What's that inert gas that people squirt into developer bottles to keep the developer from oxidizing? I just opened a brown glass bottle into which I had decanted some HC110 in September 2016 (I filled it all the way to the top, so it had minimal air), and it was still that beautiful pale yellow color of fresh HC110, and there was no gel at the bottom of the bottle which always happens with my partially-opened bottles (I didn't think that last part had to do with oxidation, but maybe it does?). Anyways, would love to keep that HC110 looking that pretty for another 3 years, so what gas do I squirt into it? I'd kinda prefer not to use the marble technique...