PROPYLENE GLYCOL

Bruce Osgood

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A few months ago I got some (1Gal.) of Propylene Glycol to mix Solution A of Pyrocat HD. It is still as good as it was when I mixed it.

Now I am wondering where else I can use Propylene Glycol. Are there solid chemicals to be avoided? Maybe Mytol or Hydraquione, Ascorbic Acid; or maybe it can be used wherever water is used?

Could somebody explain the correct use of P.G.

Thanks,
 

Dave Parker

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The Radiator in your car Bruce!!!!!


LOL

I am sorry, I could not resist!



Dave
 

epatsellis

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best results per the late Smokey Yunick, reverse flow, approx 265 degree thermostat (IIRC) and you MUST remove all water and water soluble coolant, gotta love the old time NASCAR guys, they knew how to wring every last bit out without a multimillion dollar engine program.

erie
(who lived in Holly Hill, FL; just a stones throw from Smokey's garage, and spent waay too much time hanging around there)
 

Mike Wilde

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Other photographic uses for Prop Glycol

Partick (Gadget) Gainer has tweaked me to the usefulness of this stuff, and also TriEthoAmine (not sure if I have spelled this one right - It is commonly referred to as TEA) See articles on the unblinking eye site about it, if I recall correctly.

You can make up stock solutions of agents that are otherwise used in small quantities, and are oxidising agents; i.e developers, like hydroquinone and metol, phenidone, ppd, glycin, etc. and in colour work, CD-3 and CD-4.

Usually you heating the prop gently first, in a double boiler, or if you have the luxury, on a heated magnetic mixer. Moderate heating is a great way to cut the viscosity (particularly with TEA, which is a solid below about 20C) prior to mixing in the (carefully wieghted per volume of heating dilutant) oxidising agent of interest. Read up on the chemical's properties of the dilutant agents in the CRC book (every library has one- finding the right part of the book is harder than finding the book itself) Then you know the pH, when it boils, etc.

I use this method mostly to put Phenidone into solution, because such tiny amounts of this agent (that are a bitch to measure directly) are found in most formulas for 1l of developer, and I like to make them up at most a day or two before needing them.

I use a syringe to pull lthe required mL out of the stock solution, and after squrting the syringe contents into the graduate/beaker the developer is being mixed in, rinse the syringe in the developer solution as well to get any last bits of it into the developer solution.

Prop Gly and TEA do not have large degrees of oxygen in them, either as dissolved oxygen, or as in the O component of water, that some oxidizing agents are able to gobble up as well, and in doing so are less hungry for the silver in our exposed film. When we process film, we want our developing agents to be of known 'hunger strength', in order that, combined with time, temperature, and agitation, we have a predictable, controllable, and repeatable devlopment process.
 

Gerald Koch

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Organic solvents such as propylene glycol are better solvents for organic compounds such as hydroquinone and ascorbic acid and poor solvents for inorganic compounds such as sodium sulfite and potassium bromide. This somewhat limits their usefulness. There is an expression in chemistry that "like dissolves like". You will run into problems if you always think of propylene glycol as a substitute for water.

Curiously, water truly is the universal solvent that the alchemists were searching for, and it was literally under their noses all the time.
 
OP
OP

Bruce Osgood

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Gerald Koch said:
Curiously, water truly is the universal solvent that the alchemists were searching for, and it was literally under their noses all the time.
Click to expand...

Or at least on the tip of their tounge
 

Photo Engineer

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Please be careful heating PG. IIRC, It has a lower flash point than boiling point, and the vapor is heavier than air.

Therefore, you can have a flash fire if you are not careful. The vapor rises in the container and then 'creeps' over the edge and down to the heating element or flame at which point it can ignite.

Although I have heard of no fires from this, it does not mean that you can be careless when heating PG.

PE
 

gainer

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I have learned that there is no need to heat the solutions above 150 F. If you use an electrically heated deep frier, you won't hae open flames to worry about, and you can use a candy thermometer to monitor the temperature. I usually use a microwave oven and heat in short pulses of no more than 30 seconds, measuring temperature between. I am not so much afraid of a fire as of overheating the solution.

With most burning liquids, it is best not to douse with water unless you know that the burning liquid does not float on water. Liberal use of baking soda is usually safe. When heated, it generates CO2 which is heavier than air.
 

Photo Engineer

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Patrick;

Very sensible advice.

I would add that in this case PG is water soluable, so you might be tempted to put out a PG fire with water, but it could be at the boiling point of water which would create a huge volume of scalding steam. It would put out the fire, but might scald the person putting the fire out. Keep the temperature as low as practical, as Patrick suggests.

