CELEX: 51979PC0089
Language: en
Date: 1979-02-27
Title: Proposal for a new COUNCIL DIRECTIVE (EEC) on the approximation of the laws of the Member States relating to units of measurement and repealing Council Directive of 18 October 1971 (71/354/EEC) as modified since then. (submitted to the Council by the Commission)

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COM (79) 89
Vol. 1979/0028
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 ---pagebreak--- COMMISSION OF THE EUROPEAN COMMUNITIES
                                                    COM(79)89 final
                                                    Brussels - 27 february 1979
                                 Proposal for a new
                               COUNCIL DIRECTIVE ( EEC )
on the approximation of the laws of the Member States relating to units
of measurement and repealing Council Directive of 18 October 1971
( 71 / 354/ EEC ) as modified since then .
                   ( submitted to the Council by the Commission )
 C0M(79)o9 final
 ---pagebreak---                            EXPLANATORY MEMORANDUM
I. INTRODUCTION
This Council Directive is based on Article 100 of the Treaty establishing the
European Economic Community and falls within the context of the Council
Directive of 26 July 1971 on the approximation of the laws of the Member
States relating to common provisions for both measuring instruments and
methods of metrological control ( 71/316/EEC ) , and more particularly within the
field of the Council Directive of 19 October 1971 on the approximation of the
laws of the Member States relating to units of measurement ( 71/354/78 ), as
last amended by the Council Directive of 27 July 1976 ( 76/ 770/EEC ) .
The principal aims of this Directive are to remove barriers to intra-Community
trade which still exist where the use of units of measurement is governed by
legislation in Member States and , at the same time , to promote the use of a
single system of units of measurement throughout the Community .
Such action at Community level is desirable since the concrete result would
be to do away with all conversion operations which still have to be effected
between the different systems of units of measurement . The consumer 's life is
made much easier when the information supplied to him is furnished in accordance
with a single system , thus enabling him to make proper comparisons between
different sets of data . For economic operators and for government authorities ,
the use of a single system of units of measurement makes for substantial savings
and for better understanding by all concerned , thus reducing the possibility
of errors .
All Community provisions relating to units of measurement have been incor­
porated in this Directive so that the preceding Directive can simply be
repealed . Thus , once this Directive has been adopted it will no longer be
necessary to refer to scattered texts .
 ---pagebreak---                                    - 2 -
II . BACKGROUND
On 18 October 1971 the Council adopted the first Community Directive on the
use of units of measurement in the Community ( 71/354/EEC ) . This text is
based on two mutually complementary principles : the desirability of imposing
as quickly as possible the use of a single system of units of measurement ;
the desirability of prohibiting as quickly as possible the use of any unit
which does not form part of the system chosen .
There was never any question of the Community 's inventing its own system of
units of measurement . Directive 71/354/EEC lays down definitively the use of
a system of units comprising the international system of units ( the so-called
SI system , adopted by the General Conference of Weights and Measures ( CGPM )
set up by the International Metre Convention signed in Paris on 20 May 1875 ,
to which all Member States of the Community are contracting parties ), together
with certain units which are used with the international system .
This system of units of measurement is recognized almost throughout the
world , and where a State now wishes to impose the use of a single system in
its territory it is the SI system that is chosen . Hence the Community is
demonstrating its will to follow up at European level the work which has
been carried out at international level in a much wider context .
It is not reasonable to suppose that a given system of units can be imposed
overnight or that the use of a traditional system of units which is firmly
rooted in the customs of a country can be proscribed . That is why , even in
the first Directive , the Council provided for transitional periods both for
the imposition of the system of units ultimately to be used ( this transitional
period ended on 21 April 1978 for all Mentoer States ) and for the phasing-out
of the various units of measurement that do not appear in this system . In
the latter case , the transitional periods vary according to the units of
measurement in question . Some of these units of measurement presented such
difficulties that the decision as to the date when they should disappear
was postponed .
 ---pagebreak---                                       - 3 -
When the Community was enlarged in 19 73 , account had to be taken of the very
special problem of the Imperial system of units . Since none of the original
six Member States used Imperial units as legal units of measurement , their
existence had been totally ignored in Directive 71/354/EEC . On 1 January 1973 ,
however , the Community suddenly found itself faced with two Member States in
which the use of the Imperial units of measurement was mandatory . It was there­
fore necessary to adopt appropriate provisions in the Acts relating to
accession .
