and at least three slotted openings in the circumference of the circular waveguide that provide microwave communication between the waveguide and the cavity.

Abstract: An instrument is disclosed for microwave-assisted chemical processes that avoids tuning discrepancies that otherwise result based upon the materials being heated. The instrument includes a source of microwave radiation, a waveguide in communication with the source, with at least a portion of the waveguide forming a cylindrical arc, a cylindrical cavity immediately surrounded by the cylindrical arc portions of the waveguide, and at least three slotted openings in the circumference of the circular waveguide that provide microwave communication between the waveguide and the cavity.

Abstract: An instrument for microwave-assisted chemical processes is disclosed that provides greater flexibility in carrying out microwave-assisted chemistry under varying conditions. The instrument includes a source of microwave radiation, and a cavity in communication with the source, with the cavity including at least one wall formed of two engaged portions that form a barrier to the transmission of microwaves when so engaged. The engaged portions are disengagable from one another, and one of the portions includes a microwave-attenuating opening.

Abstract: An instrument is disclosed for microwave-assisted chemical processes that avoids tuning discrepancies that otherwise result based upon the materials being heated. The instrument includes a source of microwave radiation, a waveguide in communication with the source, with at least a portion of the waveguide forming a cylindrical arc, a cylindrical cavity immediately surrounded by the cylindrical arc portions of the waveguide, and at least three slotted openings in the circumference of the circular waveguide that provide microwave communication between the waveguide and the cavity.

Abstract: A volatiles analyzer is disclosed that includes a source of microwave radiation that can selectively produce at least one predetermined frequency of microwave radiation. A cavity is in communication with the source. The analyzer includes an analytical pan balance with at least its balance pan in the cavity. The walls of the cavity form a polyhedron that focuses microwave energy of the predetermined frequency on the balance pan while supporting a plurality of TM and TE modes in the cavity.

Abstract: A volatiles analyzer is disclosed that includes a source of microwave radiation that can selectively produce at least one predetermined frequency of microwave radiation. A cavity is in communication with the source. The analyzer includes an analytical pan balance with at least its balance pan in the cavity. The walls of the cavity form a polyhedron that focuses microwave energy of the predetermined frequency on the balance pan while supporting a plurality of TM and TE modes in the cavity.

Abstract: The invention is an apparatus and method for obtaining accurate sample weight measurements during sample heating within a heating cavity by substantially reducing the convection currents that disrupt accurate sample weight measurement. The apparatus includes a heating cavity in which a sample can be placed, a source for introducing microwaves into the heating cavity, and an analytical balance for measuring the weight of the sample while the sample is in the cavity, and an air shield that is secured to the inside of the heating cavity so that the air shield will not contact the analytical balance. The air shield, which is made of material that is permeable to microwave radiation and yet absorbent of volatiles, is positioned in the heating cavity to reduce the convection current rising from the sample as the sample is heated.