1、Designation:E14761(Reapproved 2011)Standard Specification forApparatus for Microdetermination of Nitrogen by KjeldahlMethod1This standard is issued under the fixed designation E147;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the
2、year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This specification covers digestion and distillation ap-paratus used for the microdetermination of nitrogen by theK
3、jeldahl method,and modifications thereof at atmosphericpressure.NOTE1This specification is based on those originally developed bythe Committee on Microchemical Apparatus,Division of AnalyticalChemistry,American Chemical Society.22.Referenced Documents2.1 ASTM Standards:3E124 Specification for Weighi
4、ng and Drying Apparatus forMicrochemical Analysis3.Tolerances3.1 The following commercial length tolerance shall beadhered to,unless otherwise specified:Up to 10 mm1 mm10 to 100 mm2 mm100 to 200 mm3 mm200 mm4 mm4.Digestion Flasks4.1 Digestion flasks of three types shall conform to therequirements pr
5、escribed in Table 1 and Fig.1,Fig.2,and Fig.3.The flasks shall be made of shock-resistant glass with linearcoefficient of expansion not greater than 33.5 107cm/cmC.NOTE2The weighing tubes described in Specification E124 Figs.1214 are recommended for introducing solid samples into the microKjeldahl d
6、igestion flasks.Combustion boats,Fig.1 and Fig.2 ofSpecification E124,are recommended for use with waxy and nonvolatileliquid samples.5.Digestion Rack5.1 The micro Kjeldahl digestion rack shall be portable andshall consist of flask heaters(either gas or electric),a flasksupport,and a fume duct.The r
7、ack shall be supplied with a heatdeflector mounted under the burners to prevent overheating ofthe bench top.5.1.1 HeatersThe source of heat may be either electric orgas.In operation,each heater shall supply sufficient heat to a30-mL flask to cause 15 mL of water at 25C to come to arolling boil in no
8、t less than 2 or more than 3 min.Adevice shallbe provided for regulating the amount of heat supplied to theflask so that these conditions can be met.The amount of heatsupplied to the flasks also shall be so adjustable that low-temperature digestions are possible.Switches and controlsshall be conveni
9、ently located and shall remain cool enough tohandle even after long periods of operation.NOTE3Boiling chips shall be added when testing the heaters tominimize superheating,and the burners and rack shall be at equilibriumtemperature.5.1.2 Flask SupportThe support on which the bulbs of theflasks rest
10、shall shield the necks of the flasks from excessiveheating during digestion and shall be provided with circularopenings not exceeding 26 mm in diameter,centered over eachheater.5.1.3 Fume DuctThe fume duct shall provide means foradequately removing the fumes evolved during the digestionand shall sup
11、port the necks of the flasks at an angle greater than35 to the horizontal.Fume ducts meeting these specificationsare shown in Fig.4 and Fig.5.The fume duct illustrated in Fig.4 is supported and held in place by suitable clamps mounted ateither end of the digestion rack.The fume duct in Fig.5 restsup
12、on a circular support plate and is held in place by springsfrom the plate to the four glass hooks.The concave centerpermits clearance for the nut which fastens the support plate tothe center support post.6.One-Piece Distillation Apparatus6.1 The one-piece model distillation apparatus shall con-form
13、to the requirements of Fig.6.The steam-generator vesselillustrated in Fig.7 and the immersion heater in Fig.8 are1This specification is under the jurisdiction of ASTM Committee E41 onLaboratory Apparatus and is the direct responsibility of SubcommitteeE41.01Apparatus.Current edition approved Dec.1,2
14、011.Published December 2011.Originallyapproved in 1959.Last previous edition approved in 2006 as E147 61(2006).DOI:10.1520/E0147-61R11.2Committee on Microchemical Apparatus,“Recommended Specification forMicrochemicalApparatus,Micro Kjeldahl Nitrogen,”Analytical Chemistry,Vol 23,1951,p.523.3For refer
15、enced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshoho
16、cken,PA 19428-2959.United States1 recommended for use with this apparatus,although any othersuitable combination may be substituted.6.2 The steam-generator vessel,Fig.7,is a wide-mouthedcommercially available resin reaction kettle.The interchange-able cover,with flat-ground rim and four ground-glasstubulations,is held in place with a suitable clamp.Thedistillation unit is connected to the center tubulation.Two ofthe outer three tubulations are used for the leads of theimmersion-heater assembly,F
