How to weigh one-eighth of a gram of Phenidone?

[Roger Hicks]

Economies of scale? Was that an intentional pun?

Oh, bugger, no, it wasn't. And it would have been so clever if it had been...

Thanks for the other info.

Cheers,

R.

 

[jim appleyard]

Economies of scale? Was that an intentional pun?QUOTE]

No, it was international!

 

[dancqu]

...do developing agents (in particular phenidone)
oxidise more quickly in solution and, if so, is there
any way of retarding this process? Thanks, Blights.

You've in mind H2O solutions. Two important factors;
the ph of the solution and the absence or presence of
a preservative. As a general rule chemicals keep best in
an acidic solution in which is dissolved a preservative.

My earlier post this thread mentioned P. Dignan's
bisulfite-phenidone stock solution. Sodium bisulfite is
an acidic preservative. It is the A solution of an A + B
formulation. The B solution is the alkaline activator.
There are quite a few A + B formulations in
photographic usage. Dan

 

[Brook]

Thanks; fascinating. I wonder how they can do this kind of precision for $25. Economies of scale, I guess. Is it a beam balance? Electronic? Or what?

Cheers,

R.

It is a magneticly dampned beam balance. I think is must be pretty similar to Mr Gainers. Its a bit of a one trick pony in my darkroom, only comes out when mixing new Pyrocat. Mine has never been (un)perverthed as I'm a factory load kind of guy.

 

[Roger Hicks]

It is a magneticly dampned beam balance. I think is must be pretty similar to Mr Gainers. Its a bit of a one trick pony in my darkroom, only comes out when mixing new Pyrocat. Mine has never been (un)perverthed as I'm a factory load kind of guy.

Thanks very much. It's just occurred to me how they can do it: the maximum load you can weigh is of course tiny -- a hundred grains? two hundred? -- whereas an analytical balance is normally designed to handle well over 100grammes.

I completely agree about factory loads.

Cheers,

R.

 

[alexphoto]

Hi Keith
The following was published in Ag+ photographic Vol 14 pp 34-35 by Michael Maunder. I have shortened it to the basics. I have used this method of mixing Phenidone and it works.

Mixing an excipient: 5g of phenidone with 95g sodium sulphite anhydrous, gently turn the mixture over in a small bowl with a stainless steel spoon until satisfied it is properly mixed. This process is called ‘trituration’, particularly if using a mortar and pestle. Store in a dark glass bottle with an airtight cap and it will keep for years.

1g of the mixture contains 5/100=0.05 or a twentieth of a gramme. Make appropriate allowance for the sodium sulphite added and to subtract that figure from overall amount.

Substitute sodium sulphate anhydrous for the sulphite for an inert excipient, it is also a drying agent. Up to 10 grammes of sodium sulphate per litre can be ignored and will have no practical effect on developing efficiency.

Alex

 

[Keith Tapscott.]

Hi Keith
The following was published in Ag+ photographic Vol 14 pp 34-35 by Michael Maunder. I have shortened it to the basics. I have used this method of mixing Phenidone and it works.

Mixing an excipient: 5g of phenidone with 95g sodium sulphite anhydrous, gently turn the mixture over in a small bowl with a stainless steel spoon until satisfied it is properly mixed. This process is called ‘trituration’, particularly if using a mortar and pestle. Store in a dark glass bottle with an airtight cap and it will keep for years.

1g of the mixture contains 5/100=0.05 or a twentieth of a gramme. Make appropriate allowance for the sodium sulphite added and to subtract that figure from overall amount.

Substitute sodium sulphate anhydrous for the sulphite for an inert excipient, it is also a drying agent. Up to 10 grammes of sodium sulphate per litre can be ignored and will have no practical effect on developing efficiency.

Alex

Thank for that tip Alex, I have corresponded with Mike Maunder before and he`s always been helpful with practical advice on matters of photography and chemistry, but didn`t think of asking his advice on this.
I notice you`re in Devon too.
Cheers,
Keith.

 

[gainer]

But don't use that method if you are planning to use TEA or a glycol as solvent. It is better in that case to put a gram of phenidone in 100 ml of propylene glycol. Then 10 ml of that solution will contain 1/10 graam of phenidone. The solution will keep, and there will be no precipitate when you use either water or TEA or glycol as solvent for the developer stock.

 

[pnance]

While the dry mixing might be a approximation of a true solution, you might as well use a scale that can't measure to that precision as well. Mix stones and sand and watch the settling occur. The problem with phenidone and sodium sulfite is after mixing you can't see the poor quality of the mixture. You would be better off mixing phenidone in isopropyl alcohol or propylene glycol for a percentage solution, true solutions don't settle.

 

[Fanshaw]

Propylene Glycol

I would like to try making a phenidone/pglycol solution.Does anyone know of a polypropylene glycol supplier in the UK ?

Fanshaw

 

[Alan Johnson]

www.mistralni.co.uk/pricelist.php lists monopropylene glycol:
www.physchem.ox.ac.uk/MSDS/PR/1,2-propanediol.html

 

[Fanshaw]

Thanks! Just what I need.
Fanshaw