Stinkfist wrote:Can you explain what the equivalent biocarbonate concentration is?
This is the value that varies drastically from Beersmith, so just wondering how this value is calculated? I tried to find the answer in the excel file but if it is there I missed it somewhere...So if you could give an explanation I would appreciate it.
Thanks for the comments.
As you have probably noted in the chemical formulas for chalk (CaCO3) and pickling lime (Ca(OH)2, there isn't any bicarbonate shown in them. But, when these minerals are mixed in water that has a pH between roughly 6.5 and 10.5, most of their alkalinity producing ion will exist in the form of the bicarbonate ion (HCO3).
But the real reason that those minerals are expressed with equivalent bicarbonate concentrations is that Alkalinity in Bru'n Water is calculated via the water's bicarbonate concentration. So its necessary to present it as such or I would have had to add extra columns for extra anions that nobody cares about anyhow. Expressing in these equivalent terms should be more meaningful to a brewer anyhow since they need a measure relating the brewing water's anti-acid capacity. This concept was also applied to the acid addition on the Water Adjustment sheet. In that case, the acid addition produces a negative bicarbonate number. This is in fact how acid and base neutralization is calculated. If you add acid, you are taking out alkalinity (reducing the bicarbonate concentration).
In the case of Beersmith, they are probably presenting the amount of carbonate provided by the chalk addition. That should be 158.5 ppm when 1 gram/gallon is added to water. Although that's accurate, it does not represent the amount of alkalinity that is produced in the water if all the chalk actually dissolved. When fully dissolved, all that CO3 will mostly exist as HCO3 if the water pH falls between 6.5 and 10.5. The true quantity of bicarbonate produced in the water with 1g/gal chalk is 322.3 ppm.
The problem with chalk is that it is not very soluble in water and it requires an external acid to help it dissolve. In nature, CO2 dissolves in water to form carbonic acid that solublizes the chalk. That dissolution takes a long time to complete. Even in the presence of the weak acids produced in the mash, chalk does not dissolve well. Work by AJ Delange and Kai Troester have proven that only about half the chalk will dissolve in the mash in practice. So in practice, it just happens that the 158 ppm number used in some water calculations might be somewhat correct. That was just dumb luck, buts its OK. Bru'n Water tells you the true value of bicarbonate as if you actually performed the extra steps needed to dissolve the chalk fully. It can be done, take your chalk amount and put it in a plastic soda bottle with a carbonator cap and charge it with CO2. After a little shaking and some time, it too will dissolve fully. That is kind of a PITA, so Bru'n Water recommends that you use the Water adjustment sheet to calculate the chalk addition needed, and then add twice as much chalk as calculated to hopefully produce the needed alkalinity. I think that's kind of iffy, so I recommend that brewers use Pickling Lime instead. It does dissolve fully and it works every time.
So, Beersmith is sort of correct in a practical way, but Bru'n Water is more accurate, if you dissolve your chalk fully.
