Artificial Seawater

Based on “Preparation of Artificial Seawater” by Kester

Materials

1. Gloves
2. Lab Coat
3. Safety Glasses
4. 10 L Carboy with spigot
5. Access to D.I. water
6. Scale
7. Weight boats
8. Spatula
9. 1500 ml Flask
10. 500 ml Flask
11. 100 ml Flask
12. 4 Stir bars
13. 1-2 Stir plates

Salts

Solution 1: Gravimetric salts (Amounts of preparation of 7 L of ASW)

1. 5 L of D.I water
2. 167.48g Sodium chloride (NaCl)
3. 28.06 g Sodium sulfate (Na₂SO₄)
4. 4.74 g Potassium chloride (KCl)
5. 1.37 g Sodium bicarbonate (NaHCO₃)
6. 0.69 g Potassium bromide (KBr)
7. 0.18 g Boric acid (H₃BO₃)
8. 0.02 g Sodium fluoride (NaF)

Solution 2: Volumetric salts (Amounts to prepare at least double of each individual solution)

Check if these are already made first

1. 203.31 g Magnesium chloride (MgCl₂.6H₂O) A. 1000 ml of D.I. Water
2. 29.4 g Calcium chloride (CaCl₂.2H₂O) A. 200 ml of D.I. Water
3. 1.6 g Strontium chloride (SrCl₂.6H₂O) A. 60 ml of D.I. Water

Method

The steps below allow you to prepare 7L of artificial seawater. You will also have leftovers of each of the solutions 2: volumetric salts to use the next time you prepare the artificial seawater.

1. Obtain personal protective equipment, including gloves, safety glasses, and a lab coat—all are highly recommended here because you may need to break up the salt, which could get on clothes or in your eyes.
2. Obtain all materials.
3. Obtain all salts to make solutions 1 and 2.

4. First, prepare each of the volumetric salt solutions as they need extra time on the stir plates to dissolve.

   A. To prepare the magnesium chloride solution, measure 1000 ml of D.I. water weigh out 203.31 grams of magnesium chloride, and add both to a 1500 ml flask with a stir bar, put on a stir plate until dissolved

   B. To prepare the calcium chloride solution, measure 200 ml of D.I. water weigh out 29.4 g grams of calcium chloride, and add both to a 500 ml flask with a stir bar, put on a stir plate until dissolved

   C. To prepare the strontium chloride solution, measure 60 ml of D.I. water weigh out 1.6 g grams of strontium chloride, and add both to a 100 ml flask with a stir bar, put on a stir plate until dissolved

5. Now prepare solution 1, in contrast to the previous steps these salts will be directly added to the 10 L carboy

   A. First, add 5L of D.I. water to the 10 L carboy

   B. Then weigh out the following salts and add directly to the 10 L carboy with the 5L of D.I. water (Note: Some of the salts may be crumpled together it is better to pour these salts out into their respective container caps and break them apart using the spatula before weighing, remember to clean the spatula with D.I. water between salts)

    1. 167.48g Sodium chloride (NaCl)
       
    2. 28.06 g Sodium sulfate (Na<sub>2</sub>SO<sub>4</sub>)
       
    3. 4.74 g Potassium chloride (KCl)
       
    4. 1.37 g Sodium bicarbonate (NaHCO<sub>3</sub>)
       
    5. 0.69 g Potassium bromide (KBr)
       
    6. 0.18 g Boric acid (H<sub>3</sub>BO<sub>3</sub>)
       
    7. 0.02 g Sodium fluoride (NaF)
   
    8. Measure and add 373 ml of magnesium chloride, 72.3 ml  of calcium chloride, and 6.30 ml of strontium chloride to the 10 L carboy.
   

   C. Top off the 10 L Carboy with D.I. water up to the 7L mark.

   D. Add a stir bar and place it on a stirrer for 24 hours.

6. Measure the pH and salinity intermittently. pH should be around 8.1-8.2 and the salinity should be 36-38 ppt.
7. Salinity Check: Use the refractometer to measure the salinity, place a drop of the seawater on the refractometer look through the lens as you point it up towards the light, and examine the PPT mark

8. pH Check: Plug in and calibrate the pH meter

   A. Materials

   1. Kim wipes
       
   2. Sample
       
   3. pH meter
       
   4. pH buffer solutions
       
   5. DI water in a squirt bottle
       
   6. Gloves
   

   B. Make sure the pH meter is plugged in, and move the rubber stopper part so that the hole is uncovered allowing air to move in and out of the pH meter.

   C. Take the meter out of the standing solution, gently wash it with DI water, and gently pat dry with a Kim wipe.

   D. Dip in the first buffer solution and press calibrate, wait until the meter stabilizes should be within .1 of what the pH of the buffer is.

   E. Gently wash it with DI water, and gently pat it dry with a Kim wipe and repeat with other buffer solutions.

   F. Before taking a reading of your sample place it back in one of the buffers and press read to determine if the meter is correctly reading the buffer.

   G. Again, wash and dry the meter, place the meter in the sample press read, wait for the meter to stabilize, and then record the pH measurement.

   H. Clean and dry the meter, ALWAYS MOVE THE RUBBER STOPPER BACK TO COVER THE HOLE WHEN YOU ARE FINISHED USING THE METER.

   I. Press and hold the power button to shut the meter off.