48

Salinity in Seawater

ObjectiveTo familiarize students with the different methods used for measuring salinity of water.

Introduction:Salinity exerts profound impacts on the marine environment. It controls the density-dependent movement of water and it affects the distribution of plants and animals.Salinity levels are frequently monitored by oceanographers and aquaculturists.In this exploration, students use a variety of techniques to measure the concentration ofsalt in samples of seawater.

BackgroundSalinity is a measure of the concentration of dissolved ions in water expressed ingrams/liter (g/L). Often it is represented as parts per thousand (ppt) or ‰. Seawatertypically varies from 33 g/L to 37 g/L, with 35 being about average.

Equipment Required

1 hydrometer 8 Burettes2 1.0 L graduated cylinder 9 Burette stand and clamps3 thermometer 10 Graduated4 salinity refractometer 11 Erlenmeyer flasks, 150-mL5 eye droppers (3) 12 Magnetic stirrers6 Conductivity meter 13 Pipettes

Reagents and Solutions Natural seawater Distilled water (in wash bottle) Indicator solution (3.5 g, potassium chromate, K2CrO 4 per liter solution) 0.250 M Silver nitrate, AgNO 3 (42.47 g AgNO 3, reagent grade, to 1.000 L in a1-

L volumetric flask. Store solution in a tightly capped brown glass bottle.).

Methods for Measuring Salinity

1. Determination of salinity by evaporation

Since salinity can be defined as the total mass ofdissolved salts (measured in grams) in onekilogram of seawater, the most straightforwardway to measure salinity is to measure exactly onekilogram of seawater, evaporate the water, andweight the salt that precipitates out. Evaporating afull kilogram of water would take more time, sowe will shorten the process by evaporating a smallfraction of a kilogram.

49

Procedure

1. Label three Petri dishes and weigh each to the nearest 0.01 gram. Record the masses ofthe dishes.2. Using a pipette, transfer about 10 mL of the seawater to the corresponding labeledPetri dishes.3. Weigh each Petri dish with the water to the nearest 0.01 gram and record the masses onthe answer sheet. Determine the mass of the water samples by subtracting the weight ofthe dish only, and record the masses.4. Carefully place the Petri dishes in the drying oven. Leave them in the oven until dry.5. Once the samples are dry allow them to cool for a few minutes, then weigh each Petridish and record the results on the answer sheet (dish + salt). Subtract the masses of thedishes to determine the mass of each of the salt samples and record the results on theanswer sheet.6. Determine the salinity of each sample using the equation below.

1000 /

0.391000 / 37 /

10.60

ooo

o ooo oo

weight of saltSalinity X

weight of water

gramsX

grams

=

= =

7. Record your answers on the answer sheet.

2. Measuring Salinity with a Salinometer

Contrary to common belief, pure water is not avery good conductor of electricity. It becomes agood conductor when soluble salts are added, dueto the presence of positive and negative ions thatcan donate and accept electrons. The transfer ofthese electrons is what allows water to conduct,and the higher the concentration of ions in thesolution the better the conductivity (the tap waterin your house has enough ions present to be agood conductor).

An instrument called a conductivity meter isused to measure the electrical conductivity (EC)of seawater to determine indirectly the totalconcentration of salt in the water. Electricalconductivity in water is a function not just ofsalinity but also of temperature, so we will need toconsider temperature in our measurements as well.The greater the proportion of ions in the water isthe higher the conductivity. The unit ofconductivity is the micromho per centimeter.

50

Procedure

1. Pour your sample of seawater into a 500 ml beaker until it is almost filled.2. Submerge the salinity

probe into the seawatersample and allow at least30 seconds for the readoutto equilibrate.

3. Measure the electricalconductance of the water(the units of conductanceare mmhos/cm)

4. Measure the water’stemperature (allow 30-60seconds for thethermometer to equilibrate)and record the temperature.

5. The graph to right relatessalinity in parts perthousand (horizontal axis)to conductivity inmmhos/cm (vertical axis).The sloping lines representthe relationship betweenconductivity and salinity atseveral knowntemperatures. Use thisgraph to determine thesalinity values for each of your samples and record these values.

