Warning!

[johnluc]

if anyone hasnt read my last post in the water section and is thinking of buying a new salifert KH/Alkalinty test, beware, if it is the november2010 version there is a misprint in the instructions,it says to use 4 drops of KH-ind per 4ml of water. this is wrong! after a couple of tests,questions asked on this forum, and then deciding that the "free reference/check solution (no ins included) is a replacememt for your water to check accuracy i tested with 4 drops and it was of the scale, re tested using 2 drops and it was spot on, so i have now used half the kit and cannot contact makers,"webpage not available". so beware !
johnluc

 

[Runwell-Steve]

Interesting

Not sure how to tell if mine is the November 2010 version, the only date mine has on it is the expiry date on the top of the box which on mine is 11-2015. i assume it's the expiry date anyway.

My instructions also say to use 4 drops of the solution, or 2 for the low resolution test.

I just tested mine with the sample solution, using 4 drops of the indicator, with 4 ml of the water and the answer I got was spot on what it should be, so in the case of my kit 4 drops is what is meant to be used.

I was a bit confused as I had been using 4 drops all along and my Mash pH has been correct so far.

 

[johnluc]

when my kit arrived the box was a bit battered, not sealed, i can only assume if yours is correct that i was given the wrong KH-ind, supplied through amazon, anyone know how i could contact manufacturers as i dont have much confidence in it now.

No on KH-ind bottle PA1000212
No on KH bottle PA1001061
No on check sollution bottle PA 1006303
do they tally with yours

 

[Runwell-Steve]

No your numbers don't match mine at all

Mine are

KH-Ind batch: 1110-A
KH batch: 0910-A
On test solution T10-1110

 

[johnluc]

thanks steve, i think i will have to try and phone manufacturers tommorrow, hope they speak english.
also on instruction leaflet it say it is november 2010 version,more accurate than previous kits :rofl:

 

[Russell]

Two drops of indicator solution or four drops isn't going to make ha'porth of difference, except that you are more likely to see the colour change with four drops. It is probably a revision rather than a misprint. How the hell can they misprint something that was already in print, unless they had good reason to change it. With two drops they were pushing their luck anyway, in my humble view.

 

[johnluc]

russell, surely the way this kit works how can you say it wont make any difference whether you use 2 or 4 drops,if you are supposed to use 2 drops but use 4 the results are completely different resulting in substatial overdose of crs used,or am i missing something here.
johnluc.

 

[Aleman]

Actually the indicator is not just a plain indicator, and it does make a difference if you use two drops or 4 . . . . . . although if you use 4 and halve the reading you should be pretty spot on the value if you used two.

I do find it difficult to understand ow you managed to use up half the kit though, as I've had mine two years, done many brews, and many 'tests' and I still have the majority of the kit left . . .but then I have very low alkalinity water anyway

 

[johnluc]

I do find it difficult to understand ow you managed to use up half the kit though,

aleman, bit of an exageration, was very frustrated i began to feel i was a t..t.

 

[johnluc]

Hi guys sorry to go on with this but can someone check their bottles and see if they tally with mine listed,if so what instructions came with kit ie 2drops or 4 per 4ml. i think i may have an old kit with new instruction sheet.

No on KH-ind bottle PA1000212
No on KH bottle PA1001061
No on check sollution bottle PA 1006303
do they tally with yours[/quote]

 

[oz11]

My test kit has "01-2016" as best before date. It also instructs 4 drops. Mine is all labelled as batch 0111-D, 0111-B and T0111-A.

The instructions say 2010 version. I have used 4 drops without any problems, and 2 drops for the "low-resolution" mode.

 

[johnluc]

thanks oz your numbers tally closely to runwell-steve, am fairly sure i got the wrong instructions, tried to phone makers today not answering phone,webpage not available, guess ill just have to get on with it, and get another kit when next im back in the uk, not going to pay another £16.

 

[Russell]

Actually the indicator is not just a plain indicator, and it does make a difference if you use two drops or 4 . . . . . . although if you use 4 and halve the reading you should be pretty spot on the value if you used two.

Well, the indicator does not take part in the reaction. It would a pretty dumb kit if the indicator made a significant difference to the result - If that were the case we would be measuring the indicator with a calibrated pipette too. "Two drops" is hardly very precise. Water with a significant amount of chlorine in it would bleach out the colour anyway, and then the procedure would be to add more indicator until the chlorine has been used up. It isn't necessarily as straightforward as two or four drops.

