acid(H3BO3)in warm water,dilute to nearly1dm3,cool to room temperature,and dilute to1dm3.
6.2Catalyst Mixture—Prepare afinely divided,intimate mixture of30parts by mass of anhydrous potassium sulfate (K2SO4),4parts of cupric sulfate(CuSO4·5H2O)and1part of lenium powder.Alternatively,dissolve,with heating,110g of K2SO4,14.7g of CuSO4·5H2O and3.7g of lenium in600 cm3of H2SO4(density1.89Mg/m3).
6.3Indicator,Methyl Red–Methylene Blue—Dissolve0.1g of methyl red and0.05g of methylene blue in100cm3of alcohol.
6.4Indicator,Methyl Red–Bromcresol Green—Dissolve 0.08g of methyl red and0.4g of bromcresol green in100cm3 of alcohol.
6.5Sodium Hydroxide,Standard Solution(0.02M), Carbonate-Free—Prepare a0.02M carbonate-free sol
ution of sodium hydroxide(NaOH).Standardize against National Bu-reau of Standards sample No.84of potassium hydrogen phthalate in accordance with instructions furnished with the standard sample.
6.6Sodium Hydroxide,Standard Solution(0.1M), Carbonate-Free—Prepare a0.1M carbonate-free solution of sodium hydroxide(NaOH).Standardize against National Bu-reau of Standards sample No.84of potassium hydrogen phthalate in accordance with the instruction furnished with the standard sample.
6.7Sodium Hydroxide Solution(40%)—Dissolve400g of sodium hydroxide(NaOH)in600cm3of water.
6.8Sulfuric Acid(density1.89Mg/m3)—Concentrated sul-furic acid(H2SO4).
6.9Sulfuric Acid,Standard(0.01M)—Prepare a0.1M solution of sulfuric acid(H2SO4).Standardize against0.02M carbonate-free NaOH solution,using2drops of methyl red-methylene blue indicator.
6.10Sulfuric Acid,Standard(0.05M)—Prepare a0.05M solution of sulfuric acid(H2SO4).Standardize against0.1M carbonate-free NaOH solution,using2drops of methyl red-methylene blue indicator.
6.11Zinc,Granulated or Mossy.
7.Sampling
7.1Depending upon the u to which this standard will be put,sampling shall be at the discretion of the analyst,to obtain as reprentative a sample as possible of the lot to be tested.
8.Procedure A,Referee Method(Macro Method)
8.1Weigh a2-g test specimen to the nearest1mg,cut into small pieces,and place in a Kjeldahlflask.To the Kjeldahl flask add about13g of catalyst mixture(e6.2)and60cm3 of H2SO2(6.8)or,alternatively,about65cm3of catalyst solution in H2SO4.Swirl theflask until the contents are well mixed.Then boil gently until the solution is clear and continue heating for1h longer.
8.2Cool theflask and its contents to room temperature and dilute with200cm3of water.Add150cm3of40%NaOH solution to the contents of theflask,pouring slowly down the side of theflask so that the contents do not mix.Without mixing the contents of theflask,slide veral pieces of mossy or granulated zinc metal down into theflask and quickly connect theflask to the trap connected to the condenr.
8.2.1Caution—The addition of ba(NaOH)to an acid solution(H2SO4)will produce an exothermic reaction.Protect hands and eyes adequately.
福原爱宣布退役
8.3Into a suitable receivingflask place either75cm3of water and25.0cm3of0.05M H2SO4or100cm3of H3BO3 solution.Mount theflask with the acid solution(e6.1)so that the end of the delivery tube projects below the surface of the solution.While holding the stopper of the Kjeldahlflask in place,swirl the contents of theflask and mix thoroughly.Start distilling at once and continue distilling evenly until200cm3 of distillate have been collected.
N OTE2—This amount of H
2
SO
detector4
is sufficient for nitrogen content only
up to1.75%.For samples of higher nitrogen content,u a larger volume
of H
2
SO
4
.Do not u a smaller sample.
8.4Titrate the contents of the receivingflask with0.1N NaOH solution,using methyl red-methylene blue(e6.3)as indicator when H2SO4is ud as the receiving solution,or with 0.05M H2SO4using bromcresol green-methyl red indicator (e6.4)when H3BO3solution is ud.
vegetables8.5Blank—Make a blank determination by carrying out the entire procedure,using only the reagents,with the digestion mixture being heated until the volume is reduced to the same size as obtained with a digested rubber sample.
9.Procedure B,Alternative Method(Semimicro)
9.1Weigh accurately,to0.1mg,about0.1g of the sample into the micro or mimicro Kjeldahlflask.Add about0.65g of the catalyst mixture(e6.2)and3cm3of H2SO4(6.8),or, alternatively,add3.5cm3of the catalyst solution in H2SO4,to theflask.Boil gently by electrical heating and continue boiling for about30min after the digest has become a clear green color with no yellow tint.
