Abstract: A fuel-injected piston combustion engine with centrally rotating cylinder block and cylinder arranged centrally therein, the rotating cylinder block being surrounded by a stationary housing which seals it off by sealing rings, the housing being provided with two scavenging ports between angles of rotation 180.degree. and 270.degree. calculated in direction of rotation from injection nozzles, an outlet port discharging expanded gases, while an inlet port is connected with a scavenging blower. On both sides in the stationary housing there is mounted eccentrically to the axis of the housing a linear uncranked drive shaft having a rigidly attached connecting arm which at an opposite end, in a piston, is pivotally mounted movable back and forth in the cylinder, arranged in a centrally rotating cylinder block mounted free of forces, in the vicinity of a piston end wall in a connecting rod bearing.

Abstract: Electrolytic chromic acid bath for fissured chrome plating is based upon hexavalent chromium, which contains as a catalyst a water-soluble pyridinium type compound, e.g., a five carbon atom heterocyclic ring compound containing a nitrogen atom in the ring and a proton on this nitrogen atom to constitute a nitrogenous positive ion together with sulfate, or halide ions constituting the negative ions in the bath. The sulfate and/or halogen salts are preferably in the form of addition compound with the cations of pyridinium, 2-methyl pyridinium, 3-methyl pyridinium, 4-methyl pyridinium, 2,4-dimethyl pyridinium, 2,6-dimethyl pyridinium trimethyl pyridinium, methyl ethyl pyridinium, quinolinium, methylquinolinium or acridinium.