ISO 17942:2014

INTERNATIONAL ISO
STANDARD 17942
First edition
2014-08-15
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Methods for chemical analysis of
boron nitride powders
Céramiques techniques — Méthodes pour l’analyse chimique de
poudres de nitrure de bore
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 General rules in chemical analysis . 1
4 Analysis items . 1
5 Sampling, weighing, and drying of sample . 2
5.1 Sampling . 2
5.2 Weighing . 2
5.3 Drying . 2
6 Reporting analytical values . 3
6.1 Number of analyses. 3
6.2 Blank test . 3
6.3 Evaluation of analytical values . 3
6.4 Expression of analytical values . 3
7 Determination methods of total boron . 3
7.1 Classification of determination methods . 3
7.2 Fusion-acidimetric titration method . 4
7.3 Fusion-ICP-OES . 6
8 Determination methods of free boron . 8
8.1 Classification of determination methods . 8
8.2 Sulfuric acid digestion-ICP-OES and spectrophotometry . 9
8.3 Nitric acid digestion-ICP-OES .11
8.4 Methanol extraction-borate separation-ICP-OES and spectrophotometry .12
9 Determination methods of total nitrogen .16
9.1 Classification of determination methods .16
9.2 Acid pressure decomposition-distillation separation-acidimetric titration method .17
9.3 Fusion-ammonia separation-acidimetric titration method .22
9.4 Inert gas fusion-thermal conductivity method .22
10 Determination method of silicon .26
10.1 Determination method.26
10.2 Principle .26
10.3 Reagents.26
10.4 Apparatus and instrument .27
10.5 Amount of sample .27
10.6 Operation .27
10.7 Blank test .27
10.8 Drawing calibration curves .27
10.9 Calculation .28
11 Determination methods of aluminium, cadmium, calcium, chromium, cobalt, copper, iron,
lead, magnesium, manganese, nickel, titanium, vanadium, and zinc .28
11.1 Classification of determination methods .28
11.2 Acid pressure decomposition-ICP-OES .28
11.3 Fusion-ICP-OES .31
12 Determination methods of sodium and potassium .34
12.1 Classification of determination methods .34
12.2 Acid pressure decomposition-AAS.35
12.3 Acid pressure decomposition-FES .37
12.4 Acid pressure decomposition-ICP-OES .39
13 Determination methods of carbon .41
13.1 Classification of determination methods .41
13.2 Combustion (resistance furnace)-IR absorption spectrometry .42
13.3 Combustion (RF furnace)-conductometry .45
13.4 Combustion (RF furnace)-IR absorption spectrometry .47
13.5 Combustion (resistance furnace)-coulometry .49
13.6 Combustion (resistance furnace)-gravimetry .49
13.7 Combustion (resistance furnace)-conductometry .49
14 Determination method of Oxygen .49
14.1 Determination method.49
14.2 Inert gas fusion-IR absorption spectrometry .49
15 Test report .52
Annex A (informative) List of commercial certified reference materials .53
Annex B (informative) Analytical results obtained from a round robin test .54
Annex C (informative) Spectral lines for ICP-OES .58
Bibliography .59
iv © ISO 2014 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information.
The committee responsible for this document is ISO/TC 206, Fine ceramics.
Introduction
This International Standard describes the chemical analysis of boron nitride powders for use in fine
ceramics applications. Determination methods of both main and trace constituents of interest are fully
covered.
vi © ISO 2014 – All rights reserved

INTERNATIONAL STANDARD ISO 17942:2014(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Methods for chemical analysis of boron
nitride powders
1 Scope
This International Standard specifies the methods for the chemical analysis of fine boron nitride
powders used as the raw material for fine ceramics.
