Sunday, January 29, 2012
I built an improved cold trap from an aluminum pan and a stainless steel bowl. It held more ice than my original copper pipe cold trap, but the 100ml of water from the gelatin still managed to almost plug up the trap.
In previous videos, I used supercritical CO2 to dry my homemade aerogels. This time, I soaked the aerogel in methanol, then raised the temperature and pressure of the methanol itself to make it supercritical. This allows the gels to be dried without an additional solvent exchange into CO2. The downside is that it requires a chamber full of methanol at 460*F and over 1200 psi, which is a much bigger hazard than using CO2.
The aerogels dried with methanol shrank less than the ones dried with CO2, but there was still a lot of cracking, and I have yet to create a high-quality monolith.
Thursday, January 12, 2012
In a previous video, I showed how to extract caffeinated water from green coffee beans with supercritical CO2. Here, I show how to extract dry caffeine crystals from the caffeinated water (ie coffee, in this case). I used a vacuum filtration setup to create very strong coffee, then mixed it with methylene chloride in a seperatory funnel. The methylene chloride sinks below the water, taking most of the caffeine with it. By opening the funnel carefully, only the methylene chloride and caffeine can be transferred to a flask where the methylene chloride is boiled away. I then mounted a test tube in a rubber stopped and filled the tube with ice. With the stopped in the flask, I evacuated the flask and applied heat. The caffeine will sublimate and collect on the cold test tube. I scraped off the caffeine and measured the mass.
In his recent post, Chris Gammell used astronaut ice cream as a fun example of how high tech innovation trickles down to consumer-level products. Seeing an image of astronaut ice cream in my G+ feed got me thinking about making some of my own. I managed to accomplish this with a harbor freight vacuum pump, some dry ice and various hoses and fittings. The process is known as freeze-drying and allows water to pass directly from ice to vapor, thus allowing the ice cream to maintain its physical structure while it is dried.
What should I freeze-dry next?