borate and boron
- Thread starter MSHUR
- Start date
As an additive or a test kit?
I do not believe the Seachem borate alkalinity test kit is accurate or useful. The Salifert has very wide windows of uncertainty, but seems to work.
These articles explain these issues in more detail:
Boron in a Reef Tank (and its effect on pH buffering)
http://www.advancedaquarist.com/issues/dec2002/chem.htm
The Seachem Borate Alkalinity Test Kit
http://www.advancedaquarist.com/issues/june2003/chem.htm
The Salifert Boron Test Kit
http://www.advancedaquarist.com/issues/sept2003/chem.htm
I do not believe the Seachem borate alkalinity test kit is accurate or useful. The Salifert has very wide windows of uncertainty, but seems to work.
These articles explain these issues in more detail:
Boron in a Reef Tank (and its effect on pH buffering)
http://www.advancedaquarist.com/issues/dec2002/chem.htm
The Seachem Borate Alkalinity Test Kit
http://www.advancedaquarist.com/issues/june2003/chem.htm
The Salifert Boron Test Kit
http://www.advancedaquarist.com/issues/sept2003/chem.htm
:thumbsup:
Happy reefing.
Happy reefing.
I just noticed this post and I apologize for not responding sooner. I sent this information to our head chemist and this is his reply:
Our borate alkalinity test takes all the boron in the sample and treats it as if it is in the form of borate, with none in the form of boric acid. This means that we overstate the borate alkalinity, except at high pH values, where most of the boron is driven into the form of borate.
The article by Holmes-Farley gives a table (Table 1) that shows the distribution of boron species, depending upon pH. So at the pH of his tank (8.13) the table says that only about 28% of the boron in the sample will show up as borate. For his Instant Ocean experiment (pH 8.05) the table says that only about 24% of the boron will show up as borate. (He used equation 4 to develop the table. There is a problem with his table, based on equation 4, that I will mention in a moment.)
When I do the calculations based on the numbers he gives, I see that for his tank our test should give a borate alkalinity of 0.67 meq/L, and he measures between 0.4 and 0.8. For the Instant Ocean our test should give 0.75 meq/L, and he measures between 0.6 and 1.5. (I'm not sure why he has trouble seeing the endpoint.) Our test is giving the right results, and if we multiply them by 0.28 and 0.24, we get the theoretical results Holmes-Farley calculates for his tank and the Instant Ocean, respectively.
So, you are probably asking, why don't we include a scale, based on the pH of the tank, that can be used to convert the borate alkalinity our test gives to a borate alkalinity that more accurately reflects the distribution of the species? I wish it were that simple. Unfortunately, we can't do that for the same reason that Holmes-Farley's table isn't exactly accurate: the equilibrium "constant" that he uses in his calculations isn't really constant. The value of K subscript a varies with several factors, but the two that are most important are temperature and salinity. The value he uses, 2.8 x 10 superscript minus 9, is based on a standard temperature and salinity. The tanks I've worked on generally run at higher temperatures, and of course the salinity varies tremendously depending upon the type of tank. In order to account for this with the test kit, we would have to provide a nomograph that would be terribly complicated to follow.
Based on the fact that borate alkalinity is generally a small percentage of total alkalinity, we have settled on providing a reproducible value, the maximum possible contribution of the boron species to total alkalinity. In most cases this is an overstatement. It is, more accurately, a measure of total boron in the system.
That does not mean that we may never be able to provide a more accurate test. The chemists who work with alum (aluminum sulfate) have a similar problem, only slightly worse, in that the aluminum will form one of three species, depending upon pH. They managed to get around the problem by using two titrations and a little math. We may be able to do the same sort of thing, though we would have to be concerned with whether the average aquarist would object to the extra titration and work involved in calculating the borate alkalinity. We're thinking about that, and I have a little lab work yet to do.
By the way, there is a pretty nice power point presentation on this subject (and other subjects), the link to which I will include here. http://bell.mma.edu/~jbouch/OS212S00K/sld010.htm The two slides that are most useful are slides 10 and 11, but you may get something out of the other slides, as well.
Please let us know if you have any further questions about our test kit.
Our borate alkalinity test takes all the boron in the sample and treats it as if it is in the form of borate, with none in the form of boric acid. This means that we overstate the borate alkalinity, except at high pH values, where most of the boron is driven into the form of borate.
The article by Holmes-Farley gives a table (Table 1) that shows the distribution of boron species, depending upon pH. So at the pH of his tank (8.13) the table says that only about 28% of the boron in the sample will show up as borate. For his Instant Ocean experiment (pH 8.05) the table says that only about 24% of the boron will show up as borate. (He used equation 4 to develop the table. There is a problem with his table, based on equation 4, that I will mention in a moment.)
When I do the calculations based on the numbers he gives, I see that for his tank our test should give a borate alkalinity of 0.67 meq/L, and he measures between 0.4 and 0.8. For the Instant Ocean our test should give 0.75 meq/L, and he measures between 0.6 and 1.5. (I'm not sure why he has trouble seeing the endpoint.) Our test is giving the right results, and if we multiply them by 0.28 and 0.24, we get the theoretical results Holmes-Farley calculates for his tank and the Instant Ocean, respectively.
