3rd class skills + Chaos Essence

I have this question for this updates... if i kept 3rd class skills and then i want to use chaos essence... i will lose the 3rd class skills or not??

simple: if i kept rapid fire and use chaos essence change class what happend with rapid fire?

Some ppl told me i will keep other tell me i will lose it.

Thank you.

3rd class skills + Chaos Essence