Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Urea 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
Downloaded by CORNELL UNIV on June 12, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4419
ABSTRACT This monograph for Urea provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), aqueous solubility, and pKa. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Melting Point, Insoluble Matter, Residue after Ignition, Chloride, Sulfate, Heavy Metals, and Iron.
NH2CONH2
Formula Wt 60.06
CAS No. 57-13-6
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . . pKa . . . . . . . . . . . . . . . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
. . . . .
white solid buffer solutions melting point, 132–135 °C 109 g in 100 mL at 100 °C 1.0
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.0–100.5% NH2CONH2 Melting point . . . . . . . . . . . . . . . . . . . . . . . 132–135 °C Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Residue after ignition. . . . . . . . . . . . . . . . . . 0.01% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.001%
© 2017 American Chemical Society
A
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4419 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.001% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001%
TESTS Assay
Downloaded by CORNELL UNIV on June 12, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4419
(By nonaqueous titration). Accurately weigh about 0.06 g of sample into a 150 mL beaker. Add 75 mL of acetonitrile and about 2 mL of 0.1 N perchloric acid in glacial acetic acid volumetric solution from a burette. When the sample is completely dissolved, finish the titration potentiometrically using a glass electrode set, with 10% lithium perchlorate in acetonitrile (described below) as the filling solution in a fast-flow reference electrode. One milliliter of the 0.1 N perchloric acid titer is equivalent to 0.006006 g of urea.
For the Assay
L i t h i u m Pe r c h l o r a t e i n A c e t o n i t r i l e , 1 0 % S o l u t i o n . Dissolve 5.0 g of lithium perchlorate in 400 mL of acetonitrile, and dilute to 500 mL with acetonitrile.
Melting Point [Part 2: Measurement of Physical Properties; Melting Point].
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 10.0 g dissolved in 100 mL of water.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Ignite 10.0 g.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 2.0 g.
Sulfate Dissolve 4.0 g and about 10 mg of sodium carbonate in 10 mL of hydrochloric acid. Add 10 mL of nitric acid, and digest in a covered beaker on a hot plate (~100 °C) until reaction ceases. Add 5 mL of hydrochloric acid and 10 mL of nitric acid, and again digest in a covered beaker on a hot plate (~100 °C) until reaction ceases. Remove the cover, and evaporate to dryness. Dissolve the residue in 4 mL of water plus 1 mL of dilute hydrochloric acid (1:19), and filter through a small filter. Wash with two 2 mL portions of water, dilute with water to 10 mL, and add 1 mL of 12% barium chloride reagent solution. Any turbidity should not exceed that produced when a solution containing 0.04 mg of sulfate ion (SO4) is treated exactly like the 4.0 g sample. Compare 10 min after adding the barium chloride to the sample and standard solutions.
© 2017 American Chemical Society
B
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4419 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 2.0 g in about 20 mL of water, and dilute with water to 25 mL.
Iron
Downloaded by CORNELL UNIV on June 12, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4419
[Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 1.0 g.
© 2017 American Chemical Society
C
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4419 ACS Reagent Chemicals, Part 4