So, you are probably asking, why don't we include a scale, based on the pH of the tank, that can be used to convert the borate alkalinity our test gives to a borate alkalinity that more accurately reflects the distribution of the species? I wish it were that simple. Unfortunately, we can't do that for the same reason that Holmes-Farley's table isn't exactly accurate: the equilibrium "constant" that he uses in his calculations isn't really constant. The value of K subscript a varies with several factors, but the two that are most important are temperature and salinity. The value he uses, 2.8 x 10 superscript minus 9, is based on a standard temperature and salinity. The tanks I've worked on generally run at higher temperatures, and of course the salinity varies tremendously depending upon the type of tank. In order to account for this with the test kit, we would have to provide a nomograph that would be terribly complicated to follow.
Based on the fact that borate alkalinity is generally a small percentage of total alkalinity, we have settled on providing a reproducible value, the maximum possible contribution of the boron species to total alkalinity. In most cases this is an overstatement. It is, more accurately, a measure of total boron in the system.
That does not mean that we may never be able to provide a more accurate test. The chemists who work with alum (aluminum sulfate) have a similar problem, only slightly worse, in that the aluminum will form one of three species, depending upon pH. They managed to get around the problem by using two titrations and a little math. We may be able to do the same sort of thing, though we would have to be concerned with whether the average aquarist would object to the extra titration and work involved in calculating the borate alkalinity. We're thinking about that, and I have a little lab work yet to do.
By the way, there is a pretty nice power point presentation on this subject (and other subjects), the link to which I will include here. http://bell.mma.edu/~jbouch/OS212S00K/sld010.htm The two slides that are most useful are slides 10 and 11, but you may get something out of the other slides, as well.
Please let us know if you have any further questions about our test kit.
I have already discussed this old article with Gregory Morin (owner? of Seachem) in this forum when it first came out. He made no mention at the time of it being a total boron test rather than a borate alkalinity kit. It might have cleared a lot up if he had.
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Our borate alkalinity test takes all the boron in the sample and treats it as if it is in the form of borate
That would be incorrect to do since you called it borate alkalinity, sort of like assuming the bicarbonate is carbonate, isn't it? Especially if aquarists try to determine "carbonate" alkalinity by subtracting the borate alkalinity from the total alkalinity.
That would be incorrect to do since you called it borate alkalinity, sort of like assuming the bicarbonate is carbonate, isn't it? Especially if aquarists try to determine "carbonate" alkalinity by subtracting the borate alkalinity from the total alkalinity.
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The value he uses, 2.8 x 10 superscript minus 9, is based on a standard temperature and salinity. The tanks I've worked on generally run at higher temperatures, and of course the salinity varies tremendously depending upon the type of tank. In order to account for this with the test kit, we would have to provide a nomograph that would be terribly complicated to follow.
The change with temperature is fairly small. Less than a factor of 2 from 10 deg C to 30 deg C, and only 30% difference between 20 deg C and 30 deg C. Quite small over the range that reefers actually keep aquaria. Nowhere near the factor of 2-8x that your kit overestimates the borate alkalinity of the normal samples.
Your kit actually got the borate alkalinity about right for the spiked IO sample (reading just 20% high). By your current claim that it reads total boron only, it underestimated it by more than a factor of 2.
It would seem to me that if this is a total boron kit, the values are much more correct in general, and perhaps not that different than the Salifert kit. But you need to state that difference, and not claim that it is borate alkalinity, even if that sounds more marketable.
FWIW, many people have come to this forum worried that their carbonate alkalinity is too low because they subtracted your incorrect borate alkalinity from total alkalinity. So it seems that many of your kit users were being undesirably misled.
The change with temperature is fairly small. Less than a factor of 2 from 10 deg C to 30 deg C, and only 30% difference between 20 deg C and 30 deg C. Quite small over the range that reefers actually keep aquaria. Nowhere near the factor of 2-8x that your kit overestimates the borate alkalinity of the normal samples.
Your kit actually got the borate alkalinity about right for the spiked IO sample (reading just 20% high). By your current claim that it reads total boron only, it underestimated it by more than a factor of 2.
It would seem to me that if this is a total boron kit, the values are much more correct in general, and perhaps not that different than the Salifert kit. But you need to state that difference, and not claim that it is borate alkalinity, even if that sounds more marketable.
FWIW, many people have come to this forum worried that their carbonate alkalinity is too low because they subtracted your incorrect borate alkalinity from total alkalinity. So it seems that many of your kit users were being undesirably misled.
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Holmes-Farleyââ"šÂ¬Ã¢"žÂ¢s three posts on 23 January 2006 raise scientific and non-scientific issues. The scientific issue is easily resolved.
Holmes-Farley notes that the equilibrium ââ"šÂ¬Ã…"œconstantââ"šÂ¬Ã‚ varies by a factor of 2 (in other words, undergoes a 100% change) over the temperature range from 10 deg C to 30 deg C, and undergoes a 30% change over the temperature range of interest (20 deg C to 30 deg C). Using his K value of 2.8 * E ââ"šÂ¬Ã¢â‚¬Å“9 as a starting point, this change results in a 23% change in the borate to total boron ratio.
