Salinity in Seawater Objective To familiarize students with the different methods used for measuring salinity of water. Introduction: Salinity exerts profound impacts on the marine environment. It controls the densitydependent 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 of salt in samples of seawater. Background Salinity is a measure of the concentration of dissolved ions in water expressed in grams/liter (g/l). Often it is represented as parts per thousand (ppt) or. Seawater typically varies from 33 g/l to 37 g/l, with 35 being about average. Equipment Required 1 hydrometer 8 Burettes 2 1.0 L graduated cylinder 9 Burette stand and clamps 3 thermometer 10 Graduated 4 salinity refractometer 11 Erlenmeyer flasks, 150-mL 5 eye droppers (3) 12 Magnetic stirrers 6 Conductivity meter 13 Pipettes Reagents and Solutions Natural seawater Distilled water (in wash bottle) Indicator solution (3.5 g, potassium chromate, K 2 CrO 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 of dissolved salts (measured in grams) in one kilogram of seawater, the most straightforward way to measure salinity is to measure exactly one kilogram of seawater, evaporate the water, and weight the salt that precipitates out. Evaporating a full kilogram of water would take more time, so we will shorten the process by evaporating a small fraction of a kilogram. 48
Procedure 1. Label three Petri dishes and weigh each to the nearest 0.01 gram. Record the masses of the dishes. 2. Using a pipette, transfer about 10 ml of the seawater to the corresponding labeled Petri dishes. 3. Weigh each Petri dish with the water to the nearest 0.01 gram and record the masses on the answer sheet. Determine the mass of the water samples by subtracting the weight of the 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 Petri dish and record the results on the answer sheet (dish + salt). Subtract the masses of the dishes to determine the mass of each of the salt samples and record the results on the answer sheet. 6. Determine the salinity of each sample using the equation below. weight of salt o Salinity = X 1000 / oo weight of water 0.39grams o o = X 1000 / oo = 37 / 10.60grams 7. Record your answers on the answer sheet. oo 2. Measuring Salinity with a Salinometer Contrary to common belief, pure water is not a very good conductor of electricity. It becomes a good conductor when soluble salts are added, due to the presence of positive and negative ions that can donate and accept electrons. The transfer of these electrons is what allows water to conduct, and the higher the concentration of ions in the solution the better the conductivity (the tap water in your house has enough ions present to be a good conductor). An instrument called a conductivity meter is used to measure the electrical conductivity (EC) of seawater to determine indirectly the total concentration of salt in the water. Electrical conductivity in water is a function not just of salinity but also of temperature, so we will need to consider temperature in our measurements as well. The greater the proportion of ions in the water is the higher the conductivity. The unit of conductivity is the micromho per centimeter. 49
Procedure 1. Pour your sample of seawater into a 500 ml beaker until it is almost filled. 2. Submerge the salinity probe into the seawater sample and allow at least 30 seconds for the readout to equilibrate. 3. Measure the electrical conductance of the water (the units of conductance are mmhos/cm) 4. Measure the water s temperature (allow 30-60 seconds for the thermometer to equilibrate) and record the temperature. 5. The graph to right relates salinity in parts per thousand (horizontal axis) to conductivity in mmhos/cm (vertical axis). The sloping lines represent the relationship between conductivity and salinity at several known temperatures. Use this graph to determine the salinity 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 2.998x10 5 kilometers/second. In water however, the speed of light decreases to 2.25x10 5 km/second and in glass it decreases even more, to 50
about 2.00x10 5 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 that they encounter. When light moves from one medium to another in which the velocity is different, the light will bend, or refract, by an amount that is proportional to the difference in velocity between the two media. We will take advantage of this property by measuring the amount of that refraction in water samples. This is possible using a device called a refractometer. A refractometer can precisely measure the amount of refraction that is caused by the density. The refractometer consists of a blue-tinted glass prism and a beveled, clear plastic cover lens, each with a known refractive index. When a thin layer of water is placed between these two lenses it will refract light through an angle that depends upon the salinity of the water sample. When you look through the eyepiece you will see a calibrated scale with an upper blue-shaded region and a lower white region. The boundary between these two regions will cross the scale 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 the refractometer 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 the eyepiece. The boundary of the shaded region should cross the scale at the zero line. If it does not, inform your instructor so that she/he can adjust it or assign you a different refractometer. If you have a problem reading the scale you can sharpen it 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 of the 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 drop of water 1 2 3 51
