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Old 12-18-2011, 12:10 AM   #191
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Oh I wholeheartedly agree with the fact that I need to get real measurements of my water. I'd love to learn to be able to do my own tests, but have almost no clue where to begin beyond your recommendation of test kits. (and what to do with the information once I have it)
I understand the massive number of variables in the brewing process, but I'm confident in my thermometer's accuracy and saccharification rest temps, I'd like to think I use no more or less roast malts than the average brewer. I also let all my beers get at least a month in primary with generally aggressive fermenting strains of yeast. I have access to citric acid at my LHBS but that's about it, though I dare not use enough to fix the problem completely could it be used in small amounts to bring my water closer to the 5.2 mark?

With dreams of one day going pro I have every intention of dialing in my water by being able to measure water composition on every brew. So I'm not intimidated by the dedication limitations of the average homebrewer. I'd love to be pointed in the direction of proper lab equipment and guides on what to do with it. (looking for equipment that warrants its purchase in a 7bbl brewhouse...i.e. I dont need a $20k lab for a system that small)

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Old 12-18-2011, 02:04 AM   #192
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I am sure they are quite accurate enough for home brewing purposes but note that the precision (not accuracy) of 10, 10 and 4 for the three titrations. As you've noted higher accuracy is not necessary for sodium but I work with waters with alkalinities that vary from 10 - 80 ppm and thus wouldn't find ±10 ppm for alkalinity acceptable.

The chemistries for alkalinity and hardness seems to be the standard chemistries i.e. calmagite, EDTA, sulfuric acid, Bromcresol green/methyl red. The novelty is in estimating total anions by swapping cations for hydrogen and estimating the hyrdrogen ion content from pH the estimating calcium + magnesium, subtracting and assuming whatever is left over is sodium. Clearly anything which isn't calcium, magnesium or sodium is thus an interference e.g. strontium, iron, potassium, manganese, aluminum etc but these should all be present in small amounts.

Improvement in accuracy can be had by using a "digital titrator" (Hach, Hanna) at considerable extra expense for harndess (still subject to error from strontium, iron etc), alkalinity (use pH meter rather than idicator as suggested) and chloride but sulfate requires a turbidimetric method (photometer or nephelometer) and perhaps the most practical means for sodium, short of AAS or ICP, is an ISE which is quite expensive and a real PITA to use.

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Old 12-18-2011, 03:47 PM   #193
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Actually the kit's precision is not quite as low as 10, 10 and 4. But can be improved with a minor modification.

While the graduated syringes used to add the titratant are marked at these intervals, quantization error exists. The quanta is droplet size of the titratant. So I generally count drops, look at the reading on the syringe, and then divide. Example: With an as provided syringe 10 drops of titratant reads 250 ppm (of the ion measured) on the syringe. So each drop is equivalent to 25ppm. If the sample changed color on the 10th drop, I would call the measurement 237.7ppm +/- 12.5ppm (I included the extra significant figures just to show the math).

If one adds a separately obtained hypodermic needle to the syringe droplet size is significantly reduced. Now 10 drops reads 60 ppm on the syringe. Precision now becomes +/- 3ppm. I have thought of doubling the water sample size to bring precision to +/- 1.5 ppm.

I'm not a chemist, but my experience is that once one refines one aspect of an experiment another source of error pops out of the mud. You have identified one (interference ions). So I'm doubting the ability to achieve precision of +/- 1.5 ppm. But does +/-3ppm seem reasonable (which I would also like to state as accuracy)? I have eliminated the static offset (was the syringe really zeroed at the start or was it -4ppm or +3ppm) by counting observable drops.

Separately... To your knowledge, is the rule of thumb that Ca and Mg are generally in a 4:1 ratio a reasonably accurate assumption? Let's assume that we are only addressing water samples of Total Hardness <100 ppm (as CaCO3).

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Old 12-18-2011, 04:29 PM   #194
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just wanted to say thanks for this thread again, we brewed a cream ale a few days ago, and measured mash ph at 5.25 with the 2% sauermalz and 1 tsp of calcium chloride. this was with brew in a bag method, about 7.5 gallons of water total. this was all from distilled water, i hope it turns out?

we plan to brew an american brown ale today, (northern brewer caribou slobber) do you have any pointers for this one? i have distilled water, and of course my michigan tap water that has a faint sulfery smell to it...should we use the di water with 1tsp of calcium chloride, skip the sauermalz? we have gypsum on hand, along with other salts, etc. should we be adding anything else? any help would be appreciated, thanks!

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Old 12-18-2011, 04:43 PM   #195
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Originally Posted by gt541 View Post

While the graduated syringes used to add the titratant are marked at these intervals, quantization error exists. The quanta is droplet size of the titratant. So I generally count drops, look at the reading on the syringe, and then divide. Example: With an as provided syringe 10 drops of titratant reads 250 ppm (of the ion measured) on the syringe. So each drop is equivalent to 25ppm. If the sample changed color on the 10th drop, I would call the measurement 237.7ppm +/- 12.5ppm (I included the extra significant figures just to show the math).

If one adds a separately obtained hypodermic needle to the syringe droplet size is significantly reduced. Now 10 drops reads 60 ppm on the syringe. Precision now becomes +/- 3ppm.
Certainly the principles are correct. But are the drop sizes the same? How well can you detect the color change? In particular, how well can you measure pH. In the alkalinity and Cl/SO4 measurement that has a large effect as pH is lograithmic. An 0.05 error in what you determine as end point reflects as a 12% error in hydrogen ion concentration (an as cation content in that measurement). What about the effects of hydroxyl allkalinity (shouldn't really expect to see much effect from that if water is decent).