6. Rinse the probe with distilled water and repeat steps 1-5 for another sample.

3. Measuring Salinity with a Refractometer

The speed of light in a vacuum is 2.998x105 kilometers/second. In water however, the

speed of light decreases to 2.25x105 km/second and in glass it decreases even more, to

51

about 2.00x105 km/second. This decrease in light velocity is due to the increase in density

of the medium, as photons are constantly being absorbed and re-emitted by atoms thatthey encounter.When light moves from one medium to another in which the velocity is different, thelight will bend, or refract, by an amount that is proportional to the difference in velocitybetween the two media. We will take advantage of this property by measuring the amountof that refraction in water samples.This is possible using a device called a refractometer. A refractometer can preciselymeasure the amount of refraction that is caused by the density. The refractometer consistsof a blue-tinted glass prism and a beveled, clear plastic cover lens, each with a knownrefractive index. When a thin layer of water is placed between these two lenses it willrefract light through an angle that depends upon the salinity of the water sample. Whenyou look through the eyepiece you will see a calibrated scale with an upper blue-shadedregion and a lower white region. The boundary between these two regions will cross thescale at a value representing the sample’s salinity (Figure).

Procedure

1. Before you begin, carefully rinse the face of the prism and the cover lens of therefractometer with deionized water, and dry with a cloth towel.

2. Place a drop of deionized water on the lens and close the cover. Look through theeyepiece. The boundary of the shaded region should cross the scale at the zeroline. If it does not, inform your instructor so that she/he can adjust it or assign youa different refractometer. If you have a problem reading the scale you can sharpenit using the focus ring.

3. Using an eyedropper, place one or two drops of your sample onto the prism face.4. Close the prism cover being careful not to trap any air bubbles in the water on the

prism face.5. Holding the prism toward the light, look though the refractometer and note where

the intersection lies between the upper shaded portion and lower clear portions ofthe scale. This boundary represents the salinity.

6. Record to the nearest part per thousand (‰).7. Rinse the prism and cover plate in deionized water and dry with a cloth towel.8. Repeat steps 4-8 for each of the unknowns and record the salinities.

cover

1 2 3

drop of water

52

4. Measuring Salinity with a Hydrometer

A hydrometer is an instrument that measures the specific gravity, the ratio of the densityof a liquid compared to the density of pure water. The hydrometer is an empty glass tube,with a weight at its bottom to keep the instrument upright in liquid. It works similar to theegg floating in the saltwater. When placed in the water, it will float. The height that ahydrometer floats in water depends on the salt content. When there is a high level of saltin the water, the sample has a higher density and the hydrometer will float higher. Sincethe specific gravity and consequently the density of water varies with temperature (wateris denser at lower temperatures), one needs to specify the temperature of the water tousefully define salinity. For this purposes, a conversion table is needed to convert theunits. Temperature correction tables are provided at the end of this lab manual.

Procedure

1. Fill ½ L graduated cylinder with thewater samples.

2. Carefully lower the hydrometer in thecylinder and allow it to settle. Followthe manufacturer’s instructions withthe hydrometer (the hydrometer shouldnot touch the cylinder walls, andshould be read from the bottom of themeniscus).

3. Read the specific gravity from thehydrometer scale (estimate to thefourth decimal).

4. Determine the temperature of yourwater sample.

5. Using the temperature and specificgravity values, determine the salinityvalues from the correction table.

6. Rinse with freshwater after use to reduce deposits.7. Do not leave the hydrometer floating between uses. If you do, difficult to remove

deposits may form over time.

Fig. Reading density from the hydrometer. Themajor lines are labeled to 5 parts in 1000, thesecondary unlabeled lines to 1 part in 1000, and thetertiary unlabeled lines to 5 parts in 10,000. Thisdevice can be read to the fourth decimal place.

53

5. Determination of Salinity by chemical titration

This procedure depends on the rule of constant proportion. We know that chloridesmake up about 55% of the total salts (salinity) in seawater. Therefore if we know thechlorinity (the mass of chloride present) we can determine the overall salinity:

S (ppt) = 100/55 x mass Cl-(ppt )= 1.8066 x mass Cl

-(ppt)

where S = salinity (g/L) and Cl = chlorinity (g/L).This method involves chemical volumetric analysis (titration). A silver nitrate (AgNO 3)solution of known concentration is used to precipitate out the chlorides in a seawatersample.An indicator of chromate ion is used to indicate the complete precipitation of Cl as AgCl.When all of the chloride ion is exhausted, the chromate ion reacts with silver ions andproduces silver chromate Ag 2CrO 4 (s), which is red. When the instant a permanentorange tinge appears in the solution (one that doesn’t vanish with mixing), the addition ofsilver nitrate is stopped. The final solution color should look like that of orange juice.The chemical reactions are:

