Snakes have this amazing ability to almost "recycle" their urinary waste product before they expel it. When they do this and draw every last drop of usuable liquid out of that urine (it's not really recycling I just can't think of the proper term at the moment), what is left is that blob of white stuff...the urate. This is nature's way of helping snakes stay hydrated even when the only liquid they are taking in is coming from the prey animal. When the snake has access to regular, good quality prey and also a nice full water bowl like our snake's in captivity have, then they are never short of liquid so will pass urates and liquid urine. Snakes in the wild pass urine too of course when water supplies are available to them but nature has designed this wonderful back up plan for them just in case it is not.