extreme TA drop, is this even possible?

[crackers8199]

That is a really large drop in TA for an acid addition. I suspect some test error.

that's what i'm figuring...that maybe combined with the margin of error in the test, like @mgtfp mentioned.

 

[mgtfp]

i thought i had read somewhere that you only had to do that for the first few tests with the new kit, and then you could stop. is that not correct?

I don't know, never really had that issue. But if it's static electricity, then I would assume it can happen anytime, like when wearing woollen socks on a carpet. I know that can be a problem when dealing with electronic components, but I have no experience how sensitive this test is.

with the margin of error

I wouldn't really call it error (apart from above systematic error), it's just that the test has an accuracy (by the drop size) of 10ppm, so sometimes the " real" TA will be a little bit lower, and sometimes a little bit higher than your reading.

Before I had my speedstir, I sometimes simply lost count while trying to stir, drop and count at the same time. Especially with the 25ml sample sizes, I found the manual stirring quite distracting, especially towards the end of the test, when the colour starts changing around the drop, but blends back in once the drop has been stirred into the sample. So when my test results looked surprising, I tested again.

Just takes some practice...

 

[duraleigh]

i thought i had read somewhere that you only had to do that for the first few tests with the new kit, and then you could stop. is that not correct?

Correct. Usually less than a week or two.

 

[crackers8199]

wow, the speedstir really makes a difference. did my first full set of tests with the speedstir today, and both CH (1250 down to 1075) and salt (4200 down to 3600) are significantly below what i measured them at when swirling by hand.

 

[mgtfp]

The speedstir rocks . Glad you got it and like it. It also makes your kitchen lab look so much more professional. I'm sure your family commented on that - mine certainly did

But not sure if that drop can be explained just with better testing accuracy. Did you get a lot of dilution lately?

Without the speedstir, did you have a colour change in the top layers of the water sample long before the whole volume changed colour? If yes, then that might have been a sign of insufficient mixing that should have improved now with the speedstir. Important to mix after each drop until either the whole sample changes colour or the whole sample changes back to the original colour before adding the next drop. That's where the speedstir makes testing so much easier and faster (time could actually be another factor, not sure how sensitive the tests are to not adding drops fast enough - others might have more experience with that).

 

[crackers8199]

The speedstir rocks . Glad you got it and like it. It also makes your kitchen lab look so much more professional. I'm sure your family commented on that - mine certainly did

But not sure if that drop can be explained just with better testing accuracy. Did you get a lot of dilution lately?

Without the speedstir, did you have a colour change in the top layers of the water sample long before the whole volume changed colour? If yes, then that might have been a sign of insufficient mixing that should have improved now with the speedstir. Important to mix after each drop until either the whole sample changes colour or the whole sample changes back to the original colour before adding the next drop. That's where the speedstir makes testing so much easier and faster (time could actually be another factor, not sure how sensitive the tests are to not adding drops fast enough - others might have more experience with that).

we have had a decent amount of evap lately but not to the point where I would think the numbers would drop like that. I think it was just that I wasn't swirling / mixing enough when doing it by hand. now I don't have to worry about that lol