- operculated and/or very dense eggs such as unfertilized Ascaris eggs do not concentrate well in the flotation method; sedimentation technique is recommended - Main Reagent: 33% Zinc Sulfate solution - Specific Gravity Range: 1.18-1.20 - FRESH STOOL SPECIMEN: 1.18 - FORMALIN PRESERVED SPECIMEN: 1.20 - If parasites are exposed to high specific gravity, distortion and shrinkage of protozoan cyst and thin nematode eggs may occur - To ensure detection of all possible organisms, both the surface film and the sediment must be examined.