qianpeiw740
Posts: 5
Joined: Tue Sep 04, 2007 6:08 am

### measuring salt content

Would a hydrometer suffice if I want to measure the salinity of water? If not what instrument should I use and be able to obtain at a relatively low cost?
QianPei W

qianpeiw740
Posts: 5
Joined: Tue Sep 04, 2007 6:08 am

### change

Sorry. I have a new question. Does anyone know the formula/how to convert electrical conductivity to actual salinity? If you do then i can just measure the electrical conductivity and convert it.
QianPei W

staryl13
Former Expert
Posts: 404
Joined: Tue Sep 18, 2007 3:27 pm
Occupation: Research Assistant
Hi QianPei!
Check out this website, hopefully this is the conversion you are looking for-
http://www.sa.waterwatch.org.au/sw_salinity.htm
"There is a single light of science, and to brighten it anywhere is to brighten it everywhere." -Isaac Asimov

davidkallman
Former Expert
Posts: 675
Joined: Thu Feb 03, 2005 3:38 pm

### Re: measuring salt content and change

Hi QianPei,
qianpeiw740 wrote: Would a hydrometer suffice if I want to measure the salinity of water? If not what instrument should I use and be able to obtain at a relatively low cost?

Sorry. I have a new question. Does anyone know the formula/how to convert electrical conductivity to actual salinity? If you do then i can just measure the electrical conductivity and convert it.
Your two questions are mirrored in the resources I was able to find:

1. One way to measure salinity is with a CTD (Conductivity Temperature Depth) instrument. See: http://www.windows.ucar.edu/tour/link=/ ... r/CTD.html
For background see: http://www.windows.ucar.edu/tour/link=/ ... salts.html I don't have any info on how difficult it is to get access to a CTD.

2. Another resource to measure water characteristics is at:
http://ga.water.usgs.gov/edu/characteristics.html
It mentions taking the conductance of the tested water, with unfortunately no details.

Maybe someone has info on how to get access to a CTD or what the formula is in 2. above.
Cheers!

Dave

barretttomlinson
Former Expert
Posts: 932
Joined: Wed Oct 03, 2007 12:24 am
You asked if you could determine the salinity of water with a hydrometer. If you know the composition of the liquid is just sodium chloride and water the answer is yes. I found tables of the specific gravity or density of sodium chloride-water solutions in two widely available books:

Handbook of Chemistry, Ninth Edition, Norbert Adolph Lange

and

Handbook of Chemistry and Physics, 40th Edition, Charles D. Hodgman

These handbooks are reissued as a new edition every few years, but the content is actually fairly stable, so you could probably find the data in almost any edition. The Handbook of Chemistry and Physics is the more popular book, and most libraries or schools would probably have at least one copy.

davidkallman
Former Expert
Posts: 675
Joined: Thu Feb 03, 2005 3:38 pm

### Re: measuring salt content

Hi QianPei,

A good resource is:

http://www.dpi.vic.gov.au/dpi/nreninf.n ... LC0064.pdf

This page explains how to convert currency measurements into salinity measurements. It also introduces a new method of letting the water evaporate and weighing the remaining salt. Of course, this method is the most accurate (if you have the time!). The page also include the applications of water at various salinity levels.
Cheers!

Dave

davidkallman
Former Expert
Posts: 675
Joined: Thu Feb 03, 2005 3:38 pm

### Re: measuring salt content

Hi QianPei,

Note: the http://www.dpi.vic.gov.au/dpi/nreninf.n ... LC0064.pdf URL I just posted puts you on page two of a three document (I don't know why.).

To see the document from the beginning, you'll either need to hit "page up" several times (three on my system) or select page 1 at the top (where it says 2/3 - you'll need to change the "2" to a "1".
Cheers!

Dave