Supplement No. 1 Reagent Chemicals, 5th Edition The Fifth Edition of REAGENT CHEMICALSwas published in 1974. As stated a t the end of the Preface, two supplements will be issued in ANALYTICAL CHEMISTRY prior to publication of the next full edition, and reprints sized to fit REAGENTCHEMICALS will be made available. The reprints will incorporate any modifications in specifications and tests for which the American Chemical Society Committee on Analytical Reagents has given early notification following its meetings. Since the publication of the Fifth Edition, three such announcements have appeared in ANALYTICAL CHEMISTRY,as follows: 47, No. 7,1149 (1975);48, No. 4,792 (1976);and 48,No. 9, 1432 (1976).
Interpretation of Requirements O n page 5 delete the paragraph o n Particle Size for Granular Materials. Substitute the statement cited below. When a mesh or a mesh range is stated on a reagent label, the label shall include reference to a coarse sieve and to a finer sieve. The sieve number (mesh) is related to the sieve opening as indicated in the accompanying table. Sieve No., Mesh 2 4 8 10 20 30 40 50 60 80
Sieve opening, mm 9.52 4.76 2.38 2.00 0.84 0.59 0.42 0.297 0.250 0.177
When tested according to the Procedure given below, at least 95% of the material shall pass through the coarse sieve and at least 70% shall be retained on the finer sieve. This requirement applies only to materials that are 60 mesh or coarser. Procedure. The sieves used in this procedure shall be those known as the U.S. Standard Sieve Series. For the details of the standardization of such sieves, reference may be made to ASTM E 11-70. Place 25 to 100 g of the material to be tested upon the appropriate coarser standard sieve which is mounted above the finer sieve t o which a close-fitting 524
pan is attached. Place a cover on the coarser sieve, and shake the stack in a rotary horizontal direction and vertically by tapping on a hard surface for not less than 20 min, or until sifting is practically complete. Weigh accurately the amount of material remaining on each sieve. An alternate procedure may be used in which the screening through the standard sieves is carried out in a mechanical sieve shaker. This shaker reproduces the circular and tapping motion given to the testing sieves in hand sifting, but with a mechanical action, following the directions provided by the manufacturer of the shaker.
General Procedures Measurement of Physical Properties At the end of page 14 insert the statement on Color ( A P H A ) [American Public Health Association] cited below. The color intensity of liquids may be rapidly estimated by the use of platinum-cobalt standards, as described in ASTM standard method D 1209-69. This method is particularly applicable to those materials in which the colorproducing bodies have light absorption characteristics nearly identical with those in the standards. Colors having hues other than light yellow or reddish yellow cannot be determined by these standards. The platinum-cobalt color standards contain carefully controlled amounts of potassium chloroplatinate and cobaltous chloride. Each platinum-cobalt color unit is equivalent to 1 mg of platinum per liter of solution (1 ppm), and the standards are named accordingly. For example, the No. 20 platinum-cobalt standard contains 20 ppm platinum. These platinum-cobalt standards are also called APHA and Hazen standards. Apparatus. The apparatus for this measurement consists of a series of Nessler tubes, a color comparator, and a light source. These tubes must match each other with respect to the color of the glass and height of the graduation mark. They must be fitted with suitable closures to prevent loss of liquid by evaporation and contamination of the standards by dust or dirt. The most commonly used type of Nessler tube is the 100-mL tall-form tube. However, for
ANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
