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iwillwin
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Sodium ferrocyanide and hydrochloric acid
HiI recently read that sodium ferrocyanide on reaction with acids
produce harmful cyanide gas.But,sodium ferrocyanide is also used as an anti-caking substance.so when i ingest it should react with the hydrochloric acid in my stomach and produce harmful cyanide gas,right? In that
case i should be dead now.But why is it not so?
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Loptr
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Ferrocyanide and hydrochloric acid form hydroferrocyanic acid.
The cyanide is still bound to the iron, which keeps it from binding to the haemoglobin.
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careysub
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The concentration of sodium ferrocyanide in table salt is 20 to 100 ppm, of which roughly half is cyanide. If all of this were released as HCN (in
fact it is hard to get even half of it released when deliberately producing HCN under lab conditions), then the content would be 10 to 50 ppm.
Cyanide is widely distributed in the plant kingdom in low concentrations so all mammals have a built in mechanism to detoxify cyanide, and does so at
a rate (for human adults) of about 1.25 mg/min. You have to ingest cyanide at a rate exceeding this to have any toxic effect whatsoever. This would
require a salt intake (and instantaneous cyanide release, which also does not happen even in the lab) of more than 50 grams a minute to even start
create any theoretical cyanide toxicity.
To actually show cyanide intoxication symptoms you have to surge to a level about 20 times this, or 1000 grams in the space of a few minutes. This is
about four times the LD50 for sodium chloride itself. And of course, the cyanide would not actually get released since your stomach is not
really a large reaction vessel filled with strong acid.
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franklyn
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Observe This !
http://history.amedd.army.mil/booksdocs/wwi/VolXIV/VolXIVhtm...
http://web.archive.org/web/20120426064928/http://cbwinfo.com...
careysub is off by 3 orders of magnitude. An example of how misinterpretation of units and the consequences will kill you.
Inhalation of HCN in anything but the faintest trace amounts is lethal. Inhalation of trace amounts is cumulative. Affected blood
platelets remain hindered for hours.
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Texium
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Well, I observed it, and it does not refute anything that careysub stated. We're talking about
ferrocyanide here- not cyanide gas Neither of your sources even mention the half-life of cyanide, and the lethal doses given on your sources line up
with what careysub said.
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careysub
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You picked the wrong person to dispute with on the subject of cyanide toxicity franklyn.
I even you walked you through the math, with hints as to correction factors (i.e. the detox rate and the ferrocyanide to cyanide yield).
If you wish to show your math perhaps you will see your error (or I will be able to point it out).
Check out a real reference on cyanide poisoning, not those webpage summaries you looked at:
http://www.au.af.mil/au/awc/awcgate/medaspec/Ch-10electrv699...
Cumulative? From the chapter:
"Because cyanides
are present at low concentrations in several naturally
occurring environmental sources, it is not surprising
that most animals have intrinsic biochemical pathways
for detoxification of the cyanide ion."
"At lease four intracellular enzymes may be involved for cyanide detoxification. The generalized reactions of
rhodanese, mercaptopyruvate sulfurtransferase, thiosulfate reductase, and cystathionase are shown within the cell."
"Combined, these metabolic routes detoxify 0.017
mg of cyanide per kilogram of body weight per
minute in the average human. Cyanide is one of the
few chemical agents that does not follow Haber’s
law, which states that the Ct (the product of concentration
and time) necessary to cause a given biological
effect is constant over a range of concentrations
and times. For this reason, the LCt50 (the vapor
or aerosol exposure that is lethal to 50% of the exposed
population) for a short exposure to a high
concentration is different from a long exposure to a
low concentration."
Also, if you the rapidly increasing total dose on the Haber Product on the second link you provided clearly shows that it is not
cumulative.
Did you not notice?
It is only 660 mg-min/m^3 for 15 second exposure (or roughly the equivalent of an iv injection all at once of 6.6 mg), rising to 4000 mg-min/m^3 (40
mg) for a 15 minute exposure. The difference amounts to a detox rate of 2 mg a minute, a crude measure of the underlying mechanism.
[Edited on 16-2-2015 by careysub]
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woelen
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Careysub is right, ferrocyanide is nearly non-toxic. You need a lot of it before adverse effects can be observed. The cyanide ligands are bound
strongly to the iron-atom.
You can make dangerous concentrations of HCN from ferrocyanide, but this requires heating in concentrated strong acids. Even then, the reaction is
incomplete and side-reactions tend to suppress the formation of HCN.
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franklyn
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All of you stop being obtuse and pay attention.
Ingestion and inhalation of Ferrocyanide dust though sickening is not immediately acutely poisonous. True
http://pubchem.ncbi.nlm.nih.gov/compound/26129#section=Drug-...
http://pubchem.ncbi.nlm.nih.gov/compound/26129#section=Human...
http://www.inchem.org/documents/jecfa/jecmono/v05je02.htm
That is not what I cited and posted on and does not in any way reflect the risk from HCN that can
be released if improperly handled. Negating the risk I caution about is insensible and irresponsible. If anyone
has quarrels with the LD50 of HCN stated there take it up with the U.S. Army, it's their figures.
