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Explain how the development of a red color on the addition of zinc is a negative test?
Wiki User
∙ 12y ago
zinc reduces nitrates to nitrites. The development of red color therefore verifies that nitrates were not reduced to nitrites by the organism. If the nitrates were not reduced, a negative nitrate reduction reaction has occurred
Wiki User
∙ 12y ago
The development of a red color on the addition of zinc is a negative test because it indicates the absence of a reducing sugar like glucose. In the presence of reducing sugars, zinc would react to form a white or colorless precipitate, not a red color. Therefore, the red color suggests that the substance being tested does not contain a significant amount of reducing sugars.
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