9.2Cool the digest.If the micro apparatus requiring a transfer to the distillation apparatus has been ud,dilute the digest with10cm3of water and transfer with two or three 3-cm3portions of water to the distillation apparatus which has been steamed out for2min.If the mimicro apparatus has been ud,dilute the digest with16to20cm3of water and attach theflask to the distillation apparatus which has been steamed out for2min by using an empty digestionflask in place of the sample digestionflask.
9.2.1Caution—The addition of water to concentrated acid (H2SO4)will produce a violent reaction unless the water is added carefully.Pour the required amount of water slowly down the side of the tiltedflask.At the same time gently rotate theflask to facilitate mixing.This is an exothermic reaction; therefore,hands and eyes should be adequately protected. 9.3Distillation:
9.3.1H3BO3Solution in Receiving Flask—Add5cm3of the H3BO3solution and about5cm3of water to the receivingflask, add2drops of methyl red-bromcresol green indicator,(e 6.4),and place the receiver so that the end of the condenr dips below the surface of the H3BO3solution.Add about10 cm3of40%NaOH solution to the digestionflask,washing it with not more than5cm3of water.Pass steam from the generatingflask through the distillation apparatus until the total volume of solution in the receiver is about30cm3.This
will
require about 4min with the micro apparatus;the time will
vary with the mimicro apparatus,and some mild flame
heating of the distillation may be necessary during the first
minute of the distillation.Lower the receiver until the
condenr tip is well above the solution and continue distilling
for 1min.The total volume should be about 35cm 3with the
sy什么意思
micro apparatus and 35to 40cm 3with the mimicro
west coastapparatus.Wash the end of the condenr with water.
9.3.2H 2SO 4in Receiving Flask —Accurately pipet 10cm 3
of 0.01M H 2SO 4into the receiving flask.Alternatively,u
smaller volumes (below 5cm 3)delivered accurately from a
5-cm 3buret graduated in 0.2-cm 3divisions.Do not pipet风韵是什么意思
volumes below 10cm 3.Add 2drops of methyl red-methylene
blue indicator (e 6.3)to the receiver and distill as described
in 9.3.1.
N OTE 3—This volume of acid will be an excess up to about 2.5%
nitrogen in a 0.1-g test specimen.9.4Titration :
tromso9.4.1H 3BO 3Solution in Receiving Flask —Titrate the
distillate with standardized 0.01M H 2SO 4using a 5or 10-cm 3
buret graduated in 0.02-cm 3divisions.
9.4.2H 2SO 4in Receiving Flask —Titrate the distillate with
0.02M NaOH solution using a 5or 10-cm 3buret graduated in
0.02-cm 3divisions.
采用英文
9.4.3Blank —Carry a blank determination through the
entire procedure,using all of the reagents but omitting the
sample.
10.Calculation
10.1When H 3BO 3solution is ud as the receiving solution,
calculate the nitrogen content as follows:
Nitrogen,%5@~~V 12V 2!M 30.0140!/W #3100(1)where:V 15cubic centimetres of H 2SO 4required for titration of contents of the receiving flask (8.4or 9.4.1),V 25cubic centimetres of H 2SO 4required for titration of the blank (8.5or 9.4.3),
M 5molarity of the H 2SO 4,W 5grams of sample ud,and 0.01405millimole mass of nitrogen.10.2When H 2SO 4is ud as the receiving solution,calculate the nitrogen content as follows:Nitrogen,%5@~~V 22V 1!M 30.0140!/W #3100(2)
where:V 15cubic centimetres of NaOH solution required for titration of the contents of the receiving flask (8.4or 9.4.2),V 25cubic centimetres of NaOH solution required for titration of the blank (8.5or 9.4.3),M 5molarity of the NaOH solution,W 5grams of sample ud,and 0.01405millimole mass of nitrogen.10.3Calculate the percentage of NBR rubber prent in the sample if the composition of the copolymer ud in the rubber product is known.11.Report 11.1The test report shall include the following information:11.1.1Complete identification of the sample,11.1.2The average of two individual determinations,and 11.1.3The method ud—micro,mimicro,or macro.12.Precision 12.1Precision statements according to the 1988edition of Practice D 4483have not been prepared for this method at the
date of this revision.When available,they will be added to this
生活需要挫折method.
13.Keywords
polytron
13.1Kjeldahl;nitrogen;rubber The American Society for Testing and Materials takes no position respecting the validity of any patent rights asrted in connection with any item mentioned in this standard.Urs of this standard are expressly advid that determination of the validity of any such patent rights,and the risk of infringement of such rights,are entirely their own responsibility.
This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revid,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standards and should be addresd to ASTM Headquarters.Your comments will receive careful consideration at a meeting of the responsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards,100Barr Harbor Drive,West Conshohocken,PA
19428.
