We like to occasionally use mixtures of n-butane/propane for our closed loop live resin extraction. Our supplier will give it to us pre-mixed or separate. Does anyone have a good method for determining the current solvent mix in your solvent tank? We start with 70/30, but I’m sure after even just one run, that ratio is off. I’ve been racking my brain trying to figure out a reliable and safe way to figure out what I have inside my solvent tank at any given time. Is there a chart to correlate the mixture to pressure and temperature? I haven’t been able to locate one that was useful to me. Thanks!
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Given the way vapor pressure varies with temperature and mol fraction of the various components, I’m sure there is a way of using pressure readings at a couple of well chosen temperatures and some maths to figure it out.
if I’d had more coffee I might even do something stupid like make a stab at the math. 
this might help get you started
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How large is your running tank? I use a 70/30 blend as well, order in tanks pre-mixed and fill a significantly smaller tank off the premixed. As the day drags on the propane % decreases but typically I only get a days worth of running of a single fill.
Add back propane
When the yield starts getting fucky add back butane
Add back regularly so it’s in smaller amounts. I’d do it daily
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Really need to sit down and teach this maths to my phone at some point…anyone done that yet?!?
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Just run isobutane…
Fuck blends imo
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This is the way.
im pretty sure the propane goes away first.