Over time enough concentration of HCN can collect in a container of Ferrocyanide solution when opened to end you right then.
http://hazmap.nlm.nih.gov/category-details?id=7110&table...
It all depends on what ions are present. Double decomposition with CuSO4 gets you Sodium Cuprocyanide.
http://www.chemicaldictionary.org/dic/S/Sodium-cuprocyanide_...
Very little HCN is required, if this was not the case, Bulgarian hitmen back when they did the bidding of the former KGB
would not have used ampoules of HCN as a covert means of assassination by inhalation.
http://books.google.com/books?id=MXKDBAAAQBAJ&lpg=PA58&a...
Ferrocyanide does not release HCN easily but once it does the effect is all the same.
http://www.ctrl-c.liu.se/~ingvar/methods/poison.html
Not so far fetched as claimed _ http://www.sciencemadness.org/talk/viewthread.php?tid=13813
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The Volatile Chemist
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"To actually show cyanide intoxication symptoms you have to surge to a level about 20 times this, or 1000 grams in the space of a few minutes. This is
about four times the LD50 for sodium chloride itself. And of course, the cyanide would not actually get released since your stomach is not really a
large reaction vessel filled with strong acid."
You'd sooner die of choking...
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Loptr
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I thought that myfanwy94 was killed by phosgene, and not cyanide.
[Edited on 16-2-2015 by Loptr]
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gdflp
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I believe he was too.
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careysub
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franklyn:
We are not the obtuse ones here.
The whole thread was based on the OP wondering why table salt does not give one cyanide poisoning.
You made a specific claim that my calculations about the amount of cyanide ion in table salt were "off by three orders of magnitude".
You have not shown there were any errors in my calculations.
Please show that this claim is correct, or retract it. (I don't normally request retractions when people disagree with me, but you are doubling down
on it it seems.)
Also you seem not to have noticed that I have a precise idea of the toxicity of cyanide, indeed it is very little, but then there is very, very, very
little in table salt.
You complain that bringing up the toxicity of ferrocyanide (the actual material in table salt) is irrelevant (actually, its not - it is dead on
point), but then start going on about scenarios where cyanide vapor is allowed to collect in closed vessels of acidified ferrocyanide solution, or
people are actually manufacturing HCN, or using concentrated HCN in an assassination weapon all of which are really quite irrelevant to the
discussion, and the content of your earlier post.
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franklyn
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Now that everyone has uttered their Glossolalia ( cognitive dissonance would be too charitable an accusation )
Yes I understand careysub you originally refer to an amount of sodium chloride containng trace amount of Sodium Ferrocyanide as an
anticaking additive — though you did not specifically state it that way.
You do not understand I referred to H C N as the active ingredient that KILLS. Compounds denatured with trace amount of ferrocyanide
of course are not hazardous or would not be available, as you detailed.
Curiosity killed the cat and myfanwy94 as well for not being circumspect.
.
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careysub
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By your failure to defend your original assertions -
that my math was off by a factor of 1000 and that hydrogen cyanide is a cumulative poison - I take this as a concession that you were wrong to make
these claims.
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Chemosynthesis
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It's all about those dose-response curves.
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careysub
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And in this case, a strongly time-dependent one.
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franklyn
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Estimates of the Toxicity of Hydrocyanic Vapors in Man
www.dtic.mil/dtic/tr/fulltext/u2/a028501.pdf
The relevant data ( to me ) is shown on document page 9 & 10 ( pdf pages 11 , 12 )
careysub
Formulas as the following are at best a gamble. In engineering one always over designs with a broad margin for safety.
In nature distribution is mostly heterogeneous not homogeneous so estimates and averages are entirely artificial. Military
assessments assume a healthy soldier to be the subject. Most people are not.
http://www.cainstructor.com/PowerPoint/LCT 50 2012.ppt
I see it matters more to you to be right about your figures than to acknowledge your risk assessment does not scale in magnitude.
You remind me of the administrative evaluation of dangerous flaws in space shuttle booster rockets prior to the Challenger disaster.
Concerns by engineers voicing burn through of the rocket booster casing O-rings had been dismissed by NASA program managers.
The recurring failures were attributed and correlated to ambient temperature at time of each launch and it was believed that launch
was not endangered as a result. The evident risk of impending catastrophic failure was rejected. You're always right until you're not.
Bottom line, it doesn't matter if your math is correct, figures don't matter, they are irrelevant, if death results in spite of the figures.
Based only on the data your conclusion would be no different from the administrative decision to launch.
Reality Bites
http://history.nasa.gov/rogersrep/v1ch6.htm
Scroll down to chart _
[129-131] Figure 2. O-Ring Anomalies Compared with Joint Temperature and Leak Check Pressure.
http://en.wikipedia.org/wiki/Space_Shuttle_Challenger_disast...
