Answer:
In animal field studies, why do scientists usually try to work without making the animals aware that the humans are present? It is necessary to observe the animals without disturbing them. When a controlled experiment is not possible, why do scientists try to identify as many relevant variables as possible?
Answer:
When sulfurous, sulfuric, and nitric acids in polluted air and rain react with the calcite in marble and limestone, the calcite dissolves. In exposed areas of buildings and statues, we see roughened surfaces, removal of material, and loss of carved details. Stone surface material may be lost all over or only in spots that are more reactive.
Explanation:
You might expect that sheltered areas of stone buildings and monuments would not be affected by acid precipitation. However, sheltered areas on limestone and marble buildings and monuments show blackened crusts that have peeled off in some places, revealing crumbling stone beneath. This black crust is primarily composed of gypsum, a mineral that forms from the reaction between calcite, water, and sulfuric acid. Gypsum is soluble in water; although it can form anywhere on carbonate stone surfaces that are exposed to sulfur dioxide gas (SO2), it is usually washed away. It remains only on protected surfaces that are not directly washed by the rain.
Bright cherry red color is produced upon the addition of methyl red indicator to a culture of a Gram negative bacilli in MR-VP broth if the organism used the mixed acid pathway of fermentation.
What is MR-VP test?
- As part of the IMViC testing, Methyl Red (MR) and Voges-Proskauer (VP) broth is utilized as the medium in which both the Methyl Red and Voges-Prosakuer tests can be conducted.
- It is a straightforward broth made up of dextrose or glucose, buffers, and peptone.
- In the Methyl Red test, an infected tube of MR-VP broth is mixed with the pH indicator methyl red.
- The acids will overwhelm the buffers in the medium and create an acidic environment if the organism employs the mixed acid fermentation pathway and creates stable acidic end products.
- If acidic end products are present when methyl red is introduced, the methyl red will remain red.
Learn more about the MR-VP test with the help of the given link:
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