Month: May 2013

Results of Coffee Experiments

I wanted to follow up on the previous post before the end of the month, so I went ahead and ran the extractions yesterday evening. The results were just about what one would expect, with one difference: agitation did not have an appreciable effect on caffeine extraction. An additional concern was the efficiency of the extraction, so I added an additional sample to as a pseudo-standard, namely standard brewed coffee from the office Mr.Coffee machine. With this I was able to determine that the extraction was roughly 33% complete, but there is some margin of error there.

24 hour with agitation (#1) 24 hour still (#2) Office coffee (#3) Diet Coke*
Crude Caffeine Isolated (mg) 14.30 16.74 3.10 -
Total Caffeine (mg/cup)  451  550  100 29

* Literature value via the Mayo Clinic. Chosen due to how frequently my friends consume it.


The second interesting result was simply how much stronger the toddy (24 hour cold brew) was compared to standard hot drip coffee and soda; more than 5 times as much caffeine as the office brew, and 19 times as much as a cup of diet coke. To be fair, people typically drink coffee in smaller volumes. I worry that these numbers may be too high, as I'm not sure what share of the measured mass is impurities. If the numbers are close, that'd solve the riddle of why I've been so susceptible to caffeine headaches when I miss my morning coffee, I used to drink almost a cup of toddy a day.

I want to emphasize that I am not a chemist, I've not been trained as such, and having a background in materials science is not "pretty much the same thing". As such the experimental procedure was just as interesting to me as the result. I will not reproduce all the details here, as there are many many write-ups for this exact extraction out there. Several of the more frustrating bits I will, however, elaborate on. Namely the problem of emulsions. If you've ever seen oil and water, you know they separate into layers, but if you shake it enough you'll get a layer made of bubbles of one in the other that persists; That's the emulsion. Through the three trials I tried a number of methods for getting rid of the emulsion after agitating the coffee with dichloromethane.

Cleanly separated layers of coffee and dicholormethane.
Cleanly separated layers of coffee and dichloromethane before agitation.

As I couldn't get my hands on a sepratory funnel, I ended up using a column with a loose glass top stopper. This prevented me from mixing the liquids by simply inverting it slowly, so instead I swirled it such that the liquid at the top got pulled to the bottom and vice versa. This produced varying levels of emulsion across the three samples.

The resulting emulsion.
The resulting emulsion.

I tried stirring with a glass rod, and that helped some. A write up I found online suggested sonicating, which only served to worsen the problem. Waiting produced the most consistent improvement. The clear answer was to decant the whole mess and centrifuge it, but due to time constraints I opted to stop decanting right at the emulsion's edge (hence the 33% extraction, which should have been much better). The final result contained at least some contaminants, as caffeine ought to be a white solid and what was yielded was yellow to brownish red.

Resulting solids
Resulting solids

The take-away from this experiment is two-fold: agitation has no significant effect on the extraction of cold-brewed coffee, and cold-brewed coffee is ridiculously strong even given a large margin of error. Were I to repeat these experiments again I would filter after the introducing the calcium carbonate rather than allowing it to settle and pipetting off the top, and I would agitate in a sealed container (venting occasionally) and centrifuge the result to sidestep the whole emulsion issue. I've read that a sublimation purification can also reduce the apparent color, but some of the results I've seen are not promising.

Making and Installing a Bibtex style for Journal of Applied Physics

It seems the Journal of Applied Physics only officially supports REVTeX, but not BibTex. After looking around for a bit hoping to find a .bst file out there, I gave up and generated one using makebst. I had to drop in a few commands to Suppress the titles, but otherwise it was very easy. Installing it consisted of dropping it in ~/textmf/bibtex/bst/ and running sudo texhash. For the interested, and for my own sake later on, the file can be found here.

What do you put on a blog anyways?

It's been a while since I've put time into maintaining a website, and now that I've got all my hosting and DNS managed through nearlyfreespeech.net I feel I can start paying attention again. This is despite the fact that I should be pouring more time into research; I can rationalize that having a place to actively write can only help me when it comes time to pen papers and the like. In the previous incarnation of my site, I used it as an area for playing around with CSS and tossing up write-ups (generated in the same spirit of keeping myself relatively sharp on the material) on various semi-technical topics. In addition when I hit problematic spots with Ubuntu on my old Dell Mini 9 I usually wrote up the solutions when I'd pieced them together, hopefully saving others the hassle. For the curious, that mini is currently employed as the interface of an all-optical switch deep in the CIAN testbed, still trucking on years later.

I've put together a poll on the sidebar to see what people would like to see show up here. If there is an option missing, feel free to drop it in the comments. I don't anticipate an enormous number of responses, so any feedback is appreciated.

First Coffee Experiments

I've been in the habit of making weekly batches of 24 hour cold brewed coffee. Taking the name literally, this meant tossing one cup of medium grind into my french press, topping it up with water, stirring a bit, and tossing it in the fridge until the next morning. I'd noticed that every time it came time to take the coffee out, a semi-solid puck of coffee ground has floated to the top. An independent island where no extraction could occur. I decided to make an experiment of it, seeing what happens when the grounds are constantly agitated and this agglomeration wasn't allowed to happen.

The first step was figuring out how I would manage to agitate it. Stir plates are relatively expensive, but seemed like the right way to go about it. I found a few tutorials on putting together one for cheap using a computer fan, some super magnets, glue and a power supply. Save for the magnets which I was able to get for about $7 from amazon, and the fan (which was  donated by an awesome friend) I had everything on hand. It came together in just about an hour, and is still without a housing. Still, it does the job.

For the first real experiment I kept constant everything I could (being time, water/coffee ratio), though the temperature was higher than previously as I haven't found a good way to squirrel the whole setup into my fridge. After the full 24 hours of agitation (making plenty of noise) the resultant liquid was what could best be described as "muddy".

 IMG_20130511_175409_183_small

 

After being french-pressed to remove the larger particles, the resulting liquid passed freely through a coffee filter, but rapidly clogged a #1 United standard filter paper (11 micron pore size). The solid left behind had the consistency of clay, indicating that the agitation may well have been crushing the grounds into fine dust. This was further suggested by the fact that even in the flask I was filtering into, a sedimentation became apparent. I decided to allow the liquid to settle (in the fridge) for four hours before carefully removing all but the bottom-most liquid. Eight hours later there was no sediment apparent, so I decided that I'd gotten out what was going to settle out.

Shortly here I should be able to isolate the caffeine from this batch as well as a similar batch prepared under identical conditions excepting agitation, and will toss my results up then.