As Commissioner Feynman observed, the decision making was " a kind of Russian roulette " "[The Shuttle] flies [with O-ring erosion] and nothing
happens. Then it is suggested, therefore, that the risk is no longer so high for the next flights. We can lower our standards a little bit because we
got away with it last time.... You got away with it but it shouldn't be done over and over again like that."
careysub the simple explanation for iwillwin is concentration present for consumption is too low to cause any
apparent physiological effect , or it would not be permitted. You elaborate on this saying even a kilogram is marginal. Exaggerating what you said to
highlight the fallacy, how much ferrocyanide is present in the ocean, enough to kill scores you think, but one would have to swallow the whole ocean
for it to be toxic. Just because it's buffered it's no less toxic. A quantity that is lethal is no less lethal because it's assimilated at a rate too
slow to matter health wise. Incidentally that's a rationalization in support of smoking. Many of the ingredients added into the tobacco confections
called cigarettes as well as the products of their combustion are poisons in bulk. At one time filters of Parliament cigarettes were also made of
asbestos, even if particles are not aspirated — is that really a good idea. I believe one has the right to make their own choice about such things,
I wonder how many people would choose brand ' A ' table salt containing ferrocyanide over brand ' B ' without it if this was clearly disclosed.
Personally I want all beef to be irradiated so I can have a hamburger medium rare instead of well done by law.
.
[Edited on 18-2-2015 by franklyn]
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Chemosynthesis
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Just to clarify, Franklyn, you contest that a kilogram of table salt contains enough cyanide to kill a person many times over, three order of
magnitude difference from Careysub's estimates? His methodology and math looked solid to me, even though we didn't even get into average gastric
transit time, organic anion (CN) transporters, etc.
Quote: Originally posted by franklyn  | | A quantity that is lethal is no less lethal because it's assimilated at a rate too slow to matter health wise. |
This seems silly to me upon reading. Please clarify for me so I can see where I misunderstand. A dose of material per unit time that does not cause
health effects is by definition not lethal... within that dose regimen. Route of administration, dosing schedules, etc. all affect the steady state
plasma concentration. It's that concentration which is used as a measure of dose, classically.
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franklyn
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@ Chemosynthesis
How much does your pregnant wife weigh ?
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Chemosynthesis
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Franklyn, I am genuinely interested in making sure I understand what your specific issue with careysub's math is. Do you take issue with his figures
for average concentrations of ferrocyanide in table salt, or his sources on cyanide themselves? Because we could parse through in a few different
ways. The pharmacokinetics/toxicokinetics are out there (ex. Clin Pharmacokinet. 9(3):239-51; Biol. Chem. 151, 5496-5502) if you would prefer to use
other sources or try other sources of reasoning. See section 4.3 here, if you like: http://ec.europa.eu/food/fs/sc/scf/reports/scf_reports_25.pd...
I thought it was pretty generous of careysub to assume instantaneous absorption and distribution for the sake of argument.
Speaking of pregnant wives, we could estimate LD50s on white adult males of various body masses and BMIs, use that to back-calculate a volume of
distribution of cyanide, and then apply this towards additional demographics. From this we could determine how much pure cyanide mass would be
expected to cause death in 50% of the target population of choice for a single administration, even controlling for route of administration and
non-toxic protein binding (CYP450 isoforms).
We could even look into sea salt production, as with this low sodium sea salt: http://www.fda.gov/ucm/groups/fdagov-public/@fdagov-foods-ge...
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The Volatile Chemist
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O-------Kay------ This has gone on long enough. Misunderstanding prevails here. The question has been sufficiently answered.
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Loptr
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My argument was that cyanide would never form in any significant amounts within the stomach as heat is needed to begin its evolution. 
I probably should have stated it more clearly in the beginning.
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user1007
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As is probably the case as it is with ferricyanide, I think your acid concentration needs to be a lot higher, it needs to be a some what concentrated
mineral acid to form HCN gas iirc.
Sulphuric acid (not highly concentrated though) is used to adjust potassium ferricyanide bleaching solution in the ECN-2 process
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aga
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| Quote: Originally posted by iwillwin | | HiI recently read that sodium ferrocyanide on reaction with acids
produce harmful cyanide gas.But,sodium ferrocyanide is also used as an anti-caking substance.so when i ingest it should react with the hydrochloric acid in my stomach and produce harmful cyanide gas,right? In that
case i should be dead now.But why is it not so? |
The answer is self-evident in your question.
You are not dead.
Therefore the assumption that you should be dead, and/or the presumed mechanism that should cause you to be dead are incorrect.
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Loptr
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Well, you can be exposed to varying levels of a cyanide, and as a result have varying levels of cyanide poisoning.
The important thing to note is as woelen stated, and that is the cyanide ligands are strongly bound with the iron, and as a result the release of
hydrogen cyanide is not favored under the conditions within the stomach.
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