Question

What happens when ferric chloride is exposed to the atmosphere? State the observation.

Answer 1

the formula FeCl3 and with iron in the +3 oxidation state. The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted lightthey appear purple-red. Anhydrous iron(III) chloride is deliquescent, forming hydrated hydrogen chloride mists in moist air. It is rarely observed in its natural form, the mineral molysite, known mainly from some fumaroles.
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Answer 2

Ferric chloride, FeCl3, occurs in nature in the lava of Vesuvius, as the mineral molysite. In the laboratory it is prepared in the anhydrous condition by passing a rapid current of dry chlorine through a retort over heated iron wire, advantageously cut into pieces some 6 mm. in length. The ferric chloride volatilises and condenses as beautiful crystals on the upper, cooler portions of the retort.

At the end of the operation the heating is discontinued and the chlorine expelled from the apparatus by a rapid current of carbon dioxide. The salt is now rapidly transferred to a tube and hermetically sealed.

Ferric chloride may also be obtained by passing a current of dry, .gaseous hydrogen chloride over heated amorphous ferric oxide; by passing chlorine over heated ferrous chloride; and by heating together ferrous sulphate and calcium chloride.

As prepared by any of these methods ferric chloride consists of dark, iridescent, hexagonal scales, which appear red by transmitted light, but exhibit a green lustre when viewed by reflected light. It melts under pressure at 301° C., but volatilises at 280° to 285° C., at atmospheric pressure, its real melting-point at 760 mm. being 303° C. Between 321° and 442° C. its vapour density in an atmosphere of chlorine is practically constant, and corresponds to the double formula Fe2Cl8.

At temperatures above 500° C. anhydrous ferric chloride dissociates into the ferrous salt and free chlorine, the equilibrium being represented by the equation: - 

Fe2Cl6 ⇔ Fe2Cl4 + Cl2.