Thus under the terms of the Acts of Accession the Directive acquired an
Annex II comprising a list of Imperial units which were to be dealt with in
the context of the Community provisions . A paragraph 4 concerning these units
was likewise added to Article 1 of the Directive : " The classification in
Annex I of the units of measurement listed in Annex II shall be decided on
31 August 1976 at the latest . The units of measurement concerning which no
decision has been made on 31 August 1976 at the latest shall disappear on
31 December 1979 at the latest . An appropriate extension of this time limit
may be decided for certain of these units of measurement if it should be
justified for special reasons ."
The Act of Accession to the Communities consequently did not alter the
positions of principle previously adopted in Directive 71/354/EEC . On the
contrary , enlargement confirmed these principles to some extent with regard
to the Imperial system . It is perhaps worth pointing out that there was no
need to negotiate the actual principle of the adoption of the SI system with
the acceding countries , since they had shown themselves to be in favour of
the eventual adoption of the SI system throughout the Community as the only
legal system of measurements . ( The United Kingdom , for example , had decided
to adopt this system well before its accession to the Communities .)
After enlargement , therefore , there were certain decisions regarding Imperial
units of measurement which had to be taken before 31 August 1976 if these
units were not to disappear automatically on 31 December 1979 . It was also
necessary to re-examine before 31 December 1977 the fate of the units of
measurement referred to in Chapter II of Directive 71/354/EEC and to ascertain
whether certain units mentioned in Chapter III could not be made to disappear
before 1 December 1979 .
 ---pagebreak---                                       - 4 -
The Commission presented the Council with a single proposal for amendment in
order to settle all these questions and the Council adopted this amendment
on 27 July 1976 ( 76/ 770/EEC ) . The basic principles remained unchanged . The
SI system was still the only system that would be authorized in the long term .
It is set out in Chapter A of Directive 76/ 770/EEC . This chapter includes
some up-dated points in accordance with developments at international level
with respect to Chapter I of Directive 71/354/EEC . The units of measurement
not definitively adopted must eventually disappear , but the timetable for
their disappearance has been slightly changed and is broken down according
to three categories :
( a ) the units which must disappear by 31 December 1977 ( Chapter B ) ;
( b ) the units which must disappear by 31 December 1979 ( Chapter C ) ;
( c ) those units which must disappear and the date of whose disappearance has
      to be decided before 31 December 1979 ( Chapter D ) . It did not appear
      advisable in 1977 to take a final decision on these units .
III . THE PRESENT PROPOSAL FOR A DIRECTIVE
This Directive pursues the same aims as the preceding one and is based on the
same principles . Its lay-out is a little different because , for the first
time , the concept of " legal units of measurement " has been introduced at
Community level . This is now possible because the SI units of measurement ,
together with certain units which are used with this system , have been legal
units of measurement throughout the Community since 21 April 1978 . Any reference
to units of measurement , and particularly to the requirements regarding their
use , therefore becomes much more straightforward because in future it will
suffice to refer merely to the legal units of measurement .
The Annex is set out in the same way as before . Chapter I lists the legal
units of measurement which have been definitively adopted and Chapters II
and III set out the units of measurement which are still legally authorized
under certain specific conditions and until the dates laid down in Article 1 .
 ---pagebreak---                                     - 5 -
Chapter I has undergone hardly any substantial amendments since the adoption
of Directive 76/ 770/EEC . The few changes which have been made merely reflect
the developments that have taken place at international level as regards
units of measurement , more particularly as a result of the work of the General
Conference on Weights and Measures . The most significant addition is the adop­
tion of the new derived unit , the sievert , to express the equivalent absorbed
dose of ionizing radiation . This was proposed by the International Committee
of Weights and Measures for adoption by the next General Conference on Weights
and Measures , which will be held in 1979 . The Council will therefore be able
to act in the full knowledge of facts .
Article 1(b ) lays down that the units of measurement , names and symbols which
appear in Chapter II of the Annex may remain legal in the various Member
States until 31 December 1985 . Member States may , however , cease to recognize
their legal character before that date if they so desire , subject to the
provisions of Article 3 of this Directive . As regards radiological units of
measurement , the Commission has heeded the resolutions of the international
organization which is most competent in the field of radiology . The World
Health Organization has expressed a wish to have the millimeter of mercury
retained for a further period as an authorized unit of measurement in order
to help the medical profession to adapt smoothly to SI units . This unit ,
which was to have disappeared by 31 December 1979 at the latest , in accordance
with Directive 76/ 770/EEC , is therefore retained in Chapter II .
