obsolete mathematical expression second order irreversible mass action kinetics, continuous scheme Reaction scheme where the products are created from the reactants and the change of a product quantity is proportional to the product of reactant activities. The reaction scheme does not include any reverse process that creates the reactants from the products. The change of a product quantity is proportional to two reactant quantity. It is to be used in a reaction modelled using a continuous framework. <n0:math xmlns:n0="http://www.w3.org/1998/Math/MathML"> <n2:semantics xmlns:n2="http://biomodels.net/SBO/" definitionURL="http://biomodels.net/SBO/#SBO:0000062"> <n2:lambda> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000036">k</n2:ci></n2:bvar> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000010">R</n2:ci></n2:bvar> <n2:apply> <n2:times /> <n2:ci>k</n2:ci> <n2:apply> <n2:product /> <n2:bvar><n2:ci> i </n2:ci></n2:bvar> <n2:lowlimit><n2:cn type="integer"> 1 </n2:cn></n2:lowlimit> <n2:uplimit><n2:ci> 2 </n2:ci></n2:uplimit> <n2:apply> <n2:selector /> <n2:ci type="vector">R</n2:ci> <n2:ci> i </n2:ci> </n2:apply> </n2:apply> </n2:apply> </n2:lambda> </n2:semantics> </n0:math>