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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    fore, the urine be albuminous it should be heated to the boiling point and filtered before the applica- tion of the test. In applying- Trommer's or Fettl- ing1 s test to urine, a dirty yellowish-green color is frequently observed ; this is not due to the presence of sugar. [Fehling^ test is based upon the same reaction a? Trommer's, and is more delicate. Two solutions are required: I. Cupric sulphate (pure), 51.9S grams. Water, 500 cbc. II. Rochelle salt (pure crystals), 259.9 grams. Solution sodic hydrate, sp. gr. 1.12, 1,000 cbc. (Piffard.) In using, mix one volume I. with two volumes II. in a test tube, shake, add an equal volume of the urine to be tested, and boil; if sugar be present the same appearance is observed as in Trommer's test. This solution may be used in determining the quantity of sugar in urine : place 20 cbc. of the mixed solutions diluted with 60 cbc. water in a flask and boil; dilute the urine to be tested with four volumes of water ; fill a burette with the diluted urine, and from this gradually add it to the boiling liquid until the blue color has been entirely discharged; at this point read on the graduation of the burette the number of cbc. used, divide this number by five, and the quotient gives the number of cbc. urine containing 0.1 gram, sugar ; from this the quantity in any given volume of urine is obtained by simple proportion.] 1014. Explain the principles upon which Trom- mels and Fehling's tests are based. By the action of the boiling alkali glucose is con- verted into substances (glucic and melassic acids) which are very prone to oxidation and are conse- quently good reducing agents; if cupric sulphate be present it is converted into cuprous sulphate, and this is in turn decomposed with deposition of cuprous oxide. As there is deoxidation of the copper compound these tests are spoken of as reduction tests.