Do I need both potassium sorbate and potassium sulfite?

I tried to search this but could not find a definitive answer - if you can point me to an existing thread please do, otherwise give me an answer!

I am making a simple hard cider (apple juice, apple concentrate, sugar, water, yeast). When it is done, I want to back sweeten with a simple sugar/cinnamon syrup and bottle it. I do not want carbonation so that is not a problem. I just dont want bottle bombs :rockin:

LHBS guy sold me potassium sorbate, said it would stop the yeast from eating the back sweetener. Thats what I want. While searching around, I saw many posts that said you also need potassium sulfite.

So for this brew, do I need both?

http://winemaking.jackkeller.net/finishin.asp

Read the first section on "stopping fermentation"

In general, you don't really "need" the sulfite. But sorbate does work better in the presence of sulfites.

The biggest reason I'd use sulfite with sorbate in an apple cider or wine is because of the risk of MLF (because apples are very high in malic acid). MLF is not an issue in and of itself, and some people put their fresh ciders through MLF on purpose. But what happens if a cider spontaneously undergoes MLF after sorbate is added, it gets a terrible "geranium" smell that is just awful. Using the proper amount of sulfite prohibits MLF, as well as helps the sorbate work better, so it's really important to use it.

I hope that helps!

OK. I just bought the Campden tablets to go along with the P Sorbate. The PS has instructions for what quantity to use per gallon, but the tablets do not? Any advice on how many to use?

1 per gallon is the usual amount for this purpose.

http://www.winemakermag.com/guide/sulfite

Required sulfite level depends on the pH of the must.

Yeah that PH link is way above my head. Never made a wine, this is my first cider!