Is the salinity High at first when mixing ??

[newfishliny]

I mixed a five gallon bucket with salt , the right ratio
then took a reading it went to 1.030.after 2 hours it is at 1.025.
does that mean it is still mxing and with in time it will settle to aprox 1.023, any thoughts

 

[richard rendos]

It is usually the other way around. In time all the salt dissolves leaving you with higher salt concentration. Has the temperature of the water changed? Salinity is affected by temperature also.

 

[rockster]

Salinity has to either stay unchanged or increase on a newly mixed salt water. As mentioned, typically, salt does not dissolve completely when newly mixed. Factors such as temperature contributes to this lowered solubility of solids. When you use a cold (were talking much lower than room temp) water, the salt will take longer to dissolve. As you will note when stirring sugar in a cup of iced tea vs. cup of hot coffee. The reason for this phenomenon is that the water moleules in warm/hot solution are far apart from each other making the ions (OH- and H+) available to bond with solutes (salt). On the otherhand, cold water has the same ions closer together and are in turn bonded to each other making it hard for the salt ions to "squeeze" in between them. Another factor that increases salinity after prolonged standing of solution is the evaporation of pure H2O molecules leaving behind solutes...increasing salinity. You see this when you do not top off your water for a while.

 

[bang guy]

Originally posted by Rockster
Salinity has to either stay unchanged or increase on a newly mixed salt water.
I agree with this statement. However, the poster only gave the specific gravity so the Salinity of the water is unknown.
If the water was cold the S.g. would slowly drop as the water warmed. The salinity would remain unchanged.
Remember, it's the SALINITY that is important. There is no way to know the Salinity unless you read Specific Gravity AND Temperature. Also keep in mind that hydrometers are built to test water at a certain temp. Some are calibrated for 77F, or 65F or even 34F. To be accurate the water need to be near the temp the hydrometer is calibrated for.

 

[rockster]

The response was meant to assume a linear relationship between salinity and specific geavity. For a given temperature, salinity is directly proportional to the specific gravity. Ie., as SG increases, so does the salinity. I disagree with your claim that salinity does not change with increase in temperature. Salinity is measured in parts per thousand, I.e., parts per liter. You do realize that water volume expand when heated like every matter in the universe. When volume increase without increase in number of solute molecule, concentration falls (salinity and specific gravity). Ever wonder why hydrometer made by Aquarium System is designed as such?

 

[starfishjackedme]

Well, I have to do several readings to get a good one on an Aquarium Systems hydrometer. If there are ANY bubbles on the pointer then it will be very inaccurate. Sometimes it is hard to get a reading without any bubbles attached to the pointer. I always do a min. two readings to get an idea of what i'm dealing with.
One of these days i am going to go electronic and spare the headaches.

 

[rockster]

I am not referring to the accuracy (or lack thereof) of the hydrometer mentioned. Look at the scale, on the right is the SG and on the left is the salinity...linear relationship. Of course, reading will be altered when a piece of bubble is attached to the pointer. You don't have to be a rocket scientist to figure that out.

 

[bang guy]

Originally posted by Rockster For a given temperature, salinity is directly proportional to the specific gravity. Ie., as SG increases, so does the salinity.
Yes, for a given temperature. I could only think of one reason why s.g. would drop in a new batch of saltwater, that the temp increased. There my be other reasons that my brain just isn't coming up with.
I disagree with your claim that salinity does not change with increase in temperature.
Then we disagree. I do not believe Salinity changes by temp alone. At least not to a degree measureable by a hobbiest.
You do realize that water volume expand when heated like every matter in the universe.
Hogwash! If that were true then the ice cubes in my Crown Royal would be sitting on the bottom of my glass instead of making my lips cold.
Ever wonder why hydrometer made by Aquarium System is designed as such?
Nope, I could not care less.

 

[broomer5]

I agree that most salinity readings are in ppt.
Parts per thousand.
But I don't believe the relationship is parts per liter.
I think it's grams per kilogram weight/mass.
If it was ml/L - that would be equal engineering units.
A volume to volume relationship.
One liter of seawater should have an approximate mass of 1.025 kilograms.
Or 1.025 kilograms/liter - depending on temperature.
When you mix mass and volume units - temperature comes into play. You're talking mixed units.
Otherwise - if only reporting mass units - I don't think the temperature has much if any affect.
Specific gravity is a weight/volume relationship - and it will change with changes in temperature.
Salinity - as measured in ppt - will not be affected by temp.
This is my understanding - although I may be mistaken.

 

[newfishliny]

Originally posted by Bang Guy
I agree with this statement. However, the poster only gave the specific gravity so the Salinity of the water is unknown.
If the water was cold the S.g. would slowly drop as the water warmed. The salinity would remain unchanged.
Remember, it's the SALINITY that is important. There is no way to know the Salinity unless you read Specific Gravity AND Temperature. Also keep in mind that hydrometers are built to test water at a certain temp. Some are calibrated for 77F, or 65F or even 34F. To be accurate the water need to be near the temp the hydrometer is calibrated for.
you are saying in simple terms if the water is wamer then my salinity should drop as if it was cold it would stay high. the
hydrometer is a sea test and states reading from68-85f with in a range of+ 0.001

 

[rockster]

Bang Guy, say what you will. Do yourself a favor, it's time to review physics and chemistry. And before you make any snarl comments use your brain, for once.

 

[bang guy]

There's absolutely nothing wrong with my Physics here. Admittedly my brain befuddles itself far too often and my Chemistry could use a lot of work but you should be a little more humble when you are in error.
Have a nice day.

 

[bang guy]

Originally posted by NewFishLINY
you are saying in simple terms if the water is wamer then my salinity should drop as if it was cold it would stay high. the
hydrometer is a sea test and states reading from68-85f with in a range of+ 0.001
Yep, close enough. That's what I think happened. I am just guessing though. You could try repeating your proceedure after letting the water warm and see if it makes a difference.