[billnotgatez]

 A chemistry teacher is recruited as a radio operator in the first world war. He soon becomes familiar with the military habit of abbreviating everything. As his unit comes under sustained attack, he is asked to urgently inform his HQ. "NaCl over NaOH! NaCl over NaOH!" he says. "NaCl over NaOH?" shouts his officer. "What do you mean?" "The base is under a salt!" came the reply.