Positive and negative potential via two power supplies with common ground?
Yes, as long as the two supply outputs are floating (i.e. no common connection between them prior to connecting) then simply connecting two terminals together to serve as the common ground is fine.  

You would connect the negative terminal of supply 1 to the positive terminal of supply 2, then use the free terminal of supply 1 as positive rail, the connected terminals as circuit ground, and the negative terminal of supply 2 as your negative rail.