Fyndium
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How analytical grade chemicals are made?
I just unsealed a bottle of methanol that is rated as analytical grade which I bought a long time ago as expired stock. I began to wonder how these
ultra-high purity chemicals are actually made in the facilities, how they are initially synthesized, how they are purified and how they are handled
all along the way to remove all the impurities, and moreover, keep the impurities away from everything that touches the stuff. Even so, how the
bottles are made and purified to eliminate even traces of impurities?
Do the fine chemicals facilities just order bulk quality feedstock and process it to make it ultra-pure or are they made separately to prevent initial
contamination?
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Syn the Sizer
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I have wondered a similar thing. Here we can find 99.9% MeOH OTC for super cheap, I wondered is this equivalent to analytical grade MeOH. If they can
guarantee 99.9% purity in a hardware store for $10/4L as camp fuel, why do some distributors charge out the ass for "analytical" grade MeOH. Is there
something I am missing?
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Fyndium
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My local el cheapo hobby lobby sells 100% acetone for 6€ a liter. I bet the Sigma guys are jelly.
For sure, some compounds are so easy and cheap to just distill pure, probably like acetone, methanol and other stuff that they can be sold in
appreciably high purity in bulk. ACS/Pharma and other grades on the other hand means also that they are guaranteed food and drug grade. Hardware store
stuff could as well be pharma grade, but it also could contain impurities that went into it during processing and handling.
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Syn the Sizer
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The methanol for camp fuel is used for cooking so I have a feeling it is food safe as well. You don't want the risk of any toxic contaminates getting
on people food.
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Fyndium
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Methanol, food grade? No thanks, anyways. I don't think the trace impurities of some valve lubricants are that of an issue when the major component
itself will kill you with one sip.
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macckone
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How a particular chemical is made ACS Reagent grade, which is what most people mean when they say analytical grade, will vary depending on
manufacturer.
ACS also covers ultratrace chemicals that are used in specific analysis operations and have exceptional purity requirements.
How those are achieved is up to the manufacturer.
Using H2O2 as an example.
The basic preparation methodology of treating Barium Peroxide with Sulfuric acid will give an acceptable product when mixed with water to the correct
concentration.
The Ultratrace version of the same requires distillation in PTFE equipment under vacuum to achieve the maximum contaminant levels.
Glass cannot be used because silicon, sodium and boron levels would exceed the 5ppb required.
However fluorine and carbon are not measured contaminants for the ultratrace version that is intended for analysis of metal ions.
Using the Acetone example, the base reaction is cumene and oxygen to form acetone and phenol.
Because of the production method, residue after evaporation of 0.001% puts a limit on residual cumene and phenol.
There are specifications for water, methanol, aldehyde, substances reducing permanganate, acid, base and color.
As well as solubility in water. Because of the production method, only cumene is likely to reduce permanganate.
Phenol can also be measured as acidity.
The older method of production from calcium acetate and heating to decompose is more likely to lead to contaminants.
Treating with base, then calcium chloride and finally fractional distilling will lead to very pure acetone.
Treatment with permanganate before treating with base will deal with those types of contaminants.
Commercially produced acetone from the cumene process is unlikely to contain signifcant water.
Finally on methanol, it has a variety of production methods.
Distilling, drying, then redistilling will get it close to ACS grade.
The key with methanol is removing aldehydes and ketones.
Destructive distillation of wood is the oldest method of production and will require considerable clean up.
Start with distillation while acidic to remove amines then neutralization with sodium carbonate to remove acids,
then metabisulfite to remove aldehydes and ketones.
Follow with distillation over sodium hydroxide, then drying and a third distillation.
From windshield washer fluid, a simple distillation is the first step, adding calcium salts reduces foaming.
Second distillation over oxalic acid, then dry and distill over sodium hydroxide.
Activated carbon is often used in purifying solvents to remove volatile impurities and compounds that might produce a color.
After cleaning with activated carbon you always need to distill.
Chromatography grades require additional processing and it is dependent on the intended column material.
Most chemicals don't expire per se, but they may absorb moisture or degrade over time.
Methanol and Ethanol absorb moisture, Ethyl Ether forms peroxides, Acetone undergoes aldol condensation, Sodium Bicarbonate loses carbon dioxide, etc.
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unionised
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A friend of mine who used to work in the sugar industry said that they usually expected to sell a product- for people to sprinkle on their cereals or
spoon into their tea- which exceeded the specifications for analytical grade sucrose.
The biggest difference between commercial and analytical grades (and the thing that explains the price difference) is that they can provide detailed
results of the analyses they did for analytical stuff.
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unionised
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Quote: Originally posted by Fyndium  | | Methanol, food grade? No thanks, anyways. I don't think the trace impurities of some valve lubricants are that of an issue when the major component
itself will kill you with one sip. |
Do you think methanol is that toxic?
Plenty of people have survived much larger doses.
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Fyndium
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Thanks for the detailed input, macckone.
Yes, I'm aware that fermented, non-distilled alcoholic beverages (and some distillates too, for example schnapps drink) can contain a significant
amount of methanol. People in the homedistiller cited that apple and orange juices can contain up to a percentile of methanol, which sounds quite a
lot to me. The treatment for methanol poisoning is to consume large amounts of ethanol, which will make the methanol leach out when the body focuses
on breaking down ethanol so it is quite possible to survive even largish amounts of methanol.
Methanol per se can have as low numbers as 5mL for optical nerve damage in doses of 5mL and death even in 15mL so I consider it quite toxic when a
single sip is all that matters.
My idea was more that I don't believe it is intentionally added to virtually any product that is to be consumed. If I said food grade gasoline, it
sounds as silly to me (and before anyone addresses the various applications of paraffin oil...).
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Nonexistent
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| Quote: Originally posted by unionised | | Quote: Originally posted by Fyndium | | Methanol, food grade? No thanks, anyways. I don't think the trace impurities of some valve lubricants are that of an issue when the major component
itself will kill you with one sip. |
Do you think methanol is that toxic?
Plenty of people have survived much larger doses. |
Don't forget that ethanol does displace methanol in the body, so while many may have had ill affects from methanol, luckily, enough ethanol was there
to counteract it.
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