Not exactly a household word, but: When speaking of turning coal into a liquid hydrocarbon , is the process called “liquefaction” or “liquification”? While the latter sounds correct, the former seems to be technically correct. (Yet, I’ve seen both.) Anyone know why the variance? For example, a related process called “coal gasification” has no twist. It is NOT “coal gasifaction”!
…Is there a geophysicist in the house?
I’ve only ever seen liquefaction. Derived, presumably, from the Latin verb liquefacere: to melt, or dissolve.
Where have you seen the word “liquification” in use? The dictionary refuses to acknowledge its existence. 
It probably just seems like a natural transition from ‘liquify’ to ‘liquification’; you know, like ‘indemnify > indemnification’.
Liquifaction refers to soil acting like a liquid.
Liquification is the act of becoming liquid, as in condensation from a gas or the melting of a solid.
Ok, we’re closer, but frankly, a stub Wikipedia article that cites no references isn’t exactly solid evidence. We need something more tangible! Darnit, where are the genetic engineers when you need them?? 
here is a medical dictionary giving the same definition.
I found a few articles about the conversion of coal to liquid petroeum. It may be that both words are appropriate in different phases of the process.