This International Standard stipulates the analysis methods of total boron, free boron, total nitrogen,
aluminium, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, nickel,
potassium, silicon, sodium, titanium, vanadium, zinc, carbon, and oxygen in boron nitride powders for
fine ceramics. Total boron is determined by using either a fusion–titration method or a fusion–inductively
coupled plasma-optical emission spectrometry (ICP-OES). Free boron is determined by using either an
acid digestion–ICP-OES or a methanol extraction–ICP-OES. If necessary, the boron amount which arises
from the hydrolysis of boron nitride during sample treatment is corrected using spectrophotometry. Total
nitrogen is determined by using either an acid pressure decomposition–distillation separation–titration
method or an inert gas fusion–thermal conductivity method. Silicon is determined by using a fusion–
ICP-OES. Aluminium, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese,
nickel, titanium, vanadium, zinc are determined by using an acid pressure decomposition–ICP-OES or
a fusion–ICP-OES. Sodium and potassium are determined by using atomic absorption spectrometry
(AAS), flame emission spectrometry (FES), or ICP-OES following acid pressure decomposition. Carbon is
determined by using a combustion–IR absorption spectrometry or a combustion–thermal conductivity
method. Oxygen is determined by using an inert gas fusion–IR absorption spectrometry.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 12698-1:2007, Chemical analysis of nitride bonded silicon carbide refractories - Part 1: Chemical methods
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
ISO 9138, Abrasive grains — Sampling and splitting
ISO 21068-2:2008, Chemical analysis of silicon-carbide-containing raw materials and refractory products —
Part 2: Determination of loss on ignition, total carbon, free carbon and silicon carbide, total and free silica
and total and free silicon
3 General rules in chemical analysis
Chemical analysis shall be performed in accordance with general rules regulated as standards, if
available.
4 Analysis items
Analysis items specified in this International Standard shall be as follows:
a) Total boron (T.B)
b) Free boron (F.B)
c) Total nitrogen (T.N)
d) Silicon (Si)
e) Aluminium (Al)
f) Cadmium (Cd)
g) Calcium (Ca)
h) Chromium (Cr)
i) Cobalt (Co)
j) Copper (Cu)
k) Iron (Fe)
l) Lead (Pb)
m) Magnesium (Mg)
n) Manganese (Mn)
o) Nickel (Ni)
p) Titanium (Ti)
q) Vanadium (V)
r) Zinc (Zn)
s) Sodium (Na)
t) Potassium (K)
u) Carbon (C)
v) Oxygen (O)
5 Sampling, weighing, and drying of sample
The method of preparing samples shall be in accordance with ISO 9138 unless otherwise mutually
agreed upon between the analyser and customer.
5.1 Sampling
Take the sample in accordance with ISO 9138.
5.2 Weighing
Weigh the sample of the required quantity to the nearest 0,1 mg using an electric balance.
5.3 Drying
Take about 10 g of the sample into a flat-type weighing bottle (60 mm × 30 mm) and spread it uniformly
over the bottom of the bottle. Place the bottle in an air bath at (120 ± 5) °C for 2 h without a lid, and then
cool in a desiccator (desiccant: magnesium perchlorate for drying) with a lid for 1 h.
2 © ISO 2014 – All rights reserved

6 Reporting analytical values
6.1 Number of analyses
Analyse the sample twice on different days.
6.2 Blank test
Upon analysis, perform a blank test to correct the measured values.
6.3 Evaluation of analytical values
a) When the difference between two analytical values does not exceed the tolerance shown in Table 1,
the average value shall be reported.
b) When the difference between two analytical values exceeds the tolerance shown in Table 1, perform
additional two analyses. When the difference does not exceed the tolerance, the average value
thereof shall be reported. If the difference also exceeds the tolerance, the median of four analytical
values shall be reported.
6.4 Expression of analytical values
The analytical values shall be given in % (mass fraction) in dryness.
a) Total boron and total nitrogen — express the results with two to four figures according to the
method used.
b) Free boron — express the results with two to four figures according to the method used.
c) Others — express the results to the third decimal place.
Table 1 — Tolerance on analytical values
Unit: % (mass fraction)
Component total-B free-B total-N Si, Al, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, C O
Mn, Ni, Ti, V, Zn,
K, Na
a c e
Tolerance 0,30 0,30 0,001 0.005 0,01
b d f
0,40 0,005 0,05
a
Acid pressure decomposition–distillation separation–acidimetric titration method.
b
Inert gas fusion–thermal conductivity method.
c
Applicable to the content of less than 0,01 % (mass fraction).
d
Applicable to the content of not less than 0,01 % (mass fraction).
e
Applicable to the content of less than 1,0 % (mass fraction).
f
Applicable to the content of not less than 1,0 % (mass fraction).
