Moderator Note: Moved from this thread - What happens if I stop using chlorine
JoyfulNoise, what is the mannitol test for borates you use?
JoyfulNoise, what is the mannitol test for borates you use?
JoyfulNoise, what is the mannitol test for borates you use?
Out of curiosity Matt, can you add more Bromothymol Blue to make the endpoint more vivid, or can it skew results?
I also suggest you find a 50mL pyrex beaker and you use a speedstir to do the test.
Yes, you can. The BTB is just an indicator dye so, in principle, it plays no part in the reaction between the borates and mannitol. The product on Amazon is the highest possible concentration of BTB possible in water (BTB has fairly low solubility), so you do need to use a number of drops just to get the color to show. Also, that particular product is in a very lousy dropper bottle, more like a dribble bottle so it's actually quite hard to get uniform, well formed droplets from it. Even so, I have played with the droplet count and found no effect on the results when adding extra drops.
Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
Also, that particular product is in a very lousy dropper bottle, more like a dribble bottle so it's actually quite hard to get uniform, well formed droplets from it.
Yeah, it is! It appears to be a controlled dropper tip, because it does accurately and reliably dispense 40 µl drops (à la Taylor). However, the orifice is so large it wants to squirt, rather than take it slow and easy when forming a drop. The fact that it is LDPE, rather than HDPE, makes the bottle squishy, anyway. I was a little surprised to find it wasn't the standard 50 µl tip. It might be worth transferring it to a more reliable bottle.
Any vendors that sell them? I worked in a chemical lab - never mix old and new!!
I worked in a chemical lab-
Unfortunately the test is not a true endpoint titration. In the last step, you are adding drop to achieve the same color/shade of blue that you saw in the first part of the test before adding the mannitol (which turns the solution a pale yellow). So, in practice, you can over titrate the end point and get a darker blue. This is what makes the test a little tricky - you have to try to remember what blue shade you are looking for. Thankfully the transition from yellow to blue is well defined enough so that you're not stuck with some mixture of color in between drops.
Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
I agree, but thus far, I haven't found a vendor carrying 40 µl tips that fit round or cylindrical bottles over about .5 ounce. I prefer the cylinder, because the 2 oz. Boston Rounds just don't fit in but one compartment of my kit.