A note about Propylene Glycol

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LR Kalajainen - 05 Dec 2004 00:43 GMT

I recently purchased some "environmentally-friendly" propylene glycol
anti-freeze at my local auto parts store to use as a developer
preservative. I happened to buy the last gallon in stock ($10 per
gallon compared with about $9.00 plus shipping from the Internet
Chemistry Store). The store owner was happy to see it go; apparently,
according to him, and I have no way of verifying this, while the
Propylene Glycol is non-toxic when it goes into the car radiator, it
becomes more toxic while there than Ethylene Glycol. So that when it
has to be disposed of, it is more of an environmental problem than its
supposedly more toxic cousin. I don't know whether that's true of it
when it is heated to 250 degrees in order to dissolve the Phenidone and
Vit. C. Just thought it was interesting.

Larry

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PATRICK GAINER - 05 Dec 2004 03:24 GMT

> I recently purchased some "environmentally-friendly" propylene glycol
> anti-freeze at my local auto parts store to use as a developer
[quoted text clipped - 10 lines]
>
> Larry

That rather sounds like propaganda from the distributers of ethylene
glycol. I have never heard of anyone taking any kind of pains to dispose
properly of either kind of antifreeze. I'll have to ask a local mechanic
how they do it, and if there are any regulations for it.

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LR Kalajainen - 05 Dec 2004 12:27 GMT

I suspect you may be right, Pat. And if so, it's been successful
propaganda. The store owner told me that he won't stock the Propylene
stuff anymore because no one will buy it because they've been told by
mechanics that change their antifreeze for them that it becomes more toxic.

On another note, I prefer my development times in the 6-7 minute range
rather than the 9-11 minute range. Would adding a bit of carbonate (or
borax) to PC-TEA help achieve that? If so, how much do you suggest and
would it be better to add it to the PC-TEA solution directly, or would
it be better to add it at the time of dilution?
Larry

>> I recently purchased some "environmentally-friendly" propylene glycol
>> anti-freeze at my local auto parts store to use as a developer
[quoted text clipped - 15 lines]
> dispose properly of either kind of antifreeze. I'll have to ask a
> local mechanic how they do it, and if there are any regulations for it.

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PATRICK GAINER - 05 Dec 2004 22:15 GMT

> I suspect you may be right, Pat. And if so, it's been successful
> propaganda. The store owner told me that he won't stock the Propylene
[quoted text clipped - 8 lines]
> directly, or would it be better to add it at the time of dilution?
> Larry

I would first try diluting the stock less. The activity will increase.
If you use 1+50, try 1+25. You may find 1+30 or 1+40 to do what you
want. I don't think you will see any more grain as long as you keep the
contrast the same. I'm pretty sure adding carbonate to the TEA stock
would not work, though I don't know how soluble it really is.

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Dan Quinn - 05 Dec 2004 22:27 GMT

> I suspect you may be right, Pat. And if so, it's been successful
> propaganda. The store owner told me that he won't stock the Propylene
> stuff anymore because no one will buy it because they've been told by
> mechanics that change their antifreeze for them that it becomes more toxic.

Are there some short memories about? Cats and dogs lap that stuff
up. Shoes, and I've mentioned slippers, are to be kept clean of it.
While shopping the vast selection of indicator papers at
www.microessentiallab.com, I happened upon their radiator antifreeze
test paper. They tell us that the stuff will shift with use from
alkaline to acid ph which is not good.
You likely know of Micro Essential Lab if pHydrion rings a bell.
S&H is only $5 on small orders.

> On another note, I prefer my development times in the 6-7 minute range
> rather than the 9-11 minute range. Would adding a bit of carbonate (or
> borax) to PC-TEA help achieve that? If so, how much do you suggest and
> would it be better to add it to the PC-TEA solution directly, or would
> it be better to add it at the time of dilution?
> Larry

Why not add a little more TEA? It's a good base. Dan

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LR Kalajainen - 06 Dec 2004 14:55 GMT

> Why not add a little more TEA? It's a good base. Dan
>

Thanks, I'll try this along with Pat's suggestion of using a 1:30 or
1:40 dilution instead of 1:50.

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Jordan Wosnick - 06 Dec 2004 15:33 GMT

> Are there some short memories about? Cats and dogs lap that stuff
> up. Shoes, and I've mentioned slippers, are to be kept clean of it.
[quoted text clipped - 4 lines]
> You likely know of Micro Essential Lab if pHydrion rings a bell.
> S&H is only $5 on small orders.

I've read the cats and dogs stories about ethylene glycol, but
not about propylene glycol. They'll both taste sweet, but the
oxidation products are totally different -- for EG it is oxalate
(rhubarb leaf poison IIRC) while for PG it is pyruvate, a natural
metabolite that is totally non-toxic.

A quick Google search revealed that PG is used as an intravenous
carrier for water-insoluble drugs and that there may be some
toxicity associated with this use, but the fact that this is even
contemplated is a good example IMO of its relative non-toxicity.
My Merck Index states that PG is used as an antifreeze in brewing
and dairy operations, in addition to the automotive uses, and
that its heat degradation products are lactic, pyruvic and acetic
acids, and propionaldehyde. None of these are especially dangerous.

When I first tried to find PG in an automotive parts store (the
Sierra brand antifreeze), the dealer told me he couldn't sell any
of it because it was so much more expensive than conventional
antifreeze. He didn't mention anything about disposal problems. I
ended up buying from The Chemistry Store.

Jordan

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Gilbert - 06 Dec 2004 18:33 GMT

>> Are there some short memories about? Cats and dogs lap that stuff
>> up. Shoes, and I've mentioned slippers, are to be kept clean of it.
[quoted text clipped - 27 lines]
>
>Jordan

Hi Jordan,

Propylene Glycol doesn't have a sweet taste or smell. That's why there
is less risk for cats and dogs to lick it up. I haven't tasted it, but
it doesn't even smell when heated to 90 'Celcius (150 F?)

I buy 100 % pure Propylene Glycol at stores for farmers where they
sell it as a cow medicine against reduced milk production. Here in
Holland it costs about 6 Euros per litre. The cows typically get 100
ml orally every day. We are not cows, but I guess toxicity isn't very
high when cows drink it every day at such high doses.

Gilbert

Gilbert
________________
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Jordan Wosnick - 06 Dec 2004 19:58 GMT

Interesting stuff Gilbert. I could have sworn that it was sweet
as well. The dairy-farm use is indeed mentioned in my Merck Index.

>>> Are there some short memories about? Cats and dogs lap that stuff
>>>up. Shoes, and I've mentioned slippers, are to be kept clean of it.
[quoted text clipped - 47 lines]
> Nederlands forum voor
> traditionele fotografie

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John Taylor - 07 Dec 2004 02:08 GMT

Propylene glycol for heating systems has a rust inhibitor added which
makes it toxic. I don't know about automotive type however. Be careful
when using glycol near an open flame as it is flammable under certain
circumstances.

John T

>> I recently purchased some "environmentally-friendly" propylene glycol
>> anti-freeze at my local auto parts store to use as a developer
[quoted text clipped - 15 lines]
> properly of either kind of antifreeze. I'll have to ask a local mechanic
> how they do it, and if there are any regulations for it.

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