Allegiance Title Co. will relocate its Arlington office in August to Commonwealth Center, gaining highly visible first-floor space at a premium location in the city.The Dallas-based title company has signed a long-term lease for the balance of the first floor, 2,587 sf, at 4200 S. Cooper St. The 35,917-sf office building is now 71.7% leased, with 10,176 sf remaining on the second floor.