guypettigrew wrote: ↑Mon Jul 05, 2021 8:42 pm
Bit lost here! Surely alkalinity is measured in parts per million. Using twice as much water won't change this. I clearly need educating!
Guy
Chemical reactions occur on an 'equivalent' weights basis. Twice the volume of water with (for example) 100 ppm Alkalinity means twice the weight of extant Alkalinity, despite still being 100 ppm.
Example for 100 ppm (mg/L) Alkalinity (as CaCO3) and 15 vs. 30 Liters of water:
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100 mg/L x 15L = 1,500 mg of Alkalinity present within the water in the 'nominal' (as opposed to actual) form of CaCO3.
100 mg/L x 30L = 3,000 mg of Alkalinity present within the in the 'nominal' (as opposed to actual) form of CaCO3.
3 grams (3,000 mg) is twice as much Alkalinity as 1.5 grams (1,500 mg). And clearly what matters is the weight difference. The grist weight (let's call it chemical reactant #1) is fixed and not changing, but the Alkalinity (let's call it chemical reactant #2) has doubled in weight. To keep things on an even keel would require doubling the weight of the grist.
Another thing to ponder is that ppm is a weight per million parts of weight measure, whereas mg/L is a weight per unit of volume measure. These two means of measure are clearly not the same thing, despite an overall insistence that they are the same.