some samples, particularly those having darker colors, a better color match may be obtained by using 100-mL short-form Nessler tubes. For the most accurate estimation of color, it is desirable to use a comparator constructed so that white light is reflected from a white glass plate with equal intensity through the longitudinal axis of the tubes being compared. The tubes are shielded so that no light enters the tubes from the side. In most cases, satisfactory estimates of the color can be obtained by holding the sample and standards close to each other over a white plate. The best source of light is generally considered to be diffuse daylight. However, for general routine analyses, the use of a titrating lamp equipped with a “daylight” type fluorescent tube is satisfactory. Preparation of the APHA No. 500 Platinum-Cobalt Standard. Measure 500 mL of reagent water into a 1000-mL volumetric flask, add 100 mL of hydrochloric acid, and mix well. Weigh 1.245 g of potassium chloroplatinate (K2PtCld and 1.000 g of cobaltous chloride (CoClz.6HzO) to the nearest mg, and transfer to the flask. Swirl until complete dissolution is effected, dilute to the mark with reagent water, and mix thoroughly. The spectral absorbance of this APHA No. 500 standard must fall within the limits given below, when measured in a suitable spectrophotometer, using a 1-cm light path and reagent water as the reference liquid in a matched cell. Wavelength, nm 430 455 480 510
Absorbance 0.110 to 0.120 0.130 to 0.145 0.105 to 0.120 0.055 to 0.065
Preparation of the APHA Platinum-Cobalt Standards. Prepare the required color standards by diluting the volume of APHA No. 500 platinumcobalt standard given in the following table with reagent water to a total volume of 100 mL. The use of a buret is recommended in measuring the No. 500 standard. This series of standards is usually sufficient to permit an experienced analyst to make color comparisons with the necessary precision and accuracy. If a more exact estimate of color is desired, additional standards may be prepared to supplement those given by using proportional amounts of the No. 500 platinum-cobalt standard.
APHA Pt-Co ML of APHA No. 500 Pt-Co Color Standard to Dilute to 100 mL Standard No. 0.00 0 1 0.20 0.60 3 1.00 5 2.00 10 3.00 15 3.60 18 4.00 20 5.00 25 6.00 30 7.00 35 8.00 40 10.00 50 12.00 60 14.00 70 16.00 80 18.00 90 20.00 100 24.00 120 28.00 140 32.00 160 36.00 180 40.00 200 250 50.00 60.00 300 70.00 350 80.00 400 90.00 450 100.00 500
Procedure. Transfer 100 mL of the sample to a matched 100-mL tall form Nessler tube. (If the sample is turbid, filter or centrifuge before filling the tube to remove visible turbidity.) Compare the color of the sample with those of the series of platinum-cobalt standards in matching Nessler tubes. View vertically down through the tubes against a white background. Report as the color the number of the APHA standard that most nearly matches the sample. In the event that the color lies midway between two standards, report the darker of the two.
New Reagents Anthrone
TESTS Absorbance of reagent solution. Measure the absorbance of the reagent solution (see the test for Sensitivity to carbohydrates) in a spectrophotometer, using 1.00-cm cells, with sulfuric acid as reference. Record the absorbance at 425 nm and 620 nm, respectively. The absorbance should not exceed 0.75 a t 425 nm and 0.045 a t 620 nm. Solubility in ethyl acetate. Dissolve 1 g on 50 mL of freshly distilled ethyl acetate in a dry 50-mL glass-stoppered graduate. The mixture should not be heated, dissolution should be complete, and the resulting solution should be clear. Sensitivity to carbohydrates. Reagent Solution. Slowly add 132 mL of concentrated sulfuric acid to 68 mL of ice cold water in an ice bath. Allow the mixture to cool to room temperature, add 0.100 g of the sample, and heat if necessary to dissolve. Glucose Standard (1000 pg in 1 mL). Dissolve 1.00 g of glucose in water, and dilute with water to 100 mL. Pipet 10.0 mL of this solution (1 mL = 10 mg) into a 100-mL volumetric flask, and dilute to volume with water. Mark four 25-mL volumetric flasks as 0 pg (blank), 250 pg, 500 pg, and 750 pg. Add the glucose standard and water as specified, and dilute to volume with the reagent solution. Glucose standard, Water, mL mL 0 0.75 0.25 0.50 0.50 0.25 0.75 0
Flask, pg
0 250 500 750
Place all flasks in a vigorously boiling water bath for 7.0 min, allow the flasks to cool to room temperature, and determine the absorbance of each a t 620 nm against the blank in 1.00-cm cells. A plot of the absorbance against concentration should be linear, and the absorbance of the 750-pg flask should not be less than 0.90.
