Chemistry

[Aggie]

..

 

[DKT]

you might also want a safety chain or some sort of restraint to hold the tank against a wall...

KT

 

[b.e.wilson]

</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:

http://waltonfeed.com/grain/faqs/ivb2.html

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.

 

[Ed Sukach]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (b.e.wilson @ May 14 2003, 04:41 AM)</td></tr><tr><td id='QUOTE'></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....
Cost of a '44' tank of high-grade nitrogen: $70 for 200 cu ft.
Monthly rental: $5-10.


Aiee!!

Tough to try to justify all that for a ~100ml squirt of nitrogen every week or so.

I've got to visit one of the "high-end" Wine retailers. I've heard they have "spray" cans of Argon to preserve the contents of opened bottles of wine. So far, no luck finding them on this infernal machine.

 

[DKT]

we paid $135 for a recond. Wing Lynch 2 stage regulator. the nitrogen tank is about $100 and we lease the tank itself for a year. we use about two of these, maybe three, but the $100 includes the lease....compared to what the processor cost, the nitrogen is dirt cheap...

 

[Robert]

Try this:

Dead Link Removed

$195 for an empty 60 Cubic Foot N2 Cylinder. I'm sure I've seen cheaper but of course I can't find it now. Smaller tanks stick in my mind at 1/2 that price.

Then surf over to rapid and get :

http://rapidswholesale.net/Merchant2/merch...duct_Code=2G398

The high pressure twin gauge regulator $50.

http://rapidswholesale.net/Merchant2/merch...duct_Code=5R124

A picnic tap with 4' of hose. You'd need to get the right fittings and I'm not sure this is the best way.

Rapids website must be the worst in the world. But they are VERY good. Prices are also very good. I haven't ordered in awhile so caveat emptor. Ask if they still have the paper catalog. Much easier then the website. Or just ask them for advice. The people on the phone understand what they sell.

Instead of trying the high end wine stores try the online wine making places.

 

[Robert]

Next time I drive by the gas guy I'll try and remember to stop in and ask how they handle nitrogen. I know they just swap CO2 tanks.

 

[Ed Sukach]

Hah!! I think I have found a viable answer for the missing "Protectan" spray, for displacing oxygen rich air in opened, partially filled chemistry bottles.

I've just bought a BernzOmatic "Micro Torch Kit, Cat. #ST150K (also on the package is "ST9009" - I think that is for accessories).

This little puppy is a powered by Butane - filled into a transparent reservoir from a BerrnzOmatic (no idea of the catalog#) canister.

Once filled, one removes all the accessories, inserts the business end of the device into the bottle and twists the thing "on" until the appropriate gas layer is deposited. In case Moe, Larry and Curley are listening - *NO* you don't light it.

Neat, efficient, inexpensive, and readily available at Lowes ... I imagine all large hardware chains carry these.

 

[Aggie]

..

 

[Ed Sukach]

Why not just take one of the spray nozzles off an old spray can and put it on the benzomatic can that you use to fill the butane torch. Then it goes directly into the chemical storage bottle. Just take a pin and make the opening in the spray nozzle top bigger.

The Butane comes out of the original canister as a liquid. Probably no difference in application, but I'd rather load it into the chemistry bottle as a gas.
The transparent reservoir in the body of the Micro Torch gives a visual indication of the amount being dispensed -- and that gas *IS* being dispensed.

Not only that - but applied to its intended use (lit), it looks like a good way to melt sealing wax.

 

[Ole]

I fail to see any problem with butane.

It is relatively safe ("safe" is a relative term anyway), cheap, easily available, and requires no special equipment.

99.9% of all spray cans are powered by butane. If it's safe enough for whipped cream, it's safe enough for my darkroom

If I bother, I just use my lighter to seep a little butane into developer bottles. Then I refill my lighter from a bottle of the same stuff, which is made without an internal tube. That means it's always gas on top, liquid on bottom. You turn it upside down to fill a ligther.

A bottle of lighter gas costs a fraction of a bottle of Protectan...

 

[Aggie]

..

 

[Ed Sukach]

To bad we don't live close. I get a discount on large bottles of butane. I pay only about $2.50 for a huge bottle.

True.

... And then there is the thing about the butane....

:wub:

 

[Ed Sukach]

Well, gang ... I just wrung out Tetenal "Mono PK" ... In place of my usual Tetenal RA 4 PK. Interesting stuff. Mid-point target temperature seems to be 22.0 degrees Celsius ... instead of the usual RA4 35.0 degrees C. Kind of strange working with color chemicals that are that cold.

Color balance is definitely different, but once a test strip was balanced out on the ColorStar, all related values seem to be OK .. and I can see *very* little difference between the final results of the two systems.

The BernzOmatic "Mini-Torch" butane dispensing system works like a charm. Simply invert the device into the subject bottle, twist the puppy "ON" for a few seconds, shut it off - observe the drop in liquid gas level (not much), cap the bottle and - *done*. Neat. Possibly this thing is an extravagant "overkill" (US$ 20 for the "kit") but ... utterly cool. Besides, this thing is constructed so precisely, it reminds me of a Leica ... and it is *cute*!!!

From your fellow pyromaniac... ops:

 

[Jorge Oliveira]

Hello, fellows pyromaniacs

I use 'straight from the cask' (no, it's not Laphroaig) butane lighter refill.
Point it down in the dev bottle, push the valve for a few seconds.

But I would just love Ed's toy...

Jorge O

 

[Ole]

Ed, Jorge...

Unless you store your chemicals in barrels, a fraction of a second is more than enough.

I don't know the throughput of Ed's MiniTorch, but if the level drops visibly you have used far too much!

Butane is reasonably safe, but not when you use enough to get a whole room up to Lower Explosive Limit (about 5%, IIRC)!