Chapter III of the Annex is reserved more particularly for certain Imperial
units of measurement which are most commonly used and therefore die the
hardest . All these units are listed in Chapter D of the Annex to the preceding
Directive , indicating that it had not been possible to take a decision as to
the date when they should cease to be used . The present Directive provides
that the final date shall be set by the Council . Indeed the Commission did
not want , of its own initiative , to impose a precise date on those Member
States where the use of these units of measurement remains very generalized
and which are in a better position to set this Limit taking into account the
economic and social consequences of this decision .
 ---pagebreak---                                       - 6 -
For the purposes of this Directive , these units of measurement can only be
legal units of measurement in the Member States in which their use was author­
ized on 21 April 1973 . This clause was already contained in Directive
76/ 770/EEC . In accordance with the provisions of Article 1(c ) and Article 3 ,
Member States which did not authorize these units on 21 April 1973 must allow
these units to appear as a secondary indication until 31 December 1989 at
the latest .
Article 2 of this Directive rerpoduces in their entirety the provisions of
Articles 2 and 3 of Directive 71/354/EEC . The scope has thus remained un­
changed . Hence Community provisions continue to aim at the use of units of
measurement for indications appearing on measuring instruments and for the
expression of the results of measurements performed by such instruments , the
use of units of measurement in any operation where it is necessary to measure
a particular dimension and their use whenever it is necessary to express the
magnitude of dimension . These various uses are highly specific and must be
interpreted very restrictively ( stricto sensu ). All these uses provided for
in Article 2(a ) must be related to the fields covered by the Directive and
laid down in Article 2(a ), that is to say to the economic field , to operations
of an administrative nature and to the fields of health and public safety .
The terms denoting the fields of application of this Directive have been
deliberately chosen because they encompass very broad concepts , and this is
wholly in accordance with the aims of the Directive .
It was , however , necessary , to provide for various exceptions to the
applications of Article 2(a ).
The first major exception concerns the field of international transport ,
where traditionally there have been many international agreements . The Member
States and the Community are obliged to respect these international agree­
ments , which frequently employ units of measuement other than the legally
recognized ones . In this area , the Community cannot take a decision inde­
pendently of the other signatories to such agreements .
 ---pagebreak---                                      - 7 -
Spare parts cause problems of quite a different nature . Very often spare parts
bear dimension indications in order to show on what products and equipments -
which have been on the market and in use for long periods already - they can
be fitted . Frequently these scare parts have to be specially manufactured .
In these cases , if the parts have to be mounted on products or equipments
which were designed in non- SI units , the spare parts must likewise be so
designed . In order to enable these products and equipments to remain in use ,
it was necessary to provide for a derogation from the provisions of Article
2(a ). This is the purpose of Article 4 .
Article 5 provides for a very special exception in the case of representations
of SI and other units to be used in data-processing systems involving limited
sets of characters . Since the problem had already been settled at international
level , a straightforward reference to the results of the work of the Inter­
national Standards Organization ( ISO ), through a dated reference to ISO
standard 2955 of 1 March 1974 , seemed to be the most appropriate solution at
Community level .
This directive differs widely from the earlier one as regards double indication .
Directive 71/354/ EEC as amended by Directive 76/ 770/EEC , did not make special
provisions in this respect . However , practical experience has shown that it
is unrealistic to expect that units of measurement which have been in use for
a very long time and which in many cases have become part of the traditions
of a country can be dohe away with overnight without a transitional period .
What is more , experience has shown that a mere transitional period without
any provision for special arrangements is insufficient to overcome the
difficulties .
Consequently , this Directive provides not only for transitional periods in
respect of the units of measurement appearing in Chapters II and III to the
Annex , but also for double indication during a fixed period specified in
Article 1 .
 ---pagebreak---                                       - 8 -
In order to be useful and effective , the provisions regarding double indication
have to be clear and easy to apply . Hence the definition given in Article 3
is very simple : double indication is used where a unit of measurement which
does not appear in Chapter I of the Annex accompanies a    unit from Chapter I.
