salt or fresh

[lumphammer]

I have a sample of water from the bilge, based on what you could expect to find in the home is there an easy way to tell if it is salt or fresh if I don't want to risk my health by doing a taste test?

 

[Poignard]

Get the dog to taste it?

 

[lumphammer]

Pretty easy to do, harder to get him to tell me what it tastes like.
Bark once for salt, twice for fresh??

 

[Bajansailor]

The standard test for determining if water is salt or fresh (eg re water damages to cargoes) is to use silver nitrate crystals - I never have, but I think they work by changing different colours depending on if salt or fresh.

 

[Poignard]

Failing a co-operative dog, how about using a battery hydrometer and getting readings for fresh water and sea water, then comparing them with your bilge sample? Or see if soap will lather in it. Or boil it dry and see if salt remains [yeah, I know, how do you tell what remains is salt!]. Or boil it to kill any germs and let it cool before tasting it.

Personally I'd just taste it and spit it out quickly. Unless I suspected the heads had leaked into it!

 

[Saddletramp]

I had to pump a lot of what I hope was rain water out at the weekend. It looked vile with a layer of oil and diesel floating on top. Could not bring myself to taste it. Thinking about it now though, where on your tongue tastes salt? If it is the tip of your tongue then it is not so bad. I am off to get a packet of crisps to find out.

 

[ex-Gladys]

You don't have to drink it just dip your finger in and touch that on your tongue... Antifreeze and diesel mixed with a bit of fresh makes a nice cocktail. If it's got a diesel fim on it drop a TINY bit of detergent on it to break the surface tension then dip your finger in....

 

[SwedishLass]

Silver nitrate solution produces a white precipitate with chlorides which darkens in light (Basis of early photography). Much easier is to sample some of the cleanish liquid and put it on a saucer or similar in a warm place to evaporate off the water. Crystals (can be cubic if done slowly) indicate salt. Compare with tap water for fair comparison.

 

[VicS]

[ QUOTE ]
use silver nitrate crystals

[/ QUOTE ] Actually you acidify the sample with a drop of dilute nitric acid then add a drop or two of a dilute solution of silver nitrate solution. A heavy white precipitate indicates chloride ie salt water. But even tap water will give a slight precipitate. That also means the solution must be made up in distilled or demineralized water.
Not many people have silver nitrate handy so take a sample of the water along to the children's' chemistry teacher.

Sorry but no pretty colours with this one, just a white precipitate.

As a Chemist I would.....

taste it.

 

[[3889]]

If your really too fussy to taste it boil a bit and see if there is salt residue.

 

[Dyflin]

You could get a hydrometer and check the SG?

 

[jdc]

How about electrical resistivity? This is what we used to do on oil-rigs to measure the salinity of drilling mud.

Ideally you'd need to use AC rather than DC to avoid electrolysis, but provided you use stainless steel elctrodes (eg self-tappers screwed through a piece of plywood!) and make the measurement within 30s or so it should be fine. Use the resistance scale on a dvm (or analog multimeter) and calibrate with sea water and maybe a mixture of 10% sea water, 90% fresh. Remember that it is conductivity (=1/resistance) which is proportional to salt content.

 

[neale]

Just taste it man!!!!!

 

[Bajansailor]

Agreed, taste is the way to go - that is what I always do to determine if water damages to cargoes are from fresh or salt.
Just one drop on the tip of your tongue will tell you what it is - and if you are fussy, you can always have a bottle of Listerine handy....

 

[michael_w]

With such a roughty-toughty name aren't you being bit of a girly?

 

[explores]

Finger and tongue method always works for me.

 

[graham]

Salt water leaves a salt stain on clothing etc so whatabout filtering the water through a bit of coloured cloth and see if any salt residue is left as the cloth dries?

Either that or use a pair of glasses.The salt allways seems to want to stay on my specs /forums/images/graemlins/grin.gif

 

[graham]

[ QUOTE ]
Finger and tongue method always works for me.

[/ QUOTE ]
Hope you heads users are more accurate than mine. /forums/images/graemlins/laugh.gif

 

[pyrojames]

Years of tasting bilge water has given me an appreciation of many things, diesel (sweet), rotting oak, engine oil, turps (rather sharp, horrible repeating), rust (bitter), oh and salt/brackish. Never had clear sweet fresh water! /forums/images/graemlins/smile.gif

 

[pyrojames]

I thought we were talking about boats....