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In the observation tables provided in books and websites two different colors are assigned to a specific borax+salt bead in both oxidising and reducing flames. Not all basic radicals show this trend but some like Cu$^+$$^/$$^+$$^2$ does. It appears green in hot condition and blue in cold condition when made using oxidising flame.

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My question is what is done to actually reduce the temperature of the borax bead? Is it held under running tap of water or just outside the flame?

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  • $\begingroup$ "In hot" and "In cold" are really weird column headings to me. It would seem better to use "While Hot" for column and move that column to the left. Use "Cold" for the second column. You of course have to fuse the bead before you can see the "Cold" color. $\endgroup$
    – MaxW
    Commented Sep 21, 2016 at 17:25
  • $\begingroup$ The table is from ncert. By 'in cold' and 'in hot' they must have meant in hot condition and cold condition respectively. $\endgroup$
    – Tyto alba
    Commented Sep 21, 2016 at 17:42
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    $\begingroup$ I know what Borax bead tests are so I understand what the author meant. I just think the notion was phrased poorly. Also since we read left to right there is the nuance of time. I think having the hot column first then the cold column would imply time sequence better. $\endgroup$
    – MaxW
    Commented Sep 21, 2016 at 17:49
  • $\begingroup$ @tytoalba where did you find this table? I couldn't find it in ncert class 11 $\endgroup$
    – evamPUNdit
    Commented May 11, 2019 at 16:02

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"Hot" refers to the bead when just taken out of the flame of the Bunsen burner, while "cold" refers to the state when the bead cooled to room temperature. Provided the small size these beeds typically have (a toothpick like rod of magnesium oxide to carry them), this is just a matter of about a minute of exposure to ambient air. Duing this process, you may spot differences, too. Conversely, intentionally cooling the hot glass-like beads under tap water often shatters them into pieces.

Side note #1: Testing with a bead of Borax is a one quick pretest, to be confirmed by subsequent experiments. And as a good habit: once you found the ions, compare your bead made with the analyte with a reference, a bead made with a sample of known composition.

Side note #2: Of course I miss one, an entry for cobalt ... regardless of the flame (oxidation or reduction), hot or cold: an intense dark blue. Almost Yale blue.

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