Patent ID: 8293180

Claim:
An apparatus for distinguishing a liquid reducing agent, comprising: a heating element arranged in a reducing agent tank for storing a liquid reducing agent or a precursor thereof; a concentration measuring device that operates the heating element for a predetermined time and measures a concentration of the liquid reducing agent or the precursor thereof based on a temperature rise characteristic of the operated heating element; a liquid-level measuring device that measures a liquid-level of the liquid reducing agent or the precursor thereof in the reducing agent tank; and a reducing agent empty judging device that judges whether or not the liquid reducing agent or the precursor thereof is absent, based on the concentration measured by the concentration measuring device and the liquid-level measured by the liquid-level measuring device, wherein the reducing agent empty judging device judges that the liquid reducing agent or the precursor thereof is absent, when both of the concentration measured by the concentration measuring device and the liquid-level measured by the liquid-level measured device indicate that the reducing agent tank is empty, and wherein the reducing agent empty judging device disregards an error signal due to a bubble adhesion to the heating element and does not judge that the liquid reducing agent or the precursor thereof is absent, when the concentration measured by the concentration measuring device indicates that the reducing agent tank is empty and the liquid-level measured by the liquid-level measuring device indicates that the reducing agent tank is not empty.