BS 4258-7-1978 Methods of test for phosphoric acid (orthophosphoric acid) for industrial use - Determination of total phosphorus (V) oxide content quinoline phosphomolybdate gravim.pdf

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1、BRITISH STANDARD BS 4258-7: 1978 Methods of test for Phosphoric acid (orthophosphoric acid) for industrial use Part 7: Determination of total phosphorus(V) oxide content: quinoline phosphomolybdate gravimetric method UDC 661.634.2:546.185 325:543.21.062:546.185 31BS4258-7:1978 This British Standard,

2、 having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Executive Board on 31 January1978 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference CIC/25 Draft for comment 75/50841 DC ISBN 0 580 0

3、9918 0 Cooperating organizations The Chemicals Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Association of Fatty Acid Distillers British Tar Industry A

4、ssociation Chemical Industries Association* Chemical Society, Analytical Division Department of Health and Social Security Department of Industry, Chemicals and Textiles Division Department of Industry, Laboratory of the Government Chemist* Fertiliser Manufacturers Association Ltd.* Hydrocarbon Solv

5、ents Association Ministry of Agriculture, Fisheries and Food Ministry of Defence National Sulphuric Acid Association Paintmakers Association of Great Britain Ltd. Royal Institute of Public Health and Hygiene Soap and Detergent Industry Association Standardization of Tar Products Tests Committee The

6、organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Pharmacopoeia Commission Campden Food Preservation Research Association Flour Milling and Baking Research

7、Association Institute of Metal Finishing Institution of Water Engineers and Scientists National Association of Soft Drinks Manufacturers Society of Chemical Industry Textile Institute Individual expert Amendments issued since publication Amd. No. Date of issue CommentsBS4258-7:1978 BSI 09-1999 i Con

8、tents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 Field of application 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 1 7 Expression of results 2 8 Test report 3 Annex Publications relating to phosphoric acid and sodium phosphates for industrial use 4 Publicatio

9、ns referred to Inside back coverBS4258-7:1978 ii BSI 09-1999 Foreword This British Standard has been prepared under the direction of the Chemicals Standards Committee in order to provide methods for the analysis of phosphoric acid. For some years the United Kingdom has participated in the work of pr

10、eparing methods of test applicable to phosphoric acid for industrial use, organized by Subcommittee 6 (formerly Working Group 7), Phosphoric acid and condensed phosphates, of Technical Committee47, Chemistry, of the International Organization for Standardization (ISO). As international agreement is

11、reached on the methods, it is proposed to publish them as Parts of this British Standard. Part7 is based on ISO3706 “Phosphoric acid for industrial use (including foodstuffs) Determination of total phosphorus(V) oxide content Quinoline phosphomolybdate gravimetric method”, with the inclusion of some

12、 technical changes in the text; these are given below. The relevant passages are indicated by a vertical line in the margin. For printing purposes, the text of the International Standard has been used as the basis for the British Standard. The decimal comma has been used throughout; in British Stand

13、ards it is current practice to use a full point on the baseline as the decimal marker. Cross references. The related ISO publications listed in the annex correspond to Parts of this British Standard as follows. Clause reference Textual change 4.1 and 4.2.4 In ISO 3706, the relative density for hydro

14、chloric acid is given as approximately 1,19 g/ml, about38% (m/m) solution. 4.2.2 In ISO 3706, the relative density for nitric acid is given as approximately1,40g/ml, about68% (m/m) solution. 6.3 In the table in ISO3706, the heading of column2 is “aliquot part of solution A (6.1) to be taken”. 7.1.2

15、In ISO 3706, the equation is incorrectly printed as In the definition of m 4 , the word “homogenized” is incorrectly included before “assay sample”. NOTEThe corrected versions of the formula and the definition of m 4 , as printed in this British Standard, have been proposed by BSI as a technical cor

16、rection to the ISO text. Annex In ISO 3706, the title of ISO4285 was incorrectly given as “Sampling technique”. ISO publication Part of BS 4258 ISO/R 848 a Part 1 Determination of calcium content ISO/R 849 a Part 2 Determination of iron content ISO 2997 Part 3 Determination of sulphate content ISO 3

17、360 Part 4 Determination of fluorine content ISO 3361 Part 5 Determination of silica content ISO 3359 Part 6 Determination of arsenic content ISO 3706 Part 7 Determination of phosphorus(V) oxide content ISO 3707 Part 8 Determination of calcium content (flame atomic absorption method) ISO 3708 Part 9

