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Nick F
Hazard to Others
Posts: 439
Registered: 7-9-2002
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I have some semicarbazide hydrochloride, and obviously I can get NaOCl bleach. I have some Ca(OCl)2 too, but all the Ca(OH)2 in it makes filtering etc
more difficult.
Semicarbazide is made by reacting monochlorourea (normally as its sodium salt) with ammonia, to form semicarbazide and NaCl, and it is then ppted as a
salt by adding an acid, normally HCl or H2SO4.
But unfortunately I don't have access to those references  If anyone does, please
tell me how to do it! I'll have a search for info too.
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Marvin
National Hazard
Posts: 995
Registered: 13-10-2002
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Yikes, monochlorourea is stable!
Id have thought the intramolecular reaction would be intrinsically much faster than the intermolecular one producing semicarbazide. Strange. Id be
interested in more info on that one if anyone has it.
It can also be produced by reduction, eg electrolytically, or with zinc/acid of nitrourea. A prep that will probably find favour here. Not to
mention not requiring gallons of dilute bleach....
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Nick F
Hazard to Others
Posts: 439
Registered: 7-9-2002
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I got nothing when I tried Zn/HCl reduction of nitrourea, the electrolytic method looks much more promising but I've never tried it. I can't see any
reason why you couldn't fill your cell with the right amount of H2O, and simply dump into it the H2SO4/nitrourea mixture formed when making NU from UN
and H2SO4. IIRC the NU solution is acidified with H2SO4 anyway. But maybe it'd be too acidic with this method... but it would save you the hassle of
filtering, drying etc.
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PHILOU Zrealone
International Hazard
Posts: 2893
Registered: 20-5-2002
Location: Brussel
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Mood: Bis-diazo-dinitro-hydroquinonic
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By CI2Cl2 I meant I2CCl2 thus diiododichloromethane and not tetraiodoethylene....hard to discriminate I from l!
By the way:
HO-C(N4)C-OH <-H2- O=C(-N=N-)2C=O
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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IrC
International Hazard
Posts: 2710
Registered: 7-3-2005
Location: Eureka
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Mood: Discovering
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There is a fairly easy test for phosgene using a home made test paper. "Paper soaked in alcoholic solution containing 10%
of a mixture of equal parts of p-dimethylaminobenzaldehyde and colorless diphenyamine, then dried, will turn from yellow to deep orange in the
presence of approximately the maximum allowable concentration of phosgene." The permissible exposure limit for phosgene is 0.1 parts per million
(p.p.m.), so this is a fairly sensitive test. This test paper is fairly inexpensive to make: p-dimethylaminobenzaldehyde --Sigma # D 2004; 25 g.,
$8.85; diphenyamine--Sigma # D 2385; 5 g., $13.50, 25 g. $50.35.
The above is from the following link.
http://www.ars.usda.gov/Main/docs.htm?docid=3594&page=6
Phosgene generated from old Chloroform is something not well remembered in the last 50 or more years. I think in lieu of all the insects and small
furry mammals being harmed for tests unlikely to tell you anything useful about the presence of phosgene (or it's level in ppm), you should just make
this simple and reliable test paper. I do not think it beyond the amateur to calibrate the paper based upon color. Fairly simple circuitry exists
which could drive a meter by detecting and measuring the color change. Also not much of a stretch to use an opamp comparator to fire up a nice loud
piezoelectric alert when the level goes above a preset, which would be simply adjusted by turning a trimmer potentiometer on the circuit board.
This information is presented in the interest of saving countless lives and suffering on behalf of all small creatures
everywhere no matter how ugly they are.
[Edited on 11-9-2010 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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Mr. Wizard
International Hazard
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Registered: 30-3-2003
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When cleaning up bird lime from concrete under an outdoor cage, I used sodium hypochlorite bleach solution. Since bird lime contains urea and other
similar compounds I always though it produced chlorine and chloramine. It would foam up and produce a very strong chlorine smell. I would always move
the cage and birds away, and never had a problem. It does an excellent job of cleaning the concrete. I never thought about phosgene.
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