As far as I have researched, fused calcium chloride is the hydrated form of calcium chloride. If that is true, then why is it called 'fused', why not simply hydrated?
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1$\begingroup$ Typically, "fused" refers to a technique to produce synthetic crystals (en.wikipedia.org/wiki/Verneuil_process) $\endgroup$– PaulCommented Mar 3, 2017 at 10:49
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1$\begingroup$ That's a wholly different kind of "fused". $\endgroup$– Ivan NeretinCommented Mar 3, 2017 at 14:33
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$\begingroup$ Fused means it contains fused water of crystallization i.e it is in hydrated form/melted form. chemicalforums.com/index.php?topic=77259.0 $\endgroup$– Nilay GhoshCommented Mar 12, 2017 at 13:09
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2 Answers
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The term "fused" in chemistry generally refers
to become physically joined together
as by melting, adherence or other means of consolidation [1].
At an industrial scale solutions containing $\ce{CaCl2}$ are obtained either as by-products in the production of soda (by the ammonia method) and Berthelot's salt, or by the adding $\ce{HCl}$ to limewater. Solutions are then evaporated and $\ce{CaCl2}$ is isolated as a white or greyish porous mass, which is called fused calcium chloride and is generally water-free or contains trace amounts of water.
To make it clear, in this case "fused" ≠ "melted", as it's not about melting $\ce{CaCl2}$ (m.p. = $\pu{772^\circ C}$), but rather a physical adhesion as a result of a set of steps applied to calcium chloride solution (or its deliquescent form) of gradually increasing the temperature from $\pu{70 .. 80^\circ C}$ to approx. $\pu{300^\circ C}$. This results in formation of hydrated forms ($\ce{CaCl2 * x H2O}$) with subsequent complete dehydration and solidifying above $\pu{250^\circ C}$ alongside with minor partial hydrolysis to form $\ce{CaO}$ and $\ce{HCl}$.
Fused refers to the fact that this porous mass is granulated, but not dispersed, in order to increase the surface area and improve its dehumidifying ability and at the same time to prevent the salt from deliquescing swiftly.
Reference
answered Oct 14, 2017 at 22:26
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Basically, fused $\ce{CaCl2}$ is an anhydrous salt. It is called fused because it is ionic and solid crystal and is formed by electrolysis and fusing. It is highly water absorbing in nature.