L-Ascorbic Acid C6H806
REQUIREMENTS Appearance. Off-white to light yellow crystals. Absorbance of reagent solution. To pass test. Melting point. No more than a 3" range including 156 "C. Solubility in ethyl acetate. T o pass test. Sensitivity to carbohydrates. To pass test.
Formula Wt 176.13
REQUIREMENTS Assay. Not less than 99.0% C6HsOfi. Specific rotation [ a I z 5 "Not ~ . less than +20.5" nor more than +21.5". Residue after ignition. Not more than 0.1%. Heavy metals (as Pb). Not more than 0.002%. Iron (Fe). Not more than 0.001%.
Assay. Weigh accurately about 0.4 g, and dissolve in a mixture of 100 mL of oxygen-free water and 25 mL of 10% sulfuric acid. Titrate immediately with 0.1 N iodine, adding 3 mL of starch indicator solution near the end point. One milliliter of 0.1 N iodine corresponds to 0.008806 g of C~Ha06. Specific rotation. Weigh accurately about 10 g, dissolve in 90 mL of oxygen-free water in a 100-mL volumetric flask, and dilute with water to volume. Adjust the temperature of the solution to 25 OC. Observe the optical rotation in a polarimeter at 25 "C using sodium light, and calculate the specific rotation. It should not be less than f20.5" nor more than f21.5". Residue after ignition. Gently ignite 1.0 g in a tared crucible or dish until charred. Cool, moisten the char with 1 mL of sulfuric acid, and ignite again slowly until all carbon and excess sulfuric have been volatilized. Finally, ignite a t 800 f 25 "C for 15 min. The weight of the residue should not exceed 0.001 g. Retain the residue for the test for Iron. Heavy metals. To 0.1 g add 1mL of sulfuric acid, heat cautiously until the sample is charred, and ignite in an oven a t 500 "C until most of the carbon is volatilized. Cool, add 2 mL of nitric acid, heat until the acid is evaporated, and ignite again at 500 "C until all of the carbon is volatilized. Cool, add 4 mL of dilute hydrochloric acid (1 l),digest on the steam bath for 10 min, and evaporate to dryness. Moisten the residue with 0.05 mL of hydrochloric acid, add 10 mL of hot water, and digest for 2 min. Add ammonium hydroxide (10% NH3) until the solution is just alkaline, and dilute with water to 25 mL. For the standard, dilute a solution containing 0.02 mg of lead ion (Pb) with water to 25 mL. Adjust the pH of the sample and standard solutions to between 3 and 4 (using a pH meter) with 1N acetic acid or ammonium hydroxide (10% NHs), dilute with water to 40 mL, and mix. Add 10 mL of freshly prepared hydrogen sulfide water to each and mix. Any color in the solution of the sample should not exceed that in the standard. Iron, To the residue for the test for Residue after ignition, add 3 mL of dilute hydrochloric acid (1 1)and 0.10 mL of nitric acid, cover with a watch glass, and digest on the steam bath for 15 to 20 min. Remove the watch glass and evaporate to dryness. Dissolve the residue in a mixture of 2 mL of hydrochloric acid and 10 mL of water, and dilute with water to 50 mL. To the solution, add 30 to 50 mg of ammonium peroxydisulfate crystals and 3 mL of ammonium thiocyanate reagent solution. Any red color should not exceed that produced by 0.01 mg of iron (Fe) in
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an equal volume of solution containing the quantities of reagents used in the test.
Lithium Perchlorate LiC104
Formula Wt 106.39
REQUIREMENTS Insoluble matter. Not more than 0.005%. pH of a 5% solution. From 6.0 to 7.5 a t 25 "C. Chloride (Cl). Not more than 0.003%. Sulfate ( 5 0 4 ) . Not more than 0.001%. Heavy metals (as Pb). Not more than 5 ppm. Iron (Fe). Not more than 5 ppm.
