</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Robert @ May 4 2003, 05:41 AM)</td></tr><tr><td id='QUOTE'> I know you said a nitrogen tank costs alot but was that just the gas or was that including the tank cost? </td></tr></table><span class='postcolor'>
Most gas service companies will not sell a tank to you, they will rent one instead. You pay for delivery and for the gas, then pay a monthly fee for as long as you keep the tank. They won't refill customer-owned tanks for liability reasons.
Cost of a '44' tank of high-grade nitrogen: $70 for 200 cu ft.
Monthly rental: $5-10.
Delivery and pickup: $0 - $60 typically (I doubt you can get the free delivery with usage rates of less than a tank a week).
A good two-stage regulator: $300-400. Single-stage regulators ($150-200) might also work, but flow control will change over time as the tank depresurizes.
Here's a link about using gaseous nitrogen for the non-researcher:
As a researcher on anaerobic enzymes, we spent a lot of time keeping oxygen out of glove boxes, solutions, and sample storage vessels. We found liquid nitrogen to be the most economical long-term source. LN2 is mostly oxygen free (by virtue of the positive pressure in the storage vessel; LOx will condense in LN2 if a flask of LN2 is exposed to the air for a time) but we did need to use an oxygen trap on the line if we wanted rigorously-pure nitrogen. Nitrogen gas supplied by a big dewar of LN2 (a big sealed dewar) worked fine as the inert gas in the stills we used for making water- and oxygen-free solvents. LN2 is cheap, but the dewars and LP regulators are not ($500-2000, depending on size), and those you do have to buy.