How to convert Sodium Thiosulfate to Sodium Thiosulfate Anhydrous. What is the math?

Andy F 6x9

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I will be developing my negatives as I travel. Sodium Thiosulfate Anhydrous is a lot more compact so I would prefer to take that with me while traveling but I do not know how to convert the fixer formula. For example if the formula calls for 240 grams of regular Sodium Thiosulfate . What would it be for Sodium Thiosulfate Anhydrous, How do yo do the math?
 

mshchem

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158/248=0.64 "regular" is sodium thiosulfate penta hydrate × 0.64 will give the anhydrous equivalent.
 
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Andy F 6x9

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So what am I doing wrong. I am making TF-2 and the formula is as follows:

Alkaline fixer for film or paper (TF-2 by Bill Troop)

Water 40c 700ml
Sod. thiosulphate (Crys) 250g
or
Sod. thiosulphate (Anhyd) 120g
Sodium sulphite 15g
Sodium metaborate 10g
Water to make 1000ml


250*0.64=160. Then why does it say 120? is this formula wrong? It is from pictorial planet. It is a source that I like and trust. I am using sodium thiosulphate (anhy) from photographers formulary and I want to make sure I am getting the mix correct.
 

koraks

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Anhydrous molar mass: 158.11g
Pentahydrate molar mass: 248.18

120g anhydrous = 120/158.11 = 0.759 mol
0.759 mol of pentahydrate = 0.759 * 248.18 = 188g

Conversely, 250g pentahydrate = 250/248.18 = 1.007 mol
1.007 mol anhydrous = 1.007 * 158.11 = 159.3g
(which is the same as @mshchem gave you: the .64 multiplier)

Andy F 6x9 said:
It is from pictorial planet. It is a source that I like and trust.
Click to expand...

Despite this, maybe they slip up from time to time like the rest of us. Looks like they're in error, here. I assume the '120g' for anhydrous is a typo and should read '160g'.
Given that the TF2 formula to the best of my knowledge gives the quantity for the pentahydrate, I'd use that as a starting point to convert to anhydrous.
 

mshchem

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TSA is going to be curious about what you are doing. If you're traveling by car I would get a bottle of Ilford rapid fixer.
 

pentaxuser

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OP in the comments section under the video he gets asked for the conversion from pentahydrate to anhydrous and he says: use 2/3rds which gives a figure of 166. He never actually mentions a figure in grammes for the conversion from penta to anhydrous in the video but he goes on to admit in the comments in response to a question that he got the maths wrong in his book which he has amended for the 6th edition

Yes the figure of 166 is not the same as 159 but as he is using fractions and his measurements when mixing are in spoons anyway I suspect that a difference of 7 grammes is immaterial. In fact if we use your 240 instead of Finch's 250 we get 158 which has already been said

I hope this helps

pentaxuser
 
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Andy F 6x9

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First, I would like to thank everyone for being so nice when it came to answering my question. In a world were forums like Twitter can be just a cesspool or egos and anger it is so nice to see that there are still examples of the early internet were people were so supportive with one another as they move forward learning new things.

Additionally, the answer to the two questions are as follows:

1) Yes, I am flying. It would be in my luggage. I don't want to mail it because it would cost a small fortune. I can't find the rules. This stuff is not used to make bombs it is used to develop film.

2) Yes, I also think it was probably just a typo. I got the numbers from his website. His youtube series is pretty awesome. I hope someone knows him and reaches out to him in order to fix these numbers. I believe I can just add the 40grams. I wonder if I have to heat up the solution again. I hope not.

Thanks everyone once again.

-Andrew
 

pentaxuser

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mshchem said:
TSA is going to be curious about what you are doing. If you're traveling by car I would get a bottle of Ilford rapid fixer.
Click to expand...

I originally thought that this was a humorous comment and may be it is but assuming it not to be, why would TSA have any interest in someone carrying Sodium Thiosulphate when travelling by car?

I now see that the OP just said travelling and has now added it will be by plane so I now understand why it might make them curious as to what the substance was

Thanks

pentaxuser
 

mshchem

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I don't know if you are carrying a developing tank, I suppose you could put the packets of chemistry inside the tank. Don't be surprised if the bag is flagged, I suppose as long as it's not drugs or weapons it should go through. People carry all sorts of things.
Report back, I have thought about this, never tried it. Good luck with your adventure
 

BobUK

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Andy F 6x9 said:
I will be developing my negatives as I travel. Sodium Thiosulfate Anhydrous is a lot more compact so I would prefer to take that with me while traveling .............
Click to expand...
Travelling with packages of white powder it might be a good idea to take an LP of Johnny Cash at Folsom Prison, and a harmonica to pass the time away. Just in case the police stop you.

 
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