compressed in the area of said sharptaper and less highly compressed in the remaining portions thereof.
8. A microanalytical tool in accordance with claim 7 including the combination of a ball bearing in the trough formed by the V-shaped sides of said reaction chamber for promoting thorough mixing of reactants which may be placed therein when said tool is rotated about its longitudinal axis.
9. A microanalytical tool for mixing reactants and then filtering the liquid phase reaction products therefrom comprising: a hollow top-like vessel having an elongated tubular portion at one end, said tubular portion being continuous with a radial reaction chamber forming the other end of the vessel, said reaction chamber having a cross sectional area that gradually decreases outwardly along a radial axis normal to the longitudinal axis of said tubular portion, said reaction chamber having a larger internal diameter than said tubular portion, an aperture large enough to permit insertion of a pipette tip therethrough formed in said reaction chamber axially aligned with said tubular portion whereby selected reactants may be placed through the aperture into a trough formed from the sides of said reaction chamber and be retained therein for reaction when said device is held generally hori