"allen dick" wrote of oxalic acid

> Extremely poisonous?
> 
> Perhaps, but personally, from what I have seen, I would say *somewhat*
> poisonous...In small amounts, OA may even be considered non-poisonous, or even, possibly, a
> nutrient, I should think.

Define somewhat!  (and I think that I can find more palatable and safer nutrients)

OK - maybe not 'extremely', but this certainly a dangerous chemical.  Whilst the ingestion of a lethal dose of around 5g-15g (below) would perhaps be unlikely (it has a very bitter taste) the fact that it can cause serious damage by inhalation or absorption through the skin makes it a substance that we should handle with great respect.  Clearly in terms of safety for the operator, dripping a weak solution is much safer than spraying it (unless you are wearing serious protetctive gear) and either of these methods is much safer than vaporising.

As far as oxalic acid in food is concerned, I think that we need to distinguish between oxalic acid and oxalates, as we would for example between concentrated nitric acid and nitrates - there is a considerable difference in their effects on the human body!  It is also true that, whilst oxalic acid is a single substance (which may be in the anhyhrous or dihydrate forms), there is a whole range of oxalates, some of which soluble whilst others are not.

A few more quotes from websites:

http://www.inchem.org/documents/icsc/icsc/eics0707.htm
OCCUPATIONAL EXPOSURE LIMITS: 
TLV: 1 mg/m^3; STEL: 2 mg/m^3 (ACGIH 1997-1998).
EFFECTS OF SHORT-TERM EXPOSURE: 
The aerosol is corrosive to the eyes and the skin. Exposure could cause anorexia, salivation and nasal discharge with progressive weakness, respiratory distress and collapse.
EFFECTS OF LONG-TERM OR REPEATED EXPOSURE: 
The substance may have effects on the renal, cardiac, thyroid and nervous tissues, resulting in organ disturbances.

http://iilg.org/lkb/articles/faq118.html
VERY TOXIC, CORROSIVE POISON.

http://www.jtbaker.com/msds/englishhtml/o6044.htm
Inhalation: 
Harmful if inhaled. Can cause severe irritation and burns of nose, throat, and respiratory tract. 
Ingestion: 
Toxic! May cause burns, nausea, severe gastroenteritis and vomiting, shock and convulsions. May cause renal damage, as evidenced by bloody urine. Estimate fatal dose is 5 to 15 grams.

http://www.iguanaden.com/diet/oxalic.htm
Oxalic acids bind with needed nutrients and pretty much makes the needed nutrients inaccessible to the body. The main nutrient that seems to be depleted is calcium.

Peter Edwards
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