I put lo sale - thought lo used before an 's' as in lo studente ?
It's only "lo" before S followed by a consonant.
http://duolingo.com/#/comment/233855 FAQ number 3
...and before 'z' or 'p'+consonant ;-) So, 'lo zucchero' and 'lo psicologo'.
(I meant with S, but I wasn't clear, you're right) ;)