18、 Determination of chloride contentBS4258-7:1978 BSI 09-1999 iii There is no British Standard corresponding to ISO/R 847 1)and it is not intended that one will be published as the method uses as a reagent the known carcinogen benzidine and ISO/TC47/SC6 has recommended that it be withdrawn. Additional

19、 information. This standard specifies methods of test only and should not be used as a specification defining limits of purity. Reference to the standard should be in the form of words indicating that the methods of test used comply with the requirements of BS 4258. With reference to clause4, water

20、complying with the requirements of BS3978 is suitable. 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

21、 obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 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 o

22、n the inside front cover. ISO publication Part of BS 4258 ISO 3709 Part 10 Determination of oxides of nitrogen content ISO 4285 b Part 11 cGuide to sampling techniques a At the time of publication of this British Standard, ISO/R 847, ISO/R 848 and ISO/R 849 have not been transformed into Internation

23、al Standards, although they are listed as such in the Annex. b The footnote on page 1 referring to ISO 4285 states that this is at the drafting stage; this is now published. c In course of preparation. 1) At the time of publication of this British Standard, ISO/R 847, ISO/R 848 and ISO/R 849 have no

24、t been transformed into International Standards, although they are listed as such in the Annex.iv blankBS4258-7:1978 BSI 09-1999 1 1 Scope This British Standard specifies a gravimetric method using quinoline phosphomolybdate for the determination of the total phosphorus(V) oxide content of phosphori

25、c acid for industrial use (including foodstuffs). 2 Field of application The method is applicable to phosphoric acids, whether or not they are homogeneous and whether or not they contain polyphosphoric acids. 3 Principle Preliminary hydrolysis of the polyphosphoric acids by boiling in the presence o

26、f hydrochloric acid. Precipitation of the phosphoric acid in the form of quinoline phosphomolybdate in the presence of acetone. Filtration, washing, drying and weighing of the precipitate. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or wa

27、ter of equivalent purity. 4.1 Hydrochloric acid, approximately 1,18 g/ml, about36% (m/m) or approximately 12 N solution. 4.2 Citromolybdate reagent 4.2.1 Dissolve70g of sodium molybdate dihydrate (Na 2 MoO 4 .2H 2 O) in 150 ml of water. 4.2.2 Dissolve60g of citric acid monohydrate (C 6 H 8 O 7 .H 2

28、O) in 150 ml of water and add85ml of nitric acid solution, approximately 1,42g/ml, about70% (m/m) or approximately 14 N solution. 4.2.3 Add, while stirring, solution4.2.1 to solution4.2.2. 4.2.4 Add 35 ml of nitric acid solution, approximately 1,42g/ml, about70% (m/m) or approximately14 N solution,

29、then5ml of recently distilled quinoline to100ml of water. 4.2.5 Add solution (4.2.4) to solution (4.2.3) and mix. Allow to stand for at least12h and filter through the filter crucible (5.1). Store this solution protected from light, in a well-stoppered flask. 4.2.6 Add 280 ml of acetone to solution

30、(4.2.5) and dilute to1000ml with water. Do not keep this solution for more than1week. Store under the same conditions as solution (4.2.5). 5 Apparatus Ordinary laboratory apparatus and 5.1 Filter crucible, with sintered glass disk, of porosity P10 (pore size index between4 and10m). 5.2 Electric oven

31、, capable of being controlled at250 10 C. 6 Procedure 6.1 Test portion and preparation of the test solution 6.1.1 Homogeneous phosphoric acid (or phosphoric acid containing a precipitate which readily forms a suspension) Weigh by difference, to the nearest0,0002g, 5 0,2g of the test sample, in such

32、a way that there is no gain or loss of moisture. Transfer the test portion to a flask of about250ml capacity, add10ml of the hydrochloric acid solution(4.1), cover with a clock-glass and boil for about10min. Cool, add about100ml of water and10ml of the hydrochloric acid solution (4.1). Transfer the

33、solution quantitatively to a500ml one-mark volumetric flask, dilute to the mark and mix. Transfer50,0ml of this solution to a500ml one-mark volumetric flask, dilute to the mark and mix (solution A). Prepare this dilution at the time of use. 6.1.2 Non-homogeneous phosphoric acid, containing a precipi

34、tate which does not readily form a suspension Weigh by difference, to the nearest0,05%, the whole of the assay sample 2) , in such a way that there is no gain or loss of moisture. Transfer the sample to a polyethylene or polypropylene flask of suitable capacity, and homogenize by dilution or any oth

