Tin: a crackling metal

Why tin squeaks when bent

At room tem­per­a­ture, tin is a sil­very-white met­al that is eas­i­ly fusible and mal­leable. When the tem­per­a­ture drops to 13.2°С, metal­lic white tin moves to a frag­ile non-metal­lic form – gray tin. This process self-ac­cel­er­ates, as the more white tin turns to sil­ver, the swifter the sub­se­quent trans­for­ma­tion. The trans­for­ma­tion also speeds up as the tem­per­a­ture drops. This phe­nom­e­non is called the “tin pest”. If you bend a piece of white tin, you can hear a char­ac­ter­is­tic squeak – a “tin cry”. It takes place be­cause of the met­al crys­tals rub against each oth­er.

In the earth’s crust, tin is the 49th most abun­dant el­e­ment. It is also en­coun­tered in the form of com­pounds. The most wide­spread min­er­al con­tain­ing tin is cas­si­terite (SnO). Ow­ing to cer­tain of its spe­cial fea­tures, tin has played a key role in a num­ber of his­tor­i­cal events con­nect­ed with its use.

The his­to­ry of tin

Tin is one of the first met­als that hu­man­i­ty en­coun­tered. In an al­loy with cop­per, bronze was ob­tained, which was quite easy to melt and process. Hu­man­i­ty learned to smelt bronze around 3,300 BCE. Tin is men­tioned in the Old Tes­ta­ment, and in the works of Homer. The use of bronze de­fined an en­tire era – the Bronze Age. Items from bronze and tin were found in An­cient Egypt, Greece, South Amer­i­ca, In­dia and oth­er coun­tries. An­cient bronze stat­ues are well-known: the Colos­sus at Rhodes in Greece, and one of the sym­bols of Japan, the “Great Bud­dha” in the tem­ple of Ko­toku-yin in Ka­mamku­ra.

One of the sources of tin ore was the British Isles, which were called the Cas­si­terides. From this word, the main min­er­al was named that is used to ob­tain tin, cas­si­terite. The name of tin, “stan­num” prob­a­bly comes from the San­skrit root “sta”, mean­ing “hard”.

Since an­cient times, tin has not lost its im­por­tance for hu­mans. Weapons, dish­es and house­hold items were made from it and its al­loys. Due to its fusibil­i­ty and wet­ta­bil­i­ty with oth­er met­als, tin was used in sol­ders and in sol­der­ing met­al con­tain­ers. This led to the down­fall of Robert Scott’s ex­pe­di­tion. Fuel and food sup­plies were stored in met­al con­tain­ers sol­dered with tin. But be­cause of the “tin pest”, the tin dis­in­te­grat­ed and the kerosene leaked out.

The “tin pest” was well-known in Rus­sia, as in the 18th cen­tu­ry, in cold win­ters the pipes of church or­gans made from tin be­came brit­tle and crum­bled at the touch!

Tin is such an im­por­tant met­al that there was even a war for the own­er­ship of cas­si­terite de­posits in the Demo­crat­ic Re­pub­lic of the Con­go in the ear­ly 2000s! The ore is mined there man­u­al­ly, and peo­ple car­ry it on their backs to the high­way for fur­ther trans­porta­tion. But even these enor­mous ef­forts are con­sid­ered to be jus­ti­fied.

Tin also played a role in sci­ence. On the 16th of Oc­to­ber 1933, the Ger­man physi­cists Walther Meiss­ner and Robert Ochsen­feld re­port­ed that they had stud­ied tin at low tem­per­a­tures, when it be­comes su­per­con­duc­tive, and they dis­cov­ered that it starts to “re­pel” the mag­net­ic field away from it­self. The mag­net then starts to “lev­i­tate” above the su­per­con­duc­tor! This was called the “Meiss­ner ef­fect”.

Chem­i­cal prop­er­ties of tin

In the lab­o­ra­to­ry tin can be ob­tained in sev­er­al ways.

One of them is the re­ac­tion of tin salts with more re­ac­tive met­als, for ex­am­ple zinc. Zinc will dis­place tin from its salts:

SnCl₂ + Zn → Zn­Cl₂ + Sn

Also, if we put a piece of zinc in a test tube with a so­lu­tion of tin(II) chlo­ride, beau­ti­ful nee­dle-like tin crys­tals will start to grow on the sur­face of the zinc.

