What size is your cage? If it`s something around the size of a Hamster Heaven or an Alaska cage, these cages don`t need weekly emptying, but spot cleaned daily, or just a few times a week. Hamsters can sometimes find an area where they like to `go` for a pee. It can be a favoured corner, inside a tube or a box or anywhere they choose. My Russian dwarf has recently chosen his cardboard Chube tube as his urinal!
But even so, I don`t see it a smelly tube, it retains his smell, so he goes back to it daily. Not a bad thing because you can then know where he`s choosing to `go` as the damp patch shows up. My last roborovski chose a toilet roll tube to use as his favoured peeing spot and I only changed the tube if it got really stinky, but kept the tube in the same location inside the cage and he still ran into it for a pee!
Soda crystals I presume are used as a cleaning agent or similar but not something to be located near a small animal. You have no way of knowing whether they omit any aerosols if left too close to the cage. What I sometimes do is, light a scented candle, but place it in the room opposite or in the bathroom and leave the door open. The scent drifts around into the hallway, but isn`t directly near the hamster cage. Doesn`t make the hamster pee any less though!! x