4. Measuring Salinity with a Hydrometer A hydrometer is an instrument that measures the specific gravity, the ratio of the density of 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 the egg floating in the saltwater. When placed in the water, it will float. The height that a hydrometer floats in water depends on the salt content. When there is a high level of salt in the water, the sample has a higher density and the hydrometer will float higher. Since the specific gravity and consequently the density of water varies with temperature (water is denser at lower temperatures), one needs to specify the temperature of the water to usefully define salinity. For this purposes, a conversion table is needed to convert the units. Temperature correction tables are provided at the end of this lab manual. Procedure 1. Fill ½ L graduated cylinder with the water samples. 2. Carefully lower the hydrometer in the cylinder and allow it to settle. Follow the manufacturer s instructions with the hydrometer (the hydrometer should not touch the cylinder walls, and should be read from the bottom of the meniscus). 3. Read the specific gravity from the hydrometer scale (estimate to the fourth decimal). 4. Determine the temperature of your water sample. 5. Using the temperature and specific gravity values, determine the salinity values 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. The major lines are labeled to 5 parts in 1000, the secondary unlabeled lines to 1 part in 1000, and the tertiary unlabeled lines to 5 parts in 10,000. This device can be read to the fourth decimal place. 52
5. Determination of Salinity by chemical titration This procedure depends on the rule of constant proportion. We know that chlorides make up about 55% of the total salts (salinity) in seawater. Therefore if we know the chlorinity (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 seawater sample. 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 and produces silver chromate Ag 2 CrO 4 (s), which is red. When the instant a permanent orange tinge appears in the solution (one that doesn t vanish with mixing), the addition of silver nitrate is stopped. The final solution color should look like that of orange juice. The chemical reactions are: Cl - (aq) + Ag + (aq) AgCl(s) (white) (1) 2Ag + (aq) + CrO 4 2- (aq) Ag 2 CrO 4 (s) (red brown) (2) Precautions Wear protective goggles throughout the laboratory activity. Avoid getting AgNO 3 on hands since it stains the skin. The titration is carried out in a 150-mL Erlenmeyer flask, using a white background and good lighting, but away from direct sunlight. Constant but gentle stirring is essential, since the silver chloride tends to form clots, which trap some of the reagents. A magnetic stirrer is very helpful. Observable clots of silver chloride will obscure the end point, since the solutions that they contain in their interstices will leak out slowly and cause the end point to be impermanent. A stirring rod left permanently in the flask, especially if a magnetic stirrer is not used, will help to break up these curds. Procedure 1. With a pipette deliver 10.0mL seawater into 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. 53
5. Continue adding silver nitrate dropwise, mixing all the while, until orange color persists 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 Problem What 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 seawater solution (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 titration mol of AgNO 3 = (volume of AgNO 3 )(molarity of AgNO 3 ) mol of AgNO 3 = (0.0240 L) (0.250 M) = 0.00600 mol of AgNO 3 2. Determine the number of moles of Cl - ions present in the sample. mol of Cl = mol of AgNO 3 = 0.00600 mol Cl 3. Determine the grams of chloride present in the sample. 35.45 g Cl (0.00600 mol of Cl ) = 0.213 g of Cl 1 mol Cl 4. Determine the chlorinity of a 10.0 ml sample? (The density of the seawater is determined to be 1.05 g/ml.) Mass of Cl Mass of 10.0 ml of seawater 0.213 g Cl 1.05 g. ml ( 1000) = 20.3 ppt ( 10.0mL) 5. Determine the salinity of the sample. (1.80655) Chlorinity (ppt) = Salinity (ppt) (1.80655)(20.3 ppt) = 36.7 ppt Calibration - Titration Method ( 1000) = Chlorinity ( ppt ) 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 the standard, 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. 54
Table gives salinity in parts per thousand for temperatures -1 to 8 o C S.G. Temperature o C -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 55
Table gives salinity in parts per thousand for temperatures 9-18 o C S.G. Temperature o C 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 56
Table gives salinity in parts per thousand for temperatures 18.5-23 o C S.G. Temperature o C 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 57
Table gives salinity in parts per thousand for temperatures 23.5-28 o C S.G. Temperature o C 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 58
Table gives salinity in parts per thousand for temperatures 28.5-33 o C S.G. Temperature o C 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 59
salinity in PPT ( parts per thousand) Conductivity, milli ohms/cm at 25 deg C 1 1.97 2 3.80 3 5.56 4 7.28 5 8.96 6 10.61 7 12.24 8 13.86 9 15.45 10 17.02 11 18.58 12 20.12 13 21.66 14 23.18 15 24.69 16 26.19 17 27.68 18 29.16 19 30.63 20 32.09 21 33.53 22 34.98 23 36.41 24 37.84 25 39.26 26 40.67 27 42.07 28 43.47 29 44.86 30 46.24 31 47.62 32 48.95 33 50.35 34 51.67 35 53.03 36 54.37 37 55.72 60