Precautions• Wear protective goggles throughout the laboratory activity. Avoid getting AgNO3 onhands since it stains the skin.• The titration is carried out in a 150-mLErlenmeyer flask, using a whitebackground and good lighting, but awayfrom direct sunlight.• Constant but gentle stirring is essential,since the silver chloride tends to formclots, which trap some of the reagents.• A magnetic stirrer is very helpful.Observable clots of silver chloride willobscure the end point, since the solutionsthat they contain in their interstices willleak out slowly and cause the end point tobe impermanent. A stirring rod leftpermanently in the flask, especially if amagnetic stirrer is not used, will help tobreak up these curds.

Procedure

1. With a pipette deliver 10.0mL seawaterinto a 150-mL Erlenmeyer flask.2. Using a 10-mL graduated cylinder, add 5.0mL potassium chromate indicator solution.3. Add the silver nitrate solution from a burette while constantly stirring.

Cl-(aq) + Ag+(aq) AgCl(s) (white) (1)

2Ag+(aq) + CrO42-(aq) Ag2CrO4 (s) (red brown) (2)

54

5. Continue adding silver nitrate dropwise, mixing all the while, until orange colorpersists for 45 second. At this point one drop should give the desired end point.6. Record the volume of silver nitrate added.7. Determine the chloride concentration.8. Convert the chlorinity values to salinity by multiplying by 1.80655, record.

Solved ProblemWhat is the salinity of 10 ml of seawater sample (The density of seawater is about 1.05 g/ ml).If 24.0 ml of 0.250 M AgNO 3 is required to reach the end point of the seawatersolution (CrO 4

2 (aq) reaction with Ag + (aq) to give a red-brown precipitate).

1. Determine the number of moles of silver nitrate used in the titrationmol of AgNO3 = (volume of AgNO3)(molarity of AgNO3)mol of AgNO3 = (0.0240 L) (0.250 M) = 0.00600 mol of AgNO3

2. Determine the number of moles of Cl - ions present in the sample.mol of −Cl = mol of AgNO3 = 0.00600 mol −Cl

3. Determine the grams of chloride present in the sample.

(0.00600 mol of −Cl ) −

−

Clmol

Clg

1

45.35= 0.213 g of −Cl

4. Determine the chlorinity of a 10.0 ml sample? (The density of the seawater isdetermined to be 1.05 g/ml.)

( ) ( )100010.0

Mass of ClChlorinity ppt

Mass of mL of seawater

−

=

( )( ) ppt

mLmlg

Clg3.201000

0.1005.1

213.0

.

=

−

−

5. Determine the salinity of the sample.(1.80655) Chlorinity (ppt) = Salinity (ppt)(1.80655)(20.3 ppt) = 36.7 ppt

Calibration - Titration Method

38.6 ppt standard seawater:Measure out 17.5 g NaCl (table salt) and pour this into a 500-mL graduated cylinder.Fill the cylinder to the line with distilled water and carefully swirl the solution to mix thestandard, until all salt crystals have dissolved.Pour the solution into a plastic bottle and label.Follow directions for a water sample.Calibrate every six months to check technique.

