Magpie
lab constructor
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Mood: Chemistry: the subtle science.
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Parr bomb calorimeter
I recently purchased a Parr 101A bomb calorimeter which has a capacity of 350mL, IIRC. I don't intend to use it for calorimetry but plan on putting
it to higher purposes.
I need some help in identifying one of the penetrations in the lid, shown in the picture below. I think I have correctly identified the two
electrodes, ie, those that extend deep into the vessel. The one with the knurled knob appears to be a needle valve for the admission of oxygen. It's
the 4th penetration that has me puzzled. Anyone know what it is for? It has a small horizontal hole (~1/32" dia) both below the lid and above it.
Also, what kind of wire can be used for an ignition fuse. Will anything that turns red hot under the impressed voltage do the job? Also, can I simply
use 115VAC for an ignition voltage?
Thanks for any help you can give. BTW there are 2 reasonably priced Parr calorimeters on eBay at the time of this writing.
[Edited on 30-11-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Ozone
International Hazard
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OK, the two posts which go inside are the electrodes, a fuse wire is connected between them where the flat-points with the holes are (the cup with the
sample goes into the round-bent-wire. The knurled knob is actually the relief (the O2 purge/CO2 product is vented there). The fourth, smooth post
(with a hole toward the middle) is the valved fill/pressurize point. There is a special fitting for this, which connects the low-pressure side of the
O2 cylinder to the bomb. There are two O-rings which secure it into place and insure a good seal. A pressure relief between the fill-line and the bomb
is required, otherwise you blow an O-ring when you pull it off (with a significant bang, I might add).
Test the fuse for continuity from the outside with a multimeter, pressurize to 19 atm, purge, repeat once or twice (two was consistent in my Parr
3200-LE isoperibol), and fire-away.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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Thanks for the information.
You say the fourth post is valved. Is that a check valve that is in the closed position during firing?
Also, could you comment on my questions about the fuse wire and the firing method/voltage.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Ozone
International Hazard
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Yes, there is a check-valve in that port (which needs maintenance every now and then).
The wire is ni-chrome, and is standardized (thickness, etc.) to give a certain combustion value/cm (or g) which is subtracted. I'll get back tomorrow
with the actual values.
IIRC, the firing circuit is 24V DC @ 5A. About 2 sec.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Ozone
International Hazard
Posts: 1269
Registered: 28-7-2005
Location: Good Olde USA
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Mood: Integrated
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OK, the wire is Parr # 45C10. It has a value of 1400 cal/g or 2.3 cal/cm (I use a full, 23 cm piece, which is about 0.016 g).
For standardization, I use the Parr benzoic acid pellets (weigh them! They are not exactly 1g) # 3415, 26.454 MJ/kg.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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