AASHTO T 219-1987 Standard Method of Test for Testing Lime for Chemical Constituents and Particle Sizes《测定石灰化学组成和颗粒尺寸》.pdf

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1、Standard Method of Test for Testing Lime for Chemical Constituents and Particle Sizes AASHTO Designation: T 219-87 (2013)1American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3a T 219-1 AASHTO Standard Method of Test fo

2、r Testing Lime for Chemical Constituents and Particle Sizes AASHTO Designation: T 219-87 (2013)11. SCOPE 1.1. This test procedure is intended to serve as a reasonably accurate, fairly rapid means of determining the chemical limits of Type I hydrated lime and the particle size requirements of Types I

3、 and II hydrated lime on a routine basis. (See Note 1.) Note 1The chemical limits of Type II lime shall be determined in accordance with ASTM C25. 1.2. The entire procedure and the calculations it involves are based on certain hypothetical assumptions. Lime products by their very nature contain many

4、 ingredients other than those mentioned or considered in the test procedure. For our purposes, only the principal constituents usually present are considered. This aids greatly in the simplification of the test procedure to the obvious loss of some degree of accuracy. All test values to be reported

5、shall be rounded off to the first decimal place. Example: percent Ca(OH)2= 95.5 percent (rather than the 95.53 percent shown on the sample calculation sheets). The inherent accuracy obtainable through the use of this procedure is believed to be adequate for the purpose intended. The limitations of t

6、his test procedure, along with the object and intent of this same procedure, should be fully realized so that it may be evaluated as merely one approach to the problem of routine quality control. 1.2.1. The following applies to all specified limits in this standard: For the purposes of determining c

7、onformance with these specifications, an observed value or a calculated value shall be rounded off “to the nearest unit” in the last right-hand place of figures used in expressing the limiting value, in accordance with ASTM E29, Using Significant Digits in Test Data to Determine Conformance with Spe

8、cifications. 1.3. The values stated in SI units are to be regarded as the standard. 1.4. Refer to R 16 for regulatory information for chemicals. 1.5. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associa

9、ted with its use. It is the responsibility of the user of the standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 92, Wire-Cloth Sieves for Testing Purposes

10、M 231, Weighing Devices Used in the Testing of Materials R 16, Regulatory Information for Chemicals Used in AASHTO Tests T 192, Fineness of Hydraulic Cement by the 45-m (No. 325) Sieve 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is

11、a violation of applicable law.TS-3a T 219-2 AASHTO 2.2. ASTM Standards: C25, Standard Test Methods for Chemical Analysis of Limestone, Quicklime, and Hydrated Lime E29, Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications 3. APPARATUS 3.1. Electric

12、 Muffle Furnace with Temperature Controlling DeviceCapable of sustained operation at a temperature of 1100 11C (2012 20F). 3.2. Platinum CrucibleLow-form, wide-bottom type with reinforced rim and bottom, 30-mL capacity. 3.3. Metallic Tongs for Muffle Furnace750 mm in length. 3.4. BalancesA general-p

13、urpose balance shall have sufficient capacity, be readable to 0.1 percent of the sample mass or better, and conform to the requirements of M 231. The analytical balance shall conform to M 231, Class A. 3.5. Beakers400-mL capacity. 3.6. Buret100-mL capacity. 3.7. Buret50-mL capacity of alkali-resista

14、nt glass and fitted with a Teflon stopcock. 3.8. Magnetic-Type StirrerWith stirring bars preferably of the Teflon-covered type. 3.9. StopwatchWith 60-s long hand to indicate 0.2 s. The long hand is to complete one turn of the dial in 60 s. The watch should also have a short hand to register up to 30

15、 min. Operation should preferably be by successive depressions of the crown to accomplish starting, stopping, and returning to zero. 3.10. SievesConforming to M 92 as follows: 3.35, 2.00, 0.600, and 0.075 mm. 3.11. pH MeterHaving an accuracy of 0.1 pH. 3.12. pH Meter ElectrodeStandard combination. 3

16、.13. Desiccator. 4. REAGENTS 4.1. Reagent grade chemicals shall be used in all tests. 4.2. Acid Potassium Hydrogen PhthalateNational Institute of Standards and Technology Standard Sample or equal. 4.3. Bromphenol BlueTetrabromophenol sulfonphthalein. 4.4. Hydrochloric Acid. 4.5. Phenolphthalein Powd

17、er. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3a T 219-3 AASHTO 4.6. Potassium BiphthalateCrystal primary standard. This reagent is satisfactory for use as a pH standard used in Section 5.5. 4.7

