Are there such heating plates available (heating plate cum magnetic stirrer), which could control the temperature of a reaction mixture in a way that it cools the rxn mixture down at, for example, 3 or 5 degree Celsius per hour ?
I'm not sure about hot plates but you could buy double walled glass cell with inlet and outlet in between inner and outer wall so you can flow a liquid withspecific temperature and control the temperature of the reaction. The liquid would be flown and controlled by a bath circulator. Not the cheapest but possibly the most accurate, I think.