Abstract: A liquid and gas tank is provided for operation, in particular, in satellites subject to low acceleration, that utilizes a separation force produced by surface tension to collect liquid in a privileged zone of the tank without allowing gas to escape via the privileged zone. The tank includes an outer first shell element having a curvilinear shape, and having at one end a surface portion S of radius of curvature r which is concave on a side that contacts liquid. The tank also includes an inner second shell element fixed to the first element, being convex in shape on a side that contacts liquid, and curvilinear in shape and including a surface portion S' having a part which is slightly inclined relative to the surface portion S in the privileged zone forming a narrowest zone between the surface portions S and S', the surface portion S' having a radius of curvature r' which is less than the radius of curvature r, wherein liquid is urged into the narrowest zone due to a capillary effect.