Chemical Prospect (Cont.)

Holi Hai! (Aur Heavy Metal Bhi Hai!)

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.

And these are the colours we worked with.

These gave the most prominent result (thanks to Aditya Bose, who brought these).

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.

Me, trying to find Lead (Pb), without any success.

Aditya Bose, searching for Lead.

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.

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.

Battery Eliminator

Full-wave Rectifier

Since I am posting the results of my chemistry project, it occurred to me that I might also post what I did in physics. The work in this project is already complete and ready to be posted.

This is one of the simplest physics projects one can do. A device to convert household supply of Alternating Current (220V, as available in India) to Direct Current, of significantly lower voltage. It is basically a full-wave rectifier. It can be used as a battery and it supplies almost a constant voltage with a very low amount of fluctuation.

Basic Materials

• Transformer (220V to 12V)
• Capacitor
• Diode
• Soldering iron and soldering wire
• Switch
• Connecting wires
• AC wire
• Eliminator box (optional, but recommended)
• LED (optional, but recommended)
• Crocodile clips (optional)

Circuit

The LED is not shown in the circuit. It may be connected in parallel, attached with a resistance, with the capacitor, and may serve as an indication of the current supply in the DC output region.

The Finished Product

The top view of the eliminator, set in an eliminator box. The transformer, capacitor, AC wire, connecting wires, crocodile clips are visible clearly.

View without power supply.

With power supply (notice the glowing LED).

Points to be Noted

The diodes in the circuit ensures the flow of unidirectional current in the output. But the DC thus generated is variable, since the output voltage varies as a function of time. Thus, if we plot voltage vs time graph, the equation will be:

 V=V0|sin(t)|, where V0 is the peak voltage (12V in this case).

But, this output is barely valuable. To filter the output, a capacitor is added in parallel (check the circuit diagram), which, by the process of charging and discharging, maintains almost a uniform voltage in the output. Thus, with the capacitor connected, the voltage vs time graph is almost similar to the graph of the equation:

V=V0, where V0 is the peak voltage.

So, the capacitor basically acts as a filter, which maintains a fairly uniform output voltage, which is independent of time.

Chemical Prospect

Holi with Heavy Metals

Well, quite some time has passed since I had introduced myself, and it appears that irregularity is quite an intrinsic property of mine. I am still a high school student (well, thank god, this is the last year of my attending a school). Recently, I got an assignment, to test the presence of heavy metals, in the colours used in 'Holi' (the Indian festival of colours, for those who are unfamiliar with it). Though, Holi is a symbol of celebration and joy, if the test results concur with my predictions, one should like to keep those colours away from their skin.

Anyhow, I'll be performing the tests in a day or two, and I plan to post the results and details in the blog.