1、BRITISH STANDARD BS 6870-2.3: 1987 ISO 6606:1986 Analysis of aluminium ores Part 2: Chemical methods Section 2.3 Method for determination of loss of mass at 1075 C: gravimetric method ISO title: Aluminium ores Determination of loss of mass at1075 C Gravimetric method UDC 553.492:543BS6870-2.3:1987 T
2、his British Standard, having been prepared under the directionof the Non-ferrous Metals Standards Committee,waspublished underthe authorityof the BoardofBSI and comesintoeffecton 28August1987 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference NFM/31 Dra
3、ft for comment 84/42825 DC ISBN 0 580 16055 6 National foreword This Section of BS6870 has been prepared under the direction of the Non-ferrous Metals Standards Committee. It is identical with ISO6606:1986 “Aluminium ores Determination of loss of mass at1075 C Gravimetric method”, published by the I
4、nternational Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standa
5、rds; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read
6、 as “Section of BS6870”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages
7、 This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. C
8、ross-reference International Standard Corresponding British Standard ISO 8557:1985 BS 6870 Analysis of aluminium ores Section 2.2:1987 Method for determination of hygroscopic moisture in analytical samples: gravimetric method (Identical) Amendments issued since publication Amd. No. Date of issue Com
9、mentsBS6870-2.3:1987 BSI 12-1999 i Contents Page National foreword Inside front cover 0 Introduction 1 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Apparatus 1 5 Sampling and samples 1 6 Procedure 1 7 Expression of results 2 8 Test report 3 Table Precision data for loss of mass d
10、eterminations 2 Publication referred to Inside back cover4 blankBS6870-2.3:1987 BSI 12-1999 1 0 Introduction Aluminium ores when heated undergo a loss of mass. At temperatures up to 110 C the loss is due to hygroscopic moisture. At higher temperatures the loss of mass is due largely to the dissociat
11、ion of hydroxides and oxyhydroxides of aluminium and iron and also, to a lesser degree, to the dissociation of minor constituents. The total loss of mass is a function of the temperature and time of heating. There are no conditions at which the loss represents exclusively the water (hygroscopic and
12、combined) in the sample. The temperature chosen for the test,1075 C, is a compromise between such factors as furnace suitability and the absorption of water by the sample during cooling. The value obtained for loss on ignition is calculated on the basis of a dried sample. The test portion is heated
13、initially at375 25 C and finally at1075 25 C and the loss of mass determined. The crucible is covered with a loose-fitting lid after the test portion is placed in the crucible and this is left in position throughout all the subsequent operations. The presence of the lid contributes to more reproduci
14、ble results by preventing the random effects of small pieces of furnace lining falling into the crucible during heating and does not interfere with the maintenance of oxidizing conditions in the crucible. 1 Scope and field of application This International Standard specifies a gravimetric method for
15、 the determination of the loss of mass of analytical samples of aluminium ores when heated to constant mass at1075 C. The method is applicable to all aluminium ores having loss of mass values in the range of10to30%. 2 Reference ISO 8557, Aluminium ores Determination of hygroscopic moisture of analyt
16、ical samples Gravimetric method. 3 Principle Heating of a test portion in a tared crucible in a furnace at375 25 C for10min. Transfer of the covered crucible to a second furnace at1075 25 C and heating to constant mass. Correction of the resultant loss in mass for the original hygroscopic moisture.
17、4 Apparatus Ordinary laboratory apparatus and 4.1 Dishes, of inert material of sufficient size to take the required quantity of sample at a layer density of5mg/mm 2 . 4.2 Platinum crucible, approximately30mm top diameter,20mm bottom diameter and35mm deep, with matching platinum lid. 4.3 Electric fur
18、naces, capable of being controlled at375 25 C and at1075 25 C, and having provision for a flow of air through the heated cavity. 4.4 Balance, capable of being read to0,0001g. 4.5 Desiccator, containing either fresh magnesium perchlorate or activated alumina as desiccant. NOTE 1Activated alumina shou
19、ld be activated by heating at300 10 C overnight. NOTE 2When discarding magnesium perchlorate, flush down the sink using copious quantities of water. 5 Sampling and samples 5.1 Samples Laboratory samples shall be taken and crushed to pass a 1504m test sieve, in accordance with the methods specified i
20、n the relevant standards. 1) 5.2 Preparation of the test sample Take approximately10g of the laboratory sample and place in a flat dish (4.1). Spread the sample evenly to give a layer density of approximately5mg/mm 2and allow to equilibrate with the laboratory atmosphere for a minimum of2h. 6 Proced
21、ure 6.1 Number of determinations Carry out the determination in duplicate on each ore sample. NOTEThe principle of carrying out a blank determination and a check test does not apply to this method. 6.2 Preparation of crucible and test portion Heat the platinum crucible(4.2) and lid in the furnace(4.