He does not provide similar data for the effect of salinity on K, probably because Dicksonââ"šÂ¬Ã¢"žÂ¢s equation is not very user-friendly. However, if one plows through Dicksonââ"šÂ¬Ã¢"žÂ¢s equation, one finds that the effect of temperature is small compared with the effect of salinity. Some sample calculations I performed indicated that the effect of salinity on K is five times greater than the effect of temperature on K.
Of course, I had to pick starting values for Dicksonââ"šÂ¬Ã¢"žÂ¢s equation, and this involved a few assumptions, so letââ"šÂ¬Ã¢"žÂ¢s play this very conservatively. Let us assume, contrary to everything I have read in the published literature on the subject, that the effect of salinity on K is no greater than the effect of temperature. This means that, over a range of temperatures and salinities that reef keepers actually keep their aquaria, the borate/total boron ratios that Holmes-Farley gives in his Advanced Aquaristââ"šÂ¬Ã¢"žÂ¢s Online Magazine article could easily be in error by 50%.
That is the scientific issue that is easily resolved. The equilibrium ââ"šÂ¬Ã…"œconstantââ"šÂ¬Ã‚ is not constant, it is affected by temperature and salinity as well as pH, and variations in this ââ"šÂ¬Ã…"œconstantââ"šÂ¬Ã‚ materially affect the borate/total boron ratio.
The non-scientific issue involves what we do with this information. If, as Holmes-Farley began in his Advanced Aquaristââ"šÂ¬Ã¢"žÂ¢s article, he uses the table merely to indicate that the borate/boron ratio is subject to change with other factors (pH specifically), then he serves a useful educational purpose. If, on the other hand, these simple calculations are transformed into the absolute standard for borate/boron ratios, then they serve no useful purpose, and in fact do a real disservice to the aquarist and scientific communities.
And that is what has happened. He does not give us the temperature and salinity for the K value of 2.8 * E ââ"šÂ¬Ã¢â‚¬Å“9, nor does he give us the temperatures or salinities for his tank measurements, but yet he concludes that the Seachem test results fall ââ"šÂ¬Ã…"œshort of providing accurate and useful values to the aquaristââ"šÂ¬Ã‚ when compared with the Holy Writ of his back-of-the-envelope calculations, error-laden though they may be.
The central issue is best described by comparing Homes-Farleyââ"šÂ¬Ã¢"žÂ¢s evaluations, in his own words:
ââ"šÂ¬Ã…"œIn natural seawater, boron is present at about 4.4 ppm total boron. My aquarium, and the Instant Ocean salt mix that I use seem to run significantly higher (6-8 ppm). I donââ"šÂ¬Ã¢"žÂ¢t consider that difference to be important, or at least not requiring any action on my part. I would only recommend folks do anything about boron if it were very low (less than about 3 ppm where you loose any buffering that the borate provides) and higher than about 15 ppm, where it can begin to cloud the interpretation of total alkalinity tests and approach the point where it can become toxic.ââ"šÂ¬Ã‚Â
ââ"šÂ¬Ã…"œSo that is the standard that Iââ"šÂ¬Ã¢"žÂ¢m setting for evaluating the usefulness of this test kit. While great precision and accuracy are desirable attributes of any test kit, it is not especially important in a boron test kit (relative to, say, a calcium kit where an uncertainty of 33% might be a critical problem).ââ"šÂ¬Ã‚Â
He did not write this about the Seachem test kit. For the Seachem test kit, he began the same way: ââ"šÂ¬Ã…"œIn natural seawater, boron is present at about 0.41 mM (4.4 ppm total boron) and takes two different chemical forms.ââ"šÂ¬Ã‚ He then introduced the table showing the borate/boron ratios. After more discussion, he notes that borate contribution to alkalinity in natural seawater is small, but then warns ominously: ââ"šÂ¬Ã…"œIn some instances, however, the total amount of boron may be much higher than seawater. More than ten times normal levels in some cases. When boron is that high, then the borate alkalinity becomes very significant, at 1-2 meq/L, and can readily mislead aquarists interested in carbonate alkalinity.ââ"šÂ¬Ã‚ This is a straw man. His other review indicated that, at less than four times the level of natural seawater, we begin to deal with toxicity issues, which presumably render moot the question of boron alkalinity. Whether he is correct in his estimate of boron toxicity, or not, is immaterial to the present discussion. What is material is that Holmes-Farley has set two different benchmarks for the two different kits.
In one case he preordains a result. He states at the outset that a 33% error in the test result really isnââ"šÂ¬Ã¢"žÂ¢t critical. He then compares the test kit with measured experimental results (the ICP results), finds a 30% error, and summarizes the result this way: ââ"šÂ¬Ã…"œThe [competitorââ"šÂ¬Ã¢"žÂ¢s kit] has very wide windows of uncertainty, but seems to work.ââ"šÂ¬Ã‚ In the other case, he does not bother to compare the test kit results with measured experimental results (the ICP results), choosing instead to compare the results with calculated values, and summing up as follows: ââ"šÂ¬Ã…"œI do not believe the Seachem borate alkalinity test kit is accurate or useful.ââ"šÂ¬Ã‚ Given that the basis for this judgment is a list of calculated values of dubious accuracy or usefulness, I am not surprised at his conclusion. There must be a very fine line separating ââ"šÂ¬Ã…"œnot accurate or usefulââ"šÂ¬Ã‚ from ââ"šÂ¬Ã…"œvery wide windows of uncertainty, but seems to work.ââ"šÂ¬Ã‚ It appears to be a fine line that was most carefully and deliberately drawn.