By way of explanation , therefore , a unit from Chapter I  of the Annex may be
accompanied by any other unit of measurement which does    not appear in that
same Chapter I. The second unit of measurement need not    even appear in the
Annex to this Directive .
Double indication in this form may be vised until 31 December 1985 . This time
limit is extended until 31 December 1989 in the case of Imperial units of
measurement appearing in Chapter III to the Annex .
The use of the double indication system is as follows : Member States must
authorize or allow double indication on products and equipment until
31 December 1985 . For the units listed in Chapter III , the time limit is
fixed at 31 December 1989 . This obligation is to some extent an obligation
to ensure free movement ( Article 3(c )). In all cases which are not referred
to in Article 3(c ) and ( d ), Member States are free to authorize or prohibit
double indication in their territory .
The obligation to allow double indication does not apply to measuring in­
struments . It does not seem essential to require Member States to accept on
their territory measuring instruments which bear a double indication , since
in many cases Member States have already adopted rules prohibiting the
appearance on measuring instruments of any unit of measurement which is not
a legal unit of measurement , often for safety reasons .
Since the aim of this Directive is precisely to ensure that measuring in­
struments bear dimension indications solely in legal units of measurement
which have been definitively adopted , it seems desirable not to go against
national rules . Thus Member States are free to require that measuring in­
struments bear dimension indications in a single legal - unit of measurement .
 ---pagebreak---                                      - 9 -
Hie last paragraph of Article 3 lays down the practical Conditions under
which double indication can be used . The rule is that the Chapter I units of
measurement should be inscribed more conspicuously so as to avoid any possible
confusion .
IV. HARMONIZATION
This Directive , like the earlier ones , has adopted the solution of "total "
harmonization . Since the very purpose of the Directive is to impose , wherever
possible , the use of a single system of legal units of measurement throughout
the Community , total harmonization is the most efficient means of achieving
this . Thus , on the expiry of the transitional periods provided for in
Article 1 , only the units of measurement appearing in Chapter I of the Annex
may be used in the Community .
V. CONSULTATION OF PARLIAMENT AND THE ECONOMIC AND SOCIAL COMMITTEE
Under  the second paragraph of Article 100 of the EEC Treaty the opinion of
these two bodies is required . Implementation of the provisions of the Directiv
will , in some Mentoer States , necessitate an amendment of legislation .
 ---pagebreak--- THE COUNCIL OP THE EUROFEAN COMMUNITIES .
Having regard to the Treaty establishing the European Economic Community ,
and in particular Article 100 thereof ,
Having regard to Council Directive 71/354/EEC of 18 October 1971 on the
approximation of the laws of the Member States relating to units of
measurement ( l ), as last amended by Council Directive 76/770/EEC of
27 July 1976 ( 2 ),
Having regard to the proposal from the Commission ,
Having regard to the Opinion of the European Parliament ,
Having regard to the Opinion of the Economic and Social Committee ,
Whereas units of measurement are essential in the use of all measuring
instruments , to express measurements or any indication of quantity ;
whereas it is necessary to ensure the greatest possible clarity in their
use ;   whereas it is therefore necessary to make rules for their use for
economic , public health , public safety or administrative purposes ;
Whereas , however , international conventions or agreements exist in the
field of international transport which bind the Community or the Member
States ;    whereas these conventions or agreements have to be respected ;
Whereas the laws which regulate the use of units of measurement in the
Member States differ from one Member State to another and as a result hinder
trade ;    whereas , in these circumstances , it is necessary to harmonise laws ,
regulations and administrative provisions in order to overcome these
obstacles ;
 ( 1 ) O.J. N° L 243 of 29 October 1971 , p. 29
 ( 2 ) O.J. N° L 262 of 27 September 1976 , p. 204
 ---pagebreak---                                        - 2 -
Whereas units of measurement are the subject of international resolutions
adopted "by the General Conference of Weights and Measures (CGRVl ) set up by
the Metre Convention signed in Paris on 20 May 1875 » "to which all the
Member States are party;    whereas the " International System of Units" ( S.I. )
was drawn up as a result of these resolutions ;
Whereas the Council adopted Directive 71/354/EEC on 18 October 1971 on the
approximation of the laws of the Member States in order to overcome obstacles
to trade by adopting the international system of units at Community level ;
whereas Directive 71/354/EEC was amended by the Act of Accession and by