Jorge, how much gas will result from the liquid that passes through the nozzle in a second? !0 seconds at full blast will give you about a cubic meter, which is a serious amount of potentially explosive gas to let loose in a darkroom.

With a gas lighter a few seconds is correct. But a butane refill flasks fills a lighter in seconds, which in turn gives nice steady flame for HOURS, not seconds!

It takes more than a few seconds to see a visible change in the level in a lighter, which I guess is much smaller than Ed's Mini-Torch.

You are using way too much gas!

 

[Ole]

All right, panic over:

1 mol of butane weighs 58g, and will fill a volume of 22.4 liter at "standard lab temperature". Since liquid butane has a specific gravity of about 0.8, that gives about 0.3 liter (300 ml) per cubic centimeter of liquid gas. The Lower Explosive Limit of Butane is 1.6%, the Upper limit is 8.4% (I checked).

So one cc of lighter gas can make an explosive volume of (0.3/1.6)x100 or 18.75 liter. Less than a darkroom-full, but a lot more than a bottle!

Anyway: Butane is heavy enough to form a "gas blanket" covering the bottom of the airspace, so you don't need (or even want) to fill the entire volume with gas.

You're still using way too much, and my initial guess of "a few secons with a disposablegas lighter" is basically correct. A few seconds with a similar volume of liquid butane is way too much. If you need more than 300ml to top off your bottle, find a smaller one!


See for example http://info.anu.edu.au/hr/OHS/Hazard_Alerts/_Gas_Cylinders_In_Labs.pdf for some information on gas and hazards in closed spaces.

 

[Jorge Oliveira]

Ole

Thanks for the warning.

First, my 'a few seconds' is more like 1~2 sec.

I have weighted the bottle before and after a pour, spraying the gas out of the window.

My pour was 2 grams. Nice cloud, BTW.

I started using it in a shorter pour, but was under the impression that it was too little (plastic botlle still 'bulging inside' - forgot that word again!).

What do you think?

Jorge O

 

[Jorge Oliveira]

Ole

Just a note - my darkroom is in the bathroom, and the chemicals (and where I use butane) are kept in the laundry - a ventilated place.

Jorge O

 

[Ole]

Ventilation is always a good idea. What I'm worried about is an expanding cloud of butane - there is always explosive mixture on the edge of such a cloud until the whole thing is diluted enough.

Do you mean that the plastic bottle is contracting when closed tightly and left for a while?
If so, that could be for a number of reasons: Change in temperature, change in air pressure, air or butane dissolving in the liquid... If you blast enough gas into it to cool it down significantly, it will bulge as it warms up. That doesn't necessarily mean that the liquid isn't absorbing gas, though...

With the "whoosh" coming out of those refill bottles, it is difficult to get all of it to stay inside the "target" bottle. It is a lot easier with a slower rate, as from a lighter. See if you can find a cheap refillable - even a broken one which won't light. useful in a darkroom, useless to smokers

I'm probably a bit paranoid from working in the oil/gas industy for 13 years, but we take gas leaks very, very seriously here.

An "interesting" experiment to illustrate my point: Take a spray bottle of just about anything. Deodorant and hairspray are particularly impressive. Take it outside, bring a candle. Light candle. Spray just past the flame, being careful not to blow it out.
Then wait for eyebrows to regrow

 

[jbj]

In my experience bubbling an inert gas (I prefer argon but there are others) through the solution works very well and is cost-effective. The principal is simple: the inert gas displaces the dissolved oxygen. Additionally, argon is denser than ‘air’ so it also displaces the ‘air’ above the de-oxygenated solution and this prevents oxygen from reentering into the solution (providing that your seal is air tight) and negating all the effort you put into degassing it in the first place.

Correct me if I am wrong but I fail to see the logic behind spraying any gas or ‘protectant’ only on top of the solution. If you could bubble butane through the solution for a while this would work. But spraying it on top of the solution would only prevent more air/oxygen from entering the solution. And this would probably only occur if you sprayed a light stream in the headspace of the bottle for some time, not just a few quick spurts. This is the same phenomenon with using marbles. Clearly the problem is that the dissolved oxygen will still remain in solution. Oxidation still occurs.

It would be interesting to do an experiment to determine the best method, see if some of these methods actually work, and compare the effectiveness of the many that have been shared.

My method: I bubble argon through the solution while stirring on a stir plate for a couple minutes. I then attach a rubber septum to the bottle and flush the headspace with argon. This works great with D76 stock solution/ Dektol/ Fixer, etc. This may be overkill for photographic solutions, but for my real job in the laboratory it is appropriate and I can tell the difference.

Enough rambling...hope this makes sense. Good night!

 

[Flotsam]

I'm just looking to displace the air in the headroom of the partially full bottles or at least float a layer of heavier inert gas on the solution surface as a barrier. Trying to drive all the oxygen from within the solution is way above and beyond the mission.

Maybe the best low tech answer is those accordian bottles or a bladder container.

 

[uma]

in my lab,i use plastic or acralic lids floating on the solution and it helps to some extent to reduce direct contact of tank solution with air
and it is extremely cost effective

 

[Flotsam]

uma,
Exactly. Unfortunately that isn't a viable answer for the 500ml and liter bottles that the home darkroom user often needs to protect.

 

[Ole]

I typed a long comment on the stability of different chemistry mixes and the necessity of protecting them, but then I lost it!

My (tentative) conclusion is:

Most stock solutions last for a long time without protection.

Most work solutions don't.

Fixer lasts - I routinely leave mine for several weeks, then carry on where I left off.

My brown plastic bottles are never full, yet the chemicals don't "rot" while I'm away for two weeks.

I don't know anything about colour chemistry.