Ad­di­tion­al­ly, tin may be ob­tained by the elec­trol­y­sis of a tin chlo­ride so­lu­tion.

SnCl₂ →↯→ Sn↓ + Cl₂↑

Metal­lic tin is de­posit­ed on the cath­ode. If this process is car­ried out in a Petri dish, beau­ti­ful branched tin crys­tals form, to make a tin tree.

Tin is a more re­ac­tive met­al than cop­per, for ex­am­ple. So tin dis­places cop­per from its salts:

Sn + Cu­SO4 → SnSO₄ + Cu↓

Tin is re­sis­tant to the ef­fects of air and mois­ture in or­di­nary con­di­tions be­cause of the pres­ence of a ox­ide film. With con­cen­trat­ed hy­drochlo­ric acid, tin re­acts slow­ly with the for­ma­tion of hy­dro­gen trichlorostan­nate(II):

Sn + 3HCl(conc.) → H[SnCl₃] + H₂↑

Tin chlo­ride can be ob­tained in the re­ac­tion of metal­lic tin with hy­dro­gen chlo­ride gas.

Sn + 2HCl(gas) → SnCl₂ + H₂

Tin chlo­ride is sol­u­ble in small amounts of wa­ter, and with di­lu­tion it is hy­drolyzed with the for­ma­tion of a white sed­i­ment - di­hy­drate tin (II) chlo­ride:

SnCl₂(con­cen­trat­ed) + H₂O → [Sn(H₂O)Cl₂]↓

Where tin is used

All fans of elec­tron­ics know about one the most im­por­tant spheres for the ap­pli­ca­tion of tin – sol­der­ing. For a long time, an al­loy of tin and lead was used in sol­ders. But be­cause of its tox­i­c­i­ty, lead ceased to be used in sol­ders. Tin sol­ders melt at a high­er tem­per­a­ture and are some­times in­clined to form “met­al whiskers” – nu­mer­ous fine shoots that ap­pear on the sur­face of the met­al, which look like hairs. Ad­di­tion­al­ly, the prob­lem of the “tin pest” had to be solved. A small amount of an­ti­mo­ny or bis­muth is added to the tin. Nev­er­the­less, the ma­jor­i­ty of tin pro­duced is used for sol­ders. Tin is used in al­loys and an­ti­cor­ro­sive coat­ings for dish­es and oth­er items. Tin coat­ings have been used in cans since 1812, when the first can with this coat­ing was made in Lon­don. Al­loys con­tain­ing tin are used for man­u­fac­tur­ing su­per­con­duc­tors, el­e­ments of nu­cle­ar re­ac­tors, and also for mu­si­cal in­stru­ments. Bells are made from al­loys of cop­per and tin, and or­gan pipes from an al­loy of lead and tin.

Lead ox­ide is used in elec­tron­ics and op­tics. Or­gan­ics com­pounds of tin find an ap­pli­ca­tion in or­gan­ic syn­the­sis, the man­u­fac­tur­ing of lithi­um ion bat­ter­ies, and also in bio­ci­dal ad­di­tives – sub­stances that pre­vent the growth of bac­te­ria, fun­gi, al­gae etc.

One in­ter­est­ing sphere for the ap­pli­ca­tion of tin is the man­u­fac­ture of glass! To make smooth glass plates, suit­able for win­dows, for ex­am­ple, for a long time var­i­ous me­chan­i­cal meth­ods were used, such as putting heat­ed glass be­tween rollers, pol­ish­ing etc. This la­bo­ri­ous process still did not pro­vide suf­fi­cient­ly smooth and even sur­faces. A so­lu­tion was found in the 1950s by the Eng­lish en­gi­neer and busi­ness­man Sir Alas­tair Pilk­ing­ton. Melt­ed glass with a tem­per­a­ture of over 1,000 de­grees Cel­sius is poured onto the sur­face of melt­ed tin, a process which was sub­se­quent­ly named the “Pilk­ing­ton process”. The glass cools on the smooth sur­face of the melt­ed met­al. The re­sult is sheets of glass with a very smooth sur­face!

As you can see, tin is an el­e­ment which has nev­er lost its sig­nif­i­cance for hu­man­i­ty from an­cient times up to the present day.