7 Determination methods of total boron
7.1 Classification of determination methods
Total boron shall be determined by either of the following methods. If analytical results with three or
four figures are required, use method A; whereas if two figures are required, method B can be used.
— Method A, fusion–acidimetric titration method
— Method B, fusion–ICP-OES
7.2 Fusion-acidimetric titration method
7.2.1 Principle
Fuse the sample with sodium carbonate and dissolve the melt in hydrochloric acid. Adjust the solution to
pH 6,4 after removal of carbon dioxide. Add mannitol, and then titrate with sodium hydroxide solution
to pH 6,4.
This method shall be used to obtain the results of three or four figures.
7.2.2 Reagents
Reagents of analytical grade shall be used. Reagent solutions shall be preserved in plastic bottles
(products made of polyethylene, polypropylene, and tetrafluoroethylene resin are available.). The
standard solutions being SI traceable shall be used.
7.2.2.1 Water, Grade 1 or superior as specified in ISO 3696.
7.2.2.2 Sodium carbonate, anhydrous, as specified in ISO 6353-3 or that of higher grade.
7.2.2.3 Hydrochloric acid (1+1), (1+50), prepare from hydrochloric acid, respectively.
7.2.2.4 Sodium hydroxide, more than 97,0 % (mass fraction) of purity.
7.2.2.5 Sodium hydroxide solution (200 g/l), (40 g/l), (20 g/l), prepare from sodium hydroxide,
respectively.
7.2.2.6 Ethanol (95).
7.2.2.7 Ethanol–Sodium hydroxide (1+1) mixed solution, prepare by mixing the same volume of
ethanol (95) and a sodium hydroxide solution (200 g/l).
7.2.2.8 Mannitol.
7.2.2.9 Boric acid, more than 99,5 % (mass fraction) of purity.
7.2.2.10 Standard boron solution, weigh 1 g of boric acid (7.2.2.9) in a platinum crucible (for example,
30 ml) and heat it initially at a low temperature and finally at about 1 100 °C. After cooling in a desiccator,
weigh the mass of boric oxide as B O . Take the product into a 200 ml beaker together with the crucible
2 3
and add 100 ml of hot water. Heat and dissolve it. After cooling, transfer the solution into a 200 ml
volumetric flask and dilute with water to the mark.
7.2.2.11 Methyl-red indicator solution, prepare by dissolving 0,10 g of methyl-red with 50 ml of
ethanol (95) (7.2.2.6) to make up to 100 ml by adding water.
7.2.2.12 0.2 mol/ l Sodium hydroxide solution, weigh 50 g of sodium hydroxide in a polyethylene
bottle and dissolve in 50 ml of water under cooling. Stand for a few days with a cap to precipitate sodium
carbonate. Take 20 ml of the supernatant and dilute with water to 2 000 ml. Preserve it into a polyethylene
bottle equipped with an absorption tube of carbon dioxide. The volume of equivalent to the boron shall
be obtained according to the following. Take exactly 50 ml of the standard boron solution (7.2.2.10) into a
200 ml beaker and add 12 ml of hydrochloric acid (1+1) (7.2.2.3) and a few drops of methyl-red indicator
4 © ISO 2014 – All rights reserved

solution (7.2.2.11). After neutralization with the sodium hydroxide solution (40 g/l) (7.2.2.5), operate in
accordance with 7.2.5 g). Calculate the factor of this solution according to the following formula:
 
0,174850
FG=× × (1)
 
V 200
 0 
where
F is the factor of boron content of 0,2 mol/l sodium hydroxide solution per 1 ml (g/ml);
G is the weighed amount of boric acid in 7.2.2.9 (g);
V is the consumed volume of 0,2 mol/l sodium hydroxide solution after addition of mannitol in
7.2.2.12 (ml).