PE
 

sanking

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When I first started to mix developer formulas in propylene glycol I used temperatures up to around 200º F in order to get chemicals like bromide and sulfite into solution. It worked, but took a lot of heat and time. Now, if I need to use those chemicals in the formula I just mix them first in a small volume of very hot water, and I then add this to the warm glycol. I don't know for certain but I am guessing that the small amount of oxygen that goes into the solution with the water is too small to have any affect on solution life, and practical experience backs this up.

So keeping the temperature of the glycol down is definitely sound advice, especialy since there are alternative ways that make high temperature not necessary.

Sandy
 

Dave Starr

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Maybe this should go in the color section, but.... Could color processing concentrates be mixed with propylene glycol to prolong their life? C-41 developer components, for example. If you have a C-41 kit, mix the individual bottles of concentrate with PG.
 

Photo Engineer

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The concentrates of some of them already contain PG IIRC, but in some, it cannot be used.

PE
 

jgjbowen

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Sandy,
Do you have procedures to mix Pyrocat-HD with propylent Glycol, ie how hot how much water etc. to mix up 1 litre of solution A?

Thanks,

P.S. the film holders arrived save and sound. Thanks.
 

sanking

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jgjbowen said:
Sandy,
Do you have procedures to mix Pyrocat-HD with propylent Glycol, ie how hot how much water etc. to mix up 1 litre of solution A?

Thanks,

P.S. the film holders arrived save and sound. Thanks.
Click to expand...

Here are instructions for mixing Pyrocat-HD in glycol. I am also going to start a new thread of this name so if I have to provide the instructions again the thread will be easy to find.

B. MIXING STOCK SOLUTIONS WITH GLYCOL
On mixing Pyrocat-HD in Propylene Glycol. As many of you know, mixing Stock Solution A of Pyrocat-HD in Propylene Glycol provides stability of the stock solution on the order of years, similar to HC-110. Here is a very safe way to do this, measured for the 1000ml kit.

1. Weigh out all of the chemicals for Stock A. 50.0g of pyrocatechin, 10.0g of sodium metabisulfite, 2.0g of phenidone and 1.0g of potassium bromide.

2. Pre-heat in a water bath 750ml of propylene glycol to about 150F.

3. Add the pyrocatechin to the glycol and stir until dissolved. Should take no more than about a minute.

4. Now add the phenidone and stir. Should dissolve completely in about a minute.

5. Add the bromide and sodium metabisulfite to about 50-75ml of hot water at about 120F. Stir until completely dissolved, then mix with the propylene glycol solution.

6. Top off the solution with glycol to 1000ml

Once you do this a couple of times you will find it just as easy as mixing Stock A in water. Should you be concerned about the small amount of water in the solution? Absolutely not. Pat Gainer, who is the expert on these type of solutions, has recently recommended this type of mixing for his PC-TEA formula, and if he is satisfied with the stability so am I.

Sandy
 

Black Dog

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Never mix your drinks-it always makes your hangover worse
 

Gerald Koch

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sanking said:
When I first started to mix developer formulas in propylene glycol I used temperatures up to around 200º F in order to get chemicals like bromide and sulfite into solution.
Click to expand...
A perfect example that inorganic substances have a very limited solubility in propylene glycol. In developers like HC-110 which contain no water whatsoeverl you will find that Kodak had to resort to substances like diethanolamine hydrobromide and diethanolamine sulfite to provide sources of bromide and sulfite in the developer concentrate.

It is not my wish to get into a long protracted discussion over the merits of this formula or that since I no longer use these glycol concentrates. However, it is my observation that adding water to the glycol concentrates in order to get various inorganic chemicals into solution negates the whole purpose of using glycols in the first place. That is, to limit oxidation of the developing agent(s). The more water in the concentrate, the more oxidation that is possible. Such things as sodium sulfite are best added when preparing the working solutions.

