I'd like to express the concentration of silver thiourea in aqueous solution [Ag(TU)n]+1 in terms of cmolc.L-1. The protocols for soil CTC using AgTU consider the mass of Ag for calculations and reagents preparation, expressing the concentration of AgTU in terms of mol.L-1.
Experimental data makes sense when the calculations are made using the whole complex atomic weight .
Moles per cubic litres? Your units make no sense. And what do you mean by "cmolc"?
Dear Darren, thanks for the reply. I apologize for my mistake. I changed the units from dm-3 to L-1, but for some reason the -3 remained. I've already fixed it. The unit cmolc is similar to the former equivalent mol. This unit expresses the electrochemical equivalence between ions taking into account their atomic weight. It's quite popular among soil scientists and is used to express soil CTC (cation exchange capacity) in fertility evaluations. It's calculated quite easily:
[cmolc.L-1]=[atomic weight]/[valence of the ion]/100
Ex.:
cmolc.L-1 H+ = 1,008g/1/100 = 0,01008 g of H
cmolc.L-1Ca+2 = 40,08g/2/100 = 0,2004 g of Ca
1 cmolc of H+1 can be exchanged with 1 cmoc of Ca+2 from soil CTC pool. Therefore, will be necessary 20 mg of Ca+2 to displace 10 mg of H+1 from soil sorption sites.
Please, let me know if there is some mistake in my understanding. Best regards.
You are obviously familiar with concept of molarity of solutions, and consequently presumably too with the milli prefix, so what is the issue with the centi prefix?
Or is the question really about the charge of displaced exchangeable soil cations?
Dear Paul, that's really about the equivalence of cations for the exchange process.
Hi Guilherme,
I'm still not quite sure about the question but here goes. The typical cation exchange process uses a large excess of the displacing cation to limit any selectivity effects. Consequently in attempting to estimate the loss of this cation to exchange, one is faced with measuring a small difference between two large concentrations. Analytically this results in a large uncertainty. I once thought this might provide a useful quality assurance index but abandoned the idea for this very reason.
The above is the rationale for Gavin Gillman's 'compulsive exchange' technique. Gavin worked on tropical soils and no doubt had concerns about the charge attributed to ions such as Al. Google Gavin's name and CSIRO to find his papers.
If this is not your concern please define more closely, Paul.
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