Barium

Metal­lic bar­i­um is a soft, duc­tile al­ka­line earth met­al of a sil­very-white col­or. Its name comes from the An­cient Greek word mean­ing “heavy”, be­cause of the high den­si­ty of its com­pounds.

How bar­i­um was dis­cov­ered

In the form of an ox­ide, bar­i­um was dis­cov­ered by Carl Scheele and Jo­han Gahn in 1774. In 1808, bar­i­um was first ex­tract­ed in pure form by Humphrey Davy, who con­duct­ed the elec­trol­y­sis of moist bar­i­um hy­drox­ide with a mer­cury cath­ode. Davy heat­ed the bar­i­um amal­gam that was formed in this process, and af­ter the mer­cury evap­o­rat­ed, he ob­tained pure metal­lic bar­i­um.

Dis­tri­bu­tion in na­ture

This el­e­ment has high chem­i­cal ac­tiv­i­ty and is not found in na­ture in pure form. It is main­ly con­tained in the min­er­als barite (Ba­SO₄) and witherite (Ba­CO₃). One of the com­pounds of bar­i­um is its sul­fide. BaS be­came known as “Bologna phos­pho­rus” af­ter the ex­per­i­ments by the Ital­ian al­chemist Vin­cen­zo Cas­cia­ro­lo: he heat­ed barite and dis­cov­ered a sub­stance that glowed in the dark. Af­ter the sub­stance was il­lu­mi­nat­ed by the sun all day, it con­tin­ued to glow all night.

Ap­pli­ca­tion of bar­i­um and its com­pounds

In pure form, bar­i­um is used as a get­ter (gas ab­sorber) in elec­tron­ic de­vices with a high vac­u­um, and is added to liq­uid met­al coolants.

Bar­i­um com­pounds are used in the man­u­fac­ture of ce­ram­ic con­densers, piezo­elec­tric mi­cro­phones and piezo­ce­ram­ic ra­di­a­tors (bar­i­um ti­tanate), Bar­i­um com­pounds are also used in op­tics (monocrys­tals of bar­i­um flu­o­ride), in atom­ic hy­dro­gen en­er­gy for ob­tain­ing hy­dro­gen and oxy­gen in the Oak Ridge cy­cle (bar­i­um chro­mate), in nu­cle­ar en­er­gy for coat­ing ura­ni­um rods (bar­i­um ox­ide in a spe­cial sort of glass), and in var­i­ous chem­i­cal sources of elec­tri­cal en­er­gy. Bar­i­um per­ox­ide, to­geth­er with cop­per ox­ides and rare earth met­als, is used to make su­per­con­duc­tive ce­ram­ics, which can func­tion at tem­per­a­tures above 77.4 K. Bar­i­um ni­trate and chlo­rate are used in fire­works to cre­ate a green flame.

All wa­ter-sol­u­ble bar­i­um com­pounds are tox­ic and cause se­ri­ous prob­lems with the di­ges­tive tract, and paral­y­sis of the mus­cles and heart. How­ev­er, bar­i­um sul­fate, which is in­sol­u­ble in wa­ter, found ap­pli­ca­tion in medicine. “Barite por­ridge” (a sus­pen­sion of bar­i­um sul­fate) is giv­en to pa­tients for X-ray ex­am­i­na­tions of the di­ges­tive or­gans. Bar­i­um ab­sorbs X-rays well. The man­u­fac­tur­ers of Lego at­tempt­ed to make use of this prop­er­ty, adding it to plas­tic for bricks. If a child ac­ci­den­tal­ly swal­lowed a piece of Lego, it could eas­i­ly be found in the di­ges­tive tract on an X-ray scan. Un­for­tu­nate­ly, the plas­tic lost dura­bil­i­ty, and in­dus­tri­al bar­i­um sul­fate was not suf­fi­cient­ly pure and was tox­ic, so the idea was dropped.