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FAQ & Disclaimer

FAQ: Why do different programs give different results to the same calculation?

Answer: Every programmer has to make assumptions about how all of this works and what are the "best" constants to use [definitely no agreement on either issue]. No programmer starts out to make an invalid program. The results most likely do fit the observations made in their own lab. The problems come in when the programs are extended beyond experience into new situations [like yours]. A classic case of a person with two watches does not know what time it is.

Consider all of these programs to be a work in progress. It is VERY important that you always report what program you used, including version information.

Constants come from two sources: Martell & Smith Critical Stability Constants [ref#6] in the updated database from NIST and from constants determined in individual labs.


My degree, a B.A., is in Biology and Photography, NOT physical chemistry.[I was top of my class in Analytical Chemistry as an undergraduate, but that still does not qualify me as an expert.] I work as a professional technician at Stanford University's Hopkins Marine Station [35+ years]   I have been working with these equations and ideas for over thirty years. I became interesting in doing the programs when they were needed for my work with Professor David Epel, also a biologist. I saw a need for an easier to use program than what was available at the time. By working with many experts in the field and a lot of cross checking and validation, the programs came to be.

However, I am not an expert. There are likely to be errors in understanding and possibly code execution. Mistakes have been found in the past. If anything, these programs are really a community effort. As people ask questions and answers are found they are incorporated into these pages and code.

I am willing to attempt to answer any questions you have, but if it is beyond my abilities I will readily admit so.

Chris Patton: cpatton@stanford.edu