What was this (former?) member trying to communicate?

[Trask]

APUG/Photrio user “ALKOS,” who has not been seen since 2011, posted this language in a thread about formulae to push film:

To keep things simple, I'm experimenting with D-23 as a push developer ;-) Here is Hp5+@1600 in D-23 (7min@20C) followed by 0,1M Sodium Carbonate bath (3min). Shadow detail looks good enough to try @ 6400 in 10min/3min next time.

I’m not understanding what he/she is suggesting when writing “followed by 0,1M Sodium carbonate bath.” I’m thinking that ALKOS might have been European, given the use of a comma instead of a period in “0,1”. Perhaps the “M” refers to a mole? I’m hoping someone here can translate “0,1M Sodium Carbonate bath” into X grams of SC in Y ml of water. Thanks!

 

[Anon Ymous]

0,1M solution means 0,1mole of the compound in 1l of solution. This is the molarity of the solution. Now, in terms of g/l, you have to multiply the molarity (0,1 in this case) by the molecular weight of the compund.

 

[AgX]

I’m thinking that ALKOS might have been European, given the use of a comma instead of a period in “0,1”. Perhaps the “M” refers to a mole?

You are right with your thought of Europe, that designation M for molality is standard over here, but not worldwide used.

Use in the USA (Wikipedia):
The SI unit for molality is moles per kilogram.

A solution with a molality of 3 mol/kg is often described as "3 molal" or "3 m". However, following the SI system of units, the National Institute of Standards considers the term "molal" and the unit symbol "m" to be obsolete, and suggests mol/kg or a related unit of the SI.[4] This recommendation has not been universally implemented in academia yet.

 

[Trask]

So — the molecular weight of sodium carbonate is 105.9888 g/mol. As ALKOS specifies “0,1M” I’d take that to mean I’d dissolve 10,59888 of sodium carbonate in 1 liter water. Wonderful! Thanks for your guidance, Anon Ymous and AgX.

 

[Agulliver]

The mole is the worldwide standard SI unit for the concentration of a chemical solution.

0.1M (or 0,1M) is "zero point one molar" or 0.1 moles per litre of water (= 1 kg of water...assuming water is the solvent)

If you really want to know....one mole of anything is 6.022045x10^23 atoms/molecules.

Sodium carbonate would noramlly be 105.988g per mole so 10.6g in 1l of aqueous solution unless you want to go all analytical and weigh to 4 decimal places.

Anyone who's gone through basic schooling anywhere in Europe has learned this. Few remember.

 

[AgX]

The mole is the worldwide standard SI unit for the concentration of a chemical solution.

No, it is the molecular weight.

What you mean is molarity. Its SI unit is mole/m3.

And there also is molality, which is the concentration per weight of solvent. Its SI unit is mole/kg.

"M" over here means molarity, But as mole/Liter

 

[pentaxuser]

So — the molecular weight of sodium carbonate is 105.9888 g/mol. As ALKOS specifies “0,1M” I’d take that to mean I’d dissolve 10,59888 of sodium carbonate in 1 liter water. Wonderful! Thanks for your guidance, Anon Ymous and AgX.

Do you have to count out each of the 10,59888 of sodium carbonate?

pentaxuser