George,
Thank you for you explanation.  It says a hell of a lot more than I meant.
But yes, we can't be sure of the purity of Balloon Grade Helium.  It is not all
He and O2, as I stated.  There are other contaminents.
Apparently, the cylinders used for ballon grade are not O2 clean, thus it
is pure O2 that is added to the He.
Also, I understand, the filling process differs between the ballon grade and 
breathing grade gases.  With the lower grades, the cylinders are simply 
emptied before refilling, however with the higher grades, the cylinders is 
apparently filled under a vacum ensureing that the cylinder is absolutely 
empty before refilling.  Further, the cylinders on the later as O2 cleaned
which is not the case with the lower grades.

Prices vary between US$100 (ZAR500) for ballon grade up to US$200 (ZAR1000)
for spectrograhically analysed gas, here each tube is indivually analysed.

On average we pay US$140 (ZAR700) per 1.5kg (1c/m).

Dennis.


George Wrote:
Dennis, here in Florida they have "Goober Grade" helium - it comes with
air in it and some pot smoke, and is half filled with beer: you simply
use the pressure of the helium to operate the beer tap, and then fill
your tanks with the Alice B Toklas air and go diving at Peacock. If it
start wearing off, you just stop by the Strokepost and have Lush breath
on you on your way to Nells to get the "all you can eat" barbeque. You
will pass by Rennaker's trailer on the way, just roll your windows up.  

Dennis JR Harding wrote:
> 
> In South Africa there are several grades, amongst others ballon grade. 
Apparently
> under law, Ballon or party grade is supposed to have 21% O2 content, so what
the supplies do
> is to add 20% O2 by volume.  This is to curb the number of increasing
blackouts that
> occur when people breathe pure He.
> 
> There has been a significant increase in the number of outlets that provide
He filled ballons
> for marketing purposes.  Especially at restaurants.  Nearly every restaurant
in the Johannesburg area
> that caters for family entertainmnet will give each child a ballon.
> 
> There are also several other grades of He available, including that which has
been spectrographically analysed
> and that costs!
> 
> Dennis Harding
> South Africa


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