TESTS Insoluble matter. Dissolve 20 g in 200 mL of water, heat to boiling, and digest in a covered beaker on the steam bath for 1 h. Filter through a tared filtering crucible, wash thoroughly, and dry at 105 "C. The weight of the residue should not exceed 0.001 g. pH of a 5 % solution. Dissolve 10 g in 200 mL of carbon dioxide- and ammonia-free water. Determine the pH by the method described on page 27. The p H should be from 6.0 to 7.5 a t 25 "C. Chloride. Dissolve 1.0 g in 20 mL of water, filter if necessary through a chloride-free filter, and add 1mL of nitric acid and l mL of silver nitrate reagent solution. Any turbidity should not exceed that produced by 0.03 mg of chloride ion (Cl) in an equal volume of solution containing the quantities of reagents used in the test. Sulfate. Dissolve 40 g in 300 mL of water, add 2 mL of hydrochloric acid, filter, and heat to boiling. Add 5 mL of barium chloride reagent solution, digest in a covered beaker on the steam bath for 2 h, and allow to stand overnight. If a precipitate is formed, filter, wash thoroughly, and ignite. The weight of the precipitate should not be more than 0.001 g greater than the weight obtained in a complete blank test. Heavy metals. Dissolve 6.0 g in about 20 mL of water and dilute with water to 30 mL. For the control, add 0.02 mg of lead ion (Pb) to 5.0 mL of the solution and dilute with water to 25 mL. Adjust the pH of the control and sample solutions to between 3 and 4 (using a pH meter) with 1 N acetic acid or ammonium hydroxide (10% NH3), dilute with water to 40 mL, and mix. Add 10 mL of freshly prepared hydrogen sulfide water to each and mix. Any color in the solution of the sample should not exceed that in the control. Iron. Dissolve 1.0 g in 20 mL of water. 526
Add 1 mL of hydroxylamine hydrochloride reagent solution, 4 mL of 1,lO-phenanthroline reagent solution, and 1 mL of 10% sodium acetate solution, and mix. Any red color should not exceed that produced by 0.005 mg of iron (Fe) in an equal volume of solution containing the quantities of reagents used in the test. Compare 1 h after adding the reagents to the sample and standard solutions.
p-Methylaminophenol Sulfate (CHSNHC~H~OH)~*H~SO~ Formula Wt 344.38
REQUIREMENTS Assay. Not less than 99.0 nor more than 101.5%. Residue after ignition. Not more than 0.1%. Suitability for determination of phosphate. To pass test.
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TESTS Assay. Weigh about 250 mg to the nearest 0.1 mg. Transfer to a 500-mL conical flask containing 100 mL of water and 10 mL of 0.1 N sulfuric acid. Dissolve, add 0.15 mL of ferroin indicator solution,* and titrate with 0.1 N ceric ammonium nitrate* to a light green color which persists for 15 s. %HOC6H4NHCH3-1/2H2S04 - V X N X 8.61 W where V = volume, in mL, of standard ceric ammonium nitrate, N = normality of ceric ammonium nitrate solution, and W = weight, in grams, of sample. *Reagents. 1. Ferroin Indicator Solution. Dissolve 0.70 g of ferrous sulfate, F e S 0 ~ 7 H 2 0 , and 1.5 g of 1,lO-phenanthroline in 100 mL of water. 2. Standard Ceric Ammonium Nitrate Solution, 0.1 N. Preparation. Mix 59 g of ceric ammonium nitrate, (NH4)2Ce(NO&, with 31 mL of concentrated sulfuric acid in a 500-mL beaker with stirring. Cautiously add water in 20-mL portions, with stirring, allowing 2 to 3 min between each addition. Continue the addition of water until the ceric ammonium nitrate is completely dissolved. Filter, dilute to 1 liter with water in a volumetric flask, and mix. Standardization. Weigh about 200 mg of dry arsenic trioxide to the nearest 0.1 mg. Transfer to a 500-mL conical flask, add 15 mL of 10% sodium hydroxide reagent solution, and warm the mixture gently to hasten dissolution. When dissolution is complete, cool to room temperature and add 25 mL of dilute sulfuric acid (1 5 ) . Dilute to 100
ANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
mL with water and add, as catalyst, 0.15 mL of 0.01 M osmium tetroxide (0.25 g of OsO4 in 100 mL of 0.1 N sulfuric acid). (Warning. Osmium tetroxide is poisonous; avoid contact!) Add 0.05 mL of ferroin indicator solution, and titrate with the ceric ammonium nitrate solution until the reddish orange color changes to colorless or very pale blue. (Note. As the osmium tetroxide catalyst ages, 0.15 to 0.65 mL may be needed to achieve the desired action. A sluggish end point indicates insufficient osmium tetroxide.) Normality of Ceric Ammonium Nitrate = ( W x lOOO)l(V x 49.45) where W = weight, in mg, of As203 and V = volume, in mL, of (NH&Ce(NO& solution. Residue after ignition. Weigh accurately 4.9-5.1 g in a previously ignited and tared plantinum crucible or dish. Gently ignite until charred, and ignite again slowly until all carbon has been volatilized. Finally, ignite at 800 25 "C for 15 min. The weight of the residue should not exceed 0.005 g. Suitability for determination of phosphate. Dissolve 2 g in 100 mL of water. To 10 mL of this solution, add 90 mL of water and 20 g of sodiuh bisulfite, dissolve, and mix. Transfer 1 mL of this solution to each of two solutions containing 25 mL of 0.5 N sulfuric acid and 1 mL of ammonium molybdate reagent solution (for direct colorimetric phosphate). For the control, add 0.005 mg of phosphate ion (PO,) to one of the solutions. For the sample, use the remaining solution. Allow the solutions to stand a t room temperature for 2 h. The control should turn perceptibly darker blue than the sample.
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Sodium Bromide NaBr
Formula Wt 102.89
REQUIREMENTS Insoluble matter. Not more than 0.005%. pH of a 5% solution. From 5.5 to 7.5 at 25 "C. Bromate (Br03). To pass test (limit about 0.001%). Chloride (Cl). Not more than 0.2%. Nitrogen compounds (as N). Not more than 5 ppm. Sulfate (Sod). Not more than 0.002%. Barium (Ba). Not more than 0.002%. Calcium, magnesium, and Rz03 precipitate. Not more than 0.005%.
Heavy metals (as Pb). Not more than 5 ppm. Iron (Fe). Not more than 5 ppm.
Potassium (K). Not more than 0.005%.
TESTS Insoluble matter. Dissolve 20 g in 150 mL of water, heat to boiling, and digest in a covered beaker on the steam bath for 1 h. Filter through a tared filtering crucible, wash thoroughly, and dry at 105 "C. The weight of the residue should not exceed 0.001 g. Save the filtrate separate from the washings for the test for Calcium, magnesium, and R203 precipitate. pH of a 5% solution. Dissolve 10 gin 200 mL of carbon dioxide- and ammonia-free water. Determine the pH by the method described on page 27. The pH should be from 5.5 to 7.5 a t 25 "C. The pH of a 5% solution of pure sodium bromide would be 7.0 a t 25 "C. Bromate. Dissolve 1.0 g in 10 mL of freshly boiled and cooled water. Add 0.10 mL of 10% potassium iodide reagent solution, 1 mL of starch indicator solution, and 0.25 mL of 1 N sulfuric acid. No blue or violet color should be produced after standing 10 min a t 25 "C. Chloride. Dissolve 0.50 g in 15 mL of dilute nitric acid (1 2) in a small flask. Add 3 mL of 30%hydrogen peroxide and digest on the steam bath until the solution is colorless. Wash down the sides of the flask with a little water, digest for an additional 15 min, cool, and dilute with water to 200 mL. Dilute 2.0 mL with water to 20 mL, and add 1 mL of nitric acid and 1 mL of silver nitrate reagent solution. Any turbidity should not exceed that produced by 0.01 mg of chloride ion (Cl) in an equal volume of solution containing the quantities of reagents used in the test. Nitrogen compounds. Dissolve 1.0 g in 60 mL of water in a flask connected through a spray trap to a condenser, the