Council Directive 76/ 770/ EEC ; whereas these Community provisions have not
overcome all the obstacles in this field ; whereas Directive 76/ 770/ EEC
provides for the review before 31 December 1979 of the situation regarding
units of measurement , names and symbols listed in Chapter D of the Annex ;
whereas it has also proved necessary to review the situation regarding
various other units of measurement ;
Whereas it is necessary , in order to avoid serious difficulties ,
to provide for a transitional period during which units of measurement which
are not compatible with the international system can be phased out ;     whereas
it is nevertheless essential to allow the Member States wishing to do so
to bring into force as quickly as possible , on their territory , the
provisions of Chapter I of the Annex ;    whereas it is therefore necessary to
 set a limit at Community level on the duration of this transitional period
while , at the same time , leaving the Member States free to curtail that
period ;
Whereas during the transitional period it is essential , particularly for
the protection of the consumer , to maintain a clear position on the use of
units of measurement in trade between the Member States ;    whereas the
obligation on the Member States to      allow double indication on products
and equipment imported from other Member States during this transitional
period seems to serve this purpose well ;
Whereas the systematic adoption of a solution of this kind for all measuring
instruments , including medical instruments , is however not necessarily
desirable ;  whereas the Member States should therefore be able to require
that , on their territory , measuring instruments bear indications of quantity
in one single legal unit of measurement ;
 ---pagebreak---                                       - 3 -
Whereas this Directive does not affect the continued manufacture of
products already on the market ;    whereas it does , however , affect the
placing on the market and use of products and equipment "bearing indications
of quantity in units of measurement which are no longer legal units of
measurement , when such products and equipment are necessary to supplement
or replace components or parts of such products , equipment and instruments
already on the market ;    whereas it is therefore necessary for Member States
to authorize the placing on the market and the use of such products and
equipment to complete and replace components , even when they bear indications
of quantity in units of measurement which are no longer legal , so that the
products , equipment or instruments already on the market may continue to
be used ;
Whereas the International Organization for Standardization ( ISO) adopted
an international standard on 1 March 1974 on the representation of S . I. and
other units for use in systems with limited sets of symbols ;      whereas it is
therefore advisable for the Community to adopt solutions which have already
been approved on a wider international level ;    whereas the strict reference
to the standard makes it possible to adopt the ISO Standard 2955 of
1 March 1974 at Community level ;
Whereas Community provisions relating to units of measurement are to be
found in various separate Community acts ;           whereas the question of
units of measurement is so important that it is essential that reference
may be made to a single Community act ; whereas this Directive thereby
consolidates all the Community provisions on this subject and repeals
Directive 71 / 354/ EEC of 18 October 1971 /
HAS ADOPTED THIS DIRECTIVE *
 ---pagebreak---                              Article 1
The legal units of measurement within the meaning of this Directive
which are necessary for expressing quantities shall be :
a) those listed in Chapter I of the Annex to this Directive ;
b ) until a date to be fixed by the Member States , those listed in
    Chapter II of the Annex ; this date may not be set at later than
    31 December 1985 ;
c ) until a date to be fixed by those Member States , those listed
    in Chapter III of the Annex in those Member States where they
    were authorized on 21 April 1973 ; this date may not extend be­
    yond a date which shall be set by the Council under Article 100
    of the Treaty before 31 December 1989 .
                            Article 2
a) The obligations arising under Article 1 relate to measuring
    instruments used , measurements made and indications of quantity-
    expressed in units , whether for economic , public health , public
    safety or administrative purposes .
b) This Directive shall not affect the use in the field of air and
    sea transport and rail traffic    of units which it does not
    prescribe but which have been laid down by international
    conventions or agreements binding the Community or the Member
    States .
                             Article 3
a) There is double indication within the meaning of this Directive
    when an indication expressed by a unit listed in Chapter I is
    accompanied by a supplementary explanatory indication expressed
    by a unit not listed in Chapter I of this Directive .
