transition-duration", "10s" not work in my jquery

transition-duration", "10s" not work in my jquery

i have a code like this, i made that for change a navigation when > 370

  2. $(window).scroll(function () {
  3.    if ( $(window).scrollTop() > 370 ) {
  4.        $("#header").css("background", "#34495e", "transition-duration", "10s");
  5.    }

  7.    else {
  8.     $("#header").css("background", "white", "transition-duration", "10s");
  9.    }
  10. });
"transition-duration", "10s"  not work in my jquery, but another work well. thanks :)
i tried that at chromium and firefox