An experimental investigation of liquids mixing by an unlike split triplet impinging injection element is conducted. General interests are placed on the mixing mechanism characterized by liquid sheet superposition and disintegration. Patternation test and spray visualization measures overall and local mixing qualities, respectively, in terms of momentum ratios in the range of 0.5 to 6.0. Photographical evidences show that impingement by two identical secondary liquid streams is made in the shape of liquid sheet superposition. Mixing extent of unlike split triplet element is largely determined by a degree of liquid sheet disintegration after second impingement.