Salifert Alk Test Kit Question

jdeb101

Non-member
#1
I have a Salifert Alk test kit that does not expire until 2020, however I suspected the reading was off since my Alk level tested pretty low. I ran the check solution that came with the kit and it was off -1.6dkh.

Question... Is it safe to continue using the kit to test and just add 1.6dkh to whatever my readings show?
 

Chris A.

Formally toomanyfish
BRS Member
Officer
#2
Can you give a description of how you used it?
Also I know they changed the amount of drops to add from the old version. Check the directions to confirm how many drops to add.
 

Kelly's Reef

Well-Known Member
BRS Member
#3
I have a Salifert Alk test kit that does not expire until 2020, however I suspected the reading was off since my Alk level tested pretty low. I ran the check solution that came with the kit and it was off -1.6dkh.

Question... Is it safe to continue using the kit to test and just add 1.6dkh to whatever my readings show?
Drops are also not a real unit of measure, as how you do it impacts the vol. The tip of the bottle can also impact the vol
 

jdeb101

Non-member
#4
Whether I'm doing the testing correctly is not the question (I've used Salifert for years). The Alk test kit comes with a "check" solution that takes place of your water and you can use it to test the accuracy of the kit. It's supposed to come out to a specific number, I forget exactly what but let's say 4dkh and mine came out to 2.4dkh (1.6dkh under). Hopefully that makes sense.
 

jdeb101

Non-member
#6
I think the color change is subjective, that might be the issue
Can be, however I've found the Salifert kits pretty easy to use. Not sure if you've used them, but with the Alk kit the color will change from blue, to purple, then usually another 2-3 drops and it will change to pink which is the result. Despite being subjective on the color reading, it would never be that far off (1.6dkh), at least for me personally.
 

Kelly's Reef

Well-Known Member
BRS Member
#7
Do you have another solution of known dkh you can use as a control to see if it is the test or the control? Dh20 for zero and fresh made reefwater?
 

jdeb101

Non-member
#9
I guess what I'm really looking to have answered is -
A) Is it normal for a non-expired kit to be off 1.6dkh?
B) knowing this, can I safely still use the kit and just add 1.6dkh to my result to get my dkh reading?
 

Matt W

Chemist
BRS Member
#10
I guess what I'm really looking to have answered is -
A) Is it normal for a non-expired kit to be off 1.6dkh?
B) knowing this, can I safely still use the kit and just add 1.6dkh to my result to get my dkh reading?
The most likely cause of your test being inaccurate is due to the KH solution. The KH-ind - the color indicator is very stable. The acid solution is likely no longer at the desired concentration of acid or normality.

A) Short answer, not common but it happens more than you think. The reagent can become bad for a number of reasons including contamination, cap left off, crazy sh**... The expiry is actually more applicable to an unopen container.
B) Personally, I wouldn't. You don't know the reason for the reagent being off and it may continue to degrade.
 
#11
The most likely cause of your test being inaccurate is due to the KH solution. The KH-ind - the color indicator is very stable. The acid solution is likely no longer at the desired concentration of acid or normality.

A) Short answer, not common but it happens more than you think. The reagent can become bad for a number of reasons including contamination, cap left off, crazy sh**... The expiry is actually more applicable to an unopen container.
B) Personally, I wouldn't. You don't know the reason for the reagent being off and it may continue to degrade.

Thanks for you reply. I ordered new test kits. :)
 

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