Acid digestion instrument and vessel system

A combination for acid digestion comprising:

• a heating block defined by a vertically oriented shaft opening;
• a reaction vessel in said shaft formed of a polymer that is resistant to acid and other chemical attack at temperatures above 150° C. and that has a structure that when closed is sufficient to withstand pressures above atmospheric pressure;
• and
• a metal sleeve in said shaft in a defined relationship in which the sleeve covers all of the vessel that is in said shaft and some, but not all, of said vessel above said block and above said shaft;
• so that the block heats lower portions of the sleeve, the vessel, and the vessel contents while the upper sleeved and unsleeved portions of the vessel define cooler and unheated portions within the vessel.

A method for acid digestion comprising:

• inserting a metal-sleeved reaction vessel into an opening in a heating block in which the opening has a cross-section corresponding to the cross-section of the metal sleeve, and in which the reaction vessel is formed of a polymer that is resistant to acid and other chemical attack at temperatures above 150° C. and that has a structure sufficient to withstand pressures above atmospheric;
• heating the block to a temperature about 50° C. higher than the reaction temperature desired inside the reaction vessels for a time sufficient for the reagents inside the vessels to reach an equilibrium heated temperature based on the temperature of the heated block semicolon holding the sleeved reaction vessel in the heated block for a time sufficient for the contents of the reaction vessel to digest in acid at the equilibrium temperature;
• removing the heated sleeved reaction vessel from the heating block;
• removing the polymeric reaction vessel from the sleeve;
• and
• cooling the polymeric reaction vessel outside of the sleeve until the reaction vessel and its contents reach a safe operating temperature for opening the reaction vessel at ambient temperatures and pressures.