end of which dips beneath the surface of 10 mL of 0.1 N hydrochloric acid. Add to the flask 20 mL of freshly boiled 10% sodium hydroxide reagent solution and about 0.5 g of aluminum wire in small pieces, allow to stand for 1h, and slowly distil about 35 mL. To the distillate add 1 mL of 10% sodium hydroxide reagent solution, dilute with water to 50 mL, and add 2 mL of Nessler reagent. Any color should not exceed that produced when a quantity of ammonium salt containing 0.005 mg of nitrogen (N) is treated exactly like the sample. Sulfate. Dissolve 20 g in 200 mL of water, filter if necessary, and add 1mL of hydrochloric acid. Bring to a boil, add 5 mL of barium chloride reagent solution, digest in a covered beaker on the steam bath for 2 h, and allow to stand overnight. If a precipitate is formed, filter, wash thoroughly, and ignite. The weight of the precipitate should not be more than 0.0012 g greater than the
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weight obtained in a complete blank test. Barium. For the sample dissolve 6.0 g in 15 mL of water. For the control dissolve 1.0 g in 15 mL of water and add 0.1 mg of barium ion (Ba). To each solution add 5 mL of acetic acid, 5 mL of 30% hydrogen peroxide, and 1 mL of hydrochloric acid. Digest in a covered beaker on the steam bath until reaction ceases, uncover, and evaporate to dryness. Dissolve the residues in 15 mL of water, filter if necessary, and dilute with water to 23 mL. Add 2 mL of 10% potassium dichromate reagent solution and add ammonium hydroxide until the orange color,is just dissipated and the yellow color persists. Add 25 mL of methanol, stir vigorously, and allow to stand for 10 min. Any turbidity in the solution of the sample should not exceed that in the control. Calcium, magnesium, and Rz03 precipitate. T o the filtrate from the test for Insoluble matter, add 5 mL of ammonium oxalate reagent solution, 2 mL of ammonium phosphate reagent solution, and 10 mL of ammonium hydroxide. Allow to stand overnight, filter, wash with water containing 2.5% ammonia and about 0.1% ammonium oxalate, and ignite. The weight of the residue should not exceed 0.001 g. Heavy metals. Dissolve 6.0 g in about 20 mL of water and dilute with water to 30 mL. For the control add 0.02 mg of lead ion (Pb) to 5.0 mL of the solution and dilute with water to 25 mL. For the sample, use the remaining 25-mL portion. Adjust the p H of the control and sample solutions to between 3 and 4 (using a pH meter) with 1N acetic acid or ammonium hydroxide (10% NH3), dilute with water to 40 mL, and mix. Add 10 mL of freshly prepared hydrogen sulfide water to each and mix. Any color in the solution of the sample should not exceed that in the control. Iron. Dissolve 2.0 g in 40 mL of water plus 2 mL of hydrochloric acid, and dilute with water to 50 mL. Add 30 to 50 mg of ammonium peroxydisulfate crystals and 3 mL of ammonium thiocyanate reagent solution. Any red color should not exceed that produced by 0.01 mg of iron (Fe) in a n equal volume of solution containing the quantities of reagents used in the test. Potassium. Determine the potassium by the flame photometric method described on page 20. Dissolve 10 g in water and dilute with water to 100 mL. Sample Solution A. Dilute 10 mL of the solution with water to 100 mL. Control Solution B. To another 10 mL of the solution, add 0.05 mg of potassium ion (K) and dilute with water to 100 mL. Observe the emission of Control Solution B a t the 767-nm potassium line. Observe the emission of Sample Solu-
tion A a t the 767-nm potassium line and a t a wavelength of 750 nm. The difference (01) between the intensities observed for Sample Solution A at 750 nm gnd 767 nm should not exceed the difference ( 0 2 ) observed at 767 nm between Sample Solution A and Control Solution B.
