The Specific Gravity R1 Reagent contains indicators that react with the urine specimen to yield a colored complex measured at a wavelength of 600 nm. The absorbance obtained directly corresponds to the ionic strength of the sample. The ionic strength indirectly corresponds to Total Dissolved Solids (i.e. specific gravity) of the sample. Normal urine may range in specific gravity from 1.005 to 1.018. Abnormal values should be checked by an alternative method such as a refractometer. Note that Refractive Index is also an indirect method to determine Total Dissolved Solids (SG). Axiom provides controls for use with this assay. We also sell controls for use with refractometers only (R-1125-7, and R1225-7). Stability and Storage: Unopened and opened bottles are stable until expiration date noted on bottle when stored tightly capped at room temperature. If left on instrument they should be capped or taken off the instrument and capped.