I made liquid oxygen today. I think

[flatmaster]

Went to visit a Jr. High today to make liquid nitrogen ice cream.
One way is to drop the ice cream mix into the nitrogen.

I think we actually made some liquid oxygen accidentally. After doing the dots, we strain the nitrogen through a sieve to catch the ice cream and store the excess in a dewar. We didn't have it today, so it went into a stainless steel bowl. The bowl was cold enough that any liquid condensation froze even near the top of the bowl. near the coldest outer portion of the bowl, we had what we believe was blue liquid oxygen conencing on the outside and dripping off.

My question is how concentrated is this liquid oxygen? I know there is atmospheric nitrogen condensing there as well, but the boiling point of oxygen is about 12 degrees warmer than that of nitrogen.

I also saw a neat affect where the droplets were splashing. I must have been in the exact position for a flattened droplet to reflect a light on the ceiling. I saw transient, circular flashes of light where the droplets were hitting and flattening out a bit before the surface tension pulled the droplet back to a more spherical shape.

 

[mgb_phys]

Unlikely to get LOX condensing on the outside of the bowl from the air.
In theory you can get O2 forming on the surface in an LN2 tank it's one of the things the safety people got worried about and banned open our dewers but I never heard of it actually happening.

 

[f95toli]

You can certainly "make" liquid oxygen when using liquid nitrogen, or even better liquid helium.

Most of you will have seen someone demonstrate superconductivity using a high-temperature superconductor (usually YBCO). Droplets of liquid oxygen will often condense on the surface of the superconductor and sometimes they accumulate into a bigger drop hanging in the gap between the magnet and the YBCO, the oxygen is slightly blueish.