BS 5086-4-1985 Analysis of butter - Method for determination of salt content (reference method)《黄油分析 第4部分 盐含量测定方法(比对法)》.pdf

1、BRITISH STANDARD BS 5086-4: 1985 Analysis of butter Part 4: Method for determination of salt content (reference method) NOTEThis Part should be read in conjunction with Part1 “General introduction including preparation of samples”, published separately. UDC 637.2.074BS 5086-4:1985 This British Stand

2、ard, having been prepared under the direction of the Dairying Standards Committee, was published under the authorityofthe Board of BSIandcomes into effect on 31 January 1985 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference DAC/3 Draft for comment 83/5

3、5180 DC ISBN 0 580 14080 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Dairying Standards Committee (DAC/-) to Technical Committee DAC/3, upon which the following bodies were represented: Association of British Preserved Milk Manufac

4、turers Association of Public Analysts Association of Public Analysts of Scotland British Food Manufacturing Industries Research Association Creamery Proprietors Association Dairy Trade Federation Department of Trade and Industry (Laboratory of the Government Chemist) Ice Cream Alliance Limited Inter

5、vention Board for Agricultural Produce Joint Committee of the Milk Marketing Board and the Dairy Trade Federation Milk Marketing Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food National Institute for Research in Dairying Royal Association of British Dairy

6、Farmers Royal Society of Chemistry Society of Chemical Industry Society of Dairy Technology University of Reading Coopted members Amendments issued since publication Amd. No. Date of issue CommentsBS5086-4:1985 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope

7、 1 2 Definitions 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 1 7 Expression of results 2 8 Repeatability 2 9 Test report 2 Publications referred to Inside back coverBS 5086-4:1985 ii BSI 07-1999 Foreword This Part of BS5086 has been prepared under the direction of the Dairying Standards C

8、ommittee. It supersedes clause5 of BS769, which is deleted by amendment. The amount of salt is an important matter to the butter maker, or blender, and this reference method can be used to calibrate other methods and in cases of dispute. Part5 of this standard gives a rapid routine method for use du

9、ring processing. 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 This do

10、cument comprises a front cover, an inside front cover, pages i and ii, pages1and2, 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.BS5086-4:198

11、5 BSI 07-1999 1 1 Scope This Part of BS5086 describes a reference method for the determination of the salt content of butter of all types. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS 5086, the

12、following definition applies. salt content chloride content, as determined by this method, expressed as the equivalent content of sodium chloride 3 Principle The destruction of the organic matter by digestion with nitric acid is followed by argentometric titration in nitric acid solution. 4 Reagents

13、 The following reagents, which shall be of analytical reagent quality, are required. 4.1 Nitric acid, concentrated,69.0% to71.0%(m/m) (d 20= 1.42). 4.2 Nitric acid, approximately5mol/L. 4.3 Silver nitrate solution, approximately0.05mol/L. Calculate the exact concentration as follows. Prepare a0.1mol

14、/L solution of sodium chloride by dissolving 5.844 g of the salt (A R grade) in 1 L water. (The sodium chloride shall have previously been heated to300C for 1 h, and then allowed to cool in a desiccator charged with a suitable desiccant.) Pipette 10 mL sodium chloride solution into a250mL flask and

15、add1mL potassium chromate indicator solution (approximately39g/L). Titrate with the silver nitrate solution until an orange tint that persists for 30 s is obtained. Record the volume of silver nitrate solution used and calculate its concentration. 4.4 Ammonium iron (III) sulphate (ferric alum) indic

16、ator solution, saturated. Dissolve50g of ammonium iron (III) sulphate (NH 4 Fe (SO 4 ) 2 12H 2 O) in95mL of water and5mL of5mol/L nitric acid (4.2). 4.5 Potassium thiocyanate solution, approximately 0.05mol/L and standardize as follows. Pipette20mL of silver nitrate solution (4.3) into a250mL conica

17、l flask and add 25mL water,5mL5mol/L nitric acid (4.2) and 1 mL ammonium iron (III) sulphate solution (4.4). Titrate with the potassium thiocyanate solution and calculate its concentration. 4.6 Water, complying with the requirements of BS3978. 5 Apparatus Usual laboratory apparatus is required and,

18、in particular, the following. 5.1 Balance, capable of weighing to an accuracy of 0.1mg. 5.2 Conical flasks, wide-necked, of250mL capacity. 5.3 Pipette, 25mL capacity, class B, complying with the requirements of BS1583. 5.4 Graduated measuring cylinders, 15mL,25mL and100mL capacities complying with t

19、he requirements of BS604. 5.5 Burette, 50mL, class B, complying with the requirements of BS846. 6 Procedure 6.1 Weigh1.8g to2.2g of the sample, to the nearest0.001g, prepared as described in BS5086-1 into a250mL conical flask (5.2) and add 1.0 mL water (4.6) and25mL of the0.05mol/L silver nitrate so

20、lution (4.3). Warm the contents of the flask to melt the butter and shake well. Add10mL of concentrated nitric acid (4.1) and gently boil the contents of the flask until the curd is digested, i.e.the liquid is clear and the layer of fat is clear and free from solid material. NOTE 1Glass beads or oth

21、er anti-bumping agents may be added to the flask. NOTE 2If convenient, the flask and contents may be allowed to cool before proceeding. Add2mL of ammonium iron (III) sulphate (4.4) indicator solution and50mL water (4.6). Mix thoroughly and immediately titrate the excess silver nitrate with the potas

22、sium thiocyanate solution(4.5) until the solution in the flask shows an orange tint which persists for about15 s. In the same manner, carry out a blank test, determining the equivalent of25mL of the silver nitrate solution (4.3) as thiocyanate using the same volume of reagents and water (4.6) and su

23、bstituting2mL water for the test portion. 6.2 Repeat the procedure described in6.1 on another test portion.BS 5086-4:1985 2 BSI 07-1999 7 Expression of results 7.1 Calculation Calculate each duplicate value for salt content as a percentage using the following equation. Salt content = 7.2 Mean value

24、Provided that the duplicate values calculated as described in7.1 comply with the repeatability requirement of clause8, calculate the mean value and express the result to two decimal places, as the salt content of the sample. 8 Repeatability The difference between the values (expressed in accordance

25、with7.1) of two determinations carried out in rapid succession by the same analyst shall not exceed0.05% absolute. 9 Test report The following information shall be included in the test report: a) the result, expressed in accordance with clause7; b) reference to this British Standard, i.e.BS5086-4:19

26、85; c) details of the sample identity. where V 1 is the volume of thiocyanate solution used in the blank titration (in mL); V 2 is the volume of thiocyanate solution used in the sample titration (in mL); C is the exact concentration of the thiocyanate solution (in mol/L); m is the mass of the test p

27、ortion (in g). 5.84 V 1 V 2 ()C m -BS5086-4:1985 BSI 07-1999 Publications referred to BS 604, Specification for graduated glass measuring cylinders. BS 769, Methods for the chemical analysis of butter 1) . BS 846, Specification for burettes. BS 1583, Specification for one-mark pipettes. BS 3978, Wat

28、er for laboratory use. BS 5086, Analysis of butter. BS 5086-1, General introduction including preparation of samples. 1) Referred to in the foreword only and currently being superseded by Parts of BS5086.BS 5086-4: 1985 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is t

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