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Decahydrate to monohydrated conversion // processing

D19 raw chemical processing

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#1 JayneAmaraRoss

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Posted 11 June 2013 - 12:35 PM

Dear all,

I am mixing up a batch of my usual kodak D19 developer (for Tri-X super8) with a new stock of raw chemicals.

The sodium carbonate that I have just bought is decahydrate and my formula calls for monohydrated.

Does anyone know how to convert the monohydrated weight to decahydrate?

The D19 needs 52.5g monohydrated.

All suggestion are welcome

Jayne


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#2 Brian Pritchard

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Posted 12 June 2013 - 05:41 AM

The calculation is based on the molecular weight of the chemical:  Sodium carbonate is Na2Co3  which has a molecular weight of (2 X 23) + 12 + (3 x 16) = 106  Water is H2O which has a molecular weight of (2 X 1) +16 = 18.  So decahydrate has a molecular weight of 106 + (10 X 18) = 286. The molecular weight of monohydrate is 106 + 18 = 124.  The equivalent weight of decahydrate to monohydrate is 286/124 so you would need 52.5 x 286/124 gms of decahydrate = 121 gms.  

 

I have a formula that uses anhydrous Sodium Carbonate the amount is 45 gms.  So using the above calculation monohydrate would need 45 X 124/106 = 52.6 gms which is what you have quoted.

 

I hope this is clear.

Brian


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#3 JayneAmaraRoss

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Posted 18 June 2013 - 11:06 AM

Hi Brian,

Sorry for the late reply. 

Thank you very much for your help, it really saved my darkroom session!

All the best,

Jayne


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