Abstract: An improved process for preparing carbon fibers in a gaseous phase reaction comprising introducing a gas mixture comprising at least one carbon compound, at least one inorganic transition metal compound gas and at least one carrier gas into a reactor and subjecting the mixture to a temperature of 600.degree. C. to 1300.degree. C. in the reactor for inducing growth of carbon fibers.

Abstract: A mixture of sulfuric acid and hydrochloric acid essentially free from dissolved sulfur dioxide to be used in a chlorine dioxide reactor is produced by reacting chlorine and sulfur dioxide in at least two reaction zones. In the bottom of a primary reaction zone the total amount of sulfur dioxide needed for the mixed acid production is introduced in an aqueous mixture of sulfuric and hydrochloric acid containing dissolved chlorine and gaseous chlorine. The sulfur dioxide reacts with chlorine in the aqueous phase to produce sulfuric acid and hydrochloric acid. The mixed acid produced in the primary reaction zone contains dissolved quantities of sulfur dioxide and is forwarded to a secondary reaction zone. Chlorine is introduced into the lower part of the secondary reaction zone. The amount introduced can be the total amount of chlorine to be used in the production of the mixed acid for the chlorine dioxide reactor, or it can be a part of that amount, the balance being introduced in the primary reaction zone.