Refractometer - Specific Gravity in Urine / Total Protein in SerumRefractometer Specific Gravity in Urine Total Protein in Serum Protein Specific Gravity Model: Achieve accurate, quantitative measurements of specific gravity and protein determinations in biological fluids with our hand held refractometer. Simply read the numerical scales through the eyepiece. Rubber grip and optical focus system allow for easy viewing in any environment. Automatic temperature compensation allows for immediate results, even when