55

Table gives salinity in parts per thousand for temperatures -1 to 8oC

S.G. Temperature oC

-1 0 1 2 3 4 5 6 7 8

1.000

1.001 0.6 0.6 0.5 0.5 0.2 0.2 0.2 0.2 0.2 0.2

1.002 1.9 1.9 1.8 1.6 1.6 1.6 1.5 1.5 1.6 1.6

1.003 3.2 3.1 2.9 2.9 2.8 2.8 2.8 2.8 2.8 2.9

1.004 4.4 4.2 4.2 4.1 4.1 4.1 4.1 4.1 4.1 4.2

1.005 5.7 5.5 5.4 5.4 5.4 5.3 5.3 5.4 5.4 5.4

1.006 6.8 6.8 6.7 6.6 6.6 6.6 6.6 6.6 6.7 6.7

1.007 8.1 8 7.9 7.9 7.9 7.9 7.9 7.9 7.9 8

1.008 9.3 9.2 9.2 9.2 9.2 9.2 9.2 9.2 9.2 9.3

1.009 10.5 10.5 10.4 10.4 10.4 10.4 10.4 10.5 10.5 10.6

1.010 11.8 11.7 11.7 11.7 11.7 11.7 11.7 11.7 11.8 11.8

1.011 13 13 12.8 12.8 12.8 12.8 13 13 13.1 13.1

1.012 14.3 14.1 14.1 14.1 14.1 14.1 14.1 14.3 14.3 14.4

1.013 15.4 15.4 15.4 15.4 15.4 15.4 15.4 15.4 15.6 15.7

1.014 16.7 16.6 16.6 16.6 16.6 16.6 16.7 16.7 16.9 17

1.015 17.9 17.9 17.9 17.9 17.9 17.9 17.9 18 18 18.2

1.016 19.2 19.1 19.1 19.1 19.1 19.2 19.2 19.3 19.3 19.5

1.017 20.4 20.4 20.4 20.4 20.4 20.4 20.5 20.5 20.6 20.8

1.018 21.7 21.7 21.6 .21.6 21.7 21.7 21.7 21.8 22 22.1

1.019 22.9 22.9 22.9 22.9 22.9 23 23 23.1 23.3 23.4

1.020 24.2 24.2 24 24.2 24.2 24.2 24.3 24.3 24.4 24.6

1.021 25.3 25.3 25.3 25.3 25.5 25.5 25.6 25.6 25.7 25.9

1.022 26.6 26.6 26.6 26.6 26.6 26.8 26.8 26.9 27 27.2

1.023 27.8 27.8 27.8 27.8 27.9 27.9 28.1 28.2 28.3 28.5

1.024 29.1 29.1 29.1 29.1 29.1 29.2 29.4 29.5 29.5 29.8

1.025 30.3 30.3 30.3 30.4 30.4 30.6 30.6 30.7 30.8 30.9

1.026 31.6 31.6 31.6 31.6 31.7 31.7 31.9 32 32.1 32.2

1.027 32.8 32.8 32.9 32.9 32.9 33 33.2 33.3 33.4 33.5

1.028 34.1 34.1 34.1 34.1 34.2 34.3 34.5 34.5 34.7 34.8

1.029 35.2 35.2 35.4 35.4 35.5 35.5 35.6 35.8 35.9 36.2

1.030 36.5 36.5 36.5 36.7 36.7 36.8 36.9 37.1 37.2 37.3

1.031 37.7 37.7 37.8 37.8 38 38.1 38.2 38.4 38.5 38.6

56

Table gives salinity in parts per thousand for temperatures 9 - 18oC

Temperature oCS.G.9 10 11 12 13 14 15 16 17 18

1.000 0 0.2 0.3

1.001 0.5 0.5 0.6 0.6 0.7 0.8 1 1.2 1.5 1.6

1.002 1.6 1.8 1.9 2 2.1 2.3 2.4 2.5 2.8 2.9

1.003 2.9 3.1 3.2 3.3 3.4 3.6 3.7 3.8 4.1 4.2

1.004 4.2 4.4 4.5 4.6 4.8 4.9 5 5.1 5.4 5.5

1.005 5.5 5.5 5.7 5.8 5.9 6.2 6.3 6.6 6.7 7

1.006 6.8 6.8 7 7.1 7.2 7.5 7.6 7.9 8 8.3

1.007 8.1 8.1 8.3 8.4 8.5 8.8 8.9 9.2 9.3 9.6

1.008 9.3 9.4 9.6 9.7 9.8 10 10.2 10.5 10.6 10.9

1.009 10.6 10.7 10.9 11 11.1 11.3 11.5 11.8 11.9 12.2

1.010 11.9 12 12.2 12.3 12.4 12.6 12.8 13.1 13.2 13.5

1.011 13.2 13.4 13.5 13.6 13.7 13.9 14.1 14.4 14.5 14.8

1.012 14.5 14.7 14.8 14.9 15 15.2 15.4 15.7 15.8 16.1

1.013 15.8 15.8 16 16.2 16.3 16.5 16.7 17 17.1 17.4

1.014 17 17.1 17.3 17.5 17.7 17.8 18 18.3 18.6 18.7

1.015 18.3 18.4 18.6 18.8 19 19.1 19.3 19.6 19.9 20

1.016 19.6 19.7 19.9 20.1 20.3 20.4 20.6 20.9 21.2 21.3

