Organic 2 Review Problem 536

Organic 2 Review Problem 536 - 5 20 P RACTICAL O RGANIC C...

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520 PRACTICAL ORGANIC CHEMISTRY ESTIMATION OF UREA BY UREASE. This method of estimating urea is more accurate than the hypobromite method (p. 458) and is used extensively for accurate metabolic work. The method is based on the conversion of urea to ammonium carbonate and the estimation of the latter by titration with standard acid. For this purpose, two equal quantities of urea (or urine) are measured out into two flasks A and B. A is treated with 10 ml. of a strong urease preparation and some phenol- phthalein, warm water is added and the mixture is adjusted by the addition of Mjio HCl from a burette A 1 until the red colour is just discharged. This brings the mixture to about pH 8 (the optimum for urease) and also prevents loss of ammonia. The contents of B, which act as a control, are treated with mercuric chloride in order to inhibit the action of the enzyme, and then 10 ml. of urease solution are added. The solution is diluted with water and ammonium chloride added (in order to balance the ammonium chloride subsequently formed in A). Methyl-red is then added and the solution is titrated with
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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