CSS Webkit Transition - Fade out slowly than Fade in

This is what I have:

.box{
    background:#FFF;
    -webkit-transition: background 0.5s;
}

.box:hover{
    background:#000;
}

But this appends to both onmouseover and onmouseout actions, but isn't there a way to control them? Something like:

-wekbkit-transition-IN: background 1s;
-webkit-transition-OUT: background 10s;