I am an analytical chemist trying to build a new device to extract organic chemicals out of water for analysis. I am doing this on my own time, and it is basically a garage project.

Part of this device requires squirting dichloromethane-an organic solvent–through a length of capillary tubing that is 50 microns in diameter.

We have been assembling the device in open air, and it clogs. It runs for ten seconds or so and then clogs. Examination under a microscope at 150X finds dark spots in the tube.

So I have decided to put all the parts of this device in a homemade "cleanbox", clean all the parts of particles, then assemble the device under hopefully-completely-clean conditions. In normal operating conditions, the tube will be sealed away from the open air, so if we can get it assembled clean, it should stay that way. We have also placed a ten-micrometer filter upstream from the capillary tubing.

I have bought a ten-gallon glass fish tank. We will manufacture a top for it that will contain gloves, an inlet and an outlet. The inlet will have a 0.5 micron filter attached to it.

—I intend to place all the pieces in the tank, plus a small container of 1.5-micron filtered soapy water. (Laboratory soap, easily rinsable.), and seal it by putting the top on it.

—I will run bottled dry nitrogen through the filter. I don't really know how much to run. I'm thinking a gentle flow for thirty minutes should be enough to get clean air inside the tank.

– I will run a little water through the 0.5 micron filter into the tank, and wash down everything in the tank. All the sides of the tank, all the pieces, everything.

—Then I will rinse it all with clean water.

—I will repeat the soap process two more times.

—I will fill the tank with enough water to submerge all the pieces. Then I will assemble the pieces underwater.

—Then I will open the tank and take the assembled gadget out.

Any and all comments on this will be welcome.

I have to say I was wondering how much dust was in the air. It was a relief to see it was 35e6 particles 0.5 micron diameter and bigger per cubic meter. Does anybody know how many 10-micrometer and bigger particles there are per cubic meter?