7.2.3 Apparatus
Apparatus shall be as follows:
7.2.3.1 Platinum crucible (30 ml), with a platinum lid.
7.2.3.2 Electric furnace, adjustable to the temperature of (1 100 ± 25) °C.
7.2.3.3 pH meter, readable to the smallest value of 0,1 equipped with a glass electrode.
7.2.4 Amount of sample
The weighed amount of the sample shall be 0,10 g.
7.2.5 Operation
The operation shall be as follows.
a) Take the sample aliquot into a platinum crucible (30 ml) and 2 ml of the ethanol–sodium hydroxide
mixed solution (7.2.2.7).
b) Heat on a hot plate, and then evaporate until dry.
c) Add 2,0 g of sodium carbonate and heat initially at a low temperature. Elevate the temperature
gradually to start fusing (heat carefully to prevent the contents from scattering) by using an electric
furnace or a Bunsen burner and keep the temperature for 15 min ~ 30 min during fusion. Fuse the
sample at 950 °C ~ 1 000 °C. Keep the temperature as low as possible.
d) Stand the crucible for cooling with a lid and place the crucible into a 300 ml beaker. Add 50 ml of
water and 10 ml of hydrochloric acid (1+1) (7.2.2.3) and heat it on a hot plate with a watch glass to
dissolve the melt.
e) After dissolving, wash the crucible with small amount of water and add a few drops of the methyl-
red indicator solution (7.2.2.11). Neutralize the solution with a sodium hydroxide solution until its
colour turns yellow, and then add hydrochloric acid (1+50) (7.2.2.3) to return to red again.
f) Remove carbon dioxide in the solution by boiling or by purging nitrogen gas for 5 min with the
watch glass. Cool down to room temperature and wash the watch glass with small amount of water
before removing. Keep the total water volume not more than 150 ml while washing.
g) Stirring with a magnetic stirrer, titrate with 0,2 mol/l sodium hydroxide solution (7.2.2.12), depict
a titration curve around pH 6,4 using a pH meter, and determine the inflection point of the curve.
After removing the electrode, add 25 g of mannitol (7.2.2.8). Titrate again with the sodium hydroxide
solution (7.2.2.12), depict a titration curve around pH 8,5, and determine the inflection point of the
curve. Calculate the total volume of titrant between two inflection points.
7.2.6 Blank test
Perform operations of 7.2.5 a) to 7.2.5 g) without taking a sample to obtain the blank test value of boron.
7.2.7 Calculation
Calculate the content of total boron in the sample according to the following formula:
VV− ×F
()
TB. = ×100 (2)
m
where
T.B is the content of total boron in the sample [% (mass fraction)];
V is the total volume of the 0,2 mol/l sodium hydroxide solution after the first addition of man-
nitol in 7.2.5 g) (ml);
V is the total volume of the 0,2 mol/l sodium hydroxide solution of the blank test after the first
addition of mannitol in 7.2.6 (ml);
F is the factor of the 0,2 mol/l sodium hydroxide solution in 7.2.2.12 (g);
m is the weighed amount of the sample in 7.2.5 a) (g).
7.3 Fusion-ICP-OES
7.3.1 Principle
To prepare a test solution, decompose the sample using base, spray into the argon plasma flame of ICP-
OES, and measure the emission intensity at a selected wavelength.
This method can be used to obtain the results of two figures.
7.3.2 Reagents
Use only reagents of analytical grade unless stated to the contrary and prepare all solutions using
distilled or deionized water and store in polyethylene bottles.
WARNING — Hydrochloric acid causes burns and has an irritating vapour. Prevent inhalation
and contact with skin and eyes. Proceed as for sulfuric acid, carrying out the dilution in a fume
cupboard.
7.3.2.1 Hydrochloric acid, concentrated, density 1,095 g/ml.
7.3.2.2 Hydrochloric acid (1+1 solution), carefully add 50 ml of acid to 50 ml of water to a beaker
cooled in a water bath. Stir the mixture continuously. Allow to cool and store.