Okay, it will make a small difference because one is testing such a small sample that four drops will dilute the sample more than two drops will, but that is a technical and practical issue with the kit itself, and it will not be a busting lot. To halve the reading one would need to add 4ml of indicator, which is, of course, rather too much. The procedure is to use the minimum amount of indicator necessary to enable one to see the initial colour, so as to minimise the dilution effect.

It seems that the table given in the instructions is different too (in the two different batches mentioned). This might be because of the difficulty of making a standard reagent. In professional kits the alkaline test solution is the standard - not the reagent itself. You calibrate the procedure using the alkaline standard. However, in this case the -0.1 meq difference might be to compensate for the dilution effects of using four drops rather than two, the most likely reason I suspect.

This is about the third or fourth time that Salifert have changed the instructions - they seem to be struggling a bit to maintain accuracy. I suspect that they have deliberately doubled the indicator to overcome difficulties with seeing it in some waters and adjusted the table to compensate.

 

[Aleman]

As it turns out "Russell" it does indeed make naff all difference to the results using 2 drops or 4. Which sort of throws the information I was given on the kit into doubt :evil:

I have just done a test using 4ml of Alkalinity Check Soln 7.6 dKH +/-0.3 with 2 and 4 drops of indicator. . . Which removes any possibility of bleaching of the indicator due to chlorine.

Both samples hit the end point with a reading on the syringe of 0.52ml . . .7.7dKH and 2.74meq/l.

Looking at the two samples, one is obviously darker . . . but the 2 drop sample also looks as though it is just past the end point the 4 drop sample being just on it. . . . Dilution effect perhaps

My kits have an end date of 11/2013 and 03/2014

The Kit I used has batch codes

KH Ind 0309-E
KH 1108-C
Check T10-0309

The other kit is

KH Ind 1108-B
KH 1108-B
Check T07-1108

Both instructions sheets say 2 drops and the copyright is from 1997-2008.

Still, used properly the kit is more accurate than the readings you get from the water companies . . . and of the other aquarium test kits on the market this one is the one that most closely agrees with the results obtained by titration to pH 4.5.

One of the issues that I have with the kit is that it is not the amount used that you read to get the dKH but the reading of the plunger on the syringe . . .This nearly caught me out again this afternoon, and you can be sure that there are people who are reading it wrong without realising.

 

[Russell]

The trouble is that judging the end-point using the types of indicator dye suitable for this type of test is quite difficult. Unlike some indicator dyes, there is not an abrupt transition, and there are intermediate colours over quite a wide pH range, which confuses things.

It seems that Salifert have been struggling with the way people perceive colour. Early Salifert kits had what was probably a Methyl-Orange indicator, judging by its static colour. Then they changed the indicator to what is probably a methyl-red / bromocresol-green combination, again judging by its static colour. Then they changed the instructions and included the check solution. Now they seem to have changed the instructions again, four drops of indicator instead of two, and the table has been adjusted slightly too. Whereas the zero row (1 millilitre of reagent used up) was 5.71 meq/l, it will now be something lower, probably 5.48 based upon interpolation from earlier posts on here. That will cock up the mathematical approach if someone uses the wrong number.

One has to wonder why Salifert have changed it yet again. In the end it is only an approximation; these indicator dyes are a bit woolly and do not reflect the true bicarbonate end-point, even pH 4.5 by pH meter is not the true bicarbonate end point - it is fine for comparison purposes and basic quality control, but not particularly accurate on a quantitative basis, particularly at low alkalinities where small errors make a big difference. The true bicarbonate end point shifts depending upon the original composition of the water, anything from pH4.2 at high alkalinities to pH5 at low alkalinities, plus the effects of other species in the water.

Four drops of indicator will obviously give a stronger colour, but I take back the dilution effect - I wasn't thinking straight. The volume (4ml) is measured before the indicator is added, so the amount of carbonate, in absolute terms, is going to be exactly the same, so it is going to take exactly the same amount of titrant to neutralise it. The only way that the indicator can have an effect is if it is not pH-neutral, but I don't know how likely that would be.

Yes it is irritating that the syringe vs the results table go the wrong way round, at least from the intuitive point of view. It must have caught lots of people out.

 

[Good Ed]

and here was me thinking that was a simple to use kit :shock:

 

[Russell]

and here was me thinking that was a simple to use kit :shock:

It is. As Aleman said, there is nothing better out there for the price. It would be nice to know why they have changed things, but one assumes that it is an improvement and for the better.