Question:
Our labs (currently undergoing start-up from square one, pretty much) acquired a used Barnstead MP-3A Mega-Pure glass still, along with a 12-gallon Mega-Pure ACS glass reservoir. Both were used previously by a PhD in the chemistry department from which we purchased it; everything was in excellent condition, and I cleaned all the parts with Liqui-Nox and DI until satisfied everything was clean

comments?

Answer: any event, the problem is that the water _foams_. When shaken, the DI produces a small amount of persistent (15-45 seconds) foam, despite having produced over 20 gallons of water with this still, which surely should have removed any traces of any detergents that might possibly have remained. Our source water is groundwater of great age, and (thanks to the Bureau of Mines on campus) reportedly is next to free from organics. The labs are supplied water that has been softened; when I called Barnstead about this, they informed me that softened water will often produce this kind of foam. In order to test this, I supplied the still with distilled water from the aforementioned local water purification company. It _still_ foamed, even though the DI from the store didn't foam (!). So, I replaced all the tubing with glass, and it STILL foamed. As a last resort, I supplied the still with water from our deionization columns (order: activated charcoal, DI-MIX and then two DI-PLEX columns). At last, the water came out pure with the ephemeral bubbles that indicate I have distilled water without foam.