Writer: Dr. Michael Chase, 16th Could 2019


This text describes the strategy and PRELIMINARY consequence of a comparatively low price “laboratory” (kitchen) experiment on the response of seawater pH to will increase in atmospheric CO2.

When further CO2 is added to the air above seawater the chemistry of the water is anticipated to vary, and there may be a lot concentrate on the pH measure of acidity. I discover that the change in pH when equilibrium is established is instantly detectable with a low price moveable pH meter with zero.01 decision, however the measured dimension of the impact seems to be considerably smaller than reported within the current scientific literature. This text offers largely with the experimental technique and outcomes.


A schematic plan of the experimental equipment is proven within the following determine. A 2-litre “hermetic” meals storage jar incorporates seawater and air, and moveable (battery powered) devices to measure seawater pH and atmospheric CO2 stage, with alterations to the latter by injection of pulses of further CO2. The water is blended constantly by a magnetic stirrer.


The precise experimental system used is proven within the following picture, the pH meter is white, and the CO2 meter is gray, with its air consumption seen simply above the water floor. Meals storage expertise supplied the 2-litre hermetic container, the plastic “desk” that holds the CO2 meter simply above the water floor, and “Cling Movie” to guard the CO2 meter from getting moist, with a gap lower for the air consumption. Particulars of the meters used, and of the magnetic stirrer, are given on the finish of the article.

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The unique plan was to make use of a small moveable electrical fan to mix-up the air, but it surely was discovered that the batteries ran-out after about an hour, inadequate time to realize pH equilibrium, which is discovered to take round 10 hours.


CO2 was generated by including vinegar to bicarbonate of soda in a beaker (with splash guard), injected through an unused ear syringe, a plastic syringe or eye drop dispenser might be substituted:


In a draft-free room the CO2 generated within the beaker might be regarded as a comparatively dense fluid which stays there, and which might be drawn into an appropriate machine and injected into the 2-litre glass container. The goal is to get round 1000 ppm of CO2 within the 2-litre glass container, which is 1 half in a thousand, i.e. 2 ml of CO2 at atmospheric strain, which might be simply generated and captured.


Seawater samples of round 450 ml every time had been obtained from the shoreline close to Weymouth in Dorset, on the South coast of England. The shoreline had some seaweed, which can affect the pH. Every pattern was saved in a sealed 500 ml plastic bottle within the “laboratory” in a single day to heat it to the laboratory air temperature.


Every run of the experiment lasts round 12 hours, which is roughly the noticed time required for pH equilibrium to be achieved, with knowledge recording at 15-minute intervals. The runs begin mid-morning and run to round 10 pm, a interval wherein the room temperature stays pretty fixed.

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The next determine exhibits early outcomes for three runs, one with no injected CO2 (uppermost knowledge), one with injected CO2 such that round 820 ppm was measured (proven in blue with a continuing +zero.2 shift in all pH values), and one the place the ultimate CO2 stage was round 1500 ppm:



If the current progress fee of round 2.four ppm per yr of atmospheric CO2 is maintained then the extent on the finish of the 21st century might be round 600 ppm, with a change in seawater pH of round zero.15, which is significantly decrease than figures quoted within the scientific literature. Be aware that the change of zero.15 in pH applies to seawater of eight.eight pH, which is on the excessive finish of the noticed vary. Hydrogen ion focus at a pH of seven.eight is ten occasions larger than for a pH of eight.eight, so the change of pH in 7.eight pH seawater could also be even decrease than zero.15.


· pH meter: Hanna Devices HI 98108

· CO2 meter: Kane-alert-CO2

· Magnetic Stirrer: Hanna Devices HI 190M

Be aware: Water in a sealed container offers 100% humidity, and condensation could ultimately harm the electrics of the meters, all the pieces is completely dried on the finish of every run.


Readers can observe developments, and make feedback, on the following web site:

An Ocean Acidification Experiment

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