The urinometer, a type of hydrometer, was used for measuring the specific gravity of urine. 'Specific gravity' is a function of the number, density and weight of the solute particles present in the urine, and is used as a measure of the concentrating power of the kidney. The specific gravity of urine is its density compared with the density of distilled water. At 20 degrees celsius a urinometer floating in distilled water should read 1.000. If the urinometer is then placed in urine, a reading between 1.010 and 1.030 signifies that the urine is within normal levels, otherwise it contains either too much, or not enough, protein.