Thiourea NH2CSNH2
Formula Wt 76.12 REQUIREMENTS Assay. Not less than 99.0% NHzCSNHz calculated on the dry basis. Melting point. Not below 174 "C nor above 177 "C. Solubility in water. T o pass test. Residue after ignition. Not more than 0.1%. Loss on drying. Not more than 0.5%. Sensitivity to blismuth. T o pass test.
TESTS Assay. Weigh accurately about 1 g, dissolve in water, and dilute to 250 mL in a volumetric flask. To 20.0 mL of this solution in a glass-stoppered flask, add 25.0 mL of 0.1 N silver nitrate and 10 mL of ammonium hydroxide (10% "3). Stopper the flask, shake vigorously for 2 min, heat to boiling, and cool. To the cooled solution, add 60 mL of dilute nitric acid, shake vigorously, and filter through a filtering crucible or a sintered glass funnel which has been cleaned with dilute nitric acid, and wash the funnel and flask well with water. To the filtrate plus washings, add 2 mL of ferric ammonium sulfate indicator solution, and titrate with 0.1 N thiocyanate. One milliliter of 0.1 N silver nitrate corresponds to 0.003806 g of NHzCSNHz. Solubility in water. Dissolve 1 g in 20 mL of water. The solution should be clear and colorless. Residue after ignition. Ignite 10 g in a tared crucible or (dish. The rate of heating should be such that from 1to 2 h is required to volatilize the sample. When nearly all of the sample has been volatilized, cool, and moisten the residue with 0.10 mL of sulfuric acid. Continue the heating until the remainder of the sample and excess sulfuric acid have been volatilized. Finally, ignite a t 800 f: 25 "C for 15 min. The weight of the residue should not exceed 0.01 g. Loss on drying. Weigh accurately about 1.5 g and dry to constant weight at 105 "C. The loss in weight should not be more than 0.5%. Sensitivity to bismuth. Dissolve 0.10
ANALYTICAL CHEMISTRY, VOL. 49, NO. 3, MARCH 1977
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g in 10 mL of water. Add 1.0 mL of this solution to 10 mL of bismuth solution.* A distinct yellow color is produced immediately. *Bismuth Solution. Dissolve 0.23 g of bismuth subnitrate in a mixture of 12 mL of nitric acid and 80 mL of water. When dissolution is complete, dilute with water to 2000 mL.
determined end point. Add 3 g of the sample, taking care to protect the contents of the flask from moisture. Stir vigorously and titrate with Karl Fischer reagent to the same end point. Calculate the water content of the sample from the titer and volume of Karl Fischer reagent consumed by the sample.
REVISIONS IN REQUIREMENTS ( - C G H ~ - ~ N H ~ - ~ C H ~ ) ~ ~ ~ H C I AND TESTS o-Tolidine Dihydrochloride
Formula Wt 285.22
REQUIREMENTS Assay. Not less than 98%. Residue a f t e r ignition. Not more than 0.1%. Sensitivity. To pass test (0.1 ppm free chlorine). Solubility. To pass test. Water (HzO). Not more than 1%.
