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I'm clean when I'm black, Di...

I'm clean when I'm black, Dirty when white; Get too close, And you might sneeze. What am I?

Correct answers: 13

The first user who solved this task is Djordje Timotijevic.

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Tom Papa: Friends Over 30

Ask anybody over 30 -- if they tell you they have more than 10 friends, you know theyre counting co-workers.

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Paul Karrer

Died 18 Jun 1971 at age 82 (born 21 Apr 1889).Swiss chemist who investigated the constitution of carotenoids, flavins, and vitamins A and B2, for which he shared the 1937 Nobel Prize for Chemistry (with Sir Norman Haworth of Great Britain). He studied plant pigments, particularly the yellow carotenoids, which are related to the pigment in carrots. He determined the chemical structure of the carotenoids (1930), showed that some of these substances are transformed into vitamin A in the animal body, then determined the structure of vitamin A itself. He also confirmed the constitution of vitamin C proposed by Albert Szent-Györgyi, showed lactoflavin to be part of the complex originally described as vitamin B2 , and studied vitamin E.

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