I have bought some anhydride of trichloroacetic acid (TCA) and would like to prepare an acidic solution. My problem is, that I don't know how much "powder" to mix with how much water to produce an x% acidic solution of TCA. I am aiming for as close to 100% as possible. From what I know, I need to measure pH to derive the concentration (I only have some litmus paper to do that)? Does there exist formulas or tables, that I can follow? Sources of these?

EDIT: Based on a comment, I obtained these values:

I have bought 1 kg of TCA powder of

1000 g / 163.38 gmol^-1 = 6.1207 mol
18.01528 gmol^-1 * 6.1207 mol = 110.27 g of water

somehow I need to dissolve 1 kg of powder into 110.27 mL of water. How can that work? I doubt 1 kg of powder can be dissolved in such a tiny amount of water.

EDIT2: Wikipedia says Solubility in water: Soluble in 0.1 parts. Does this mean I need 0.1 * TCA amount for a 100% solution? That would mean I need to dissolve 1 kg of TCA in 100 mL of water.

EDIT3: If you have any idea about the true solubility of TCA, please help, there seems to be a lot of misinformation out there. 1000 g / 100 mL seems very strange to me! You can see the strange data here, from multiple sources.

EDIT4: I have asked my Chinese supplier about how they prepare their TCA solution and he said they use 120g - 154.1g / 100 mL recipe for a "standard" solution. The concentration can then be calculated by mole or by mass, but naturally is never 100%. The only way a 100% liquid TCA could exist would be to melt it down into liquid form.

  • $\begingroup$ Dig around online for preparing stock solutions. From what I have seen 6.1N TCA is ~100% w/v. So look up how to prepare solutions using Normal or Equivalents of a reagent. I believe since TCA is mono protic 6.1N ~ 6.1M however I dont do wet chemistry anymore - so I'd have to let someone else give you a proper answer. $\endgroup$ – jbussing Apr 27 '19 at 23:19
  • $\begingroup$ @Mithoron I guess the idea is, that all the molecules of the anhydride react with all the molecules of water? Where can I get the molar mass of the anhydride? $\endgroup$ – user1095108 Apr 27 '19 at 23:35
  • $\begingroup$ Yes, it is. It's just a matter of calculating how many moles of anhydride you have and (carefully and slowly) adding same amount of water. Be careful as anhydride may be dangerous itself and reaction vigorous. $\endgroup$ – Mithoron Apr 27 '19 at 23:40
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    $\begingroup$ @Mithoron I calculated I get 110 mL of 100% acid for 1 kg of powder, I find that unbelievable. 1000 g / 163.38 gmol^-1 = 6.1207 mol, 6.1207 mol * 18.01528 gmol^-1 = 110.27 g (mL). That's such a tiny amount for 1 kg of powder. How can I pour 1 kilo into 110 mL of water, seems bizarre? $\endgroup$ – user1095108 Apr 28 '19 at 0:36
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    $\begingroup$ You should add it to question - edit it, otherwise it may be put on hold. Molar mass of water is much smaller so values seems reasonable, but may be somewhat problematic ;) That's another thing worth asking in body of question. $\endgroup$ – Mithoron Apr 28 '19 at 1:21

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