This is called a double standard. It has nothing to do with chemistry.
It is tempting to address other comments that Holmes-Farley made in his three posts of 23 January 2006, and under normal circumstances I would. This forum is designed for just that sort of exchange, an exchange that challenges each participant, forcing each participant to justify each argument, ultimately leading towards a better understanding of the chemistry. But these are not normal circumstances, and these other issues are mere distractions from the main point, which is that Holmes-Farleyââ"šÂ¬Ã¢"žÂ¢s verdict on the Seachem test kit is based on a double standard that has all the appearances of a stacked deck in favor of one kit over the other. This may be the way one does many things, but it is not the way one does science.
George L. Batten, PhD
Research Director
Seachem Laboratories, Inc.
Holmes-Farley notes that the equilibrium ââ"šÂ¬Ã…"œconstantââ"šÂ¬Ã‚ varies by a factor of 2 (in other words, undergoes a 100% change) over the temperature range from 10 deg C to 30 deg C, and undergoes a 30% change over the temperature range of interest (20 deg C to 30 deg C). Using his K value of 2.8 * E ââ"šÂ¬Ã¢â‚¬Å“9 as a starting point, this change results in a 23% change in the borate to total boron ratio.
He does not provide similar data for the effect of salinity on K, probably because Dicksonââ"šÂ¬Ã¢"žÂ¢s equation is not very user-friendly. However, if one plows through Dicksonââ"šÂ¬Ã¢"žÂ¢s equation, one finds that the effect of temperature is small compared with the effect of salinity. Some sample calculations I performed indicated that the effect of salinity on K is five times greater than the effect of temperature on K.
Of course, I had to pick starting values for Dicksonââ"šÂ¬Ã¢"žÂ¢s equation, and this involved a few assumptions, so letââ"šÂ¬Ã¢"žÂ¢s play this very conservatively. Let us assume, contrary to everything I have read in the published literature on the subject, that the effect of salinity on K is no greater than the effect of temperature. This means that, over a range of temperatures and salinities that reef keepers actually keep their aquaria, the borate/total boron ratios that Holmes-Farley gives in his Advanced Aquaristââ"šÂ¬Ã¢"žÂ¢s Online Magazine article could easily be in error by 50%.
That is the scientific issue that is easily resolved. The equilibrium ââ"šÂ¬Ã…"œconstantââ"šÂ¬Ã‚ is not constant, it is affected by temperature and salinity as well as pH, and variations in this ââ"šÂ¬Ã…"œconstantââ"šÂ¬Ã‚ materially affect the borate/total boron ratio.
The non-scientific issue involves what we do with this information. If, as Holmes-Farley began in his Advanced Aquaristââ"šÂ¬Ã¢"žÂ¢s article, he uses the table merely to indicate that the borate/boron ratio is subject to change with other factors (pH specifically), then he serves a useful educational purpose. If, on the other hand, these simple calculations are transformed into the absolute standard for borate/boron ratios, then they serve no useful purpose, and in fact do a real disservice to the aquarist and scientific communities.
And that is what has happened. He does not give us the temperature and salinity for the K value of 2.8 * E ââ"šÂ¬Ã¢â‚¬Å“9, nor does he give us the temperatures or salinities for his tank measurements, but yet he concludes that the Seachem test results fall ââ"šÂ¬Ã…"œshort of providing accurate and useful values to the aquaristââ"šÂ¬Ã‚ when compared with the Holy Writ of his back-of-the-envelope calculations, error-laden though they may be.
The central issue is best described by comparing Homes-Farleyââ"šÂ¬Ã¢"žÂ¢s evaluations, in his own words:
ââ"šÂ¬Ã…"œIn natural seawater, boron is present at about 4.4 ppm total boron. My aquarium, and the Instant Ocean salt mix that I use seem to run significantly higher (6-8 ppm). I donââ"šÂ¬Ã¢"žÂ¢t consider that difference to be important, or at least not requiring any action on my part. I would only recommend folks do anything about boron if it were very low (less than about 3 ppm where you loose any buffering that the borate provides) and higher than about 15 ppm, where it can begin to cloud the interpretation of total alkalinity tests and approach the point where it can become toxic.ââ"šÂ¬Ã‚Â
ââ"šÂ¬Ã…"œSo that is the standard that Iââ"šÂ¬Ã¢"žÂ¢m setting for evaluating the usefulness of this test kit. While great precision and accuracy are desirable attributes of any test kit, it is not especially important in a boron test kit (relative to, say, a calcium kit where an uncertainty of 33% might be a critical problem).ââ"šÂ¬Ã‚Â
He did not write this about the Seachem test kit. For the Seachem test kit, he began the same way: ââ"šÂ¬Ã…"œIn natural seawater, boron is present at about 0.41 mM (4.4 ppm total boron) and takes two different chemical forms.ââ"šÂ¬Ã‚ He then introduced the table showing the borate/boron ratios. After more discussion, he notes that borate contribution to alkalinity in natural seawater is small, but then warns ominously: ââ"šÂ¬Ã…"œIn some instances, however, the total amount of boron may be much higher than seawater. More than ten times normal levels in some cases. When boron is that high, then the borate alkalinity becomes very significant, at 1-2 meq/L, and can readily mislead aquarists interested in carbonate alkalinity.ââ"šÂ¬Ã‚ This is a straw man. His other review indicated that, at less than four times the level of natural seawater, we begin to deal with toxicity issues, which presumably render moot the question of boron alkalinity. Whether he is correct in his estimate of boron toxicity, or not, is immaterial to the present discussion. What is material is that Holmes-Farley has set two different benchmarks for the two different kits.
