How to determine colour of a compound and precipitate.....
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If you're speaking about the processes we undertake to experimentally determine the flame color and/or ppt. color, then the simplest answer is that we burn them or get them to precipitate, and then observe what color appears (if any - sometimes compounds don't radiate visible or detectable wavelengths of light in response to flame tests, and lots of precipitates are completely colorless or white).
If you're talking about diagnosing a compound from the color of the flame or precipitate, then it's a bit more complex, but essentially we rely on the historical evidence of prior experimenters, and the other physical properties of the compound, to establish its identity. Flame tests and precipitate colors aren't usually definitive, and are usually used as corroborative tests to confirm or deny a suspected identity.
If you're asking about how we distinguish one color from another similar color, then there are two answers: one for definitive, analytical work, and one for more general experimentation.
1) If it's a high quality test in a working lab, we use equipment which parses the (reasonably) exact wavelength of light being absorbed or emitted.
2) If the situation doesn't require a very exact answer, then we use our best judgement, or burn a sample of the compound we think it is side by side with the unknown compound to see if the color emitted is the same. (the same goes for precipitate, except that we don't have to do it at the exact same time unless the colors change rapidly or some such due to decomposition).
Hope this helps. ^^
If you're talking about diagnosing a compound from the color of the flame or precipitate, then it's a bit more complex, but essentially we rely on the historical evidence of prior experimenters, and the other physical properties of the compound, to establish its identity. Flame tests and precipitate colors aren't usually definitive, and are usually used as corroborative tests to confirm or deny a suspected identity.
If you're asking about how we distinguish one color from another similar color, then there are two answers: one for definitive, analytical work, and one for more general experimentation.
1) If it's a high quality test in a working lab, we use equipment which parses the (reasonably) exact wavelength of light being absorbed or emitted.
2) If the situation doesn't require a very exact answer, then we use our best judgement, or burn a sample of the compound we think it is side by side with the unknown compound to see if the color emitted is the same. (the same goes for precipitate, except that we don't have to do it at the exact same time unless the colors change rapidly or some such due to decomposition).
Hope this helps. ^^
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