Character Analysis
Alberto is Primo's best friend and is with him for almost his entire imprisonment in Auschwitz. Levi sums up his character nicely:
Alberto entered the Lager with his head high, and lives in here unscathed and uncorrupted. He understood before any of us that this life is war; he permitted himself no indulgences, he lost no time complaining or commiserating with himself and with others, but entered the battle from the beginning. (5.6)
So, Alberto is tough (he sees his time at Auschwitz as a "war"), but he's also smart. He uses his powers of reasoning to negotiate prison life, and this allows him to set up several economic arrangements that provide him and Primo with extra food. Supremely resourceful, we learn that Alberto is "one of those fellows who immediately finds everything they need" (17.26).
This guy's a true friend, too. Both he and Primo take the test for the Chemical Kommando, but out of the pair only Primo is eventually accepted. He's genuinely happy that his friend made it, and there's not even a "shadow of envy" when Alberto finds out the news (15.11).
In the end, Alberto is evacuated with the "healthy" prisoners. Defying the rules, he comes by Ka-Be to say goodbye to his friend. Primo never sees him again, because almost all those prisoners died on the forced death march (17.28).