Thanks, which begs the question, do any home brewers bother with single mixed gas bottles? …
Yes they do.
… As if all we really want or need the gas for most of the time is carbonation and serving, well is there any benefit to getting anything other than pure co2?
No there isn't.
And to really stir things up and have people ask "why is HE giving advise on kegging?". At the same time I'm going to argue with something
@fury_tea wrote (sorry!). I'm going to lose a lot of forum cred writing this!
Nitrogen as a propellant is a tool for pushing beer about large properties without causing the beer to over carbonate (from too much CO2 pressure). Obviously it is going to be a very rare home-brewer to need this. Nitrogen as an enhancer of head was a development by Guinness way back in the 1950s. Guinness stout at that time was sold through handpump. They had even developed the "high cask, low cask" system to exaggerate the creamy head that it had become famous for. But the problem was they had little control over the care needed to serve it successfully. They had tried "keg" with CO2, but drinkers didn't like what this did to the beer (high levels of CO2 creates a lot of acidic carbonic acid).
So they kept the CO2 down by using nitrogen, but also figured that if they cooled the beer and used very high pressures they could get nitrogen to dissolve in the beer and it would come out of solution slowly and in very fine bubbles. It even created the swirling "cascade" effect from the bubbles like the best hand pumped stuff.
But then came the really clever bit: The stout wasn't as good as the best hand-pumped Guinness (cue lots of folk choking on their "nitro keg" beer), it was freezing cold for a start, so you get a gang of very clever marketing folk to (successfully it seems) make this new product appear better than the old stuff and tie the new techniques into being responsible for the improvements (they weren't improvements, they were techniques to
emulate the old stuff, but for people getting badly kept Guinness they were improvements).
Soon the "nitro keg" replaced the CO2 keg that was still being put out to the rest of the world (early "nitro keg" was only available in Ireland) and the hand pumped stuff disappeared.
There, that's damned any reputation I had around here? Perhaps I've done my bit for "fake news" as I've written it off the top of my head. And why is it odd I should give advice on kegging? Because I'm a lifelong "Real Ale" drinker! But I figured recently (40 years too late) that kegging was the only way I could emulate "Real Ale" (see my "treatise"
https://drive.google.com/open?id=0BwzEv5tRM-5EQUhZbDNPdmV1bWc). I had to throw off a lifetime of believing you couldn't use CO2 in "Real Ale" home brewing and also learnt very subtle techniques to make it work - it is this subtle knowledge that I can use to give sound advice on "kegging" in general. That treatise even includes a bit on mixed gas, to get very low concentrations of CO2 in beer (something you can't do with a "breather" and CO2).
<EDIT: Corrected for my continued inability to correctly use "advice" and "advise". Flippin' English language!>