7.3.2.3 Nitric acid, ρ 1,42 g/ml.
7.3.2.4 Sodium peroxide (Na O ).
2 2
7.3.2.5 Sodium carbonate, anhydrous.
6 © ISO 2014 – All rights reserved

7.3.2.6 Ethanol.
7.3.2.7 Boron standard solution, containing 1,000 g of boron (B) per litre. Do not dry. Dissolve 5,716 g
of anhydrous H BO (B fraction = 0,174 9), accurately weighed to at least four significant figures, in
3 3
reagent water and dilute in a 1 l volumetric flask with reagent water. Transfer immediately after mixing in
a clean polytetrafluoroethylene (PTFE) bottle to minimize any leaching of boron from the glass container.
The use of a non-glass volumetric flask is recommended to avoid boron contamination from glassware. A
1 ml of this standard solution contains 1,0 mg of boron.
7.3.3 Apparatus
Apparatus are ordinary laboratory apparatus and the following:
7.3.3.1 Glass beaker, with a range of appropriate volumes (100 ml, 250 ml).
7.3.3.2 Volumetric flask, with a range of appropriate volumes (100 ml, 250 ml, 500 ml, and 1 000 ml).
7.3.3.3 Burette, with a 0,1 ml scale and a maximum volume of 50 ml.
7.3.3.4 One-mark pipette, suitable for the transfer of each sample solution or standard solution.
7.3.3.5 Nickel crucibles.
7.3.3.6 Burner, such as a Mecker burner or a Bunsen burner.
7.3.3.7 Desiccator, containing dried silica gel as the drying agent.
7.3.3.8 Inductively coupled plasma emission spectrometer.
NOTE Refer to the manufacturer’s instructions for operation.
7.3.4 Procedure
7.3.4.1 Preparation of test solution
a) Weigh, to the nearest 0,001 g, approximately 1,0 g of the test sample, and transfer the test sample in
a nickel crucible.
b) Add 2,0 g of anhydrous sodium carbonate and 2,0 g of sodium peroxide and mix intimately. Heat
over a burner slowly at first and gradually raise the temperature to the full heat until complete
fusion.
CAUTION — When heating the sample in the burner, carbon dioxide is produced. So be
careful when heating the sample.
c) Cool to ambient temperature and place in a 250 ml beaker. Extract with approximately 150 ml of
water containing 2 ml to 3 ml ethanol, heat to boiling until the melt from the walls of the crucible
has been separated. Remove the crucible and wash it with a small amount of water.
d) Add 10 ml of hydrochloric acid (7.3.2.1) and heat to 100 °C until the melt is completely dissolved.
Pour the dissolved sample into a 250 ml volumetric flask, make up to the mark, and mix.
e) Pipette 25 ml of the solution from the 250 ml volumetric flask into a new 250 ml volumetric flask,
make up to the mark, and mix. This solution is used as the test solution.
7.3.4.2 Blank test
Carry out the procedure given in 7.3.4.1 without the sample, but omit the fusion of the flux. Designate
the resulting solution as blank solution.
7.3.4.3 Preparation of the calibration curve
a) To a series of six 100 ml volumetric flasks, add respectively 0 ml, 1 ml, 5 ml, 10 ml, 20 ml, and 50 ml
boron standard solution (7.3.2.7). Add to each flask 5 ml hydrochloric acid 1+1, dilute to mark, and
mix.
b) Spray a portion of each solution into the argon plasma flame of the inductively coupled plasma atomic
emission spectrometer, and measure the emission intensity for boron at 249,677 nm, 249,772 nm,
or 208,809 nm. Interferences may be encountered. Carefully choose the optimum wavelength free
from concomitants.
7.3.5 Calculation
Determine the concentration of boron in the test solution and in the blank from the calibration curve.
Calculate the boron content, B, as total boron, expressed in percent mass fraction, from Formula (3):
CC− ×V
()
TB. = ×10 (3)
m
where
T.B is the total boron content in mass fraction (%);
C is the concentration, expressed in milligrams per litre, of boron in test solution;
C is the concentration expressed in milligrams per litre, of boron in blank test;
V is the volume, in millilitres, of the test solution described in 7.3.4.1 d);
m is the mass, in grams, of the test portion.
