Abstract: Heating of polyvinyl chloride, in particular plasticizer-containing polyvinyl chloride, to a temperature of from 250.degree. to 500.degree. C. in the absence of oxygen gives a low-chlorine, carbon-containing residue, plasticizer and hydrogen chloride.

Abstract: Process for conditioning waste sulfuric acid which is prone to precipitation of tars or resins, which comprises adding emulsifiers, preferably long-chain polyethers, to the waste sulfuric acid.

Abstract: The invention relates to the dioxane adduct of 2-hydroxynaphthalene-6-carboxylic acid which adduct comprises 1 mol of 1,4-dioxane and about 2 mol of 2-hydroxynaphthalene-6-carboxylic acid per mol. The invention further relates to a process for the preparation of this adduct, wherein the 2-hydroxynaphthalene-6-carboyxlic acid is dissolved in dioxane or a mixture thereof with water or with an organic solvent and then allowed to crystallize.

Abstract: The invention relates to the dioxane adduct of 2-hydroxynaphthalene-6-carboxylic acid which adduct comprises 1 mol of 1,4-dioxane and about 2 mol of 2-hydroxynaphthalene-6-carboxylic acid per mol. The invention further relates to a process for the preparation of this adduct, wherein the 2-hydroxynaphthalene-6-carboxylic acid is dissolved in dioxane or a mixture thereof with water or with an organic solvent and then allowed to crystallize.

Abstract: The invention relates to a process for purification of 2-hydroxynaphthalene-6-carboxylic acid by recrystallization. In this process, the crude acid is recrystallized from water-miscible linear or cyclic aliphatic ethers, aliphatic polyethers or aliphatic hydroxy ethers or from at least 10% strength by weight aqueous solutions of these ethers. Recrystallization from a 35-90% strength by weight aqueous solutions of 1,4-dioxane is particularly preferred.

Abstract: A process is described for the removal of dimethyl ether in methyl chloride by catalytic cleavage by means of hydrogen chloride. Dimethyl ether is present as an impurity in crude methyl chloride produced by the catalytic esterification of methanol. The crude methyl chloride is cooled so that water and hydrogen chloride separate out. Gaseous hydrogen chloride is then added to the methyl chloride in an amount corresponding to at least twice the molar amount of dimethyl ether, and the gaseous mixture is passed over a methanol esterification contact catalyst at an elevated temperature.

Abstract: A process for the separation of heavy metal components, especially of compounds of cadmium, mercury and lead, from crude phosphoric acid obtained according to the Odda process, which comprises adjusting this crude phosphoric acid with ammonia to a pH of from 0.5 to 1.5, contacting it subsequently with a diorganyl-dithiophosphorus compound and an adsorbent, and then separating the acid from the absorbent containing the heavy metal impurities.

Abstract: In the regeneration of aqueous waste sulfuric acid by distilling off water often foam is formed which severely interferes with the work-up of the acid. This formation of foam is suppressed by adding alkylsulfonic and/or alkylarylsulfonic acids.

Abstract: The foam formation arising when aqueous waste sulfuric acid is concentrated can be suppressed by adding aromatic nitro compounds such as nitrobenzene to the acid.

Abstract: Gray cast iron can be protected against corrosion by the vapors of boiling concentrated sulfuric acid when a compound containing positive nitrogen, e.g., nitrogen oxide, is introduced into the gas space between the cast iron to be protected and the boiling sulfuric acid.

Abstract: Gray cast iron can be protected against corrosion in boiling concentrated sulfuric acid if the acid contains precious metals such as gold or the metals of the platinum group. It is possible to add small amounts of compounds of the precious metal to the acid or to bring both the gray cast iron and the acid into contact with metal sheets or wires of the precious metal. It is also possible to use small amounts of the precious metal as an alloying element of the gray cast iron.

Abstract: When distilling or boiling concentrated sulfuric acid in a vessel of gray cast iron the corrosion resistance of the apparatus is improved by using an alloy containing from0.2 to 1.6 % of silicon0 to 0.2 % of phosphorus0.6 to 2.5 % of copper0 to 3.5 % of nickelBesides the usual elements for gray cast iron and a graphite portion in a finely divided form in a pearlitic skeleton.

Abstract: Contaminated sulfuric acid which may contain water, organic compounds and inorganic salts is converted to almost pure concentrated sulfuric acid by passing the acid through a Pauling plant and distilling the concentrated contaminated acid.Addition of nitric acid improves the decomposition of organic compounds and ammonium salts of the contaminated acid.

Abstract: Two-step-process for regenerating dilute sulfuric acid which may contain organic and inorganic impurities such as heavy metal salts. In the first step the impure acid is distilled in vacuo and in the second step concentrated in a Pauling apparatus.