Outlines of the clinical chemistry of urine / by C.A. Mac Munn.

  • Macmunn, Charles A., 1852-1911.
Date:
1889
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Licence: Public Domain Mark

Credit: Outlines of the clinical chemistry of urine / by C.A. Mac Munn. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    If too little urine is available the method of mixture with distilled water may be adopted. Thus, suppose it is necessary to add three times as much water as urine to enable the urinometer to float (there are four volumes pre- sent), and that the specific gravity of the mixture is 1003, then the specific gravity of the urine = 1000 +(3 x 4) = 1012. But if the instrument is incorrect, the error is magnified by the number of volumes used. Hence it is not advisable to rely too much on this method (Tyson). For small quantities of fluid, Wilson's specific gravity balls may be used. These are simply small hollow balls of glass, and the specific gravity ■of a fluid is determined by putting different balls into it until one will float. Balfour Stewart and Gee describe how they are made, and state that they will show a difference in the third place (of decimals) in the density of a liquid.* In taking the specific gravity with the specific gravity bottle a chemical balance is required. The absolute weight of a given volume of fluid divided by the absolute weight of -an equal volume of distilled water gives the specific gravity. In taking the specific gravity, the urine of twenty-four hours ■should he collected, and a sample selected from it. Estimation of Total Solids.—By means of a simple formula, known in this country as Christison's formula, and abroad as that of Haeser or Trapp, we can determine approximately the amount of solid matters excreted in the urine in twenty-four hours. The last two figures of the specific gravity expressed in four figures are to be multiplied by 2'33 (Haeser and Christison), or by 2 (Trapp), or 2-2 (Loebisch). Thus, if a person passes 1,200 c.c. of urine in twenty-four hours, and the specific gravity of a sample taken from it is 1022, then 22x2-33 = 51-26 grams in 1,000 c.c, nr 1 onn o . 51-26 x 1,200 or m 1,200 c.c.= —j-qqq^ = 61-51 grams. Although this method answers for rough clinical estima- * Stewart and Gee : Lessons in Elementary Pract. Physics, 1885.