8 Determination methods of free boron
8.1 Classification of determination methods
Boron nitride may somewhat tend to receive hydrolysis and yield equivalent of boron oxide and ammonia;
only the latter evaporates. The determination of boron oxide in boron nitride may be critical when the
equivalence between total boron and total nitrogen is evaluated. There are two approaches to extract
boron oxide in boron nitride with acid or methanol, but either of them is accompanied by the slight
dissolution of boron nitride. Extraction of only boron oxide without dissolving boron nitride is difficult.
However, the contribution of boron generated from boron nitride can be evaluated by the determination
of ammonia whose amount is equivalent to the boron.
Boron oxide shall be determined by any of the following methods. Both method A and method B include
the correction procedure for the boron amount which arises from the hydrolysis of boron nitride during
sample treatment stages. If analytical results with three or four figures are required for the total
boron, method A or C shall be used; whereas if two figures, either method A or C, without the correction
procedure or method B, can be used.
— Method A, Sulfuric acid digestion–ICP-OES and spectrophotometry
— Method B, Nitric acid digestion–ICP-OES
8 © ISO 2014 – All rights reserved

— Method C, Methanol extraction–borate separation–ICP-OES and spectrophotometry
8.2 Sulfuric acid digestion-ICP-OES and spectrophotometry
8.2.1 Principle
Dissolve the sample in sulfuric acid and filtrate the insoluble. Determine boron by using ICP-OES. If
analytical results of three or four figures for the total boron are determined, the correction procedure
including ammonia determination of 8.2.5 a) and 8.2.5 c) to 8.2.5 f) shall be necessary.
8.2.2 Reagents
Reagents shall be as follows.
8.2.2.1 Water, as specified in 7.2.2.1.
8.2.2.2 Sulfuric acid, 0,5 mol/l, prepare with sulfuric acid.
8.2.2.3 EDTA solution (5 g/100 ml), prepare with EDTA.
8.2.2.4 Sodium hydroxide solution (20 g/100 ml), prepare with sodium hydroxide.
8.2.2.5 Phenol.
8.2.2.6 Acetone.
8.2.2.7 Sodium phenoxide solution, take 55 ml of a sodium hydroxide solution (20 g/100 ml) (8.2.2.4)
in a beaker and gradually add 25 g of phenol (8.2.2.5) to the solution cooling in cold water. After cooling,
add 6 ml of acetone (8.2.2.6) and dilute with water to 200 ml. Store in a dark room below 10 °C.
8.2.2.8 Sodium hypochlorite solution, [1 % (mass fraction) of available chlorine]. Prepare by diluting
a commercial sodium hypochlorite solution, 5 % ~ 12 % (mass fraction) of available chlorine content,
with water. Prepare fresh immediately before use.
+
8.2.2.9 Ammonium ion standard solution (NH 1 mg/ml).
NOTE A commercial standard solution being SI traceable is available.
+
8.2.2.10 Ammonium ion standard solution (NH 0.1 mg/ml), take 10 ml of an ammonium ion
+
standard solution (NH 1 mg/ml) (8.2.2.9) into a 100 ml plastic volumetric flask and dilute with water
to the mark.
NOTE Products made of polyethylene, polypropylene, and tetrafluoroethylene resin are available for the
plastic volumetric flask.
8.2.2.11 Boron standard solution (B 1 mg/ml).
NOTE A commercial standard solution being SI traceable is available.
8.2.2.12 Boron standard solution (B 0,1 mg/ml), take 10 ml of a boron standard solution (1 mg/ml)
(8.2.2.11) into a 100 ml plastic volumetric flask, and dilute with water to the mark. Prepare fresh immediately
before use.
NOTE Products made of polyethylene, polypropylene, and tetrafluoroethylene resin are available for the
plastic volumetric flask.
8.2.3 Instruments
Instruments shall be as follows.
8.2.3.1 ICP optical emission spectrometer.
8.2.3.2 Spectrophotometer.
8.2.4 Amount of sample
The weighed amount of sample shall be 0,5 g.
