This blue Litmus test paper by Precision Laboratories is a foolproof pH test to determine if something is acidic. The Blue Litmus test paper does not come with a color chart as it cannot provide you with a defined pH value. The test strip will turn red if dipped into an acidic solution (pH <7). It will remain unchanged in an alkaline solution. Although there is no color chart, the strip will turn various shades of red, getting darker the more acidic the solution. We have tested the blue litmus with multiple pH buffers. The blue paper is blue at pH 8. At pH 7, the sample is maybe just a little red. The real change to red seems to start with pH 6.5 and lower.

Instructions:
Remove one Blue Litmus test paper from the vial, being careful not to touch the strip anywhere other than where you grasp it.
Dip the strip into the solution to be tested for 1-2 seconds and remove.
The test strip will turn red in seconds if dipped into a solution that is acidic, and will remain unchanged if not.
NOTE: The solution must be water-based.

Disclaimer: Precision Laboratories products are not approved for use as medical devices. Products and product information is for informational purposes only and not intended for use to diagnose, treat, cure or prevent any medical condition.

Documentation