35、er method which does not involve any loss of the constituents. 2) The definition of the term “assay sample” will be given in ISO4285, Phosphoric acid for industrial use Sampling technique. (At present at the stage of draft.) If the assay sample is not available, a test sample may be taken from the l

36、aboratory sample, which must first be thoroughly mixed so as to render it completely homogeneous. In this case, weigh, to the nearest0,05%, about25g and treat it as described for the assay sample.BS4258-7:1978 2 BSI 09-1999 After homogenizing, weigh by difference, to the nearest 0,05%, a test portio

37、n containing about5g of the original phosphoric acid, place in a250ml beaker and add10ml of the hydrochloric acid solution (4.1) cover with a clock-glass and boil for about10min. Cool, add about 100 ml of water and10ml of the hydrochloric acid solution (4.1). Transfer the solution quantitatively to

38、a500ml one-mark volumetric flask, dilute to the mark and mix. Transfer 50,0ml of this solution to a500ml one-mark volumetric flask, dilute to the mark and mix (solution A). Prepare this dilution at the time of use and filter if necessary. NOTEHomogenization may generally be achieved by simple diluti

39、on with water (or dilute hydrochloric acid solution), with prolonged stirring in a stoppered flask, the quantity of liquid added being weighed to the nearest0,05%. When this treatment is insufficient, a more effective treatment should be carried out depending on the particular case (treatment with h

40、ot water with stirring in a stoppered flask, for example). Finally, in the case where an insoluble deposit remains which adheres to the walls of the vessel containing the assay sample or which cannot be dispersed, it should be recovered, weighed and analysed separately. 6.2 Blank test Carry out a bl

41、ank test at the same time as the determination, following the same procedure and using the same quantities of all the reagents as used in the determination. 6.3 Determination Depending on the expected phosphorus(V) oxide content, transfer to a400ml beaker the aliquot portion of solution A (6.1) show

42、n in the following table. Dilute to about 100ml and add 100ml of the citro-molybdate reagent (4.2). Cover the beaker with a clock-glass and warm, inside a fume cupboard, on a hot-plate, until its contents reach75 5 C and maintain at this temperature for about30s. (Do not use a flame and do not mix,

43、either during the addition of the reagent or during the heating, so as to avoid the formation of clots.) Allow to cool to ambient temperature, stirring three or four times with a glass rod during cooling. Heat the filter crucible (5.1) in the oven (5.2) controlled at250 10 C, and leave for15min star

44、ting from the stabilization of the temperature. Allow to cool in a desiccator containing silica gel in good condition and weigh to the nearest0,0001g. Decant the liquid through the filter crucible (5.1) and wash the precipitate six times, by decantation, using about 30 ml of water each time. Transfe

45、r the precipitate quantitatively to the filter crucible (5.1) with the aid of a jet of water from a wash-bottle. Then wash the precipitate four times, removing each portion of wash water by suction. Place the filter crucible in the oven (5.2) maintained at250 10 C and leave for15min starting from th

46、e stabilization of the temperature. Allow to cool for not more than30min in a desiccator containing silica gel in good condition and weigh to the nearest0,0001g. 7 Expression of results 7.1 Method of calculation and formulae The total phosphorus(V) oxide content, expressed as a percentage by mass of

47、 P 2 O 5 , is given by the formulae: 7.1.1 Homogeneous phosphoric acid (see6.1.1) 7.1.2 Non-homogeneous phosphoric acid (see6.1.2) where m 0is the mass, in grams, of the test portion (6.1); m 1is the mass, in grams, of precipitate obtained with the aliquot portion of the test solution (6.3); m 2is t

48、he mass, in grams, of precipitate obtained with the corresponding aliquot portion of the blank test solution (6.2); m 3is the total mass, in grams, of water or other reagents added for the homogenization (see6.1.2, note); m 4is the mass, in grams, of assay sample taken (see6.1.2); Expected P 2 O 5co

49、ntent Aliquot portion of solution A (6.1) to be taken % (m/m) ml Less than 30 50 From 30 to 50 25 Greater than 50 20BS4258-7:1978 BSI 09-1999 3 D is the ratio of the volume of the test solution (solution A) (6.1) to the volume of the aliquot portion taken for the determination (6.3); 0,032 07 is the factor for conversion of quinoline phosphomolybdate to phosphorus(V) oxide. 8 Test report The test report shall include the following particulars: a) the reference of the method used; b) the results and the method of expression used; c) any unusual featu