NOVELTY - Uses single-piece contactor shaft (135) assembly to avoid the need for precise alignment on installation.    USE - For use in alkylation of liquid butane with sulfuric acid.    ADVANTAGE - Single-piece contactor shaft avoids precise and time-consuming alignment, thus minimizing vibration and stress forces.    DETAILED DESCRIPTION - The alkylation reactor and contactor shaft assembly comprises:    (i) means for mixing liquid butane and sulfuric acid in the reactor vessel (120);    (ii) hydraulic head (125) having an open-end portion and a closed-end portion, removable attached to an end of the vessel and in fluid communication with the vessel, the head having a circular aperture in a central portion and the center axis of the aperture being parallel with the longitudinal axis of the vessel;    (iii) bell-shaped bearing housing (130) having an open-end portion and a closed-end portion, the open-end portion having larger diameter than the closed-end portion, the open-end portion being fixed to an outer portion of the closed-end portion, the closed-end portion has circular aperture and the central axis in the closed-end portion of the bearing housing being aligned with the center axis of the circular aperture in the hydraulic head;    (iv) a single-piece contactor shaft (135) of cylindrical shape and having first end portion and second end portion, the shaft being 51-61 ins long and 2-4 ins diameter, the first end portion being disposed through and protrudes from circular aperture in the head to form a first annular passageway between the shaft and the head, the first end portion is configured for receipt of a rotatable mixing blade, the second end portion is disposed through and protrudes from the aperture in the closed end portion to form a second annular passageway between the shaft and the bearing housing, and the second end portion of the single-piece contactor is configured for attachment to a rotatable motor shaft;    (v) a doughnut-shaped mechanical seal (140) for preventing passage of the liquid butane and sulfuric acid and the alkylate product through the first passageway;    (vi) a doughnut-shaped support bearing (145) for supporting the contactor shaft and disposed in the second passageway;    (vii) a rotatable mixing blade (150) of radially symmetrical configuration and with a centrally located aperture; and    (viii) an electric motor (155) for generating a rotational force for driving the shaft assembly. The reactor and shaft assembly is configured so that during operation, the contactor shaft is driven by rotation of the motor shaft (160) and the mixing blade is driven by the rotation of the shaft, to mix the liquid butane and sulfuric acid.    INDEPENDENT CLAIMS are included for:    (a) the hydraulic head and contactor shaft assembly; and    (b) a method for mixing liquid butane and sulfuric acid in the reactor vessel assembly.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional side view of the contactor assembly.    vessel (120)    hydraulic bead (125)    bearing (130)    contactor shaft (135)    seal (140)    bearing (145)    mixing blade (150)    motor (155)    motor shaft (160)    coupling (165)