My original posting included the tex file generated by C-c C-e l l.
Perusing it will show you that babel is not used anywhere in this export.

On the (remote) chance that my problem might be caused by my use of emacs
25.2, I just installe emacs 26 from the emacs-snapshot packages for Debian
testing, ang got exactlu the same prolem.

The org-relevant part of my .emacs is as follows :

(require 'org)
(require 'org-ref)

Then, later

;; Septembre 2018 : org-mode

;; touches globales : À revoir ?
(global-set-key "\C-cl" 'org-store-link)
(global-set-key "\C-ca" 'org-agenda)
(global-set-key "\C-cc" 'org-capture)
(global-set-key "\C-cb" 'org-switchb)
;; Chemin de la bibliothèque ditaa
(setq org-ditaa-jar-path "/usr/share/ditaa/ditaa.jar")
;; Autoriser les évaluations Babel
(setq org-confirm-babel-evaluate nil)
;; Langages connus
(org-babel-do-load-languages
 'org-babel-load-languages
 '((ditaa . t)
   (emacs-lisp . t)
   (R . t)
   (python . t)
   (sagemath . t)
   (julia . t)
   (gnuplot . t)
   (maxima . t)
   (stan . t)
   (mathematica . t)
   (sqlite . t)
   ;; (sh . t)
   ))

Like it or not, believe it or not, this setup is sufficient to create the
problem I reported.

HTH,

--
Emmanuel Charpentier


Le mar. 27 nov. 2018 à 15:20, Eric S Fraga <esflists@gmail.com> a écrit :

> On Sunday, 25 Nov 2018 at 21:36, emanuel.charpentier@gmail.com wrote:
> > I forgot to add that, when exporting to plain tex or ODT, #+language*
> > *seems* to be honored : the table of contents is entitled "Table des
> > matières".
> >
> > The problem is therefore probably in ox-latex.el (but way above my
> > level of competance in em...
>
> But it works just fine for me.  Have you actually had a look at the
> LaTeX that is created?  I wonder whether you might have a setting for
> the LaTeX export that includes other settings than just the default or
> which doesn't allow the language setting to be included?
>
> --
> Eric S Fraga via Emacs 27.0.50, Org release_9.1.14-1034-gafcb1d
>