We present the first study of the β decay of 23 Al undertaken with pure samples. The study was motivated by nuclear astrophysics questions. Pure samples of 23 Al were obtained from the momentum achromat recoil separator (MARS) of Texas A&M University, collected on a fast tape-transport system, and moved to a shielded location where β and β-γ coincidence measurements were made. We deduced β branching ratios and log ft values for transitions to states in 23 Mg, and from them determined unambiguously the spin and parity of the 23 Al ground state to be J π = 5/2 + . We discuss how this excludes the large increases in the radiative proton capture cross section for the reaction 22 Mg(p, γ ) 23 Al at astrophysical energies, which were implied by claims that the spin and parity is J π = 1/2 + . The log ft for the Fermi transition to its isobaric analog state (IAS) in 23 Mg is also determined for the first time. This IAS and a state 16 keV below it are observed, well separated in the same experiment for the first time. We can now solve a number of inconsistencies in the literature, exclude strong isospin mixing claimed before, and obtain a new determination of the resonance strength. Na(p, γ ) 23 Mg have both been suggested as possible candidates for diverting some of the flux in oxygen-neon novae explosions from the A = 22 into the A = 23 mass chain.