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how much water to add to 4oz of 99.9% DMSO to make it 70 % ?
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In this mixture, 99.9% of volume is pure DNSO.
So, the volume of the pure DMSO is 4*0.999 oz = 3.996 oz.
We want this volume, 3.996 oz, be 70%, or 0.7, of the new volume V of the mixture.
So, we write 0.7*V = 3.996 oz.
It gives V =
= 5.708571429 oz.
It means that the volume 5.708571429 - 4 = 1.708571429 oz of water should be added.
You may round it to 1.71 oz of water. ANSWER
Solved.