18、. Sodium Hydroxide50 percent solution. 5. PREPARATION OF SPECIAL SOLUTIONS 5.1. Standardized Sodium Hydroxide Solution: 5.1.1. This solution shall have a normality of 1.000 0.015 when the normality of the solution is accurately determined by direct standardization against a National Institute for St

19、andards and Technology (NIST) Potassium Hydrogen Phthalate acidimetric standard. This acidimetric standard shall be used without prior crushing or drying. Once the standard sample bottle has been opened, it should be restoppered, sealed with plastic tape, and stored in a desiccator pending further u

20、se. For the purpose of this standardization, 8.1691 g of the prescribed acid potassium hydrogen phthalate shall be considered as equivalent to 40.00 mL of 1.000 Normal NaOH. 5.1.2. Prepare the desired volume of 1.0 Normal NaOH by measuring out 52.3 mL of the 50 percent NaOH solution and dilute with

21、distilled water to 1-L volume. 5.1.3. Standardize the sodium hydroxide solution by accurately determining the mass, to the nearest 0.1 mg, from 7.5 to 8.5 g of original acid potassium hydrogen phthalate. Transfer the weighed material to a 400-mL beaker. Add 185 mL of carbon dioxidefree distilled wat

22、er at a temperature of 25 to 28C (77 to 83F), and stir the mixture gently until the crystals dissolve. The carbonate-free distilled water can be prepared by boiling 1 L of distilled water and cooling it to room temperature. Add five drops of prepared phenolphthalein indicator, and titrate the prepar

23、ed standard with the sodium hydroxide solution to be standardized. Titrate to a visual end point of light pink, which will persist for at least 60 s. Record the number of mL of sodium hydroxide solution required for the titration. Calculate the normality of the sodium hydroxide solution as follows:

24、mass of acid potassium phthalate in gNaOHmL of NaOH requirehydrogend 0.204228N =(1) 5.2. Standardized Hydrochloric Acid SolutionThis solution shall have a normality of 1.000 0.015 when the normality is accurately determined by direct comparison with the previously standardized sodium hydroxide. This

25、 solution is prepared by adding 86 mL of concentrated HCl to the distilled water such that the final volume is 1 L. 5.2.1. Determine the normality of the acid solution according to the following procedure: Transfer an approximate 40-mL portion of the acid solution to be standardized into a 400-mL be

26、aker. Use a buret to deliver this volume and accurately record the volume delivered. Add 140 mL of distilled water plus five drops of the prepared phenolphthalein indicator to the contents of the beaker, and titrate the contents of the beaker by adding from a buret some of the previously standardize

27、d sodium hydroxide. Titrate to a visual end point of light pink, which will persist for at least 60 s. Record the number of mL of sodium hydroxide solution required for the titration. Calculate the normality of the hydrochloric acid solution as follows: mL of NaOH required of NaOH usedHCl = mL of HC

28、l usedNN(2) 5.3. Phenolphthalein Indicator SolutionPrepare this solution by dissolving 0.5 g of powdered phenolphthalein, A.C.S. Grade, in 50 mL of absolute ethyl alcohol and add 50 mL of distilled water. 2016 by the American Association of State Highway and Transportation Officials.All rights reser

29、ved. Duplication is a violation of applicable law.TS-3a T 219-4 AASHTO 5.4. Bromphenol Blue Indicator SolutionPrepare this solution by dissolving 0.1 g of powdered bromphenol blue in 7.5 mL of 0.02 Normal NaOH and dilute the resulting solution to 250 mL. 5.5. Potassium Hydrogen Phthalate Reference S

30、olution (0.05 Molar)Prepare this solution by dissolving 10.21 g of potassium biphthalate crystal primary standard in distilled water and dilute to 1 L. It is necessary to dry the salt before use in preparing this solution. 5.6. Color Reference Standard for Use with Bromphenol Blue Indicator Solution

31、Transfer 2.0 mL of the prepared bromphenol blue indicator solution to a 400-mL tall-form titration beaker. Add 250 mL of the 0.05 molar potassium hydrogen phthalate reference solution, and then add from a 10-mL buret 1.86 mL of the 1.000 Normal NaOH solution. The resulting solution should be blue co

32、lored with a slight purple cast. This solution should be tightly stoppered and set aside to act as a visual color reference standard for comparison purposes in the titration to pH 4.4. The end point of this solution, when prepared as directed, shall have a pH of 4.4 and be of the color described. 6.

