Just got my Red Sea Test Kits -- Wow

[Twistofer]

I've switched to the Red Sea Reef Foundation Pro and Algae Control Pro Kits, and I'm impressed. Years ago I tried them and couldn't get consistent results.

I can see where some people can be unsure whether or not the endpoint has been reached, but you really need to read the instructions.

In the Reef Foundation Pro, there are intermediate color changes until you get the final color, eg. red to magenta to purple to blue. Almost anywhere between these colors, you can get reversal of the color. I really like the fact that you have a titration "instrument" that holds the syringe and can gently add a drop or two. While learning the test, I did write down the dose, where those intermediate changes occurred, until I was sure of the "true" endpoint, i.e. where the endpoint color, as shown on the card, persisted. The color card was very accurate to my eyesight and interpretation. IMO, the end color should persist for about 10 to 30 seconds, unless otherwise specified by the instructions. The alkalinity was definitely a "different beast," as you said Jonathan (in a previous thread), but I did reach the "orange" endpoint as shown on the card.

In Quantitative Analysis (Chem 301-302 in College), I always hated colorimetric tests which measured the shade of the color when using a comparison chart. The color wheel gizmo supplied with the Algae control kit is cool, well built, but the weaker shades for phosphate and nitrate really bug my eyes. Even under sunlight or "Cool white" illumination, I find it hard to tell the difference between 0.08 and 0.16 ppm PO4. (My old SeaChem test were just as bad). Too bad there are no cheap colorimeters.

Overall, I think these tests are great for the home marine chemist.

[kory1006]

The Alk and Ca are pretty easy to find the end points on, I still have a little trouble with the Mg. my other issue is getting 1ml of solution in the syringe.

[saltydog1]

http://www.youtube.com/watch?v=VT9tEHp828w

Regarding getting 1ml solution in the syringe...looks like I've been doing it wrong!
This video shows the correct way.

[Twistofer]

Originally Posted by kory1006

The Alk and Ca are pretty easy to find the end points on, I still have a little trouble with the Mg. my other issue is getting 1ml of solution in the syringe.

I'm not sure what you mean by 1 ml in the syringe. There is about a 0.1 to 0.15 ml air bubble in the syringe. This air bubble makes up for the air that is in the titration tip. If you were to need the total 1 ml, this residual air will push the last little bit of solution into the test vial. It gets confusing because you are told to read the end of the plunger rather than the top of the solution in the syringe as the amount of solution used. The amount delivered into the test vial is the 1.0 ml minus the plunger reading. The air space is very necessary for test accuracy. It also helps deliver a more uniform drop size.

[kory1006]

I suppose that makes sense. I was getting the solution to the 1 ml mark and leaving the bubble, and not adjusting the bottom of the plunger to the mark. Ill go try again.

[sleepydoc]

Watch the videos, but regardless, you're interested in the amount of reagent used. It really doesn't matter if you have an air bubble, start at 1 ml or at .8, read the top of the stopper or the bottom, as long as you have enough to reach the titration end point.

[kory1006]

Originally Posted by sleepydoc

Watch the videos, but regardless, you're interested in the amount of reagent used. It really doesn't matter if you have an air bubble, start at 1 ml or at .8, read the top of the stopper or the bottom, as long as you have enough to reach the titration end point.

With using the plunger at the 1ml mark, I cannot find the end point for my calcium, it never turns blue. Now if I get the solution to the 1ml mark, I am able to get to the blue endpoint.

[Twistofer]

Originally Posted by kory1006

With using the plunger at the 1ml mark, I cannot find the end point for my calcium, it never turns blue. Now if I get the solution to the 1ml mark, I am able to get to the blue endpoint.

If there is solution to the 1 ml mark, and you push the plunger all the way down to the bottom of the syringe, you have most likely used 1.15 ml of titrating solution (I believe that's Ca 3). The tip accounts for about 0.1 to 0.15 ml of solution which must be taken into account when you titrate. You are actually adding more titrant by about 0.1 to 0.15 ml. That ends up with having a higher concentration of Ca in the long run. You then have to make the calculation using the concentration listed in the instuctions. The concentration is 5 ppm Ca per 0.01 ml of solution used. (0.01 ml = 5 ppm). Therefore your Ca is 575 ppm. [(1.15*5)/0.01]

+1 on Sleepydoc...watch the videos. Read the instructions carefully and follow them to the letter. Seriously, because they correspond to the titration chart on the back of the instruction card.

[bertoni]

You can just draw two syringes the correct way, with the bubble, and add the results after titrating. The calcium level likely is just very high.