Process for preparing halophosphazene mixtures

A process for producing high cyclic chlorophosphazene oligomers having the recurring unit --NPCl.sub.2).sub.n wherein n ranges from 3 to about 7, said process comprising establishing in an inert solvent a dispersion of finely divided ammonium chloride in an amount sufficient to initiate formation of chlorophosphazene by reacting hydrogen chloride with from about 10 to about 65 weight percent of the total ammonia used in the process, heating said dispersion to the reflux temperature of the solvent, adding simultaneously to said dispersion phosphorus pentachloride as a solution of from about 40 to about 70 weight percent of phosphorus pentachloride in an additional amount of said solvent at a rate such that no free concentration of phosphorus pentachloride is allowed to exist in the reaction mass and ammonia such that the total amount of ammonia employed for both the formation of ammonium chloride and the chlorophosphazene is from the theoretical amount required to react with phosphorus pentachloride to about 30 percent by weight in excess of the theoretical amount, maintaining the reflux temperature for from about 1/2 to about 2 hours after completing the addition and recovering the cyclic chlorophosphazene oligomers.