BS 4431-1989 Methods of sampling and test for liquefied anhydrous ammonia《液化无水氨的取样和试验方法》.pdf

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1、BRITISH STANDARD BS 4431:1989 Methods of sampling and test for Liquefied anhydrous ammonia UDC 661.518:543BS4431:1989 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes into effect on 30J

2、une1989 BSI 08-1999 First published February 1969 First revision June 1989 The following BSI references relate to the work on this standard: Committee reference CIC/37 (formerly CIC/21) Draft for comment 87/50629 DC ISBN 0 580 17065 9 Committees responsible for this British Standard The preparation

3、of this British Standard was entrusted by the Chemicals Standards Committee (CIC/-) to Technical Committee CIC/37 (formerly CIC/21) upon which the following bodies were represented: Association of Public Analysts British Coal Corporation Chemical Industries Association Department of Trade and Indust

4、ry (Laboratory of the Government Chemist) Fertiliser Manufacturers Association Ltd. Institute of Trading Standards Administration Ministry of Agriculture, Fisheries and Food Ministry of Defence Amendments issued since publication Amd. No. Date of issue CommentsBS4431:1989 BSI 08-1999 i Contents Page

5、 Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Method for collecting the test portion 1 3 Determination of residue on evaporation 3 4 Determination of oil content by the gravimetric method 3 5 Determination of oil content by the infra-red spectrometric method 4 6 Determination of

6、 water content by the Karl Fischer method 5 7 Determination of carbon dioxide content 6 8 Test report 6 9 Method of sampling for the subsequent determination of oxygen by gas chromatography 7 Appendix A Guidance on the sampling of liquefied anhydrous ammonia 8 Appendix B Determination of the evapora

7、tion factor, F 10 Figure 1 Apparatus for collecting the test portion 2 Figure 2 Diagram of sampling apparatus for the subsequent determination of oxygen by gas chromatography 7 Figure 3 Illustration of equipment for sampling from tank wagons and storage tanks 9 Figure 4 Graph of evaporation factor a

8、gainst pressure in vessel 11 Table 1 Standard oil solutions for calibration graph 5 Publications referred to Inside back coverBS4431:1989 ii BSI 08-1999 Foreword This British Standard has been prepared under the direction of the Chemicals Standards Committee. It supersedes BS4431:1969, which is with

9、drawn. The principal differences between this revision and the previous edition are as follows: a) a general procedure for taking the test portion has been introduced, based on international test methods; b) a method of sampling for the determination of oxygen is described; c) a general test report

10、clause has been introduced. For many years the UK has participated in the work of Sub-committee4, of Technical Committee47, Chemistry, of the International Organization for Standardization (ISO). However, ISO7103-1982 “Liquefied anhydrous ammonia for industrial use Sampling Taking a laboratory sampl

11、e”, which was produced by Technical Committee47, was disapproved by the UK as the procedure is not used in the UK. ISO test methods applicable to anhydrous ammonia will not be implemented as Parts of BS4431 as they refer to ISO7103. This revision retains the guidance on sampling given in the previou

12、s edition and therefore the use of the evaporation factor has been retained for the calculation of results. Where appropriate, the methods have been based on international test methods, and the International Standards that are related to the methods described in the clauses are as follows. The metho

13、d for determination of water content, described in clause6, refers frequently to BS2511:1970, possession of which is essential. It was assumed in the drafting of this British Standard that the methods described would be carried out by fully trained and supervised personnel. WARNING. Liquefied anhydr

14、ous ammonia is a highly corrosive, toxic substance, which boils at33.3 C at standard atmospheric pressure. Its action on the skin is strongly corrosive, producing severe and painful burns. Contact with the eyes can cause permanent blindness. Its vapour is strongly irritant to the mucous membrane and

15、 eyes, and produces a suffocating effect on the respiratory tract. Obtain advice for the safe storage and handling of liquefied anhydrous ammonia from manufacturers and suppliers. Prohibit smoking and sources of ignition during the sampling of ammonia. NOTEMixtures of ammonia gas and air can explode

16、, if ignited, when the proportion of ammonia gas is within the limits of16% to27% by volume. 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 no

17、t of itself confer immunity from legal obligations. Clause Related International Standard 2 3 ISO4276 4 5 ISO7106 6 ISO7105 Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to12, an inside back cover and a back cover. This standard has been updated

18、(see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS4431:1989 BSI 08-1999 1 1 Scope This British Standard describes methods of test and sampling for liquefied anhydrous ammonia suitable for general industrial purpos

19、es. NOTE 1In the methods described the ammonia is sampled by volume but the calculations are by mass. The density has been taken as0.68g/mL, at about33 C, at which temperature liquid ammonia has a vapour pressure of10 5Pa 1) . A corrective evaporation factor is applied in each case to allow for loss

