Double majors, of the sort you pick out yourself, can be very difficult. Definitely talk with your academic adviser as soon as possible about what the work load is going to be. If the Chemistry program at the university offers a double major, then they've put some work into a practical lesson plan, so that's better if that's the case.
Only you can be a judge of you ability to handle an extra workload. And thermostatically theoretically, any additional knowledge is a useful distinguishing characteristic for you and your future. However, the analytical courses seems, to me, almost diametrically opposed to the topics of Chemical Engineering. I'm not saying that a chemical engineer never runs an analysis, just that getting deep into analytical theory seems not to be advancing your own chemical engineering knowledge.
*[EDIT] fix auto corrected word