precipitated low molecular weight fluoropolymer can be controlled by controlling the rate of cooling the reaction gas the separator or collector is for example of a settling chamber type using gravitational force of a collision plate or guide plate type using inertial force or of a cyclon type or bug filter type using centrifugal force for efficient separation and collection of the precipitated particles of the low molecular weight fluoropolymer it is important that the linear velocity of the reaction gas in the separator or collector be as low as possible the reaction apparatus needs to include pumps blowers and or fans transferring the reaction gas into the cooler and then into the separator or collector and after separating and collecting the precipitated fluoropolymer for returning the gas phase to the reactor the capacities of the pumps blowers and or fans should be such that the hot reaction gas can be extracted preferably continuously from the reactor before decomposition of the molecular weight reduced fluoropolymer existing in the gas if the reaction gas is extracted too slowly a considerable portion of the molecular weight reduced polymer decomposes within the reactor on the other hand extracting the reaction gas at an excessively high rate worsens the heat efficiency of the reactor it is suitable that the volume of the reaction gas extracted in every minute is nearly equal to the interior volume of the reactor a nickel tube about 25 mm in diameter and 1 m in length was used as a reactor the tube was kept heated at 500 u00b0 c and a mixture of 5.