8.2.5 Operation
The operation shall be as follows.
a) Take the sample into a 200 ml plastic beaker (products made of polyethylene, polypropylene,
and tetrafluoroethylene resin are available), and add 15ml of 0,5 mol/l sulfuric acid (8.2.2.2) and
35 ml of water. While stirring it occasionally at room temperature, let it stand for 2 h. Wash out the
solution into a 100 ml volumetric flask and dilute with water to the mark. After shaking well, filter
the solution with a dried filter paper. This filtrate shall be used as the sample solution.
b) Spray a portion of the solution of 8.2.5 a) into an Ar plasma of ICP-OES and measure the emission
intensity of boron at optimum wavelength, for example, 249,77 nm.
NOTE The optimum wavelengths used for the measurement depend on the performance of each ICP
spectrometer. Select the wavelength at which the measurement is not affected by concomitants. For
equipment which can be used to measure with higher order spectrum lines, higher wavelength shall be used
considering spectral interference and sensitivity.
+
c) Take an aliquot of the sample solution 8.2.5 a) (NH 5 μg ~ 100 μg) in a 100 ml plastic volumetric
flask (products made of polyethylene, polypropylene, and tetrafluoroethylene resin are available)
and add water to make about 30 ml.
d) Add 1 ml of the EDTA solution 8.2.2.3 and 10 ml of the sodium phenoxide solution (8.2.2.7) and mix
well.
e) Add 5ml of the sodium hypochlorite solution (8.2.2.8) and dilute with water to the mark and shake
well. Keep the temperature of the solution at 20 °C ~ 25 °C and let it stand for 30 min.
f) Take an aliquot of the solution in an absorption cell and measure the absorbance in the vicinity of
630 nm.
8.2.6 Blank test
Perform operations of 8.2.5 a) and 8.2.5 b) without taking a sample to obtain the blank test value of
boron and perform operations of 8.2.5 a) and 8.2.5 c) to 8.2.5 f) to obtain the blank value of ammonia.
8.2.7 Drawing calibration curves
a) Take 15 ml of 0.5 mol/l sulfuric acid (8.2.2.2) and 35 ml of water into several 100 ml plastic flasks
(products made of polyethylene, polypropylene, and tetrafluoroethylene resin are available), then
add exactly 0 ml ~ 10 ml of the boron standard solution (8.2.2.12) stepwise. Dilute with water to
the mark and mix well. These solutions for the calibration curve shall contain 0 μg ~ 1 000 μg of
boron. Operate the step of 8.2.5 b) and establish the relation between the emission intensity and the
amount of boron to draw a calibration curve.
+
b) Take exactly 0 ml to 20 ml of the ammonium ion standard solution (8.2.2.10) stepwise (NH
0 μg ~ 200 μg) into several 100 ml plastic flasks (products made of polyethylene, polypropylene,
and tetrafluoroethylene resin are available) and add water to make about 30ml. Operate the steps
10 © ISO 2014 – All rights reserved

of 8.2.5 c) to 8.2.5 f) and establish the relation between the emission intensity and the amount of
ammonium to draw a calibration curve.
8.2.8 Calculation
Obtain the amount of boron by 8.2.5 a) to 8.2.5 b) and 8.2.6 referring to the calibration curve drawn
in 8.2.7 a); whereas obtain the amount of ammonia by 8.2.5 c) to 8.2.5 f) and 8.2.6 according to the
calibration curve drawn in 8.2.7 b). Calculate the content of free boron (boron oxide) in the sample
according to the following formula:
   
AA− ×3,,220 −−AA ×1 930
() ()
10 200
   
FB. = ×100 (4)
m
where
F.B is the content of free boron as boron oxide in the sample [% (mass fraction)];
A is the amount of boron in the sample solution obtained by 8.2.5 b) and 8.2.7 a) (g);
A is the amount of boron in the blank test solution obtained by 8.2.6 and 8.2.7 a) (g);
A is the amount of ammonim ions in the sample solution obtained by 8.2.5 f) and 8.2.7 b) (g);
A is the amount of ammonium ions in the blank test solution obtained by 8.2.6 and 8.2.7 b)
(g);
m is the weighed amount of the sample in 8.2.5 a) (g);
3,220 is the conversion factor of boron (B) into boron oxide (B O );
2 3
1,930 is the conversion factor of ammonium ion into the equivalent boron oxide (B O ).