In one case he preordains a result. He states at the outset that a 33% error in the test result really isnââ"šÂ¬Ã¢"žÂ¢t critical. He then compares the test kit with measured experimental results (the ICP results), finds a 30% error, and summarizes the result this way: ââ"šÂ¬Ã…"œThe [competitorââ"šÂ¬Ã¢"žÂ¢s kit] has very wide windows of uncertainty, but seems to work.ââ"šÂ¬Ã‚ In the other case, he does not bother to compare the test kit results with measured experimental results (the ICP results), choosing instead to compare the results with calculated values, and summing up as follows: ââ"šÂ¬Ã…"œI do not believe the Seachem borate alkalinity test kit is accurate or useful.ââ"šÂ¬Ã‚ Given that the basis for this judgment is a list of calculated values of dubious accuracy or usefulness, I am not surprised at his conclusion. There must be a very fine line separating ââ"šÂ¬Ã…"œnot accurate or usefulââ"šÂ¬Ã‚ from ââ"šÂ¬Ã…"œvery wide windows of uncertainty, but seems to work.ââ"šÂ¬Ã‚ It appears to be a fine line that was most carefully and deliberately drawn.
This is called a double standard. It has nothing to do with chemistry.
It is tempting to address other comments that Holmes-Farley made in his three posts of 23 January 2006, and under normal circumstances I would. This forum is designed for just that sort of exchange, an exchange that challenges each participant, forcing each participant to justify each argument, ultimately leading towards a better understanding of the chemistry. But these are not normal circumstances, and these other issues are mere distractions from the main point, which is that Holmes-Farleyââ"šÂ¬Ã¢"žÂ¢s verdict on the Seachem test kit is based on a double standard that has all the appearances of a stacked deck in favor of one kit over the other. This may be the way one does many things, but it is not the way one does science.
George L. Batten, PhD
Research Director
Seachem Laboratories, Inc.
mr. batten
i start this thread just to find out what boron is all about. i am not chemist and never will. but, i love my hobby and i wouls like to know how to measure boron more accurate to avoid any problem with my corals. i am using seachem salt in combination with tropic marine. i know seachem salt have hi level of boron,why?. hi level of boron is toxic to corals and they get darker after time. to avoid boron biuld up in my tank water ,i am using 50/50 ratio.
why seachem using hier level of boron to begin with?
thankx, michael
i start this thread just to find out what boron is all about. i am not chemist and never will. but, i love my hobby and i wouls like to know how to measure boron more accurate to avoid any problem with my corals. i am using seachem salt in combination with tropic marine. i know seachem salt have hi level of boron,why?. hi level of boron is toxic to corals and they get darker after time. to avoid boron biuld up in my tank water ,i am using 50/50 ratio.
why seachem using hier level of boron to begin with?
thankx, michael
It is tempting to address other comments that Holmes-Farley made in his three posts of 23 January 2006, and under normal circumstances I would. This forum is designed for just that sort of exchange, an exchange that challenges each participant, forcing each participant to justify each argument, ultimately leading towards a better understanding of the chemistry. But these are not normal circumstances, and these other issues are mere distractions from the main point, which is that Holmes-Farleyââ"šÂ¬Ã¢"žÂ¢s verdict on the Seachem test kit is based on a double standard that has all the appearances of a stacked deck in favor of one kit over the other. This may be the way one does many things, but it is not the way one does science.
WOW. I'd better take my own time out before I blast back at what is a very serious accusation that profoundly offends me.
I will come back with an approriate response in due time.
WOW. I'd better take my own time out before I blast back at what is a very serious accusation that profoundly offends me.
I will come back with an approriate response in due time.
boxfishpooalot
Active member
HOLY CRAP! That was an unessary response from Seachem!
George Batten
In Memoriam
MSHUR, boron can contribute to buffering, which is helpful in reducing pH swings. It contributes less to buffering than carbonate, but it helps. Boron also increases the solubility of calcium at a given pH and alkalinity, through ion competition. In other words, a little boron in the tank allows the addition of a little more calcium without precipitation. Aside from the chemistry, boron is a desirable trace element. Reference 13 from Holmes-Farley's article "Boron in a Reef Tank" indicates that some plants, diatoms, and algae have an absolute requirement for it. The tank is a closed system, so it is not unusual to see some boron depletion with time, through calcification and consumption. That is why we add a little more.
