How can I distinguish whether a metal that I have is tin ($\ce{Sn}$)? I am specifically looking for a chemical reaction that will happen only with tin and not with other metals such as $\ce{Al,~Cu,~Fe,~\ldots}$. Do such reactions exist? What are they?
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$\begingroup$ I think this question would be incomplete without mentioning what metals the sample could be made of, i.e. all of the metals. $\endgroup$– M.A.R.Commented Sep 19, 2015 at 14:22
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$\begingroup$ @inɒzɘmɒЯ.A.M It could be made of: $\ce{Al,~Ti,~V,~Fe,~Co,~Ni,~Cu,~Zn,~Sn}$. $\endgroup$– user7576Commented Sep 19, 2015 at 14:52
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1 Answer
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Beside determining the volumic density (tin: 7.31 g/ccm, aluminum: 2.7 g/ccm, etc. pp) and as asked here on chemistry SE, there is a quick pre-test. In German it is known as "Leuchtprobe", literally "illumination probe". Be reminded to protect yourself properly (safety googles, fume hood, gloves).
In a first instance, you have to reduce the tin compound. For this, a little of your solid under investigation is finely mixed together with some grains of zinc (Zn). In a porcelain dish, to this mixuture is added 5 mL of 20 m% aqueous HCl. Await this reaction ceased. Zn will produce hydrogen, and because it is freshly created (statu nascendi), it is of superiour reducing power compared to bottled hydrogen gas, and the solution is cooled to room temperature.
Then dip a cool test tube, partially filled with cold water, into this solution. While still wetted by the solution, rapidly place the test tube into the upper part of the non-luminous flame of a Bunsen burner. Blue fluorescence is an almost specific evidence for tin (caused by $\ce{SnCl2}$, and stannanes), already at low concentrations.
Presence of arsenic may hamper this fluorescence. Niob-compounds yield some similar fluorescence, too. Beside using tin-free chemicals and equipment to be used -- and prior to the test of your unknown -- do at least once the test in known absence of tin, and once with a sample with tin to learn how to discern the two instances.
answered Sep 19, 2015 at 16:52
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2$\begingroup$ One can better detect the fluroescence by adding potassium permanganate into the test tube to create a dark background. (Or so I heard; I let others do that test in the ion lottery practical course.) $\endgroup$– JanCommented Sep 19, 2015 at 17:04
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$\begingroup$ I agree with this comment; a test tube partially filled with a cold aqueous potassium permanganate solution increases the contrast compared to a test tube simply filled with blank water. Own practical experience in the lab (not only during the initial (in)organic Marcha analítica separation process $\endgroup$ Commented Sep 19, 2015 at 20:45
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$\begingroup$ but as TA, too) that a test tube hold too long unshaken eventually leads to a bumping solution, including a stain on cloth and skin. $\endgroup$ Commented Sep 19, 2015 at 20:56
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1$\begingroup$ Don't look at the fluorescence too long, because the water in the tube locally overheats within ten seconds: splash! $\endgroup$– KarlCommented Oct 13, 2023 at 16:08
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1$\begingroup$ @Karl And safety glasses/goggles. And chemically speaking, to perform the test at least once with a blank (no tin) and once with presence of tin as each measurement is a comparison against a reference. The illumination in the lab (fluorescent tube / LED lumiophore / day light) can influence how well it is seen, too. $\endgroup$ Commented Oct 13, 2023 at 16:23