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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: illotio on April 07, 2021, 04:39:21 PM

Title: Need help with concentrations:
Post by: illotio on April 07, 2021, 04:39:21 PM

Hi all,

I would need some help please, I am trying to find out an adequate concentration of Phosphoric acid to brush over steel and create a conversion layer that will improve the adhesion of Epoxy paint. Based on the study "Influence of Phosphoric Acid on the Adhesion Strength between Rusted Steel and Epoxy Coating" I would need to apply 50g/L of phosphoric acid. However I only have a bottle that contains 85% phosphoric acid. How many ml of phosphoric acid (85%)should I mix with deionised water if I want to have 100 ml of solution?

Please let me know and thank you for your *delete me*
Roman.

Title: Re: Need help with concentrations:
Post by: Borek on April 07, 2021, 07:43:24 PM

85% phosphoric acid has density of 1.69 g/mL. Take as much acid as needed, put it into 80 mL of water (actually any volume a bit smaller than required will do, note that adding concentrated acid to water is safer than the other way around), shake to mix, fill up to 100 mL.