Urometer

UROMETER is an areometer designed specifically for determining the specific gravity of urine. The areometers (floods) of Geissler or Vogel used for this purpose are equipped with a scale on a thin, long neck with graduation marks from 1.000 to 1.040, which are 1–1.5 mm apart from each other. The submerged part of the urometer is equipped with a thermometer with a red mark indicating the temperature at which the instrument is calibrated. When determining the specific gravity of urine with such a urometer, either the urine is brought to this specially marked temperature, or for every 3 degrees of temperature above that indicated by the red mark, 1° is added to the specific gravity read on the urometer, and conversely, the same amount is subtracted for each drop in the temperature of the urine under investigation by 3° below the temperature indicated on the scale by the red mark. To achieve more accurate readings of degrees, densities from 1.000 to 1.040 are distributed over 2 or 4 instruments. The scale of the urometer proposed by Heller has other divisions graduated according to Baumé. Heller's urometers present the inconvenience that the figures obtained with their help must be converted to the readings of the aforementioned areometer; each division of Heller's urometer corresponds to 7 divisions of Geissler's urometer. In addition, the instrument is less accurate. A source of error when using a urometer is the capillarity of the instrument or its inaccurate graduation. To eliminate the latter, it is necessary to calibrate each newly acquired areometer with a reliable sample or with a 0.2% sodium chloride solution, the specific gravity of which at 15° is equal to 1.000. Lohnstein proposed a weight urometer to avoid errors arising from capillarity when using ordinary urometers. For clinical purposes, using the ordinary Vogel urometer is sufficient. To determine the specific gravity of urine using a urometer, a cylinder is carefully filled with urine up to ⁴/₅ of its capacity (to avoid foam), into which a clean and dry urometer is immersed, and the scale is read to see which degree it has descended to. A temperature correction is made. The cylinder must be wide enough so that the urometer does not touch its walls. UROROSEIN, a red urinary pigment of protein origin, discovered by Nencki and Sieber and described by them in 1882. According to Salkowski's research, the chromogen of urorosein is indoleacetic acid; it is possible that the chromogen composition also includes a glycine derivative—indolaceturic acid. Under the influence of concentrated HCl and a very dilute KNO₂ solution, the chromogen turns into urorosein. Urorosein is insoluble in ether and chloroform (distinguishing it from indirubin and skatolred). It dissolves well in water, ethyl alcohol, and amyl alcohol. A solution of urorosein in amyl alcohol gives a sharp absorption band in the green part of the spectrum between D and E (wavelength λ = 557 mµ). The color disappears upon the addition of alkalis and reappears upon acidification. The chromogen of urorosein is salted out with ammonium sulfate. The chromogen of urorosein has been detected both in normal urine and in many pathological states, for example, in diabetes, typhoid fever, nephritis, cancer, etc. For the detection of urorosein in urine, see Urine. If nitrous acid is formed in standing urine under the influence of bacteria, the red coloration may appear after a single acidification with HCl. To detect urorosein in blood, proteins are first removed with trichloroacetic acid. The appearance of urorosein in the blood indicates the presence of severe uremia, since urorosein is formed exclusively in severe azotemia or hyperindicanemia.