 ---pagebreak---                                   - 2 -
 b ) Member States may authorize , on their territory, double indication
     using the units of measurement listed in Chapter III until 31
     December 1989t and, using other units of measurement not listed in
     Chapter I , until 31 December 1985*
 c ) Member States shall authorize or tolerate on products and
     equipment double indication using the units of measurement listed
     in Chapter III until 31 December 1989 » and , using other units of
     measurement not listed in Chapter I , until 31 December 1985*
d) However, Member States may require that measuring instruments bear
     indications of quant ity in one single legal unit of measurement *
e ) When use is made of double indication in accordance with the
     provisions of this Directive , the indication expressed by the unit
     of measurement listed in Chapter I shall be preponderant . The
     indications expressed by the units of measurement not listed in
     Chapter I of the Annex shall be expressed notably in characters at
     most equal in size to those of the corresponding indication in
     units listed in Chapter I of the Annex.
                              Article 4
Member States shall authorize the placing on the market and the
use of products and equipment bearing indications of quantity in
•units of measurement which are no longer legal units of measurement ,
when these products and equipment are necessary to complete or replace
 components or parts of such products , equipment and instruments
 already on the market and bearing such indications .
                              Article 5
 ISO Standard 2955 of 1 March 197 4» "Information processing -
Representations of S.I. and other units for use in systems with
 limited character sets"applies in the field covered by its
 paragraph 1 .
 ---pagebreak---                                  - 3 -
                             Article 6
Council Directive fl/354/EEC of 18 October 1971» as amended by the
Acts concerning the Accession to the European Communities and most
recently amended by Council Directive l6/no/EE£ of 27 July 1976 ,
shall stand repealed on 1 October 1981 .
                             Article 7
a) Member States shall adopt and publish before 1 July 1981
    the laws , regulations and administrative provisions necessary in
    order to comply with this Directive , which shall enter into force
    an 1 October 1981         and shall inform the Commission thereof .
b ) Once this Directive has been notified, Member States shall also
    ensure that the Commission is informed, in sufficient time to
    enable it to submit its comments , of any draft laws , regulations
    or administrative provisions which they intend to adopt in the
    field covered tor this Directive .
                             Article 8
This Directive is addressed to the Member States *
 ---pagebreak---                                                 ANNEX
                                             CHAPTER I
             LEGAL UNITS OF MEASUREMENT REFERRED TO IN ARTICLE 1 a
1 . SI UNITS AND THEIR DECIMAL MULTIPLES AND SUBMULTIPLES
    1.1 . SI base units
                                                            I                  Unit
                               Quantity
                                                                    Name                 Symbol
           Length                                                metre                m
           Mass                                                  kilogramme      I    kg
           Time                                                  second               s
           Electric current                                      ampere                A
          •Thermodynamic temperature                       |     kelvin                Κ
           Amount of substance                                   mole                  mol
           Luminous intensity                              j     candela              cd
                                                           !
           Definitions of SI base units :
           Unit of length
           The metre is the length equal to 1 650 763-73 wavelengths in vacuum of the radiation
           corresponding to the transition between the levels 2p10 and 5d, of the krypton 86 atom.
           (Eleventh CGPM ( I960), resolution 6).
           Unit of mass
           The kilogramme is the unit of mass ; it is equal to the mass of the international prototype
           of the kilogramme.
           (Third CGPM (1901 ), page 70 of the conference report).
           Unit of time
           The second is the duration of 9 192 631 770 periods of the radiation corresponding to
           the transition between the two hypcrfine levels of the ground state of the caesium 133
           atom .
           (Thirteenth CGPM (1967), resolution 1).
            Unit of eiectric ciment
           The ampere is that constant current which if maintained in two straight parallel conductors
           of infinite length, of negligible circular cross-section and placed one metre apart in a
           vacuum, would produce between these conductors a force equal to 2 X 10~7 newton
           per metre of length.
            (CIPM (1946), resolution 2, approved by the ninth CGPM (1948)).
 ---pagebreak---     Unit of thermodynamic temperature
    The kelvin, unit of thermodynamic temperature, is the fraction 1 /273*16 of the thermo­
    dynamic temperature of the triple point of water.
     (Thirteenth CGPM ( 1967), resolution 4).
     Unit of amount of substance
    The mole is the amount of substance of a system which contains as many elementary
     entities as there arc atoms in 0 012 kg ot carbon 12.
     When the mole is used the elementary entities must be specified and may be atoms, mole­
     cules, ions , electrons , other particles or specified groups of such particles.
     (Fourteenth CGPM ( 1971 ), resolution 3 ).
      Unit of luminous intensity
     The candela is the luminous intensity , in the perpendicular direction , of a surface of
      1 /600 000 m3 of a black body at the temperature of freezing platinum under a pressure
      of 101 325 newtons/m2.
