TNoel Posted March 9, 2007 Share Posted March 9, 2007 Hello, I am fairly new to this hobby. My tank has been going for about 2 1/2 months now. Every thing has been going pretty well. My question is this. I have 2 different hydrometers. They read about 5 points difference. I have access at work to some high quality refractometers. Where can I find a chart to convert RI to salinity or specific gravity. I know some of the hand held, hobby models, already have the conversion, but the ones we use for QC don't. Thanks, Tom Quote Link to comment Share on other sites More sharing options...
DChemist Posted March 9, 2007 Share Posted March 9, 2007 (welcome) I found this in a quick look... "For example, at 20ºC the refractive index of pure water is 1.333, while the refractive index of seawater (salinity = 35 ppt) is 1.339." I'll dig around work to see what I can find. By the way, where do you work? Quote Link to comment Share on other sites More sharing options...
impur Posted March 9, 2007 Share Posted March 9, 2007 Welcome to the board!!!! I have some 35ppt salinity solution for calibrating refractometers if you need to calibrate. Sounds like you might have that stuff at your job though. Sorry i don't have an answer to your question though :( Quote Link to comment Share on other sites More sharing options...
DChemist Posted March 9, 2007 Share Posted March 9, 2007 Here's a helpful link... http://www.reefkeeping.com/issues/2004-06/rhf/index.php From the data in the article I found you can calculate your salinity from your refractive index measurement. At 20 degrees C (68 degrees F) and for salinities between 30 and 39... (RI x 5473.9) - 7296.8 = salinity Quote Link to comment Share on other sites More sharing options...
TNoel Posted March 10, 2007 Author Share Posted March 10, 2007 Thanks for the info. Impur I really appreciate the offer, I may take you up on it, I'll let you know. We do all of our testing at 25 C . I will talk to a chemist next week to see how much difference the temperature difference would make, unless someone here knows. My water tested @1.3389 the LFS told me that was on the high side, but it looks to me that it is about right. What do you guys think. I am trying to figure out where my hydrometer is when the RI is correct. Thanks, Tom Quote Link to comment Share on other sites More sharing options...
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