How to test purity of Helium?

[Popopo]

I bought a tank that is supposed to be pure Helium, but I hear mixed stories about it. I don't wanna return the tanks. I wouldn't know how to get nitrogen or argon and I just hope I am done buying my supplies. That said, if it won't be certain I'd have to buy new tanks but I just really hope my tanks contain enough Helium. So how can I test this out for myself?

 

[Odwin]

So you can use Archimedes principle to find the volume of helium in the balloon. You just need a sensitive enough scale. The bouyant force on the helium balloon is equal to the weight of the air it displaces.
Fb=da * g * V,
where da is the density of air and V is the volume of the balloon. Now tie the balloon to an object, something like a wood block, whose weight you know to be w1. Next weigh the block with the balloon tied to it. The weight registered on the scale now will be the weight of the block minus the buoyant force on the balloon.
w2 = w1 -Fb
w2 = w1 - da * g * V
V = (w1 - w2) / da / g
So now you know the volume of helium in the balloon. The mass of the helium is thus
m = V * dh.
m = (w1 - w2) * (dh / da) / g

Or in other words. If you dont have the right instruments you can forget it to check

 

[russlinjimmies]

If it was purchased from a mainstream source the helium itself is probably pure, but mixed with enough oxygen to not actually be fatal.

 

[Greenberg]

I bought a tank that is supposed to be pure Helium, but I hear mixed stories about it. I don't wanna return the tanks. I wouldn't know how to get nitrogen or argon and I just hope I am done buying my supplies. That said, if it won't be certain I'd have to buy new tanks but I just really hope my tanks contain enough Helium. So how can I test this out for myself?

There is no label of the contents on your tank?