Introduction to the study of organic chemistry : a text-book for students in the universitites and technical schools / by John Wade.

  • Wade, John.
Date:
1898
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Licence: Public Domain Mark

Credit: Introduction to the study of organic chemistry : a text-book for students in the universitites and technical schools / by John Wade. Source: Wellcome Collection.

    450/490 (page 428)
    [Estimation of Urea in Urine.—Hypobromite process is the best. 150- 250 c.c. flask containing 10 c.c. caustic soda in which bromine has been dissolved, without rise of temperature—colour should be bright yellow, not red from excess of bromine. 5 c.c. urine in small test tube which can be passed down neck of flask without spilling urine. Flask then corked and placed in beaker of water, and connected by glass tube through cork and rubber tube to clip burette, nearly filled with water and inverted in cylinder of water. Burette raised or lowered until level of water same inside and outside, and reading noted. Clip then opened, and urine slowly poured into hypobromite by tilting flask. Clip left open until generating flask has returned to original temperature, then burette raised until water again level, and reading taken. Difference between two readings = no. of c.c. of nitro- gen. 37'1 c.c. of moist nitrogen at 18° and 760 mm. = 0T gram urea, or no. of c.c. x 2'7=no. of milligrams of urea in sample. In Allen’s modification 21 times weight of potassium cyanate is added to urea, to prevent, by mass action, reconversion of urea into ammonium cyanate, and the bromine, dis- solved in potassium bromide solution, is added to the mixture of the urea- cyanate solution with caustic soda.] CHAPTER XXXIII Uric Acid.—Saturate 100 c.c. urine with ammonium chloride (about 30 grams required), add a few drops of ammonia, and after 15 minutes filter. Pierce filter, wash ppt. into test tube with little water, dissolve in very little boiling caustic soda, cool, and filter. Acidify filtrate with dil. hydrochloric acid. Uric acid slowly pptd. ; collect, wash, and apply murexide test. Qualitative Tests for Uric Acid (p. 200).—Insol. water and dil. acids; sol. alkalies. Murexide test. [.Estimation of Uric Acid in Urine.—Ppt. as ammonium urate, and titrate with dil. permanganate. 100 c.c. urine, saturated with finely powdered ammonium chloride as above, stirring vigorously. Add few drops of ammonia, still stirring, and after 15 minutes transfer to filter and wash with sat. solu. of ammonium sulphate, until no chlorides. Rinse ppt. of acid ammonium urate off filter with hot water, dilute to 100 c.c. with cold water, and add 20 c.c. cone, sulphuric acid, and stir, thus raising temperature to about 60°. Then quickly run in permanganate (N/20=T578 grams per litre) until piuk tint ceases to vanish instantly on shaking. Further decolourisation may occur on standing, but this is to be disregarded. 1 c.c. permanganate = 0'00375 gram uric acid.] [Alloxan.—5 grams uric acid (twice pptd. from cone, sulphuric acid), 10 c.c. cone, nitric acid + 5 c.c. water (=nitric acid sp.-gr.=l'3). Proceed as directed.] [.Parabanic Acid.—From 5 grams alloxan as directed.] Urea (and Allantoin) from Uric Acid.—On 5 grams as directed. Test urea. CHAPTER XXXIV Potassium Ferrocyanide.—Boil 5 grams potassium cyanide with 3'5 grams cryst. ferrous sulphate and 50 c.c. water, filter and crystallise. Test ferro- cyanide. Add bromine to hot soln. of 3 grams of ferrocyanide until ferric chloride ceases to give blue ppt. with sample. Crystallise and test ferri- cyanide. Heat 2 grams powdered ferrocyanide to redness in test tube. Break up, powder, and boil with water. Evap. filtered solution and test for cyanides. Qualitative Tests for Cyanides (p. 2i)5).—Ferroeyanides; ferric salts, dark blue; ferrous salts, light blue. Carbon monoxide with warm cone, sulphuric, hydrocyanic acid with dil. sulphuric acid. Copper salts, chocolate. Insol. ferroeyanides decomposed by caustic soda. Ferricyanides : brown colour with ferric, dark blue with ferrous. Simple cyanides: mercuric