5:5:2 what does it mean?

[Ronaldo]

( 5 : 5 :2 v/v)

i think it 5ml from the first solvent , and 5 ml from another solvent , and 2 ml

but what if i have to make up to 100 ml with these three solvent using the same percent ( 5 : 5 :2 v/v)



thanks

[bisnettrj2]

If it were me, I would do the following:

Fill one 50 mL volumetric with solvent A

Fill one 50 mL volumetric with solvent B

Fill one 20 mL volumetric with solvent C

Combine all in a beaker, allow to equilibrate (in case of any exothermic/endothermic mixing reactions), then fill a 100 mL volumetric with the mixture. That way, you keep your 5:5:2 ratio without having to make any complicated measurements of volume.

If you need to make more, or will need more in the future, you could go 250:250:100 and combine to give 600 mL of a 5:5:2 mixture.

[Ronaldo]

Thank u very much bisnettrj2 for your way of prepare it but the combine mixture will be ( 120 ml ) how can i put it in 100 ml flask ?

any way i like your method

[danko]

Ronaldo,

If you absolutely insist on preparing 100 mL of the mixture, then you’ll need to use the following volumes:

41.67 mL : 41.67 mL : 16.67 mL

Does it help?

Best Regards

[lmh]

bisnettrj2 suggested making up a slight excess because if you mix solvents whose volumes add up to exactly 100mL, you may not end up with 100mL. For example, 50mL water + 50mL methanol makes 50%MeOH, but not 100mL! There is a volume change.

Bisnettrj2's method makes exactly the solvent you describe, and relies on you to measure the correct volume.

[bisnettrj2]

lmh, danko, thanks for helping me out here...

[Ronaldo]

speacial thanks to you all