22、3) controlled at1075 25 C for15min. Remove the covered crucible from the furnace and place in the desiccator(4.5) to cool. Weigh the crucible and lid, to the nearest0,0002g, as rapidly as possible after they have cooled to ambient temperature and within1h of placing them in the desiccator. 1) Where
23、no International Standards exist, the relevant standards shall be the national standards. Two International Standards on this subject are currently in preparation: ISO6137, Aluminium ores Method of sampling, and ISO6140, Aluminium ores Preparation of samples.BS6870-2.3:1987 2 BSI 12-1999 Add approxi
24、mately1g ( 0,01g) of the test sample to the platinum crucible, distribute it evenly over the bottom of the crucible, replace the lid and weigh the crucible, lid and contents to the nearest0,0002g. Record the mass of the test portion (m 1 ) At the same time, weigh test portions for the determination
25、of hygroscopic moisture by the procedure specified in ISO8557. 6.3 Determination of loss on ignition Place the covered crucible and contents, with the lid slightly displaced, in the furnace(4.3) controlled at375 25 C and heat for10 1min. Transfer the partially covered crucible and contents to the fu
26、rnace controlled at1075 25 C and heat for602min. Remove the covered crucible and contents from the furnace, ensuring that the lid is now fully in position, and place in the desiccator to cool. Weigh the covered crucible and contents, to the nearest0,0002g, as rapidly as possible after they have cool
27、ed to ambient temperature and within1h after they have been placed in the desiccator. NOTEPrior to each weighing, inspect the outside of the crucible lid and brush if necessary. Return the covered crucible and contents to the furnace controlled at1075 25 C and heat for a further30 2min. Allow to coo
28、l in the desiccator and re-weigh as soon as possible after the crucible and contents have cooled to ambient temperature and within1h of placing them in the desiccator. If the difference between the weighings after the first and second heatings at1075 C exceeds0,0005g, repeat the heating, cooling and
29、 weighing steps, until this requirement is met. Use the minimum mass of the crucible, lid and contents to calculate the minimum mass of the heated sample (m 2 ). 7 Expression of results 7.1 Calculation of the loss on ignition Calculate the loss on ignition (LOI), expressed as a percentage by mass, u
30、sing the formula where 7.2 General treatment of results 7.2.1 Precision A planned trial of the method was carried out by nine countries with a total of sixteen laboratories participating. Two determinations were carried out by each analyst on each of four samples. From the results obtained, the repe
31、atability, reproducibility and reproducibility index have been calculated and are presented in the following Table. Table Precision data for loss of mass determinations where 7.2.2 Acceptance of analytical values The analytical value for the test sample shall be accepted when the difference between
32、the two values for the test sample does not exceed2.77s was calculated from the appropriate value of S wgiven in the Table. When the range (absolute difference) of the two values for the test sample is greater than2,77s w , additional determinations shall be carried out on the test sample. 7.2.3 Cal
33、culation of final result The final result is the arithmetical mean of the values for the test portions calculated to the fourth decimal place and rounded off to the second decimal place as follows: 1) When the figure in the third decimal place is less than5, it is discarded and the figure in the sec
34、ond decimal place is kept unchanged. 2) When the figure in the third decimal place is5and there are figures other than0in the fourth decimal places, or when the figure in the third decimal place is greater than5, the figure in the second decimal place is increased by one. m 1 is the mass, in grams,
35、of the test portion; m 2 is the mass, in grams, of the test portion after heating; H is the hygroscopic moisture content, as a percentage by mass, of the equilibrated sample. Sample Mean loss in mass at 1075 C Components ofstandard deviation Reproducibility index %(m/m) s w s b 2s MT/12/12 14,47 0,0
36、64 0,215 0,45 MT/12/4 25,24 0,050 0,126 0,27 MT/12/1 26,43 0,090 0,101 0,27 MT/12/9 27,53 0,078 0,195 0,42 s w is the within-laboratory standard deviation; s b is the between-laboratories standard deviation.BS6870-2.3:1987 BSI 12-1999 3 3) When the figure in the third decimal place is5and there are
37、no figures other than 0 in the fourth decimal places, the5is discarded and the figure in the second decimal place is kept unchanged if it is0,2,4,6or8and is increased by one if it is1,3,5,7or9. 8 Test report The test report shall include the following information: a) details necessary for the identi
38、fication of the sample; b) reference to this International Standard; c) the result of the analysis; d) reference number of the result; e) any characteristics noticed during the determination and any operations not specified in this International Standard which may have had an influence on the result
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