How to convert specific gravity to ppm?

[Creetin]

I am adding a saltwater clhorine generator for my pool and i need to bring salt to about 3200 ppm. I want to use my refractometer but i need to convert it to specific gravity.
Any help is appreciated!!

[disc1]

It's not a direct conversion. There is a lot of math involved. It would be easiest just to look up a table. 3200ppm = 3.2ppt if the refrac you are using reads ppt. The one I use for my saltwater tank the 3.2ppt is around 1.002 S.G. I don't think you would want to use a refractometer to read something that low unless it was specifically designed to highlight that low range.

[bertoni]

There's a chart in this article that has some information on relating salt content to refractive index, which is what you need:

http://reefkeeping.com/issues/2004-06/rhf/index.php

The CRC Handbook of Chemistry and Physics should have the full table.

[Boomer]

Creetin


That is pretty easy BUT. Almost all refracts in this hobby are table salt refracts, unless you have a Vee-Gee or Vital-Sine refract. Who's refract do you have ? Your refract should have ppt on it if it is Hand-Held like we use in this hobby. If it is a hobby grade refact 1.0264 = 35 ppt NaCl or 35,000 ppm NaCl (35 ppt NaCl is NOT the same as 35 ppt seawater on a refract). Calibrate the meter in RO/DI water to read zero. On that meter you want it to read 3.2 ppt NaCl (= 3200 ppm NaCl) = 1.002414 SG NaCl ( rounded off 1.002 SG). You can also go by the std for pools of 1 tsp. of salt per 1 gallon of pool water ( but that may be difficult to calculate)

You are better off if you use a TDS meter if you have one. Most factory TDS meters are also as ppm NaCl. Yo do not HAVE to have 3200 ppm the range for pools is 2500 - 6000 ppm. The reason behind the 3200 ppm is that it is optimal for no taste. Meaning, at 3200 ppm you will not taste the salt in the water and have a better salt content needed than say 2500 ppm. When you get into the upper 3000's you will taste salt in the water. Lastly, as noted by disc1, a refract is kind'a a bad idea for a pool measurement.

Here is what I mean. Look where that 1.002 is or 3.2 is. You will not be able to distinguish the difference, barley, between 2 ppt and 3 ppt or 3 ppt 4 ppt. Then there is the error factor or accuracy which is +/- 1 ppt. That means **if you got it right on 3.5 ppt half-way "mark" the REAL reading is somewhere between 3.4 - 3.6 ppt.

http://www.drsfostersmith.com/images/bigimages/lg_refractometer.jpg

[Creetin]

A big Thank you!!! I just have a standard hobby grade refract. I found some salt test strips (Sigh I know) that seem to be reading what the salt water chlorine generator is. Its reading 3100 ppm which is in range 2800-3600ppm. If its too high or too low it wont run. After some time the cells have been known to degrade and not read as accurately so i was wanting a good way of measurement. (Not test strips.) :)
Thank you SIR!
Thanks bertoni and disc!

[bertoni]

You're welcome!

[disc1]

Very welcome!

[Boomer]

Ditto