hello Borek
i am trying to get a specific pH with 5 of 6 knowns
the knowns are 5 gallons of water.
the pH of 3 of the final product,
the amount of phosphoric acid 4.799 ml THIS AMOUNT CAN NOT BE EXCEEDED
the amount of sodium hydroxide 3343mg THIS AMOUNT CAN NOT BE EXCEEDED
and the amount of caffeine 1889.502453 mg THIS AMOUNT CAN NOT BE EXCEEDED
what i do not know is how much citric acid is needed to bring the pH to 3.
What i am not sure or is whether or not the citric acid is augmenting the pH or if it would be the Phosphoric acid that is changing the pH in this
Yes Borek you are correct this is for a soft drink, these values are directly from the nutrition label once converted from the eemental values to the compound values, by brother in law who is the regional manager for ConAgrafoods has confirmed that all the chemicals are used in soft drinks and the amounts of the simple compounds, i.e. phosphoric acid, sodium hydroxide... are accurate. what he can not confirm is the amounts of the complex compounds that are formed once added to the soft drink, i.e. phosphoric acid + sodium hydroxide which forms mono, di, or tri sodium phosphate depending on the pH. (which has replaced the emulsifier of gum arabic in dark softdrinks.
if i understand you correctly in what you say, in this formula it does not matter if the sodium compounds are of citrate or of phosphate, they will adjust by them selves. so for example if i use di sodium all of the sodium is used but i have excess of phosphorus if i use mono sodium phosphate i use up all the phosphosphorus but have excessive amount of sodium.
now if i add citric acid, the excess sodium /hydroxide will react with the citric acid to form sodium citrate. so i am trying to figure out how much sodium phosphate is formed and how much sodium citrate is formed, as well as if the caffeine citrate is formed and if so how much citric acid is needed to form the caffiene citrate, and or how much more is needed to change the pH to 3
i am trying to figure out exactly how much di sodium phosphate i need to add,
how much phosphoric acid i need,
how much sodium citrate i need
how much caffeine citrate is needed
how much citric acid i need
While I suggested to use NaOH in calculations doesn't mean you need to use NaOH when preparing the mixture. Think about it this way: it doesn't matter whether you add 1 mole of disodium phosphate or 1 mol of phosphoric acid and 2 moles of NaOH - the resulting solution is identical. There is an infinite number of combinations of citric acid/citrate salts/phosphoric acid/phosphate salts/NaOH that yield pH 3.0 solution. They all share some dependency of the amounts three main components - main components being citric acid, phosphoric acid and NaOH. As amount of NaOH needed is a function of the citric acid/phosphoric acid ratio, I suggested starting calculations with their mix and calculating amount of NaOH needed. Once you know these you can easily calculate what salts will bring the right result.
i much rather use di sodium phosphate in granular form and tri sodium citrate
Solutions of both these salts have a pH above 7, no way to mix them and get pH around 3. You may have better luck mixing phosphate with just citric acid.
The real question is what you are really trying to do. Do you need just a right pH, or some specific concentrations of citrate/phosphate, or some specific ratio of them, or just a a concentration of P in the solution? You have mentioned caffeine, so my guess is that you are trying to recreate some basic characteristic of a soft drink?