Polverone
Now celebrating 21 years of madness
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OTC cyanamides?
This looks interesting, as cyanamides may lead to other compounds, guanidine nitrate among them:
Patent GB710143
http://l2.espacenet.com/espacenet/viewer?PN=GB359652&CY=...
Looks nicer than constructing your own arc furnace.
Edit:
Looks like this is actually a well-known process. Ullmann says:
Calcium cyanamide was probably first obtained in the laboratory in 1877 by heating calcium carbamate to red heat [3]. In 1889 it was prepared in
larger quantities by heating thoroughly mixed, finely pulverized urea and calcium oxide [4].
[3] E. Drechsel, J. Prakt. Chem. 16 (1877) 180 – 200. [4].
[4] F. Emich, Monatsh. Chem. 10 (1889) 321 – 352.
IIRC, ethyl carbamate can be formed simply by boiling urea with ethanol. Reaction with Ca(OH)<sub>2</sub> should yield calcium carbamate.
[Edited on 7-7-2003 by Polverone]
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chemoleo
Biochemicus Energeticus
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I found this interesting entry in Ashfords Dictionary of Ind. Chemistry:
| Quote: | lead cyanamide
PbNCN (247.22).
Yellow pigment. d: 6.8 kg/l. Slightly
soluble in water forming alkaline solutions. Its use in paint is controlled in many countries.
Uses:
anticorrosion pigment (primer paints)
Production
• lead acetate + cyanamide (salt formation)
Derivatives
N-cyanoimido-S,S-dimethyldithiocarbamate |
Now, has anyone ever seen lead cyanamide as anticorrosion primers or paint? I haven't but felt it's worth asking, as I am sure the cyanamide
could be extraced from it!
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Rosco Bodine
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lead cyanamide
I haven't seen it , lead based paint pigments are pretty much gone from use , unless there is some special case use where no substitute would work .
The lead cyanamide was used as a anti-fouling paint
on the bottoms of boats , as marine barnacles will not
attach , grow and accumulate on the toxic lead cyanamide
paint or its slowly hydrolysing surface . I would suppose it is very very slightly soluble and eroded very slowly in water like most of the toxic
anti-fouling paints .
There were also some mercury based anti-fouling paints
used at one time , but I believe they are pretty much
out of use also .
Copper and chromium based anti-fouling paints are
what is used presently .
Regarding the cyanamide , from what references I have read , the calcium acid cyanurate is probably a better starting point , than mixing urea and
lime ....since it
eliminates the vapor - solid phase mixture reaction stages
which are incomplete and need fluidized beds and higher temperatures , while not producing as high a yield or as pure a product . The urea method
proceeds through
the cyanurate as an intermediate , therefore simply using the preformed cyanurate in pure form should skip over
that inefficient reaction stage of the urea process .
Urea may be rapidly decomposed converted to cyanuric acid
in 85% yield by heating with ammonium chloride
( US2527316 ) , and then the pure calcium cyanurate
can be made and isolated separately . Thermal decomposition of the calcium acid cyanurate at ~350C should
first give the normal calcium cyanate , with evolution of
cyanic acid , and upon further heating above 500C the calcium cyanate should decompose with evolution of CO2 , leaving the pure calcium cyanamide .
Attached is a patent process US2213441 for lead cyanamide yellow paint pigment , produced from calcium cyanamide . Some of the examples provide free
acid cyanamide and sodium acid cyanamide as an intermediate which could be used for producing other different end products than lead cyanamide .
Attachment: US2213441 Free Acid Cyanamide , Sodium Acid Cyanamide from Calcium Cyanamide.pdf (366kB)
This file has been downloaded 1276 times
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Engager
Hazard to Others
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Preparation of calcium cyanamide from urea and calcium carbonate.
[Edited on 8-3-2010 by Polverone]
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Picric-A
National Hazard
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Quote: Originally posted by Polverone  |
IIRC, ethyl carbamate can be formed simply by boiling urea with ethanol. Reaction with Ca(OH)<sub>2</sub> should yield calcium carbamate.
[Edited on 7-7-2003 by Polverone] |
Ethyl carbamate only forms very slowly by the reaction between ethanol and urea at rtp.
A more efficient/ quicker method is the reaction between urea nitate and ethanol, which IRRC produces quantitive yields.
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