Weight titration techniques are, in my opinion, by far the best way to bring “volumetric analysis” into the 20th (let alone 21st) century. Such techniques should have taken chemistry teaching by storm as soon as automatic balances good to 0.01 gram became commonplace. Not only are relatively inaccurate glass burets greatly outclassed, but so are pipets and volumetric flasks. Such glassware is expensive, hard to clean well, and difficult to use properly.

Years ago I coined the term “molamity” to designate the concentration units of moles of solute per kilogram of solution, and my students routinely performed titrations with uncertainties of 1 part per thousand. My text, Chemical Equilibrium and Analysis (1), included a lab titled “High-precision Assay of Mohr’s Salt by Gravimetric Titration”. Students routinely achieved part per thousand results.

W. B. Guenther published a good article titled “Supertitrations: High Precision Methods” (2). B. Kratochvil and C. Maitra published “Weight Titrations: Past and Present” (3), with many citations.

A good technique is to use a squeeze bottle, as recommended by Hawkes, of the type that delivers through a channel molded into the side of the bottle. The top cap is replaced with a fine-tip medicine dropper so that the endpoint may be determined more precisely than a hard-to-control squeeze would permit. Squeezes are used to get close to the endpoint, and then the dropper is used to nail it down accurately. I like to have another medicine dropper in the receiving beaker, so that a small portion of the analyte can be kept in reserve to avoid over-running the endpoint.

Gravimetric titrations should become the gold standard, and volumetric glassware should be seen in museums only.

Literature Cited

1. Ramette, Richard W. Chemical Equilibrium and Analysis; Addison-Wesley: Reading, MA, 1981.
2. Guenther, W. B. J. Chem. Educ. 1988, 65, 1087.
3. Kratochvil, B.; Maitra, C. American Laboratory 1983, 15, 22–29.