1.017 20.9 21 21.2 21.3 21.6 21.7 22 22.2 22.5 22.7

1.018 22.2 22.3 22.5 22.6 22.9 23 23.3 23.5 23.8 24

1.019 23.5 23.6 23.8 23.9 24.2 24.3 24.6 24.8 25.1 25.3

1.020 24.7 24.8 25.1 25.2 25.5 25.6 25.9 26.1 26.4 26.6

1.021 26 26.1 26.4 26.5 26.8 26.9 27.2 27.4 27.7 27.9

1.022 27.3 27.4 27.7 27.8 28.1 28.2 28.5 28.7 29 29.2

1.023 28.6 28.7 28.9 29.1 29.4 29.5 29.8 30 30.3 30.6

1.024 29.9 30 30.2 30.4 30.6 30.8 31.1 31.3 31.6 31.9

1.025 31.1 31.3 31.5 31.7 31.9 32.1 32.4 32.6 32.9 33.2

1.026 32.4 32.6 32.8 33 33.2 33.4 33.7 33.9 34.2 34.5

1.027 33.7 33.9 34.1 34.3 34.5 34.7 35 35.2 35.5 35.8

1.028 35 35.1 35.4 35.6 35.8 36 36.3 36.5 36.8 37.1

1.029 36.3 36.4 36.7 36.8 37.1 37.3 37.6 37.8 38.1 38.4

1.030 37.6 37.7 38 38.1 38.4 38.6 38.9 39.1 39.4 39.7

1.031 38.9 39 39.3 39.4 39.7 39.9 40.2 40.5 40.7 41

57

Table gives salinity in parts per thousand for temperatures 18.5 - 23oC

Temperature oCS.G.18.5 19 19.5 20 20.5 21 21.5 22 22.5 23

0.999 0 0.1 0.2 0.3

1.000 0.5 0.6 0.7 0.8 1 1.1 1.2 1.4 1.5 1.6

1.001 1.8 1.9 2 2.1 2.3 2.4 2.5 2.5 2.7 2.8

1.002 3.1 3.2 3.3 3.4 3.6 3.7 3.8 4 4.1 4.2

1.003 4.4 4.5 4.6 4.8 4.9 5 5.1 5.3 5.4 5.5

1.004 5.7 5.8 5.9 6.1 6.2 6.3 6.4 6.6 6.7 7

1.005 7.1 7.1 7.2 7.4 7.5 7.6 7.7 7.9 8.1 8.3

1.006 8.4 8.5 8.7 8.8 8.9 9.1 9.2 9.3 9.4 9.6

1.007 9.7 9.8 10 10.1 10.2 10.4 10.5 10.6 10.7 10.9

1.008 11 11.1 11.3 11.4 11.5 11.7 11.8 11.9 12 12.2

1.009 12.3 12.4 12.6 12.7 12.8 13 13.1 13.2 13.4 13.6

1.010 13.6 13.7 13.9 14 14.1 14.3 14.4 14.5 14.8 14.9

1.011 14.9 15 15.2 15.3 15.4 15.6 15.7 16 16.1 16.2

1.012 16.2 16.3 16.5 16.6 16.7 17 17.1 17.3 17.4 17.5

1.013 17.5 17.7 17.8 17.9 18 18.3 18.4 18.6 18.7 18.8

1.014 18.8 19 19.1 19.3 19.5 19.6 19.7 19.9 20 20.1

1.015 20.1 20.4 20.5 20.6 20.8 20.9 21 21.2 21.3 21.6

1.016 21.4 21.7 21.8 22 22.1 22.2 22.3 22.5 22.7 22.9

1.017 22.9 23 23.1 23.3 23.4 23.5 23.6 23.8 24 24.2

1.018 24.2 24.3 24.4 24.6 24.7 24.8 24.9 25.2 25.3 25.5

1.019 25.5 25.6 25.7 25.9 26 26.1 26.4 26.5 26.6 26.8

1.020 26.8 26.9 27 27.2 27.3 27.4 27.7 27.8 27.9 28.2

1.021 28.1 28.2 28.3 28.5 28.6 28.9 29 29.1 29.2 29.5

1.022 29.4 29.5 29.6 29.8 30 30.2 30.3 30.4 30.7 30.8

1.023 30.7 30.8 30.9 31.2 31.3 31.5 31.6 31.7 32 32.1

1.024 32 32.1 32.2 32.5 32.6 32.8 32.9 33.2 33.3 33.4

1.025 33.3 33.4 33.7 33.8 33.9 34.1 34.2 34.5 34.6 34.7

1.026 34.6 34.7 35 35.1 35.2 35.4 35.6 35.8 35.9 36

1.027 35.9 36.2 36.3 36.4 36.5 36.7 36.9 37.1 37.2 37.5

1.028 37.2 37.5 37.6 37.7 37.8 38.1 38.2 38.4 38.5 38.8

1.029 38.6 38.8 38.9 39 39.1 39.4 39.5 39.7 39.9 40.1

1.030 39.9 40.1 40.2 40.3 40.6 40.7 40.8 41 41.2 41.4

1.031 41.2 41.4 41.5 41.8 41.9 42 42.1 42.3 42.5

58

Table gives salinity in parts per thousand for temperatures 23.5 - 28oC

Temperature oCS.G.

