Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Litmus Paper Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
ABSTRACT This monograph for Litmus Paper provides, in addition to common physical constants, a general description including applications. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Ash, Phosphate, Rosin Acids, and Sensitivity.
Note: When litmus paper is used in a solution, the length taken of a 0.6 cm wide strip should not exceed 0.5 cm.
GENERAL DESCRIPTION Applications . . . . . . . . . . . . . . . . . . . . . . . . pH indicator
SPECIFICATIONS Ash . . . . . . . . . . . . . . . . . . . Phosphate (PO4) . . . . . . . . . . . Rosin acids (for blue paper only). Sensitivity . . . . . . . . . . . . . . .
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Maximum Allowable 0.4 mg per strip (about 3 cm2) Passes test Passes test Passes test
TESTS Ash Carefully ignite 10 strips in a tared, preconditioned crucible, and finally ignite at 600 ± 25 °C for 15 min.
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Cut five strips into small pieces, mix with 0.5 g of magnesium nitrate in a porcelain crucible, and ignite. To the ignited residue, add 5 mL of nitric acid, and evaporate to dryness. Dissolve in 25 mL of approximately 0.5 N sulfuric acid, and continue as described.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4201 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Rosin Acids Immerse a strip of blue paper in a solution of 0.10 g of silver nitrate in 50 mL of water. The color of the paper should not change in 30 s.
Sensitivity Drop the pieces from six strips of paper into 100 mL of test solution in a beaker, and stir continuously. Blue paper should change color in 45 s in 0.0005 N acid. Red paper should change color in 30 s in 0.0005 N alkali.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4201 ACS Reagent Chemicals, Part 4
