Take known volume of dry ether and an HCl cylinder. Bubble gaseous HCl through ice-cold ether at a rate where almost no gas can exit the liquid (indicated by bubbler). After about 20-30 min, a concentration of 3-5M should be reached. I do this procedure in a sealable Schlenk bomb so that I don’t lose HCl over time and I can recurrently use as needed. The concentration of HCl can be measured by titrating the solution into 0.1M NaOH using two drops of phenolphthalein indicator.
Be very mindful of the cooling temperature (ice-water bath) because HCl solubility in ether increases at lower temperatures. I’ve heard of explosion accidents occurring because people cooled with dry-ice/acetone and then proceeded to warm the closed vessel to room temperature.
In a sample titration, 10 mL of 0.1M aq. NaOH was neutralized with 0.25mL of the HCl in ether solution, which gave 4M for the concentration. Doesn’t matter that the mixture is biphasic.
Phenolphthalein indicator was made by dissolving indicator in absolute ethanol so that a 0.5% wt solution is attained.
Notes
- HCl in ether can be purchased from various chemical vendors (Sigma-Aldrich, Oakwood, TCI), but can be rather expensive if large amounts are needed. Sigma-Aldrich and TCI bottles always came in Sure/Seal bottles, but Oakwood ones did not.
- The procedure can be carried out without an HCl tank by generating your own gas in-situ. HCl can be generated by gradually dripping concentrated sulfuric acid (98%) onto solid NaCl.