23.5 24 24.5 25 25.5 26 26.5 27 27.5 28

0.998 0.1 0.2 0.3 0.6

0.999 0.5 0.6 0.7 0.8 1 1.2 1.4 1.5 1.8 1.9

1.000 1.8 1.9 2 2.1 2.4 2.5 2.7 2.9 3.1 3.2

1.001 2.9 3.1 3.2 3.4 3.6 3.8 4 4.2 4.4 4.5

1.002 4.4 4.6 4.8 4.9 5 5.1 5.4 5.5 5.7 5.9

1.003 5.8 5.9 6.1 6.2 6.3 6.6 6.7 6.8 7.1 7.2

1.004 7.1 7.2 7.4 7.5 7.7 7.9 8 8.3 8.4 8.5

1.005 8.4 8.5 8.7 8.9 9.1 9.2 9.3 9.6 9.7 10

1.006 9.7 9.8 10.1 10.2 10.4 10.5 10.7 10.9 11 11.3

1.007 11 11.3 11.4 11.5 11.7 11.9 12 12.2 12.4 12.6

1.008 12.4 12.6 12.7 12.8 13 13.2 13.4 13.6 13.7 13.9

1.009 13.7 13.9 14 14.1 14.4 14.5 14.7 14.9 15 15.3

1.010 15 15.2 15.3 15.6 15.7 15.8 16.1 16.2 16.5 16.6

1.011 16.3 16.5 16.7 16.9 17 17.3 17.4 17.5 17.8 17.9

1.012 17.7 17.9 18 18.2 18.3 18.6 18.7 19 19.1 19.3

1.013 19.1 19.2 19.3 19.5 19.7 19.9 20 20.3 20.4 20.6

1.014 20.4 20.5 20.6 20.9 21 21.2 21.4 21.6 21.8 22

1.015 21.7 21.8 22 22.2 22.3 22.5 22.7 22.9 23.1 23.3

1.016 23 23.3 23.4 23.5 23.6 23.9 24 24.3 24.4 24.7

1.017 24.3 24.6 24.7 24.8 25.1 25.2 25.3 25.6 25.7 26

1.018 25.6 25.9 26 26.1 26.4 26.5 26.8 26.9 27.2 27.3

1.019 27 27.2 27.3 27.6 27.7 27.8 28.1 28.2 28.5 28.6

1.020 28.3 28.5 28.6 28.9 29 29.2 29.4 29.6 29.8 30

1.021 29.6 29.8 30 30.2 30.3 30.6 30.7 30.9 31.1 31.3

1.022 30.9 31.2 31.3 31.5 31.7 31.9 32 32.2 32.5 32.6

1.023 32.2 32.5 32.6 32.8 33 33.2 33.4 33.5 33.8 33.9

1.024 33.7 33.8 33.9 34.2 34.3 34.5 34.7 35 35.1 35.4

1.025 35 35.1 35.2 35.5 35.6 35.9 36 36.3 36.4 36.7

1.026 36.3 36.4 36.7 36.8 36.9 37.2 37.3 37.6 37.7 38

1.027 37.6 37.8 38 38.1 38.4 38.5 38.8 38.9 39.1 39.3

1.028 38.9 39.1 39.3 39.4 39.7 39.8 40.1 40.2 40.5 40.7

1.029 40.2 40.5 40.6 40.8 41 41.2 41.4 41.6 41.8

59

Table gives salinity in parts per thousand for temperatures 28.5 - 33oC

Temperature oCS.G.28.5 29 29.5 30 30.5 31 31.5 32 32.5 33

0.998 0.7 0.8 1.1 1.2 1.5 1.6 1.9 2 2.3 2.4

0.999 2 2.3 2.4 2.5 2.8 2.9 3.2 3.4 3.6 3.8

