Reading API tests

**linda-b** · 01-20-2013, 02:11 PM

I noticed that when comparing the colour of the water against the API colour chart, there is a variation of colour depending on whether the tube is held right up against the chart or slightly away from the chart. The colour is lighter when the tube is a about an inch away from the chart due to light behind the tube. This makes a particular big difference to the nitrate test; it appears to vary between 10 and 40 as you move the tube away from the chart. So can someone please advise on the best way to take a reading.

**MrJim** · 01-20-2013, 02:22 PM

IIRC the instructions say to put it up against the white on the card~I agree it's hard to read and I'm somewhat color blind so I ask everyone else in the family their opinion.

**Goes to 11!** · 01-20-2013, 02:32 PM

Originally Posted by MrJim

IIRC the instructions say to put it up against the white on the card.

Good memory

, That's exactly what it says.

Originally Posted by From the API kit instructions

6. Read the test results by matching
the test solution against the
Ammonia Test Color Chart. The
tube should be viewed against
the white area beside the color
chart. Color comparisons
are best made in a well-lit area.

This is exactly what you should do.

**Lady Hobbs** · 01-20-2013, 02:37 PM

I do my tests on a piece of paper towel. And allow the tests to sit there for 5 minutes before taking a reading.

The paper towel is there for another reason, too! One of those tests will make stains on a white counter top. Blue-green spots all over that nothing will get rid of. They also will make discolorations in a stainless steel sink. Poor the liquid directly down the drain and don't let it run down the sink.

**linda-b** · 01-20-2013, 02:47 PM

Originally Posted by Lady Hobbs

I do my tests on a piece of paper towel. And allow the tests to sit there for 5 minutes before taking a reading.

The paper towel is there for another reason, too! One of those tests will make stains on a white counter top. Blue-green spots all over that nothing will get rid of. They also will make discolorations in a stainless steel sink. Poor the liquid directly down the drain and don't let it run down the sink.

Thank you Lady Hobbs for your advise. I'm aware of the staining and always throw the liquid down the drain. I was more concerned with the apparent variation in colour as you move the tube away from the card. My nitrate test is usually in the orange region - around the 30 if right up against the card and around 15 if I move it away. I wanted some expert opinions.

**vafa** · 01-20-2013, 04:19 PM

i actully emailed the company and asked this question.
they said that it should be against the white on the chart but you should leave a 1 cm space between them.
so there you go

**Rocksor** · 01-20-2013, 04:49 PM

Originally Posted by vafa

i actully emailed the company and asked this question.
they said that it should be against the white on the chart but you should leave a 1 cm space between them.
so there you go

That's a change from what the company has said before when people have emailed them.

**Lady Hobbs** · 01-20-2013, 05:14 PM

I find no comparison at all between 10 and 40 nitrates. 10 is a slight orange color and 40 is darned near a deep burnt orange or reddish color.

**linda-b** · 01-20-2013, 09:05 PM

Originally Posted by Lady Hobbs

I find no comparison at all between 10 and 40 nitrates. 10 is a slight orange color and 40 is darned near a deep burnt orange or reddish color.

I think you may be missing my point. What I'm saying is if you hold the tube right up against the chart (ie touching), the colour appears closer to a scale of 40; however, if you move the tube away from the chart, thereby allowing light behind the tube, the colour appears lighter giving an apparent reading closer to 10. This is what I am trying to clarify as it can make a big difference to the reading depending on where you hold the testtube.

**Cermet** · 01-20-2013, 11:38 PM

Warning - people come and go at companies and hence the companies' policy on what to do also changes with these people; so, unless the company creates a permanent reference paper people answering the phone will often give what they think should be done. So, take any new information with a gain of salt. In general, always following write instructions because the person who devised the test, and is now, most likely long gone, is the person who has the correct method.

Until the company starts printing new instructions with their kits, I'd not use the 1 cm set off distance.

If following the correct instructions causes you to read a near 40 ppm nitrate, you really, really need a huge water change and then need to do larger weekly changes to keep it much lower.