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I think you are going at it the hard way. Try something like this: 1. Weigh the tank "empty" (1 ATA of air will remain.) Use a digital scale at one of the parcel express places. 2. Measure the volume by filling with water using a graduated beaker. (Do not add simple green to O2 clean the tank at the same time as it will form little bubbles and screw up the measurments.) 3. Look up the density of the steel. 4. Review the gas laws. Things are not ideal at 3000 PSI. 5. You still need the air density number you needed earlier. 6. Its all math from here on - do it right. If the tank is solid steel without trapped air voids this should be as accurate as you are ever going to get without elaborate equipment. This should get accurate results In message <199710312036.MAA19813@gl*.oz*.ne*> Jammer Six writes: > First of all, thanks to all who responded, I appreciate your efforts. > > I've learned, beyond doubt, that the weight of air changes based on > pressure, temperature, and humidity. > > I asked the question with one eye on my other current quest, the bouyancy > of tanks. > > What I had hoped to do was to weigh the tanks, full and empty, and work > backwards, and determine how much air they REALLY hold (as opposed to how > much air the manufacturers and dive store wizards CLAIM they hold). > > It now appears that that is impossible, given the equipment and finances > available to me. > > It has been proposed to sink the tanks, measure the water, and arrive at > the volume of the cylinder. > > Then fill the tank with water, measure the water, and use Boyle's law to > calculate the weight of the tank full. > > The weights, full and empty, can then be compared to the weight of the > volume of sea water, to arrive at full and empty bouyancies. > > The problem that I have with this procedure is doesn't it match what the > dealers and manufacturers did? > > Aren't we going to arrive at the same figures they did? > > Why don't we just believe them, then? > > What I want to do is weigh the tanks, empty and full, and use those > weights to calculate bouyancy and gas capacity. > > The problems with that are lots and lots. > > Getting all the gas in all the tanks to the same temperature. > Getting all the tanks to their working pressure at that temperature. > Getting an ACCURATE weight, probably to the 100th of a pound. > Developing a system that will allow this to be accomplished on different > days (sequentially). > > Comments? > > Thanks! > > Lyle > > --------- > "Huh?" > --Jammer, 1992 > --------- > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. ------------- Dick Barker dickb@es*.co* http://www.eskimo.com/~dickb/ Are you qualified to join OFDA? http://www.eskimo.com/~dickb/ofda.html San Juan Isl Dive Charter? http://www.eskimo.com/~dickb/starfire.html -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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