1.000 3.4 3.6 3.7 4 4.1 4.4 4.5 4.8 4.9 5.1

1.001 4.8 4.9 5.1 5.1 5.4 5.5 5.8 5.9 6.2 6.4

1.002 6.1 6.3 6.4 6.6 6.8 7 7.2 7.5 7.6 7.9

1.003 7.4 7.6 7.7 8 8.1 8.4 8.5 8.8 9.1 9.2

1.004 8.8 8.9 9.2 9.3 9.6 9.7 10 10.1 10.4 10.5

1.005 10.1 10.2 10.5 10.6 10.9 11 11.3 11.5 11.7 11.9

1.006 11.4 11.7 11.8 12 12.2 12.4 12.6 12.8 13.1 13.2

1.007 12.8 13 13.1 13.4 13.6 13.7 14 14.1 14.4 14.7

1.008 14.1 14.3 14.5 14.7 14.9 15.2 15.3 15.6 15.7 16

1.009 15.4 15.7 15.8 16.1 16.2 16.5 16.6 16.9 17.1 17.3

1.010 16.7 17 17.1 17.4 17.5 17.8 18 18.2 18.4 18.7

1.011 18.2 18.3 18.6 18.7 19 19.1 19.3 19.6 19.7 20

1.012 19.5 19.6 19.9 20.1 20.3 20.5 20.6 20.9 21.2 21.3

1.013 20.8 21 21.2 21.4 21.6 21.8 22.1 22.2 22.5 22.7

1.014 22.2 22.3 22.6 22.7 23 23.1 23.4 23.6 23.8 24

1.015 23.5 23.6 23.9 24 24.3 24.6 24.7 24.9 25.2 25.3

1.016 24.8 25.1 25.2 25.5 25.6 25.9 26.1 26.3 26.5 26.8

1.017 26.1 26.4 26.5 26.8 27 27.2 27.4 27.7 27.8 28.1

1.018 27.6 27.7 27.9 28.1 28.3 28.5 28.7 29 29.2 29.4

1.019 28.9 29 29.2 29.5 29.6 29.9 30 30.3 30.6 30.8

1.020 30.2 30.4 30.6 30.8 30.9 31.2 31.5 31.6 31.9 32.1

1.021 31.5 31.7 32 32.1 32.4 32.5 32.8 33 33.3 33.4

1.022 32.9 33 33.3 33.4 33.7 33.9 34.1 34.3 34.6 34.8

1.023 34.2 34.5 34.6 34.8 35 35.2 35.5 35.6 35.9 36.2

1.024 35.5 35.8 35.9 36.2 36.4 36.5 36.8 37.1 37.2 37.5

1.025 36.8 37.1 37.2 37.5 37.7 37.8 38.1 38.4 38.6 38.8

1.026 38.2 38.4 38.6 38.8 39 39.3 39.4 39.7 39.9 40.2

1.027 39.5 39.8 39.9 40.2 40.3 40.6 40.8 41 41.2 41.5

1.028 40.8 41.1 41.2 41.5

60

salinity in PPT( parts per thousand)

Conductivity,milli ohms/cm at 25 deg C

1 1.972 3.803 5.564 7.285 8.966 10.617 12.248 13.869 15.4510 17.0211 18.5812 20.1213 21.6614 23.1815 24.6916 26.1917 27.6818 29.1619 30.6320 32.0921 33.5322 34.9823 36.4124 37.8425 39.2626 40.6727 42.0728 43.4729 44.8630 46.2431 47.6232 48.9533 50.3534 51.6735 53.0336 54.3737 55.72