Titration Practice Projects

[After this post, I acquired a top of the line automatic titration from Hanna Instruments and in love with it. I have also learned a lot more tricks to get the best from manual titration. I am currently titrating acids, esters, and formol number which is a measure of nitrogen.]

I’m quickly finding out that titration has to be well practiced. You also must have an idea of the math and numbers involved before you proceed. Spirits will require a much different set of numbers than ferments so it will be good to have an idea of that going in. This will dictate sample sizes, glassware sizes, and titrant concentrations.

My first practice sample was a 5% acetic commercial vinegar I had on hand. I immediately made errors thinking I should be working with a 25 ml sample while Youtube chemists start with 5 ml. In many cases we will be working with very small samples so we must be prepared to work with them using appropriate pipettes [I currently use only a 2.0 ml sample of of vinegars].

My error became apparent when I ran out of room in my small Erlenmyer flask. It takes roughly 40 ml of 0.1 N NaOH to reach the end point of a 5 ml sample so my 25 ml sample would have required 200 ml and been quite a waste of NaOH!

I’m also starting to appreciate phenolphthalein. Many demonstration videos never even use a pricey pH meter to determine their end point and the mid century spirits chemists didn’t either. The pH meter somewhat obstructs the mouth of the flask as you try to add titrant, but it is helpful to get numerical queues about your pace as you build titration intuition. Possibly the pH meter will be requisite when we titrate dunder and molasses washes where the indicator color may not be visible.

To reduce equipment, I thought I’d use pipettes I already own (plus measurement by a scale) and avoid the classic extra tall graduated burette. These burettes are cheap enough on ebay and are starting to look pragmatic. They would reduce the expense of a scale if you did not own one. [I have started to enjoy the tall buret. I use it for 0.1N NaOH while I use my automatic pipeter for 1.0N NaOH. If you learn the math well enough, you can start with 1.0 and finish with 0.1. This technique becomes valuable when you are checking up on heavy rum ferments that are 15+ g/L.]

The volume of NaOH titrant is starting to add up and it may make sense to buy precise concentrated amounts and cut it with volumetric flasks down to other standardized amounts. The price appears to be more for the standardization rather than material because its basically all water. [This holds up and I would never purchase anything less than 1.0N]

I propose three exercises that will test skill sets and segue into distillery work:

First, we will analyze commercial Kombuchas to see if they have a measurable ester content as well as their distribution of acids between fixed and volatile. My theory is that the best Kombuchas have ester contents (ethyl acetate), they also have fixed acids in addition to free volatile acids. They also may be additionally force carbonated to make them extra delicious (de-gassing may be important to measurements).

We may then create our own Kombucha and compare our numbers.

For a second project, we will manipulate a commercial vinegar such as a balsamic and take measurements along the way. We will freeze concentrate a vinegar to increase its acetic acids and aroma as well as possible added sugars. We will then salt out a precise amount of acid to bring the acidity back to our starting level. After we separate the non-volatile salts, we will get a product that hopefully we only increased in aroma and non-volatile extra while keeping the acid constant. [The measurements may be made with NaOH, but the salting of the acids may best be done with CaOH. We can use the molecular weights to learn how to interchange one for the other.]

This may help us create faux aged balsamics (though they may benefit from time resting at a low pH). We also may be able to create faux grand cru concentrated vinegars from other substrate categories. Another possibility may be to concentrate to typical 5% level odd vinegar projects that did not achieve enough acidity (i.e. if our banana vinegar is only 4%, but we want 5%).

Thirdly, we would make small scale vinegars, drawing inspiration from Noma Ferments, while adding measurements. We can explore the idea of fusel oil in vinegar production by adding our collection of fraction 4’s from the birectifier. The old literature describes higher alcohols like butanol being able to reduce to butyric acid and producing fruitier vinegars. [It turns out the old literature may not be correct and fusel oils in vinegar may only become esters.]