Abstract: A method and a system for resistance seam welding of a foil and at least one foil support of a fuel cell system. During welding, the thin foil, together with the thicker foil support, is moved relative to the roller electrode while resting on a flat support element. In a suitable welding system, a counter-electrode is designed as a flat support element, such as a welding strip, that is displaceable relative to the roller electrode, the roller electrode being in rolling contact with the foil support, but not with the foil. Depending on whether one foil is to be welded to one or two foil frames, the support element may be designed having a high or a low specific electric resistance.

Abstract: A membrane module for hydrogen separation includes a stack of flat membrane packs disposed adjacent one another so as not to exert a force on one another and a rotationally symmetrical pressure shell enclosing the stack of flat membrane packs. A feed space for a reformate gas is disposed between every two membrane packs in the stack. Each membrane pack has a pair of membrane assemblies and a support structure disposed therebetween and each membrane assembly includes a hydrogen-selective flat membrane supported by at least one membrane frame.

Abstract: A method and a system for resistance seam welding of a foil and at least one foil support of a fuel cell system. During welding, the thin foil, together with the thicker foil support, is moved relative to the roller electrode while resting on a flat support element. In a suitable welding system, a counter-electrode is designed as a flat support element, such as a welding strip, that is displaceable relative to the roller electrode, the roller electrode being in rolling contact with the foil support, but not with the foil. Depending on whether one foil is to be welded to one or two foil frames, the support element may be designed having a high or a low specific electric resistance.

Abstract: A membrane module for hydrogen separation includes a stack of flat membrane packs disposed adjacent one another so as not to exert a force on one another and a rotationally symmetrical pressure shell enclosing the stack of flat membrane packs. A feed space for a reformate gas is disposed between every two membrane packs in the stack. Each membrane pack has a pair of membrane assemblies and a support structure disposed therebetween and each membrane assembly includes a hydrogen-selective flat membrane supported by at least one membrane frame.

Abstract: The invention relates to the production and purification of salts of 6,8-bis (amidiniumthio)octanoic acid, its enantiomers (+)-6,8-bis(amidiniumthio)octanoic acid and (-)-6,8-bis (amidiniumthio)octanoic acid and of the esters of these compounds as well as to their use to produce dihydrolipoic acid and .alpha.-lipoic acid.

Abstract: The invention is relative to a thioctic acid with a predominant amount of an enantiomer and a novel modification, in the case of which the X-ray powder diffractograms show a characteristic reflex in the range of 23.4 to 22.7.degree. 2 theta(Cu) which shifts in the direction of the smaller angular values as the enantiomer content increases.

Abstract: The invention relates to (+) and (-)-8-halogen-6-hydroxy-octanoic acid enantiomers wherein the halogen is Cl, Br, or I, and their respective preparatory processes.

Abstract: The invention relates to (+) and (-)-8-halogen-6-hydroxy-octanoic acid enantiomers wherein the halogen is Cl, Br, or I, and their respective preparatory processes.

Abstract: The invention relates to the production and purification of salts of 6,8-bis(amidiniumthio) octanoic acid, its enantiomers (+)-6,8-bis(amidiniumthio)octanoic acid and (-)-6,8-bis (amidiniumthio)octanoic acid and of the esters of these compounds as well as to their use to produce dihydrolipoic acid and .alpha.-lipoic acid.

Abstract: The synthesis of pure enantiomers of 8-chloro-6-sulfonyloxy-octanoic acids and their alkyl esters and of pure enantiomers of 6,8-dichloro-octanoic acid and its alkyl esters as intermediates for the synthesis of the enantiomers of .alpha.-liponic acid as well as a method for converting the two enantiomers of 8-chloro-6-hydroxy-octanoic acid into an enantiomer of .alpha.-liponic acid.

Abstract: Method for the conversion of the enantiomers of .alpha.-lipoic acid into the corresponding racemic mixture by racemizing the .alpha.-lipoic acid (pure optical isomers of .alpha.-lipoic acid or mixtures of optical isomers of .alpha.-lipoic acid wherein one of the optical isomers is present in excess) at temperatures of between 110.degree. C. and 200.degree. C. at pressures of from normal pressure up to 50 bar for a reaction time of 10 to 48 hours.

Abstract: RS-thioctic acid with a novel morphology which is obtained by a recrystallization process.

Abstract: The pure enantiomers of alpha-lipoic acid are obtained by formation of the diastereomeric salt pairs with the optical antipodes of alpha-methylbenzylamine in solution.

Abstract: The subject matter of the invention are S-substituted 2-azido-3-mercapto-propionic acid esters of the general formula ##STR1## in which R.sup.1 is a methyl or ethyl group and R.sup.2 is an unsubstituted or substituted alkyl group, a cycloalkyl group, an unsubstituted or substituted aromatic or heteroaromatic group or a benzyl group, and a process for their production by reaction of a methyl or ethyl ester of 2-chloroacrylic acid with a corresponding thiol to form an S-substituted 2-chloro-3-mercapto-propionic acid ester and subsequently exchanging the chlorine atom with an azido group as well as use of the compounds of formula (I) as intermediate products in the production of D,L-cysteine or derivatives of D,L-cysteine.

Abstract: The subject matter of the invention is a process for the production of N-acetyl-2,3-dehydroaminocarboxylic acid esters by reaction of the corresponding 2-azido-carboxylic acid esters with a mixture of one part by volume of acetic anhydride and 1.5 to 5 parts by volume of acetic acid in the presence of rhenium VII sulfide and/or oxide and at a temperature between 50.degree. and 150.degree. C., in a given case, in the simultaneous presence of dry hydrogen chloride.