Practical Medical Chemistry, for Physicians and Students

Overview

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 Excerpt: ...multiplied by 6.25. Kjeldahl-Gunning Method.--By this method all of the nitrogen of the protein molecule is formed into ammonia, and this is then combined with sulphuric acid. An excess of alkali is added and the ammonia is distilled over into standard sulphuric acid, where its amount may be determined by ...
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Overview

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 Excerpt: ...multiplied by 6.25. Kjeldahl-Gunning Method.--By this method all of the nitrogen of the protein molecule is formed into ammonia, and this is then combined with sulphuric acid. An excess of alkali is added and the ammonia is distilled over into standard sulphuric acid, where its amount may be determined by titrating the excess of acid with standard alkali. Place from 0.7 to 3.5 grammes of the material, according to the probable amount of nitrogen present, in a 500-c.c. Kjeldahl flask, add 10 grammes of powdered potassium sulphate and about 20 c.c. of concentrated sulphuric acid. Place flask in hood over a small gas flame and gradually increase heat until the contents of the flask appear perfectly clear. Cool and dissolve residue in 300 c.c. of distilled water, cool in ice water, add a few drops of Congo-red solution, and then sufficient cold saturated solution of sodium hydroxide to render the mixture strongly alkaline. Connect the flask with a condenser and distil until two-thirds of the contents have passed over. Collect the distillate in a beaker containing a measured amount of standard sulphuric acid. The excess of sulphuric acid, that unnentralized by the ammonia. is then determined by titrating with a standard alkali solution, using Congo-red as the indicator. Example:--2 grammes of the sample treated as above and distilled into 25 c.c. of t H,S04. Suppose 15 c.c. of, NaOH are required to neutralize the excess of acid--then 10 c.c. of the i5 II2S04 must have been neutralized by the ammonia. Now 10 c.c. H,S04 will be neutralized by 0.01693 gramme of ammonia, representing 0.01393 gramme of nitrogen. If there be 0.01393 gramme of nitrogen in 2 grammes of the material, there must be 0.090 gramme in 100 grammes. The sample therefore contains 0.696 per cent....
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Product Details

  • ISBN-13: 9781150047336
  • Publisher: General Books LLC
  • Publication date: 5/28/2012
  • Pages: 82
  • Product dimensions: 7.44 (w) x 9.69 (h) x 0.17 (d)

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