[seniour_baloch]

I read water is essential for any acid. When HCl is dissolved in water, it produces H+ ions which cause the litmus paper to change it colour! But if HCl gas is liquidified and then tested with liquid, what would be the results? As wel as this pure liquid HCl is corrosive or not?

[Arkcon]

Look at the periodic table.  What sort of compound is liquid hydrogen chloride?  You may be able to come up with a conclusion that would be helpful to you on an exam.  Let's see it.

[delta609]

The thing about acids being corrosive isn't that they "eat" through materials. It's the fact that they react through materials.  If the HCl isn't dissociated in water it's not as prone to react, hence less corrosive. 

[Mitch]

I think HCl would still be highly reactive even in the gas phase, am I just really wrong in thinking this?

[Arkcon]

I would bet it would corrode ferrous metals rapidly, gaseous or liquid.  However, addressing the original posting: liquified anhydrous hydrogen chloride, would it dissociate into H⁺ and Cl^-?  Compare and contrast: ionization of glacial acetic acid (note: I didn't ask if it can hurt your hand) or perhaps, the ionization of molten NaCl -- in what situations does ionization occur?  And why?

[9-92-6-19]

HCl would not be an acid if it were cooled down into the liquid phase; it would be more appropriately hydrogen chloride, not hydrochloric acid. That being said, if there is any water in the air then it will protonate H₂O and act like an acid.