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?
Answer
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.
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