Need help with Lamotte Ca test kit
- Thread starter benf
- Start date
CW from the OC
New member
You have to read it right when the color changes. After a few seconds it will change back, you titrate more, and get higher and higher readings. It is not the best test IMO for this very reason. I've about given up on testing CA and just test Alk for the most part due to this.
Billybeau1
Premium Member
Ben, have you seen my recent test thread ?
www.reefcentral.com/forums/showthread.php?s=&threadid=1306742
www.reefcentral.com/forums/showthread.php?s=&threadid=1306742
kzooreefer
New member
What kind of distilled water did you buy? If it was drinking water a lot of bottlers add calcium and/or other minerals back into their bottled drinking waters. That said I don't think I've ever seen one exceed 100 mg/l. From my expereince with the EDTA method for calcium, metals, such as iron and zinc in particular, read as hardness and give false high results. I've never had a problem with the LaMotte kits except in cooling towers where I had high levels of zinc in the water. I could never get a good end point. Is this your first time using LaMottes Kit? No offense meant but are you sure you are using it correctly? The kit tests for both total and calcium hardness and with saltwater you do a dilution and with distilled water you would not. I just checked mine with my DI water and after I put the calcium reagent tab in the water was a solid blue, no calcium.
benf
Premium Member
i bought from the local grocery store a 1gal jug of distilled water...originally i tried using my RODI water, but thought that was the reason for my high numbers. I double ckd when doing the test i was using the saltwater instructions...I am guessing i should be looking for a DARK blue? Do u have to hold it up to the light or is it to be viewed while on the counter?
kzooreefer
New member
The gallon jugs of distilled water at the store, if inteneded say for ironing laundry, should not contain any calcium. But if they are labeled as drinking water they may contain it. Kind of hit and miss.
The LaMotte kit I use is #4824-DR-LT, there is another kit sold by Marine Depot #3609 which from the comments I read on that site is a little different than mine, it has a purple to blue end point which I gather is harder to read than my red to blue end point.
With the kit I have, for testing RO/DI water I just fill the tube to the 12.9 mL mark with the water and add 6 drops of sodium hydroxide. As soon as I put the calcium reagent tablet into the water I get a deep blue color which indicates no calcium. If calcium were present it would turn red then I would titrate the sample with EDTA till it turned blue. It is not always a deep blue but I have no problem seeing the color change. For saltwater you have to dilute the sample as the kit can't read that high of a calcium concentration. So I do the 1 to 12.9 dilution. After I add the sodium hydroxide and the calcium indicator tablet I get a redish pink color. When I titrate with the EDTA I get a light blue end point right around the 80 mark (80 x 12.9 x .4 = 412 ppm Ca).
Now the reason I asked if you are familar with the LaMotte kit is because they contain reagents also for doing Total Hardness. My kit contains Hardness Reagent #5 and Hardness Tablets #6 which are only used for Total Hardness. I have at times mixed these up with the Sodium Hydroxide Reagent and Calcium Hardness Indicator Tablets for the Calcium Test as the bottles look similar. I would just double check that you did the test right.
The LaMotte kit I use is #4824-DR-LT, there is another kit sold by Marine Depot #3609 which from the comments I read on that site is a little different than mine, it has a purple to blue end point which I gather is harder to read than my red to blue end point.
With the kit I have, for testing RO/DI water I just fill the tube to the 12.9 mL mark with the water and add 6 drops of sodium hydroxide. As soon as I put the calcium reagent tablet into the water I get a deep blue color which indicates no calcium. If calcium were present it would turn red then I would titrate the sample with EDTA till it turned blue. It is not always a deep blue but I have no problem seeing the color change. For saltwater you have to dilute the sample as the kit can't read that high of a calcium concentration. So I do the 1 to 12.9 dilution. After I add the sodium hydroxide and the calcium indicator tablet I get a redish pink color. When I titrate with the EDTA I get a light blue end point right around the 80 mark (80 x 12.9 x .4 = 412 ppm Ca).
Now the reason I asked if you are familar with the LaMotte kit is because they contain reagents also for doing Total Hardness. My kit contains Hardness Reagent #5 and Hardness Tablets #6 which are only used for Total Hardness. I have at times mixed these up with the Sodium Hydroxide Reagent and Calcium Hardness Indicator Tablets for the Calcium Test as the bottles look similar. I would just double check that you did the test right.
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kzooreefer
New member
I think that is the problem with that model kit, the purple to blue colors are almsot indistinguishable. With the kit I have the deep blue color can't be missed. My calcium indicator tablets have number T-5250-H on them. Yours must be different.
kzooreefer
New member
One trick I use when doing titrations and looking for a color change is to place it on something with a white background with lots of light available such as a piece of paper and in teh kitchen. It helps contrast the colors better. Also have you used this for a calcium reading from your saltwater? Did you see the color change there?
Billybeau1
Premium Member
I had no problems seeing the change to pure blue.
I hold the vial up in a north window for natural light. At night I use it in a small room with the incandescent light behind me. Works good either way.
I don't know why the alk tested low. Yes tried it numerous times. Someone even suggested waiting a little longer for the color to change. Still no soap.
benf, I think your alk is closer to 9.2 but you could always pick up an API kit to see which one is closer. They are real cheap and very accurate to the 1 dkh.
Someone recently suggested doubling the water sample on the API for finer accuracy like the Elos.
I haven't tried it yet but its on my list of things to try.
I hold the vial up in a north window for natural light. At night I use it in a small room with the incandescent light behind me. Works good either way.
I don't know why the alk tested low. Yes tried it numerous times. Someone even suggested waiting a little longer for the color to change. Still no soap.
benf, I think your alk is closer to 9.2 but you could always pick up an API kit to see which one is closer. They are real cheap and very accurate to the 1 dkh.
Someone recently suggested doubling the water sample on the API for finer accuracy like the Elos.
I haven't tried it yet but its on my list of things to try.
benf
Premium Member
<a href=showthread.php?s=&postid=11801751#post11801751 target=_blank>Originally posted</a> by Billybeau1
I had no problems seeing the change to pure blue.
I hold the vial up in a north window for natural light. At night I use it in a small room with the incandescent light behind me. Works good either way.
I don't know why the alk tested low. Yes tried it numerous times. Someone even suggested waiting a little longer for the color to change. Still no soap.
benf, I think your alk is closer to 9.2 but you could always pick up an API kit to see which one is closer. They are real cheap and very accurate to the 1 dkh.
Someone recently suggested doubling the water sample on the API for finer accuracy like the Elos.
I haven't tried it yet but its on my list of things to try.
thanks for the info...i plan to pick up an Elos kit today for both alk and Ca. I know there was an issue posted before with Salifert alks kits running high...so i am thinking the Lamotte at 7.6dkh may be correct which bothers me cause i have been lowering my alk dosing cause of the salifert numbers. Its a shame we can loose so much money in Corals cause of a $20 test kit. I think if the Elos kit comes close to one of the other brands i will from here on out alternate test kits on my weekly test so it alarms me when something isnt just right before its too late!
