EarthTech's BLP Gas-Phase Replication Effort - 6JAN98

-- aftermath of 1st run....changes for future runs

The very first run of our BLP experiment exhibited some problems. Upon heating the chamber to about 200° C the gas pressure increased to 12 torr rather than the expected 3.5 torr. When we applied power to the tungsten filament, it burned out very quickly.

This is what the apparatus looked like immediately after opening of the chamber. Note that the tungsten filament is broken in the center, all the KNO3 that was in the pan is gone, and there is a black soot-like material coating the 6-32 nuts on the right, the ceramic tube, and the upper end of the filament power lead on the left.

If you look closely between the stainless pan and the wire-mesh basket you can see some KNO3 that was apparently placed there in a liquid state and then solidified.

As a result of the many constructive suggestions received on Vortex and our own analysis of the problems we decided to make several changes in the apparatus. The picture on the left shows the apparatus in its modified state.

The pan and wire-mesh basket are gone. We decided that the KNO3 was too close to the heating elements. It is now located in the short stainless steel "test tube" that is visible in the lower right portion of this photo. Besides being located away from the hot end of the cartridge heater and the filament, this test tube is further protected from heat radiation by a thin stainless steel heat shield located between the test tube and the cartridge heater. Both the test tube and the heat shield are supported with stainless steel wires captured between nuts (not visible) on the 6-32 stud. Also we have reduced the quantity of KNO3 from 0.3 grams to 0.1 grams.

The new filament was taken from a 12v automobile brake lamp. It is the heavier of the two filaments found in those bulbs. It's room temperature resistance is about 0.5 ohms and it draws about 25 watts at 12 volts. It is constructed of much heavier tungsten wire than the original filament, which came from a 100 watt household lamp. To better accommodate the higher currents, the copper lead wires for the filament were increased in size substantially.

The K thermocouple supported by the ceramic tube has been straightened so that it is located near the top of the chamber relatively far from both the cartridge heater and the filament.

Present Status (evening 6JAN98):

The chamber has been reassembled, leak-tested, and baked out under high vacuum at 100° C for several hours. Tomorrow we expect to fill the chamber with H gas and start the 2nd run. Stay tuned to Vortex-L for further updates.