As far as bromide is concerned, a suitable amount of benzotriazole (which is readily soluble in glycol) might be substituted as a restrainer.
 

gainer

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I wanted to eliminate sulfite, if it was only to be used to facilitate the synergism between catechol and metol. In Pyrocat MC, the H2SO4 tied to metol kept metol from dissolving in glycol, but I figured that the metol base would be soluble. TEA could remove the H2SO4, but seemed to need a little water to make it work. Neutralized ascorbic acid and metol need no sulfite to develop film, so enough extra TEA to neutralize the ascorbic acid was added with a little more water.
When phenidone or p-aminophenol base are used with catechol, a small amount of PC-TEA might serve as a "starter" to eliminate the need for sulfite. I haven't tried this yet. Benzotriazole could certainly be used in place of bromide. I have not found a need for antifog in Pyrocat MC. The glycols are hygroscopic and can pick up water from the air each time the container is opened. If this were a problem, putting a drop of the concentrate on a snip of film and leaving it in daylight should give an indication of the severity.
 

sanking

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This needs to be put into perspective. The Stock Solution A of Pyrocat-HD mixed in water is a fairly stable solution, lasting up to a year or even more in favorble storage conditions. Realistically, I doubt very much that the addition of 50ml of water with 950ml of propylene glycol is going to result in much oxidation of the developing agents. I have one of these solutions now that is almost two years old, and it tests the same as when it was mixed. I estimate that at the very least this solution will last at least five years. From a practical perspective, how much more stability is needed?

Yes, one could substitute BZT for bromide, and eliminate the sulfite. But this could potentially change the performance of the formula in ways not anticipated, and given the high stability of Stock Solution A with the small amount of water I just don't see any compelling reason to make this kind of change.

Sandy King
 

BrianShaw

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Dave Parker said:
The Radiator in your car Bruce!!!!!
Click to expand...

One other use... but I don't recommend it... I believe it is also used as principal ingredient (?... after H2O) in one of the laxatives used to prep for a colonoscopy. I thought GP was poisionous, or is that only for canines? :confused:
 

Gerald Koch

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Ethylene glycol is quite poisonous. It has a sweet taste and when used as an antifreeze has caused the deaths of numerous animals. Propylene glycol has been proposed as a safer alternative but it is not completely safe either and can also cause poisoning. All the glycols act to depress the central nervous system. Ethylene glycol has an additional toxicity in that is it is converted to oxalic acid in the body and causes kidney failure.
 

Photo Engineer

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Propylene Glycol is listed as a non-toxic antifreeze substitute for ethylene glycol in the brewing and dairy industry. It is also used as an emulsifier in foods.

LD orally in rats is 25 ml/kg. This means that a 50 kg person (about 100 lbs (I know, I know, I rounded)) would have to ingest 1250 ml or over 1 quart for it to be fatal, If that person were a rat.

Reference, Merck Index, 12th edition.

PE
 

Gerald Koch

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Photo Engineer said:
LD orally in rats is 25 ml/kg. This means that a 50 kg person (about 100 lbs (I know, I know, I rounded)) would have to ingest 1250 ml or over 1 quart for it to be fatal, If that person were a rat.
Click to expand...
I thought propylene glycol was safe BUT there was a recent article describing kidney failure in patients receiving IV's where propylene glycol was the solvent for the medication. This has led the FDA to lower the safe dose of propylene glycol to 1.875 grams per day for a 75 kg person.

Perhaps PG is more toxic when it directly enters the blood than when it is ingested.

1. Arbour RB. Propylene glycol toxicity related to high-dose lorazepam infusion: case report and discussion. Am J Crit Care 1999;8:499-506.
2. Cawley MJ. Short-term lorazepam infusion and concern for propylene glycol toxicity: case report and review. Pharmacotherapy 2001;21:1140-1144.
3. Reynolds HN, Teiken P, Regan ME, et al. Hyperlactatemia, increased osmolar gap, and renal dysfunction during continuous lorazepam infusion. Crit Care Med 2000;28:1631-1634.
 
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Photo Engineer

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LD by injection and LD by ingestion are often very very different. I don't disagree with what you say, but I doubt many people are going to inject it.

I wonder why all of the recipients were getting Lorazepam that way?

In any event, the lowering of the safe dose may only apply to injection, do you know?

PE
 

Gerald Koch

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It appears the half of the propylene glycol ingested is excreted unchanged by the kidneys so it gets into the bloodstream whether by ingestion or by injection. Hopefully, no one is going to be ingesting or injecting it. My intention was mainly to warn that this stuff may not be as innocuous as often stated. Be careful with proper storage if you have small children and pets in your home.
 

Kirk Keyes

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Photo Engineer said:
LD orally in rats is 25 ml/kg. This means that a 50 kg person (about 100 lbs (I know, I know, I rounded)) would have to ingest 1250 ml or over 1 quart for it to be fatal,
Click to expand...

Ron - I'm sure that's an "LD50" for lethal dose in 50% of the population. So only 50% of the 50kg rat-people would die from drinking 2 1/2 pints of propylene glycol.

It's not quite as toxic as you make it sound!

Kirk
 
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