Essentials of chemistry : inorganic and organic, for the use of students in medicine / by R.A. Witthaus.

  • Rudolph August Witthaus
Date:
1879, ©1878
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Licence: Public Domain Mark

Credit: Essentials of chemistry : inorganic and organic, for the use of students in medicine / by R.A. Witthaus. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    Note.—I have given none of the more elaborate and so- called accurate quantitative processes for urea, as they are all more or less subject to error, require corrections and care, and expenditure of time in the performance. All the processes hitherto devised a^ subject to an error from the presence in the urine of kreatinin. and other substances, which are decomposed by the reagents used ; one of the products of the decomposition is urea, and this, being in turn decomposed, vitiates the result. Two processes have been very generally used by practitioners : Liebig's and Davy's. The former requires the use of a titrated solution whose preparation is difficult and uncertain, and which deteriorates rapid]} ; it is also open to the objection that the result obtained requires correction-;, as it is modified by the de- gree of concentration of the urine and by the presence of sodium chloride or albumen. Davy's process i? only approximative and requires corrections for variations in barometric pressure and temperature. The most ne irly accurate process which I am acquainted with is that devised by Dr. J. C. Draper, in which the urea is decomposed and the carbon dioxide formed is weighed as barium carbonate. 1005. To what pathological causes may diminution or increase of elimination of urea be due? A diminution may be due to some condition in- terfering with the normal transformation of albu- minous substances in the body, as in certain chronic diseases; more frequently, however, a diminished proportion of urea in the urine is not due to a diminution in the production, but to the fact that the urea formed has not been separated by the kidneys, as in ursemia, and in diseases attended with dropsical effusions. An excess of urea occurs in fevers and in true diabetes, in which it indicates the amount of waste of tissue, and is, therefore, a grave symptom. 1006. How much uric acid is normally excreted in 24 hours f From 0.3 to 0.8 gram.