Sodium thiosulfate unit conversion?

[Candlejack]

I was wondering if there was a conversion to go from grams of sodium thiosulfate to approximate milliliter or teaspoons. Thank you! (I looked on google and didnt see one)

 

[juan]

Sodium thiosulfate comes in various forms (crystals, powder, etc.) so it’s hard to give a set figure. If it’s for something inexact, such as the aTF-2 fixer I use, 1 cup= 240-grams.

 

[Candlejack]

Sodium thiosulfate comes in various forms (crystals, powder, etc.) so it’s hard to give a set figure. If it’s for something inexact, such as the aTF-2 fixer I use, 1 cup= 240-grams.

Yup its relatively inexact, and Im using crystal form. Just trying to get an idea what 150 grams would look like in ML.
Or 4 heaping teaspoons would be in grams.
(Different formulas given all over)

 

[halfaman]

Wikipedia says sodium thiosulfate density is 1,67 grams per cm3 which is the same as 1,67 grams per mililiter (ml). I am not going to enter in the imperial units mess...

 

[fgorga]

My thoughts...

Any such conversion factor you find is not likely to give reproducible results. Such mass to volume conversion factors work OK when the solid involved is a fine powder. There the variability introduced is small. However, sodium thiosulfate pentahydrate (common photographic hypo) is most commonly supplied as fairly large crystals. These crystals do not pack well and thus the actual amount in a teaspoon is likely to be quite variable from one spoonful to the next.

One of the keys to success in lab work ( including the photography lab) is consistency. Using mass to volume conversions is one way to introduce inconsistencies and thus is best avoided especially when one can buy an electronic balance for relatively little money. See, for example, https://www.amazon.com/Portable-Electronic-Adapter-Analytical-Laboratory/dp/B07DX7B571. (I have no direct experience with this particular item, it was the first inexpensive balance that reads to 0.1 g I came to at Amazon. )

 

[Candlejack]

My thoughts...

Any such conversion factor you find is not likely to give reproducible results. Such mass to volume conversion factors work OK when the solid involved is a fine powder. There the variability introduced is small. However, sodium thiosulfate pentahydrate (common photographic hypo) is most commonly supplied as fairly large crystals. These crystals do not pack well and thus the actual amount in a teaspoon is likely to be quite variable from one spoonful to the next.

One of the keys to success in lab work ( including the photography lab) is consistency. Using mass to volume conversions is one way to introduce inconsistencies and thus is best avoided especially when one can buy an electronic balance for relatively little money. See, for example, https://www.amazon.com/Portable-Electronic-Adapter-Analytical-Laboratory/dp/B07DX7B571. (I have no direct experience with this particular item, it was the first inexpensive balance that reads to 0.1 g I came to at Amazon. )

Thank you! I think the company recommends 100 to 200 grams per liter, which is a wide margin, but i realize that if i fluxate in my usage, ie 120g one day and 180g the other, it may have a different effect on the image.

 

[Candlejack]

Wikipedia says sodium thiosulfate density is 1,67 grams per cm3 which is the same as 1,67 grams per mililiter (ml). I am not going to enter in the imperial units mess...

Cool Ill look for the article, thatll give me a good guesstimate.

I might have a scale squirreled away somewhere. I wonder where. Ugh.

 

[Donald Qualls]

i realize that if i fluxate in my usage, ie 120g one day and 180g the other, it may have a different effect on the image.

This is fixer we're talking about, not developer. Fixing should be carried to completion, and the only difference between 120 g/L and 180 g/L is capacity -- i.e. how much film or paper the solution can fix. I used to mix one-shot fixer with 60 g/L of thiosulfate, measured with a tablespoon (though the tablespoon weight equivalents were originally arrived at with a very sensitive beam scale).

There shouldn't be any difference in the image as long as fixing is complete.

 

[fgorga]

Cool Ill look for the article, thatll give me a good guesstimate.

I might have a scale squirreled away somewhere. I wonder where. Ugh.

This value of the density is useless for your application. It is the value for the density of the crystal.

It would be useful if you could pack the crystals into whatever container your were using to measure the volume in a uniform way without significant air space and to do that reproducibly. However, none of that is likely!

 

[Candlejack]

This value of the density is useless for your application. It is the value for the density of the crystal.

It would be useful if you could pack the crystals into whatever container your were using to measure the volume in a uniform way without significant air space and to do that reproducibly. However, none of that is likely!

Yup. That hit me as well. Dang. Hmm. I could potentially just weigh teaspoons and average them out.

 

[Candlejack]

I just dont want to weigh everytime, and the reason im saying that is that I have a small space to work in.

 

[fgorga]

This is fixer we're talking about, not developer. Fixing should be carried to completion, and the only difference between 120 g/L and 180 g/L is capacity -- i.e. how much film or paper the solution can fix. I used to mix one-shot fixer with 60 g/L of thiosulfate, measured with a tablespoon (though the tablespoon weight equivalents were originally arrived at with a very sensitive beam scale).

There shouldn't be any difference in the image as long as fixing is complete.

Agreed!

Where the variation might play into ones practice is in the number of prints one can safely fix per volume of solution. If one never pushes the limit of the capacity of fixer, it will not be an issue otherwise one runs the risk of under-fixing some prints.

Again, I stress that reproducibility is a great asset in doing lab work of any kind. And part of that prtactice is making the solutions exactly the same each and every time.

 

[Candlejack]

Agreed!

Where the variation might play into ones practice is in the number of prints one can safely fix per volume of solution. If one never pushes the limit of the capacity of fixer, it will not be an issue otherwise one runs the risk of under-fixing some prints.

Again, I stress that reproducibility is a great asset in doing lab work of any kind. And part of that prtactice is making the solutions exactly the same each and every time.

Thank you, I really appreciate all of yalls advice and input. It makes alot of sense !

 

[Petrochemist]

I just dont want to weigh everytime, and the reason im saying that is that I have a small space to work in.

The form of the sodium thiosulphate has an impact on how much volume a given weight will take up, So just pick a plastic cup/container, weigh your soild into it & mark the level.
Use this volume until you get a different form of Sodium Thiosulphate or until you loose the cup.
Calibrating your container like this will be plenty accurate enough & only needs you to weigh it once.

 

[Doremus Scudder]

This is fixer we're talking about, not developer. Fixing should be carried to completion, and the only difference between 120 g/L and 180 g/L is capacity -- i.e. how much film or paper the solution can fix.

Not quite correct Donald. Fixer capacity is usually limited by the build-up of argentothiosulfates, i.e., byproducts from fixing, in the solution. When the dissolved silver compounds reach a certain level, the fixing reaction no longer goes to "completion," i.e., water-soluble compounds are no longer formed. The "strength" of the fixer has more of an effect on fixing speed.

Note that fixers like Ilford's Rapid Fixer that have two recommended dilutions (in this case 1+4 and 1+9) have the same capacity per liter.

@OP,

Get yourself a cheap digital kitchen scale. They all read out in grams as well as other units. That will be more than adequate for weighing out sodium thiosulfate for fixer. They're cheap and easily available. Find a suitable vessel and use the tare function to zero the readout before pouring in your chemical. EZPZ and much less variance than using volume measures here.

FWIW, I use spoon recipes for several things, but use the scales when it's a better choice, as in this case.

Best,

Doremus