I should note that the boron levels quoted in the article on Boron in a Reef Tank for Seachem salt are way too high. Our web site lists a boron content of 16 ppm for Reef Salt solution though it doesn't specify the strength of the solution. Recently I had an outside laboratory do some ICP-atomic emission analytical work for us, and the boron levels for both Marine Salt and Reef Salt were 16 ppm at a concentration of 34.75 grams per liter. This is 3.6 times the level in natural sea water, not the 12 times quoted in the article.
I hope this helps.
George
I should note that the boron levels quoted in the article on Boron in a Reef Tank for Seachem salt are way too high. Our web site lists a boron content of 16 ppm for Reef Salt solution though it doesn't specify the strength of the solution. Recently I had an outside laboratory do some ICP-atomic emission analytical work for us, and the boron levels for both Marine Salt and Reef Salt were 16 ppm at a concentration of 34.75 grams per liter. This is 3.6 times the level in natural sea water, not the 12 times quoted in the article.
I hope this helps.
George
Boron also increases the solubility of calcium at a given pH and alkalinity, through ion competition.
I've heard folks from Seachem assert that before, and I challenged it before. I still think that is untrue. I cannot see how the small amount of borate (on a molar basis) can interact with any significant amount of the much larger concentration of calcium, and it certainly doesn't interact with carbonate in a significant way. Millero ("Chemical Oceanography") lists the forms of calcium present in seawater, and borate-calcium complexes do not make the cut in impacting calcium.
I should note that the boron levels quoted in the article on Boron in a Reef Tank for Seachem salt are way too high.
Let's keep the proper historical content for this discussion, shall we.
You folks used to sell a product that was way too high in borate, and your own reps (including Leo Morin when he was around) came online at various venues to explain why that was desirable. It would not appear to be a "'mistake" of mine or anyone else's. It was a choice that Seachem intentionally made to provide excessive borate.
Since those analysis and articles came out, Seachem decided to reformulate their salt mix to have less borate. That is very good, in my opinion. It still has more than NSW, and I don't see the benefit to that, but it may not be a significant problem compared to the previous salt version.
I've heard folks from Seachem assert that before, and I challenged it before. I still think that is untrue. I cannot see how the small amount of borate (on a molar basis) can interact with any significant amount of the much larger concentration of calcium, and it certainly doesn't interact with carbonate in a significant way. Millero ("Chemical Oceanography") lists the forms of calcium present in seawater, and borate-calcium complexes do not make the cut in impacting calcium.
I should note that the boron levels quoted in the article on Boron in a Reef Tank for Seachem salt are way too high.
Let's keep the proper historical content for this discussion, shall we.
You folks used to sell a product that was way too high in borate, and your own reps (including Leo Morin when he was around) came online at various venues to explain why that was desirable. It would not appear to be a "'mistake" of mine or anyone else's. It was a choice that Seachem intentionally made to provide excessive borate.
Since those analysis and articles came out, Seachem decided to reformulate their salt mix to have less borate. That is very good, in my opinion. It still has more than NSW, and I don't see the benefit to that, but it may not be a significant problem compared to the previous salt version.
OK, I will begin in this post and those that follow to address the George's assertions about my review of Seachem's borate alkalinity test kit.
For those who do not care to wade through a lengthy chemistry discussion, I'll simply say that in light of George's concerns, I stand by my earlier review and its criticism of the Seachem borate alkalinity test kit. In short, to most aquarists without a detailed chemistry background the discussion that follows may sound like the ancient debate on how many fairies can fit on the head of a pin. They will probably have to decide who they are inclined to believe. In this case, the two sides are George, representing Seachem. They make the kit, and presumably have lots of testing experience with it, and benefit from its sales. Or myself, who has an extensive chemistry background, but no inside information on the design or ingredients of the kit or its capabilities, but also with no financial interest to be had from the functioning of the kit one way or the other.
For those who do not care to wade through a lengthy chemistry discussion, I'll simply say that in light of George's concerns, I stand by my earlier review and its criticism of the Seachem borate alkalinity test kit. In short, to most aquarists without a detailed chemistry background the discussion that follows may sound like the ancient debate on how many fairies can fit on the head of a pin. They will probably have to decide who they are inclined to believe. In this case, the two sides are George, representing Seachem. They make the kit, and presumably have lots of testing experience with it, and benefit from its sales. Or myself, who has an extensive chemistry background, but no inside information on the design or ingredients of the kit or its capabilities, but also with no financial interest to be had from the functioning of the kit one way or the other.
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The Seachem borate alkalinity kit claims to measure borate alkalinity, and encourages aquarists to subtract that value from their total alkalinity to determine the carbonate alkalinity (which is what corals actually use to calcify).
George admits above that the Seachem kit doesn't actually measure or report borate alkalinity. It measures total boron (borate plus boric acid). All arguments about how much of the total boron is present as borate aside, the borate alkalinity will be significantly less than the total boron for any pH and salinity attained in a real reef aquarium.
How much less is the essence of his major criticism above. But it is indisputably less. In my reef aquarium, where I know the salinity and the temperature (35 ppt, about 26 deg C), it is far less than the total boron.
Since that complication is known to them, why would Seachem call this a borate alkalinity test kit? The potential complications above would seem to suggest that this was an inappropriate chemical test for borate alkalinity in a reef aquarium under any circumstances likely to be attained. Maybe it is fine for total boron. If the kit said that, I'd have far less to criticize, and might even recommend the kit.