2 3
8.3 Nitric acid digestion-ICP-OES
8.3.1 Principle
Nitric acid digestion–ICP-OES is a method in which the soluble compounds in the boron nitride powder
are obtained by treatment with diluted nitric acid. After filtration, the free boron in filtrate is determined
by inductively coupled plasma–atomic emission spectroscopy.
8.3.2 Reagents
During the analysis, use only reagents of recognized analytical grade and only water of equivalent purity.
8.3.2.1 Water, use water purified in accordance with ISO 3696.
8.3.2.2 Nitric acid, ρ 1,42 g/ml.
8.3.2.3 Nitric acid, (1+9), Nitric acid (8.3.2.2) diluted 1+9.
8.3.2.4 Boron standard solution, containing 100 mg of boron (B) per litre. Transfer 10 ml of the boron
standard solution (7.3.2.7) to 100 ml volumetric flask up to mark with water and mix.
8.3.3 Apparatus
Apparatus are ordinary laboratory apparatus and the following.
8.3.3.1 Glass beaker, with a range of appropriate volumes (250 ml).
8.3.3.2 Volumetric flask, with a range of appropriate volumes (100 ml, 250 ml).
8.3.4 Procedure
8.3.4.1 Preparation of test solution
Weigh, to the nearest 0,001 g, approximately 3,0 g of the test sample, and transfer to a 250 ml glass
beaker. Add 100 ml of the nitric acid (1+9) and heat to boiling for approximately 3 h. Cool the solution
and then filter through a 15 cm paper of medium porosity. Rinse the beaker and wash the residue with
water. Transfer the filtrate to 250 ml volumetric flask make up to mark with water and mix. This solution
is used as the test solution.
8.3.4.2 Blank test
Carry out the procedure given in 8.3.4.1 without the sample, but omit the fusion of the flux. Designate
the resulting solution as blank solution.
8.3.4.3 Preparation of the calibration solution and calibration curve
To a series of four 100 ml volumetric flasks, add respectively 0 ml, 1 ml, 5 ml, and 10 ml boron standard
solution (7.3.2.7). Add to each flask 5 ml nitric acid (1+9), dilute to mark, and mix. Aspirate the calibration
solutions into the inductively coupled plasma-atomic emission spectrometer (7.3.3.8). Measure the
emission intensities for boron at 249,677 nm, 249,772 nm, or 208,809 nm.
8.3.5 Calculation
Determine the concentration of boron in the test solution and in the blank from the calibration curve.
Calculate the boron content, F.B, as free boron, expressed in milligrams per kilogram, from Formula (5):
CC− ×V
()
FB. = (5)
m
where
F.B is the content of free boron as boron oxide in mg/kg (mass fraction);
C is the concentration, expressed in milligrams per litre, of boron in test solution;
C is the concentration expressed in milligrams per litre, of boron in blank test;
V is the volume, in millilitres, of the test solution;
m is the mass, in grams, of the test portion.
8.4 Methanol extraction-borate separation-ICP-OES and spectrophotometry
8.4.1 Principle
Convert boron oxide in the sample into a volatile borate by heating with methanol, trap into a calcium
hydroxide solution and determine the boron in the solution using ICP-OES. If analytical results of
three or four figures for the total boron are determined, the correction procedure including ammonia
determination of 8.4.5 b) shall be necessary.
12 © ISO 2014 – All rights reserved

8.4.2 Reagents
Reagents shall be as follows.
8.4.2.1 Water, as specified in 7.2.2.1.
8.4.2.2 Methanol.
8.4.2.3 Calcium hydroxide saturated solution, add 500 ml of water to 5 g of calcium hydroxide and
seal with an airtight stopper. After shaking vigorously, use the supernatant. Prepare fresh immediately
before use.
8.4.2.4 Hydrochloric aci
...