1、BRITISH STANDARD CONFIRMED JULY1990 BS3762-3.14: 1985 Analysis of formulated detergents Part3: Quantitative test methods Section3.14 Method for determination of carbonate content NOTEIt is recommended that this Section be read in conjunction with the information in the “General Introduction”, publis
2、hed separately as BS3762-0. UDC 661.185:543.272:546.264BS3762-3.14:1985 This BritishStandard, having been prepared under the directionof the Chemical Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 31 January1985 BSI12-1999 The committees responsible
3、 for this BritishStandard are shown inPart0. The following BSI references relate to the work on this standard: Committee reference CIC/34 Draft for comment84/50244 DC ISBN 0 580 14129 2 Foreword This Section of BS3762 has been prepared under the direction of theChemicals Standards Committee and supe
4、rsedes methodD3 of BS3762:1964. This standard describes a method of test only and should not be referred to as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in conformity with BS3762-3.14. A British Standard does not purport to i
5、nclude 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 document comprises a front cover, an inside front cover, pa
6、gesi andii, pages1 to4, 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. Amendments issued since publication Amd. No. Date of issue CommentsBS3
7、762-3.14:1985 BSI 12-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 1 6 Expression of results 2 7 Test report 2 Figure 1 Absorption train 3 Publication referred to Inside back coverii blankBS3762-3.14:1985 BSI 12-1999 1 1 Scope This Se
8、ction of BS3762 describes a method of analysis for the determination of carbonate content of formulated detergents. The carbonate content may be expressed as carbon dioxide or as sodium carbonate. NOTEThe title of the publication referred to in this Section is given on the inside back cover. 2 Princ
9、iple Carbon dioxide is liberated from carbonate and bicarbonate present in the sample on the addition ofacid. The carbon dioxide evolved is passed through solutions of chromic-sulphuric acid, to free it from sulphur dioxide, and a desiccant to free it from water. It is then absorbed in a weighed bul
10、b containing an absorbent for carbon dioxide. Thebulb is then reweighed. Chlorine bleaches, if present, are first destroyed bythe addition of hydrogen peroxide. 3 Reagents The reagents shall be of a recognized analytical reagent quality. Water complying with the requirements of BS3978, from which ca
11、rbon dioxide has been removed, for example by boiling, shall be used throughout. 3.1 Hydrogen peroxide,6% solution approximately. 3.2 Absorbent for carbon dioxide, granules,12mesh to20mesh. NOTE“Carbosorb AB” is suitable. A self-indicating grade is preferred. 3.3 Desiccant. Calcium sulphate, anhydro
12、us, granular,8mesh to20mesh. NOTEA self-indicating grade is preferred. 3.4 Antifoam agent. Butanol or a suitable agent of the silicone type. 3.5 Chromic-sulphuric acid solution. Dissolve approximately10g of powdered potassium dichromate in50mL of water and add carefully approximately950mL of concent
13、rated sulphuric acid ( =1.84g/mL). 3.6 Hydrochloric acid, c(HCl)=5mol/L approximately. 3.7 Methyl orange indicator solution 3.8 Sulphuric acid, concentrated, ( =1.84g/mL). 4 Apparatus Ordinary laboratory apparatus and the following are required. 4.1 Absorption train, filled with reagents and assembl
14、ed as illustrated in Figure 1, and comprising the following: a) Guard tube, straight type(A). b) Dropping funnel, of volume approximately25mL and with a long stem(B). c) Flask, flat-bottom,250mL or500mL(C). d) Condenser of short length, water-cooled(D). e) Gas washing bottles, Drechsel type(E),(F),(
15、G). NOTE 1Bottles of such a construction as to have integral back-suction traps are to be preferred (see note2). f) Absorption tube, Fleming type(H). Alternatively a U-tube with two stop-cocks may be used. g) Trap, between the source of controlled vacuum and the absorption train. NOTE 2The volume of
16、 air space within the train should be kept to the minimum. Apparatus with ground-glass joints is preferred, and the joints should be well greased with a heavy stopcock grease. Other connections should be glass-to-glass, held in place with good-quality flexible plastics tubing; castor oil is a good l
17、ubricant and seal for such connections. If the gas-washing bottles do not have integral back-suction traps, additional empty gas-washing bottles should be inserted between the condenser and vessel E and between the absorption tube H and vessel G, to act as safety traps. 5 Procedure 5.1 Test portion
18、Weigh, to the nearest0.01g, an appropriate amountof well mixed sample so as to contain100mg to200mg of carbon dioxide. NOTEIf the sample is a physical mixture of detergent and adjuncts and is difficult to sample accurately, it may be desirable to weigh a larger sample, dissolve in water, dilute to a
19、 specified volume and use a portion containing100mg to200mg of carbon dioxide. 5.2 Determination Transfer the test portion to flask C and add50mL of water. NOTEA lesser amount of water may be added if a liquid test portion is used. Add a boiling aid and10mL of butanol or a small amount of other anti
20、-foaming agent. If chlorine bleaches are present, add slowly sufficient hydrogen peroxide to destroy the bleach, i.e.until further additions produce no effervescence.BS3762-3.14:1985 2 BSI 12-1999 Insert the flask in the apparatus and draw a current of air through the train for a few minutes to swee
21、p out all carbon dioxide; regulate the suction so that only two bubbles to four bubbles per second pass through the apparatus. With suction still on, close the tap of funnel B and check that there are no leaks; then discontinue the suction. Close the taps of absorption tube H and remove it from the
22、train. Temporarily block the tubing of the train to prevent ingress of moisture or carbon dioxide. Momentarily open and shut the inlet of H, then weigh the vessel. Re-insert the vessel into the train and open the taps. Fill funnel B with hydrochloric acid solution, add a few drops of methyl orange i
23、ndicator and re-insert tube A. Add the acid slowly to the test portion and then allow air to bubble through the train at two bubbles to four bubbles per second. Slowly heat the solution in the flask to boiling and continue boiling for3min to4min. The solution should now be red, indicating an excess
24、of acid. If it is not, allow the flask to cool slightly, close the tap of funnel B and refill with the acid; re-insert tube A. Add the acid slowly and continue as previously. After the boiling is discontinued, continue the passage of air at two bubbles to four bubbles per second through the system f
25、or at least15min. Close the taps of tube H and re-weigh it as before. NOTE 1It is recommended that the apparatus and technique should be checked occasionally with a sample of known carbonate content, e.g.anhydrous sodium carbonate which has been dried for2h at105 C. NOTE 2The carbon dioxide absorbin
26、g granules and desiccant should be changed when they are about half exhausted. The chromic-sulphuric acid should be replaced when a greenish colour develops. 6 Expression of results The carbonate content, expressed as a percentage bymass of carbon dioxide (CO 2 ), is given by the expression The carb
27、onate content, expressed as a percentage by mass of sodium carbonate (Na 2 CO 3 ), is given by the expression where m 1 is the increase in mass of absorption tube H (ing); m 2 is the mass of the test portion (ing). 7 Test report The test report shall include the following information: a) a reference
28、 to this BritishStandard, i.e.BS3762-3.14; b) the results and the method of expression used; c) the test conditions. m 1 m 2 -100 m 1 m 2 -240.8 BS3762-3.14:1985 BSI 12-1999 3 Figure 1 Absorption train4 blankBS3762-3.14:1985 BSI 12-1999 Publication referred to BS3978, Water for laboratory use. BS376
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