How Do I Calculate A Percentage of Powder And Water?

I need to mix a powder with water to come up with a 20% solution for a topical application. How do I calculate the volume of the powder to the water to make 20% of the powder?



Thanks!



-SFHow Do I Calculate A Percentage of Powder And Water?
In all my many years in industry using a varity of solid in water suspensions or mixtures, there were only two types that were used: I assume that the question is asking about adding powders such as clay or titanium dioxide, etc to water in order to form a suspension or slurry.

1) What I would call a mass/mass (or in earlier language, weight/weight)

This is a suspension ( remember the powder does not dissolve in the water) in which 100g mass of the finished suspension would contain 20g of powder and 80g of water.

2) Mass/ volume : this is a system where 100cm鲁 of final suspension would contain 20g of powder.



I have not come across any system defined as 20g of solid in 100cm鲁 (or g) of water.



On reflection, even if you wish to make a solution - the powder dissolves in the water:

a 20% solution w/w or m/m is prepared: 20g powder + 80g H2O

OR a m/v solution: 20g powder plus water to a final volume of 100cm鲁How Do I Calculate A Percentage of Powder And Water?
A 20% solution consists of 20 g of solute diluted to 100 mL with water.