Is there any reason that you will not make that change to the kit?
I've had to clean up the mess left behind when folks come into this and other on line forums, worried that they have inadequate carbonate alkalinity based on total minus borate alkalinity. In reality, they were fine, but just had been mislead by the mislabeling of the kit.
I'll expand the chemistry debate in subsequent posts.
George admits above that the Seachem kit doesn't actually measure or report borate alkalinity. It measures total boron (borate plus boric acid). All arguments about how much of the total boron is present as borate aside, the borate alkalinity will be significantly less than the total boron for any pH and salinity attained in a real reef aquarium.
How much less is the essence of his major criticism above. But it is indisputably less. In my reef aquarium, where I know the salinity and the temperature (35 ppt, about 26 deg C), it is far less than the total boron.
Since that complication is known to them, why would Seachem call this a borate alkalinity test kit? The potential complications above would seem to suggest that this was an inappropriate chemical test for borate alkalinity in a reef aquarium under any circumstances likely to be attained. Maybe it is fine for total boron. If the kit said that, I'd have far less to criticize, and might even recommend the kit.
Is there any reason that you will not make that change to the kit?
I've had to clean up the mess left behind when folks come into this and other on line forums, worried that they have inadequate carbonate alkalinity based on total minus borate alkalinity. In reality, they were fine, but just had been mislead by the mislabeling of the kit.
I'll expand the chemistry debate in subsequent posts.
He does not provide similar data for the effect of salinity on K, probably because Dicksonââ"šÂ¬Ã¢"žÂ¢s equation is not very user-friendly.
Friendly or not, let's see how that impacts my analysis.
from my review:
"In order to assess the accuracy of this test kit, I made several standard test samples. One consisted of Instant Ocean salt mix made to a salinity of 35 ppt (measured via conductivity to be 53 mS/cm). A second sample consisted of water from my aquarium, also at a salinity of 35 ppt (also measured via conductivity). "
So both of those samples were at a salinity of 35 ppt. That is the exact salinity for which Millero ("Chemical Oceanography") gives values for the pKa for boric acid/borate. Those are the pKa values used in my analysis in the review. Consequently, any worry about the change in the boric acid/borate pKa with salinity had no impact on whether the Seachem borate alkalinity kit is accurately able to measure my samples. It did not accurately do so.
Again, it might be useful as a total boron test, but in my exact tests, where the dissociation constants are well known, it did not provide the right answer for borate alkalinity.
Would it in any aquarium? No. It will always provide total boron.
How accurate do we want such a kit to be? Well, to within 10% would be good.
Question for George:
At normal reef aquarium temperatures of say 75 to 85 deg F, and normal reef aquarium pH of 7.8-8.5, is there any salinity where the borate alkalinity gets to within 10% of the total boron? What salinity?
We know that it does not (cannot, being a total boron test) at salinity = 35 ppt, and 75-85 deg F, and pH 7.8-8.5.
I'll address temperature in the next post.
Friendly or not, let's see how that impacts my analysis.
from my review:
"In order to assess the accuracy of this test kit, I made several standard test samples. One consisted of Instant Ocean salt mix made to a salinity of 35 ppt (measured via conductivity to be 53 mS/cm). A second sample consisted of water from my aquarium, also at a salinity of 35 ppt (also measured via conductivity). "
So both of those samples were at a salinity of 35 ppt. That is the exact salinity for which Millero ("Chemical Oceanography") gives values for the pKa for boric acid/borate. Those are the pKa values used in my analysis in the review. Consequently, any worry about the change in the boric acid/borate pKa with salinity had no impact on whether the Seachem borate alkalinity kit is accurately able to measure my samples. It did not accurately do so.
Again, it might be useful as a total boron test, but in my exact tests, where the dissociation constants are well known, it did not provide the right answer for borate alkalinity.
Would it in any aquarium? No. It will always provide total boron.
How accurate do we want such a kit to be? Well, to within 10% would be good.
Question for George:
At normal reef aquarium temperatures of say 75 to 85 deg F, and normal reef aquarium pH of 7.8-8.5, is there any salinity where the borate alkalinity gets to within 10% of the total boron? What salinity?
We know that it does not (cannot, being a total boron test) at salinity = 35 ppt, and 75-85 deg F, and pH 7.8-8.5.
I'll address temperature in the next post.
Holmes-Farley notes that the equilibrium ââ"šÂ¬Ã…"œconstantââ"šÂ¬Ã‚ varies by a factor of 2 (in other words, undergoes a 100% change) over the temperature range from 10 deg C to 30 deg C, and undergoes a 30% change over the temperature range of interest (20 deg C to 30 deg C). Using his K value of 2.8 * E ââ"šÂ¬Ã¢â‚¬Å“9 as a starting point, this change results in a 23% change in the borate to total boron ratio.
Once again, we can ask whether this impacted my analysis.
Millero ("Chemical Oceanography") gives the following values:
20 deg C pKa = 8.647
25 deg C pKa = 8.588
30 deg C pKa = 8.530
Without any math at all we can make the following qualitative conclusions:
At any pH below the pKa, less than half of the total boron is in the borate form. So at any pH below 8.5, the borate alkalinity is less than half of the total boron. If the kit reports total boron as borate alkalinity, then at pH 8.5 it will be off by a factor of 2 or so, and more than that below pH 8.5.
