At last, the experiment is over! And
it has been quite successful. We (the friends in my group and I), have found heavy metals in the colours (abir or gulaal) used in Holi. It took a long time to post the result,
principally because my school was fussing over my taking pictures in the school
lab.
Where, What and Who
 |
| This is my school's chemistry lab, the one in which we worked, pursuing our quest. |
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| And these are the colours we worked with. |
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| These gave the most prominent result (thanks to Aditya Bose, who brought these). |
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| The team, Aditya Bose, Titikhyu Dixit and Prabaha Gangopadhyay (that's me). This snap, most certainly, has not been taken in my school's lab. |
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| Me, trying to find Lead (Pb), without any success. |
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| Aditya Bose, searching for Lead. |
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| My friend, Titikhyu Dixit, performing flame test. The guy peeking in is a classmate of mine. |
The Test
Primarily, we tried to find Lead, and spent a lot of time over it, without any success. It is highly probable that Lead was present in trace amounts and the precipitate being too small in quantity, was being masked by the colour of the original solution itself. Anyhow, we have no proof of its presence.
We spent a lot of time on the Bunsen burner, performing flame test, taking many observations. Two flame colours were very distinct – faint greenish blue and grassy green.
 |
| The greenish blue flame... very faint. |
 |
| The grassy green flame. |
These flame colours pointed at the presence of Zinc (Zn) and Barium (Ba) respectively.
Confirmation
After the flame tests were over, wet tests were performed, to confirm the presence of Zinc and Barium.
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| The original solution (mixture of the colour and water). |
The solution did not give any precipitate, against test for normal radical groups (Group IV), i.e. test, exploiting theories of ionic equilibrium (solubility product, to be more specific). But, when Sodium Hydroxide (NaOH) was added, traces of white precipitate was observed, after keeping the test tube at rest for some time.
Zn2+ + 2NaOH = Zn(OH)2 ↓ + 2Na+
 |
| The patches of white precipitate in test tube. |
The result of the test for Barium was very prominent. Firstly, the green flame was very clear and bright, unlike the whitish blue one. Secondly, upon addition of Potassium Chromate (K2CrO4), very prominent orangeish yellow precipitate (supposed to be yellow, but most probably, the colour of the original solution interfered) was observed.
Ba2+
+ K2CrO4
= BaCrO4
↓ + 2K+
 |
| The satisfactory precipitate. |
Conclusion
Well, heavy metals, as it seems, are present in the colours, thrown at each other during Holi. That is pretty harmful, because, absorption through skin, is one the principal routes of heavy metal entering our body. Generally, small amount does not cause any significant problem. But, skin irritation is common, and upon heavier influx, one may feel nauseated. So, it is better to limit the celebration to a safe point.
