Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Xylenes (Dimethylbenzenes) 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 Xylenes provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), aqueous solubility, and density. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Color (APHA), Residue after Evaporation, Substances Darkened by Sulfuric Acid, Sulfur Compounds, and Water.
C6H4(CH3)2
Formula Wt 106.17
CAS No. 1330-20-7
Note: This reagent is generally a mixture of the ortho, meta, and para isomers and may contain some ethylbenzene.
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . . Density . . . . . . . . . . . . . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
© 2017 American Chemical Society
clear liquid solvent boiling point, 140 °C insoluble 0.87
A
DOI:10.1021/acsreagents.4423 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥98.5% xylene isomers plus ethylbenzene (ethylbenzene not to exceed 25%) Maximum Allowable Color (APHA) . . . . . . . . . . . . . . . . . . . . . . . 10 Residue after evaporation . . . . . . . . . . . . . . . 0.002% Substances darkened by sulfuric acid . . . . . . . . Passes test Sulfur compounds (as S) . . . . . . . . . . . . . . . . 0.003% Water (H2O) . . . . . . . . . . . . . . . . . . . . . . . . 0.05%
TESTS Assay Analyze the sample by gas chromatography using the general parameters cited in [Part 2: Chromatography; Recommended Procedures; Gas Chromatography]. The following specific conditions are also required. Column . . . . . . . . . . . . . . . . . . . . . . . . . . Type I, methyl silicone Measure the area under all peaks, and calculate the area percent of each peak. The total percent of xylenes is the sum of the percents of ortho, meta, and para isomers and of ethylbenzene. Correct for water content.
Color (APHA) [Part 2: Measurement of Physical Properties; Color (APHA); Procedure for Color (APHA)].
Residue after Evaporation [Part 2: Gravimetric Methods; Residue after Evaporation]. Evaporate 100 g (115 mL) to dryness in a tared, preconditioned dish on a hot plate (~100 °C), and dry the residue at 105 °C for 30 min.
Substances Darkened by Sulfuric Acid Shake 15 mL with 5 mL of sulfuric acid for 15–20 s, and allow to stand for 15 min. The xylene layer should be colorless, and the color of the acid should not exceed that of a color standard composed of 1 volume of water and 3 volumes of a color standard solution (described below).
For the Determination of Substances Darkened by Sulfuric Acid
C o l o r S t a n d a r d S o l u t i o n . In a 1 L volumetric flask, add 5 g of cobalt chloride hexahydrate, 40 g of ferric chloride hexahydrate, and 20 mL of hydrochloric acid. Dilute to the mark with water.
Sulfur Compounds Place 30 mL of approximately 0.5 N potassium hydroxide in methanol in a conical flask, add 6.0 mL of the sample, and boil the mixture gently for 30 min under a reflux condenser, avoiding the use of a rubber stopper or connection. Detach the condenser, dilute with 50 mL of water, and heat on a hot plate (~100 °C) until the xylenes and methanol have evaporated. Add 50 mL of bromine water, and heat for 15 min longer. Transfer the solution to a beaker, neutralize with dilute hydrochloric acid (1:3), add an excess of 1 mL of the acid, and concentrate to about 50 mL. Filter if necessary, heat the
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4423 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
filtrate to boiling, add 5 mL of 12% barium chloride reagent solution, digest in a covered beaker on a hot plate (~100 °C) for 2 h, and allow to stand for at least 8 h. If a precipitate is formed, filter, wash thoroughly, and ignite. Correct for the weight obtained in a completed blank test.
Water [Part 2: Titrimetric Methods; Water by the Karl Fischer Method; Coulometric Procedure; Coulometric Procedure for Samples Using Karl Fischer Reagent, Method 2]. Use 100 µL (87 mg) of the sample.
© 2017 American Chemical Society
C
DOI:10.1021/acsreagents.4423 ACS Reagent Chemicals, Part 4
