4 ms·
Their table seems reasonable, but the first example they work through is wrong. >Example 1: >Suppose a scientist has a bottle of 99% IPA (C1) that they want t
by beervirus 6y ago
Their table seems reasonable, but the first example they work through is wrong.
>Example 1:
>Suppose a scientist has a bottle of 99% IPA (C1) that they want to dilute down to 70% (C2). To end with 50mL of 70% IPA (V2), how much volume of 99% IPA should they use and dilute with distilled water to create the final solution?
>99% x V1 = 70% x 50mL = 35.35mL
>Thus, adding 35.35mL of distilled water to 14.65mL of 99% IPA creates a 50mL solution of 70% IPA.
(They reversed the water and IPA quantities.)
- Wistar 6y agoGood catch!
- Dylan16807 6y agoThe table's garbage. It's showing the total volume as exactly equal to water volume plus alcohol volume, out to four digits. That's not how it works. A mixture of water and alcohol (whether ethanol or isopropyl) gets more compact because the different molecules can pack together better, by up to a few percent.
- Wistar 6y agoIs it inaccurate enough that it cannot be used to safely create disinfectant-grade 70% dilutions from 99% or 91%?
- beervirus 6y agoIf you're measuring things by slopping them into a measuring cup instead of weighing them out to the milligram, you'll never know the difference.
- Dylan16807 6y agoIt won't matter for "eh somewhere between 55% and 75% is fine", but if you have a good measuring cup you could easily see the difference in volume. I don't know why the chart assumes you're measuring down to thirds of milligrams, though...