chemical content of European swimming pool products

[eur]

Hi

I found this page, looking for the CYA content of the chlorine tabs I bought in France:

http://ile-de-france.sante.gouv.fr/santenv/legion/prodpis.htm

Trouble is, I don't fully understand the numbers.

NOM DATE SOCIETE CL2 PRODUIT AGR
CARREFOUR CHLORE PASTILLES 50/20 02/11/94 ELF - ATOCHEM 50 ACIDE TRICHLORO-ISOCYANURIQUE 1934

So Cl₂ = 50 and trichloroisocyanuric acid (C₃Cl₃N₃O₃) =1934, but what? milligram? The tablets weigh 20 gram each, so they are 99% something else? That can't be true.

It probably is a relative number, independent of tablet weight. Also, the chlorine content varies with the same AGR (?) value. The Wikipedia entry of trichloroisocyanuric acid is probably written by a pool-chemicals salesman:

Benefits of TCCA in Swimming Pool- [sic]
* Available with 90% chlorine concentration
* Due to high chlorine content, handling is easy for large pools.

http://en.wikipedia.org/wiki/Trichloroisocyanuric_acid

Can somebody explain to me how the chlorine concentration can vary in a pure substance with a known formula?

Or is this just more obfuscation from pool-chemical sellers?


I'm so happy I found TFP. I was wading through all kinds of stuff and outraged by the prices. Solid info was nowhere to be found. I'm still attending Pool School.

 

[JasonLion]

Not knowing french, it is a little bit difficult to be sure, but those appear to be 55% trichlor and 45% filler. Pure trichlor has 90% available chlorine, but these have only 50% available chlorine, so they are 55% trichlor and the rest is inert.

The way things like % available chlorine is calculated is weird, it is easy for the percentages to add up to more than 100%. If you really want to know, read here, but I don't recommend trying to understand it.