Because of the way the equations work, each 0.3 pH units below the pKa takes the borate down by about a factor of 2. So at pH 8.2, the borate alkalinity will be only about a quarter of the total boron. At pH 7.8, the borate alkalinity will only be about 1/8 of the total boron. I show that in table form in the review itself:
http://www.advancedaquarist.com/issues/june2003/chem.htm
For this reason, the errors associated with the Seachem borate alkalinity test kit portraying total boron as borate alkalinity rise as the pH drops. From a factor of 2 at pH 8.55 to a factor of 5.5 at pH 7.9. That is basically true at any temperature between 20 deg C (68 deg F) and 30 deg C (86 deg F).
So did it impact my test kit analysis? My tank samples were at 26-27 deg C when withdrawn from my tank. They may have cooled a few degrees before testing, but not by too much that time of year. Certainly not below 20 deg C. The more cooling the more the pKa rises, and the more of the total boron would have been in the boric acid form. So there is no way that the temperature effects would have skewed my results so that the Seachem borate alkalinity test kit that reports total boron would have accurately stated the borate alkalinity in the samples that I was testing.
Once again, we can ask whether this impacted my analysis.
Millero ("Chemical Oceanography") gives the following values:
20 deg C pKa = 8.647
25 deg C pKa = 8.588
30 deg C pKa = 8.530
Without any math at all we can make the following qualitative conclusions:
At any pH below the pKa, less than half of the total boron is in the borate form. So at any pH below 8.5, the borate alkalinity is less than half of the total boron. If the kit reports total boron as borate alkalinity, then at pH 8.5 it will be off by a factor of 2 or so, and more than that below pH 8.5.
Because of the way the equations work, each 0.3 pH units below the pKa takes the borate down by about a factor of 2. So at pH 8.2, the borate alkalinity will be only about a quarter of the total boron. At pH 7.8, the borate alkalinity will only be about 1/8 of the total boron. I show that in table form in the review itself:
http://www.advancedaquarist.com/issues/june2003/chem.htm
For this reason, the errors associated with the Seachem borate alkalinity test kit portraying total boron as borate alkalinity rise as the pH drops. From a factor of 2 at pH 8.55 to a factor of 5.5 at pH 7.9. That is basically true at any temperature between 20 deg C (68 deg F) and 30 deg C (86 deg F).
So did it impact my test kit analysis? My tank samples were at 26-27 deg C when withdrawn from my tank. They may have cooled a few degrees before testing, but not by too much that time of year. Certainly not below 20 deg C. The more cooling the more the pKa rises, and the more of the total boron would have been in the boric acid form. So there is no way that the temperature effects would have skewed my results so that the Seachem borate alkalinity test kit that reports total boron would have accurately stated the borate alkalinity in the samples that I was testing.
Now I'll address specific accusations in the posts above.
The non-scientific issue involves what we do with this information.
Exactly. Seachem suggests that we simply give up, and call all total boron as borate alkalinity, and proceed to subtract it from total alkalinity to get carbonate alkalinity. While I think that is absurd, if they had simply explained that is what the kit allowed, my criticisms would have been different. I would have suggested an alternative way to use the information that the kit generates, rather than simply rejecting it as inaccurate.
when compared with the Holy Writ of his back-of-the-envelope calculations, error-laden though they may be.
huh? As I showed above, there was no significant error at all for my samples. You might be thinking of what someone running a reef tank at 20 ppt salinity at pH 9.2 and 56 deg C would experience as error, but it my case, the data analysis was quite accurate.
Please show me how mine was in error. Not salinity. Not temperature. What then?
The non-scientific issue involves what we do with this information.
Exactly. Seachem suggests that we simply give up, and call all total boron as borate alkalinity, and proceed to subtract it from total alkalinity to get carbonate alkalinity. While I think that is absurd, if they had simply explained that is what the kit allowed, my criticisms would have been different. I would have suggested an alternative way to use the information that the kit generates, rather than simply rejecting it as inaccurate.
when compared with the Holy Writ of his back-of-the-envelope calculations, error-laden though they may be.
huh? As I showed above, there was no significant error at all for my samples. You might be thinking of what someone running a reef tank at 20 ppt salinity at pH 9.2 and 56 deg C would experience as error, but it my case, the data analysis was quite accurate.
Please show me how mine was in error. Not salinity. Not temperature. What then?
If, on the other hand, these simple calculations are transformed into the absolute standard for borate/boron ratios, then they serve no useful purpose, and in fact do a real disservice to the aquarist and scientific communities.
On the contrary, how are aquarists served by a boron alkalinity kit that you admit can be off by a factor of 2-8 fold on the high side (by measuring total boron only)?
I simply pointed out in my review, quite correctly, that it gives inaccurate values. You admit to the same. How is that a disservice?
On the contrary, how are aquarists served by a boron alkalinity kit that you admit can be off by a factor of 2-8 fold on the high side (by measuring total boron only)?
I simply pointed out in my review, quite correctly, that it gives inaccurate values. You admit to the same. How is that a disservice?
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