pH Test - 5 drops or 4?

[phalcon51]

Recently the color of my pH samples has gotten more intense and it makes it difficult to accurately determine what the proper color match is on my Taylor test kit. Nothing has changed in the chemicals I'm using however the water temp has gone from 74 deg. to 64 deg. in the last 12 days. I've found that if I only use four drops of solution I get a much more accurate color reading than if I use 5 drops. Is this still accurate? Can water temperature affect the color this way?

Below are a couple of pictures demonstrating the difference.

Thanks,

Gary

5 drops

4 drops

 

[JamesW]

The color with 5 drops looks fine. I would say right at about a pH of 7.4 to 7.5. You should use 5 drops. You could get a new bottle of the pH reagent to compare drop size and sample color.

 

[chem geek]

I have a similar issue with my test kit and I use 3-4 drops instead of 5 and it works fine. It may be that my comparator has faded or that the indicator dye is more concentrated (more likely the former).

 

[JasonLion]

The color is the same, regardless of how many drops you use. What varies with the number of drops is the saturation of the color. For some people, using four drops works better, for other people using six drops works better. Whatever works for you is good, the reading should be the same regardless, only the ease of matching the color really varies.