Charles Sansom

They've been doing this for many years. I remember learning about it in Propulsion Engineering school in the Navy. The sodium melts at engine operating temperatures and splashes around inside the valve to help carry away excess heat. It's typically the exhaust valves which have the sodium inside them.

When I was in high school I was rummaging around in the chemical room in our science lab and found a jar of potassium chunks in mineral oil. That was in the middle seventies. Recently I had the opportunity to rummage around in there again and that same jar of potassium chunks is still there, never having been opened. I wonder just how stable the stuff is after all this time. It came from a reputable chemical supply house, but there's really no telling how long it was there when I found it the first time. I also found a jar of benzene that has probably been there since the sixties or so in that same chemical room. No telling what else lurks in there.

Higher purity is certainly an advantage of buying from a supplier, but seems to me that more expensive, regulations and long shipping times are certainly disadvantages. I've not synthesized many things, mostly have done it just to explore the science. In a lot of cases, you can't get as good a product with home synthesis, though that's not always true. It often comes down to economics: it's just not as cost effective in many cases to synthesize when you can buy the stuff ready-made for cheaper. However, the returns in experience and understanding when performing syntheses at home are hard to put a price on. I say synthesize it! Even if it costs more, it's a great exercise, you get something you can use, and you've gained experienced an invaluable educational opportunity.

I subscribe to Nuts and Volts magazine. It has for several years now been running a column about near space exploration using weather balloons. It is authored by Paul L. Verhage, and he along with several universities have done a lot of work in this area. You will not have to reinvent the wheel if you subscribe to this magazine and go look at all the past issues online. Alternatively, there used to be, don't know if it's still there, an extensive treatment of this by the same author on the Parallax website, but I don't remember exactly on the website it was. The information is in quite a few chapters. It describes airframes, the balloons, the flight computers, cameras, batteries, solar cells, etc. etc. There are FAA rules that must be adhered to if you're going to stay within the law in this activity also. You would do well to access all of this information from both sources. I don't know if the info on the Parallax site has ever been updated, but I know that he describes a new design for his airframes in the latest Nuts and Volts edition, and he has come out with different flight computer designs in the past. Do a little digging around, you'll find a wealth of information. Good luck! Charlie