The invention relates to a thermal inverter (1, 2) for generating from a parent compound a first fluid of first molecules (H2) with a first molecular weight and a second fluid of second molecules (O2) with a second molecular weight, whereby the first molecular weight of the first molecules (H2) is less than the second molecular weight of the second molecules (Oz). In a reaction device (1) the parent compound is decomposed into a mixture compound of the first molecules (H2) and the second molecules (O2). In order to improve the efficiency of such a thermal inverter the invention proposes a gas separator device (2) comprising a mixture inlet (26) for the mixture compound of the first and the second molecules at a bottom section (24) of the gas separator device (2) and a first (27) and a second outlet (28) at a top section (25) of the gas separator device (2), the first outlet (27) providing substantially the first molecules (H2) and the second outlet (28) providing substantially the second molecules (O2), the gas separator device (2) further comprising guiding elements (6) for guiding the first and second molecules (H2, O2) from the mixture inlet (26) towards the first and second outlet (27, 28) in a coiled path, wherein the coiled path is confined by a sidewall (29).