The default conversion from mass to mol for Si uses the gram formula wt for SiO2. If your data are reported as ppm of Si, then you need to have the following in the SOLUTION data block: Si 5.25 as Si or Si 5.25 gfw 28.08 (default is equivalent to Si 5.25 as SiO2). David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 "Teresa Melo" <tmelo@xxxxxxxxx To: <dlpark@xxxxxxxx> > cc: In-Reply-To: <000901c0d593$4af43100$f15588c1@xxxxxxxxxxxxxxxxxxx> Subject: input file PHREEQC 05/05/01 11:43 AM Dear Dr Parkhurst, Just a quick question to check if I can use Si data instead of SiO2 (in ppm) in the PHREEQC input file. The following Solution 1 has 5.25 mgL-1 of Si. Is the input file correct or do I need to convert the Si to SiO2? SOLUTION 1 temp 20.8 pH 7.65 units ppm Na 128.0000 K 10.4000 Ca 13.0000 Mg 6.4400 Si 5.2500 Cl 132.0000 Alkalinity 136.0000 as HCO3 S(6) 68.6000 as SO4 N(5) 0.0000 as NO3 N(+3) 0.0000 as NO2 Amm 0.0000 as NH4 Al 0.0053 B 0.2200 Ba 0.0650 Br 0.3210 F 0.5200 Fe 0.3220 Li 0.0182 Mn 0.0242 Sr 0.1150 Thanks a lot for your kind help. Regards, Teresa
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