After the step in Section 7.2 has been completed and the sample has cooled,
add 2 mL of water and 3 mL of 30% H O . Cover the vessel with a watch glass or vapor 2 2
recovery device and return the covered vessel to the heat source for warming and to start
the peroxide reaction. Care must be taken to ensure that losses do not occur due to
excessively vigorous effervescence. Heat until effervescence subsides and cool the vessel.