20、 through sampling at atmospheric pressure. Clause2 describes a general method for collecting the test portion with minor variations given for particular methods. Clause3 describes a method for the determination of residue on evaporation, which applies to products giving a residue value greater than

21、or equal to100mg/kg. Clause4 describes a gravimetric method for the determination of the oil content (non-volatile at about105 C), which applies to products having an oil content greater than or equal to10mg/kg. Clause5 describes a method for the determination of the oil content (non-volatile at abo

22、ut105 C) in which the method used for the isolation of the oil content is as described in clause4, but the determination is made using infra-red spectrometry. This is more sensitive than the gravimetric method and applies to products with an oil content less than10mg/kg. Clause6 describes a method f

23、or the determination of the water content by the Karl Fischer method, which applies to products with a water content greater than or equal to25mg/kg. Clause7 describes the determination of carbon dioxide by a titrimetric method, which applies to products with a carbon dioxide content greater than or

24、 equal to15mg/kg. Clause9 describes a method of sampling for the subsequent determination of oxygen by gas chromatography. In Appendix A guidance is given on the sampling of anhydrous ammonia and in Appendix B a method for the determination of the evaporation factor, F, is described. NOTE 2The title

25、s of the publications referred to in this standard are listed on the inside back cover. 2 Method for collecting the test portion 2.1 Principle A known volume of anhydrous ammonia is collected in a graduated, chilled(35 C to 40 C) glass tube fitted with a modified Drechsel head and is allowed to begi

26、n to evaporate at ambient temperature and pressure. 2.2 Reagents 2.2.1 General. During the collection of the test portion, use only reagents of recognized analytical grade and water complying with grade3 of BS3978. 2.2.2 Ethanediol (ethylene glycol), of water content not greater than0.1%(m/m). NOTEC

27、are should be taken to avoid absorption of atmospheric moisture as ethanediol is very hygroscopic. 2.2.3 Barium hydroxide, standard volumetric solution, c(Ba(OH) 2 )=0.05mol/L. Weigh, to the nearest0.0005g,15.774g of barium hydroxide octahydrate (Ba(OH) 2 .8H 2O), dissolve in a little water, transfe

28、r quantitatively the solution to the one-mark volumetric flask(2.3.2), dilute to the mark and mix. 2.2.4 Freezing mixture, consisting of solid carbon dioxide and methanol (technical grade is suitable), capable of reaching a temperature of between35 C and40 C. 2.3 Apparatus 2.3.1 General. Use ordinar

29、y laboratory apparatus and the following. 2.3.2 One-mark volumetric flask,1000mL, complying with BS1792. 2.3.3 Apparatus for collecting the test portion (seeFigure 1). 2.3.3.1 Glass test tube of total capacity 250mL, having a reference mark at200mL, fitted via a24/29 ground glass modified Drechsel h

30、ead to an arm with a three-way stopcock, with a key made from polytetrafluoroethylene (PTFE), and a side arm(3). 2.3.3.2 Dewar vessel, capable of containing the test tube(2.3.3.1) and the freezing mixture(2.2.4) while leaving the graduation mark visible. 2.4 Procedure 2.4.1 General. Carry out the pr

31、ocedure in accordance with2.4.2, if appropriate, and2.4.3. Do not attempt to subdivide the test portion. 2.4.2 Additional details for test portions to be used in the methods described in clauses3, 6 and7. 1) 10 5Pa =10 5 N/m 2=1bar.BS4431:1989 2 BSI 08-1999 2.4.2.1 Clause3. Initially weigh the test

32、tube assembly(2.3.3.1) to the nearest0.0001g. 2.4.2.2 Clause6. Introduce2mL of the ethanediol(2.2.2) into the test tube immediately before assembling the apparatus(2.3.3). 2.4.2.3 Clause7. Add10.0mL of the standard barium hydroxide solution(2.2.3) to the test tube before assembling the apparatus(2.3

33、.3). NOTEWhen sampling direct from a cylinder or other pressurized vessel (seeAppendix A), note the gauge pressure at that time in order to determine the evaporation factor, F (seeAppendix B). 2.4.3 Common details. Three-quarters fill the Dewar vessel(2.3.3.2) with the freezing mixture(2.2.4), immer

34、se the test tube(2.3.3.1) in the Dewar vessel(2.3.3.2) and insert the modified Drechsel head (see2.3.3.1). Connect the inlet arm(1) to the ammonia sample point and attach to the outlet arms(2) and(3) pieces of tubing of sufficient length to lead away the escaping ammonia safely. Ensure that the liqu