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Originally Posted by gt541 View Post
I have thought of doubling the water sample size to bring precision to +/- 1.5 ppm.
That's certainly a good way to go. Whatever the coefficient of variation may be doubling the sample will halve it.

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Originally Posted by gt541 View Post
I'm not a chemist,
Neither am I.

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Originally Posted by gt541 View Post
but my experience is that once one refines one aspect of an experiment another source of error pops out of the mud.
That's also been my experience. It's a constant battle to refine and I expect real chemists experience it the same way. In my (non chemistry) career I took lots and lots of measurements and that was certainly the case for the things I did measure (gain, delay, temperature, symbol error rate, location, time....)


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You have identified one (interference ions). So I'm doubting the ability to achieve precision of +/- 1.5 ppm. But does +/-3ppm seem reasonable (which I would also like to state as accuracy)? I have eliminated the static offset (was the syringe really zeroed at the start or was it -4ppm or +3ppm) by counting observable drops.
At this point I suspect that the interference ions' contributions to the error budget would be small compared to the error induced by incorrectly identifying the end points of the titrations. Using a pH meter for the two that involve acid/base would doubtless drop those errors greatly.

The real answer to the question would come by doing a collaborative study. Samples of know composition would be parceled out to a number of investigators who would analyze the samples using the kits and statistics accumulated. The manufacturer could then supply the usual inter and intra laboratory CVs. The fact that no accuracy or precision data is stated in the instructions does create some suspicion.

Second best would be a careful error analysis in which we figure out exactly how the errors propagate and what the effects of things like a couple ppm potassium and/or strontium might be. My gut says that 10% would be about as good as you could get using this combination of measurements. But that is gut and bear in mind that 10% should be more than adequate for this application.

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Originally Posted by gt541 View Post
Separately... To your knowledge, is the rule of thumb that Ca and Mg are generally in a 4:1 ratio a reasonably accurate assumption? Let's assume that we are only addressing water samples of Total Hardness <100 ppm (as CaCO3).
My own calcium hardness usually runs around 60 and my magnesium around 50 for a 1.2:1 ratio in terms of ppm as CaCO3. Those numbers correspond to 24 and 12.15 mg/L for an approximately 2:1 ratio in those terms. I don't know if that's typical or an outlier. You could go back over the archives here where lots of people have posted their water reports and get an idea from those reports. You could also buy a total/calcium hardness kit and measure the two (or rather obtain the 2 from total and calcium measurements).
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Old 12-18-2011, 05:50 PM   #196
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Old 12-18-2011, 06:21 PM   #197
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Originally Posted by Veedo View Post
just wanted to say thanks for this thread again, we brewed a cream ale a few days ago, and measured mash ph at 5.25 with the 2% sauermalz and 1 tsp of calcium chloride. this was with brew in a bag method, about 7.5 gallons of water total. this was all from distilled water, i hope it turns out?
Was that measured with a pH meter or strips? If with a pH meter reduce the sauermalz to 1% next time. If strips, get a pH meter.

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we plan to brew an american brown ale today, (northern brewer caribou slobber) do you have any pointers for this one? i have distilled water, and of course my michigan tap water that has a faint sulfery smell to it...should we use the di water with 1tsp of calcium chloride, skip the sauermalz? we have gypsum on hand, along with other salts, etc. should we be adding anything else? any help would be appreciated, thanks!
Try pouring the water back and forth between buckets or, perhaps simpler, draw your brewing water by spraying through one of those sprayers that goes on a garden hose. This should get rid of the sufidic smell. Or you could try stripping the insulation of several pieces of copper wire (the stuff used to wire houses is fine) and throwing those pieces of stripped wire into a pot full of the water. Take them out and clean them (rinse thoroughly afterwards) when they turn dark.

As for the mineral adjustments. I'd say use the same additions (after dilution and sulfide treatment). Enough dilution should be used to get the water down to the low mineral levels discussed in the Primer.
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Old 12-18-2011, 06:39 PM   #198
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measured with a ph meter. is 5.3 the magic number? interesting bit about the copper wire...will try this.

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Old 12-18-2011, 07:10 PM   #199
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AJ

I think the drops are of uniform size as the hypo needle is cut square to its axis (i.e. not sharp) with no burrs inside or out so surface tension should enforce consistency.

The color changes are sharp and rapid. I also was under the impression that these indicators had very consistent pH transitions points.

The collaborative study is interesting, but one would need to be somewhat assured that all investigators had consistently good experimental technique.

I guess the cleanest method would be for me to carefully measure a water sample (multiple times to observe my own variation) and then have the same sample measured by an outside lab that would provide error bars about their measurements.

As to the Ca/Mg ratio, your results indicate the 4:1 rule is at least suspect. So instead of being lazy I'll use the Ca Test Kit I also have.

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Old 12-18-2011, 08:59 PM   #200
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Quote:
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measured with a ph meter. is 5.3 the magic number? interesting bit about the copper wire...will try this.
You'll get as many answers as people you ask. I generally shoot for 5.4 - 5.5. Generally you get an 0.1 pH drop for each % sauermalz so if you got 5.35 with 2% you should get 5.35 with 1% and 5.45% with none. Curious as to what you base malt is and what its DI water mash pH might be.

The copper wire trick is borrowed from vintners who often transfer their wine through a copper chute whose job it is to pick up sulfides. Others dose the wine with copper sulfate (ick!) or use copper wire.
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