How to Mix IPA for Inspecting Correction Results

[mike2977]

I bought some 71% IPA and I have a 32oz bottle. How much ounce of IPA do I need to make around 11% IPA? I'm bad at calculations so if someone can help that would be great.

Using the same spreadsheet as above, here are the results I got:



Note that the concentrations are less than the original example values I'm still keeping in the spreadsheet. This is because the calculated values are based on the amount of water in the bottle, not the full volume of the bottle.

[mike2977]

I figured out how to show the formulas in the Excel spreadsheet (been awhile since I did this,) so if anyone would like to critique this, please do, as I don't want to hold myself out as an expert on this:

[Kyle_Elantra]

I bought some 71% IPA and I have a 32oz bottle. How much ounce of IPA do I need to make around 11% IPA? I'm bad at calculations so if someone can help that would be great.

4.96 oz of 71% will yield 3.52 oz which is 11% off 32 oz.

So use 5 oz.

[Kyle_Elantra]

Mike you want to do this:

(32 x .11)/.71

If you need help with this in Excel shoot me a PM.

[matryx]

4.96 oz of 71% will yield 3.52 oz which is 11% off 32 oz.

So use 5 oz.

Thank you!

[Kyle_Elantra]

You're welcome!

[mike2977]

Mike you want to do this:

(32 x .11)/.71

If you need help with this in Excel shoot me a PM.

Kyle was kind enough to both PM and call me for an interesting discussion on how this formula works and where I was off on my spreadsheet calculations.

I had challenged using the volume of the container in the calculation, stating to him and above that it should be the volume of the water that the IPA is mixed with. However, when calculating concentration by volume (not concentration of the solution itself,) Kyle is correct and I am incorrect. An analogy would be that if you had 100 pennies in a fixed size container, and 10 of them were red, and wanted to know the % of red pennies, you'd use 100 as the divisor and not 90, the amount of other than red colored pennies.

Given Kyle's formula and response above, here is a screen capture of his spreadsheet with the result for the 32 oz bottle at .71 IPA. I'm also showing the calculations for the 6 oz bottle that had been requested earlier and apologize for any confusion I may have caused by my earlier responses.



The second picture is the same spreadsheet with the formulas of the cells so those with Excel can do future calculations themselves.

[Kyle_Elantra]

Great write up Mike!

I'm glad that we were able to talk about this.

For Column F you could use A2-E2 to avoid having to convert the negative.

[matryx]

When using mineral spirits do you mix it with water or just use it straight?

I have a container left I had for years in the garage but it ain't sure if this stuff goes bad.

[Mike Phillips]

When using mineral spirits do you mix it with water or just use it straight?

Mineral Spirits do not dilute with water so you use it straight. If the container has been sealed tightly it's probably okay to use. If you pour it out and it has a very strong nasty solvent smell I would not use it because it's cheap enough to get the good/better stuff at any Box Hardware Store for less than $10.00.

Get the odorless version as this means more of the nasty V.O.C.'s which are also carcinogens have been removed. (that's why it doesn't smell as strong).

See the first page of this thread for an example of a quality, easy to find brand of Mineral Spirits.