35、id anhydrous ammonia flow is controlled by means of a by-pass so that the apparatus is not subjected to high pressures. Quickly turn the stopcock to introduce the liquid anhydrous ammonia into the test tube. As soon as the liquid anhydrous ammonia has reached the200mL graduation mark, turn the stopc

36、ock to isolate the branch into the test tube and to open the outlet arm(2). Close the liquid anhydrous ammonia sample point valve to allow the liquid ammonia in the inlet and outlet arms(1 and2 respectively) to evaporate before disconnecting the apparatus. Remove the test tube containing the test po

37、rtion from the Dewar flask and place it in a bath of cold running water. Allow the ammonia to evaporate slowly through arm(3). Turn the stopcock to the open position to ensure that no liquid anhydrous ammonia is trapped within the valve. NOTENumbers in parentheses in medium type refer to Figure 1. F

38、igure 1 Apparatus for collecting the test portionBS4431:1989 BSI 08-1999 3 3 Determination of residue on evaporation 3.1 Principle A test portion is evaporated at ambient temperature, the residue is weighed and the residual ammonia is titrated with standard sulphuric acid solution and the residue is

39、 calculated by difference. 3.2 Reagents 3.2.1 General. During the analysis, use only reagents of recognized analytical grade and water complying with grade3 of BS3978. 3.2.2 Sulphuric acid, standard volumetric solution, c(H 2SO 4 )=0.050mol/L. 3.2.3 Methyl red indicator solution,1g/L in95% (V/V) eth

40、anol. NOTEThe ethanol may be replaced by industrial methylated spirits95% (V/V) complying with BS3591, or such spirits diluted as required. It should be noted that the use of industrial methylated spirits is governed by the Methylated Spirits Regulations,1983 (SI1983 No.252). It is not permissible t

41、o use duty-free ethanol, received under the provisions of the Alcoholic Liquors Duties Act1972, Section10, for purposes for which industrial methylated spirits is an acceptable alternative. 3.3 Apparatus Use ordinary laboratory apparatus. 3.4 Procedure Collect the test portion in accordance with cla

42、use2. When the evaporation of ammonia is complete, apply gentle suction to the outlet to remove residual ammonia. Allow the test tube assembly to reach ambient temperature, wipe with a clean, dry cloth and weigh to the nearest0.0001g. Remove the modified Drechsel head(see2.3.3.1) and add about50mL o

43、f water to the test tube. Add one or two drops of the methyl red indicator solution(3.2.3) and titrate with the sulphuric acid solution(3.2.2) until the indicator changes from yellow to red. 3.5 Expression of results The residue on evaporation, expressed as a percentage by mass, is given by the expr

44、ession 4 Determination of oil content by the gravimetric method 4.1 Principle A test portion is evaporated at ambient temperature, the oil in the residue is extracted with1,1,2-trichlorotrifluoroethane, the organic solvent is evaporated and the resulting residue is weighed. 4.2 Reagents 4.2.1 Genera

45、l. During the analysis, use only reagents of recognized analytical grade and water complying with grade3 of BS3978. 4.2.2 Solvent, 1, 1, 2-trichlorotrifluoroethane. 4.2.3 Hydrochloric acid solution, c (HCl)=40g/L, (made up by diluting hydrochloric acid of density approximately1.19g/mL). 4.2.4 Methyl

46、 red indicator solution, as described in3.2.3. 4.2.5 Silica gel, complying with BS3523. 4.3 Apparatus 4.3.1 General. Use ordinary laboratory apparatus and the following. 4.3.2 Electric oven, capable of being controlled at105 2 C. 4.3.3 Platinum dish, capacity approximately70mL. 4.4 Procedure 4.4.1 T

47、est portion. Collect the test portion in accordance with clause2. 4.4.2 Isolation of the oil. When the evaporation of ammonia is complete, apply gentle suction to the outlet tube to remove residual ammonia. where M 1 is the mass of the test tube assembly (in g); M 2 is the mass of the test tube asse

48、mbly containing the residue after evaporation(ing), M 3 is the mass of ammonia in the residue after evaporation (in g) and is given by the expression V 1 0.0017 where V 1 is the number of millilitres of the sulphuric acid solution used for the titration (in mL); 0.0017 is the mass of ammonia (NH 3 )

49、 equivalent to1mL of the standard volumetric sulphuric acid solution(in g); F is the evaporation factor (seeAppendix B); 200 is the volume of liquid ammonia collected in the test tube (in mL); is the density of liquid ammonia, i.e.0.68(ing/mL).BS4431:1989 4 BSI 08-1999 Heat the platinum dish(4.3.3) for30min in the electric oven(4.3.2) controlled at105 2 C. Allow to cool to ambient temperature in a desiccator containing the activated silica gel(4.2.5) and weigh to the nearest0.0001g. Add a little water and several drops of the hyd