An object of the present invention is to provide a reaction solution for use in emulsion polymerization, in which foaming is suppressed in deoxygenation operations such as bubbling operation of inert gas and deaeration operation. .. In order to solve the above problems, a reaction solution for use in emulsion polymerization, comprising water, a monomer, a surfactant and an organic solvent having an octanol/water partition coefficient (Log Kow) of 0.5 or more. A reaction solution is provided which is characterized by containing. [Selection diagram] None
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