33、 TEST PROCEDURE 6.1. Sample Preparation: 6.1.1. Take a representative 2-L (1/2-gal) portion of the powdered lime to be analyzed and mix well by thoroughly shaking, inverting, etc., in a 4-L (1-gal) bucket fitted with a double friction-type lid. 6.1.2. The portion of material chosen for actual analys

34、is shall be taken from the well-mixed material contained in the bucket. After each withdrawal, special precaution should be taken to replace the lid on the bucket so as to minimize atmospheric contamination of the material to be analyzed. 6.2. Titrimetric Analysis of Various Alkaline Components of t

35、he Sample: 6.2.1. Titration to pH 8.3 with HClWeigh out a 2.9- to 3.1-g portion of the well-mixed material contained in the bucket accurately to the third decimal place on an analytical-type balance. The weighed sample shall then be transferred quantitatively to a 400-mL beaker. Slowly add 150-mL of

36、 distilled water to the sample contained in the beaker, and titrate immediately with approximately 1.0 Normal HCl to a prescribed end point of pH 8.3 using the pH meter. Gentle stirring of the mixture to be titrated shall be accomplished through the use of a magnetic-type stirrer. The first 50 mL of

37、 titrant may be added rather rapidly, after which continued additions of titrant shall be made in “rapid dropwise” fashion until a pH indication of nine or slightly less is obtained. A suitable rate for this rapid dropwise addition has been found to be approximately 12 mL/min. After attaining a mome

38、ntary pH indication of nine, or slightly less, proceed with the titration by adding titrant at the rate of approximately 2 mL/min. until the pH is in the vicinity of pH 8.5, and then add acid in four-drop increments until the prescribed end point of 8.3 or slightly less for 60 s is reached. The pres

39、cribed end point for this portion of the titration shall be taken to that point at which the addition of one two-drop increment of titrant produces a pH meter indication of 8.3 or slightly less when observed exactly 60 s after the addition of titrant. The first occurrence of such an end point in the

40、 normal course of the titration shall be considered as the end point for this portion of the analysis. The volume of titrant required to reach this end point should be recorded before proceeding with the further addition of HCl. The end point can also be obtained by taking a series of readings of pH

41、 versus mL of HCl added and making a plot; the sharpest slope of the curve gives rise to the end point. 6.2.2. Titration to “Measured Excess” of HClAfter the pH 8.3 end point has been reached, continue to add hydrochloric acid titrant to the sample contained in the beaker to a point where a total of

42、 approximately 100 mL of titrant has been added to the sample since the beginning of the titration. The sample mixture contained in the titration beaker at this point shall be considered as containing a “measured excess” of hydrochloric acid. Record the total volume of acid added to the sample since

43、 the beginning of the titration before proceeding with the back-titration. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3a T 219-5 AASHTO 6.2.3. Back-Titration to pH 4.4 with NaOHTitrate the sample

44、 mixture plus the “measured excess” of hydrochloric acid contained in the beaker with approximately 1.0 Normal NaOH to a pH meter indication of 4.4 or of slightly greater than 4.4 when observed exactly 10 s after a one-drop addition of titrant. The first occurrence of such an end point in the normal

45、 course of the back-titration shall be taken to be the prescribed end point for this portion of the analysis. For an alternative method of obtaining the end point, see the last sentence in Section 6.2.1. 6.3. Determination of Percent Loss on IgnitionWeigh out 2.9 to 3.1 g, accurately to 0.1 mg, of t

46、he well-mixed material contained in the bucket. Transfer the material by means of a spatula directly from the bucket to a previously ignited and weighed platinum crucible, after which the crucible and sample portion that it contains shall be placed uncovered in an electric muffle furnace maintained

47、at a temperature of 1100C (2012F), where it shall be allowed to remain for a required ignition period of 3 h. After the sample has been ignited in this fashion, it should be removed from the furnace and placed on a piece of ceramic board for a period of 10 to 30 s prior to placing the crucible in a

48、desiccator for further cooling. If several samples are being run simultaneously, it has been found expedient to remove all of the samples from the furnace, place them on the ceramic board, and then proceed to place them in the desiccator. After they have been placed in the desiccator, replace the de

49、siccator lid with a small opening. The heated air will expand through the opening for a period of several seconds after which the lid should be closed. The residue for the loss on ignition shall be allowed to cool for 30 min prior to the mass determination. The mass determination shall take place promptly after the cooling period so as to avoid possible contamination of the highly reactive quicklime residue. The actual mass determination of this residue shall be accomplished as rapidly as possible so as to prevent hydration of th