TESTS Assay. Weigh accurately about 1.5 g and transfer to a 400-mL beaker. Dissolve in 250 mL of water, warming gently if necessary, then cool to 0 “C. Add 5 mL of concentrated hydrochloric acid and 5 g of potassium bromide, and titrate with 0.5 N sodium nitrite, keeping the temperature below 5 “C. As the end point is approached, titrate dropwise, stirring thoroughly after each addition, until a blue color is produced immediately when a glass rod dipped into the titrated solution is streaked on starch-iodide test paper. One milliliter of 0.5 N sodium nitrite corresponds to 0.01426 g of o-tolidine dihydrochloride. Residue a f t e r ignition. Place 1 g in a tared porcelain crucible, add 0.5 mL of sulfuric acid, and slowly ignite in a hood. Heat in a furnace at 800 f 25 “ C to constant weight. The weight of the residue should not exceed 0.001 g. Sensitivity. Dissolve 0.135 g in 50 mL of water. Add this solution, with constant stirring, to 50 mL of dilute hydrochloric acid (3 7 ) . Add 1 mL of this solution to 20 mL of water containing 0.0025 g of free chlorine.* A distinct yellow color is produced. *Chlorine Standard (0.5 mL = 0.002 mg Cl). Pipet 1.0 mL of sodium hypochlorite and dilute with carbon dioxide-free water to 1 L. Solubility. Dissolve 0.5 g in 50 mL of water. Dissolution is complete and the solution is colorless to light yellow. (Any blue color seen initially will be caused by free chlorine in water, since this is a basic or neutral solution.) Water. Place 25 mL of methanol in a dry titration flask and add Karl Fischer reagent to a visually or electrometrically
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Calcium Chloride, Anhydrous (For drying) O n page 166 change the name of the reagent to Calcium Chloride Desiccant.
to percussion. For safety in transportation, trinitrophenol is usually mixed with a minimum of 10% of water. O n page 446, add the test cited below. Melting point (dried). Carefully transfer a small amount of dried sample (prepared in the test for Insoluble in benzene) to a capillary tube, and run the melting point using an oil immersion bath. O n page 446 i n the test for Insoluble in benzene, increase the quantity of sample i n the first sentence from “5 g” to “5 to 15g.”Also insert after the first sentence the note cited below. * (Note. Add water to the remaining dried sample before discarding it.) On page 446 in the test for Insoluble a n d resinous matter, replace “10 g” by “a sample equivalent to 10 g on a dry basis” i n the first line.
Formamide
Potassium Perchlorate
On page 276, change the requirement for Freezing point to “Not below 2.0 “C nor above 3.0 “C.” On page 276-277, delete the requirement and test for pH of 50% aqueous solution.
O n pages 503-504, revise the test for Heavy metals to read as follows: Heavy metals. Dissolve 3 g in hot water and dilute with water to 60 mL. For the control, add 0.01 mg of lead ion (Pb) to 10 mL of this solution and dilute with water to 50 mL. For the sample use the remaining 50-mL portion. Adjust the pH of the control and sample solutions to between 3 and 4 (using a pH meter) with 1 N acetic acid or ammonium hydroxide (10% NH3), and equalize if necessary the volumes of the two solutions with water. Add 10 mL of freshly prepared hydrogen sulfide water to each and mix. Any color in the solution of the sample should not exceed that in the control.
Hydrochloric Acid O n page 299, add the test for Appearance cited below. Appearance. Mix the material in the original container, pour 10 mL into a test tube (20 X 150 mm), and compare with distilled water in a similar tube. The liquids should be equally clear and free from suspended matter.
Magnesium Perchlorate (For drying) On page 373, change the name of the reagent to Magnesium Perchlorate Desiccant.
Methanol O n pages 400 and 402, change the expression for Acidity (as HCOOH) to Acidity (as CH3COOH).
Nitric Acid On page 418, add the Note cited below. Note. This material may darken during storage due to a photochemical reaction.
Picric Acid O n page 446 add the Caution cited below. Caution. Trinitrophenol explodes when heated rapidly or when subjected
ANALYTICAL CHEMISTRY, VOL. 49, NO. 3 , MARCH 1977
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Silica Gel (For drying) On page ,528, change the name of the reagent to Silica Gel Desiccant. On line 5 of the test for Suitability f o r moisture absorption, change the limit for the increase i n weight from 31 r/O to 27%.
Sulfuric Acid On page 630 i n the requirements for Appearance a n d f o r Color (APHA), delete the phrase “as received and after dilution to 2 N.” Also on page 631 in the test for Color (APHA), delete the last sentence, and add the test for Appearance cited below. Appearance. Mix the material in the original container, pour 10 mL into a test tube (20 X 150 mm), and compare with distilled water in a similar tube. The liquids should be equally clear and free from suspended matter.