      (Thirteenth CGPM ( 1967), resolution 5).
      1.1.1. Special name and symbol of the SI unit of temperature for expressing Celsius
               temperature
                                                                             Unit
                                 Quantity
                                                                   Namc                 Symbol
               Celsius temperature                            degree Celsius        °C
               Celsius temperature t is defined as the difference t = T – T» between the two
               thermodynamic temperatures T and T0 where T0 = 273*15 kclvins. An interval
               of or difference 'in temperature may be expressed either in kclvins or in degrees
               Celsius. The unit of 'degree Celsius' is equal to the unit 'kelvin'.
1.2. Other SI units
       1.2.1 . Supplcmentary SI units
                                                                             Unitv
                                 Quantity
                                                          | '      Namc                 Symbol
               Plane angle                                    radian                 rad
               Solid angle                                    steradian               sr
                (Eleventh CGPM , 1960, resolution 12).
               Definitions of supplementary SI units :
                Plane angle unit
               The radian is the plane angle between two radii which, on the circumference
                of a circle, cut an arc equal in length to the radius.
                (International standard ISO 31-1).
 ---pagebreak---          Solid angle unit
         The steradian is tlic solid allele which has its apex at the centre of a sphere and
         which describes on the surface of the sphere an area equal to that of a square
         having as it* side the radius of the sphere.
          ( International standard ISO 31-1 ).
1.2.2. Dcrivcd SI unit*
         Units derived coherently from SI base units and supplementary SI units are given
         as algebraic expressions in the form of products of powers of the SI base units
         and/or supplementary SI units with a numerical factor equal to 1 .
1.2.1 . Derived SI units having names and symbols
                                            I          Unir                            Kxpression
                                                                                                 In terms of base
                     Quantity              j     Name          Symbol
                                                                              In other
                                                                              SI units   |     or supplementary
                                                                                                      SI units
         Frequency                            hertz         Hz                                s- 1
         Force                                newton        Ν                               ' m ■ kg • s-2
         Pressure, stress                     pascal        l'a              N • m-2          m-1 • kg • s-2
         Energy , work' quantity
         of heat                              joule         J               N • m             m2 • kg • s-2
        Power(l), radiant flux r watt                       W               J-s-1             m2 ■ kg • s-'
         Quantity of electricity ,
        electric charge                       coulomb       C                                 s • A
         Electric potential , po­
         tential difference,elec- \
         tromotive force                 1    volt          V               W - A-'           m2 • kg • s-3 • A-1
         Electric resistance                  ohm                           V • ,A-1          m2 • kg • s-3 • A-2
         Conductance                          sicmens       S               A • V- 1          m-2 • kg-1 • sa • A'
         Capacîtance                        r farad         F               c-v- 1            m-2 ■ kg-1 • s* • A2
        Magnctic flu \                        weber      I Wb               V ' S '           m2 • kg ■ s-2 • A -1
        Mangeiic flux density                 resla         Τ             I Wb • m"2' | kg • s-2 • A-1
         Inductance                           henry                         Wb - A-'          ni2 • kg • s -2 • A -2
        Luminous flux                         lumen         Im                              ,cd ■ sr
        Illuminance                           lux           Ix              Im • m~2      ! m"2 • cd * sr
                                                                                          i
                                                                          j
         Activity ( of a radio­
         nuclide )                            becquerel  | i>q
                                                         I
                                                                                              s" 1
         Absorbed dose,speci-
         fic energy imported ,
         kerma , absorbed dose
         index                                gray          Oy              J • j*"'          m 2 • s-2
         Dose equivalent, dose
         equivalent index                     sievert       Sv              J • kg"1          m2 • s-2 .
        (') Special names for the unit of power : the name volt-ampere (symbol 'VA') when it m used to
             express the apparent power of alternaimK electric current , and var (symbol 'v.ir') when it in used
             to exprtss reactive electric power . The 4 var' is not included in CCl'M resolutions .
        Units derived from SI b.isc units may be expressed in terms of the unit.\ listed in
        Chapter A.
        In particular, derived SI units/m.iy be expressed by the special names and symbols
        given in the above table ; for example, the SI unit of dynamic viscosity may be
        expressed as m~ l ■ kg • s-1 or N • s • m~3 or Pa • s.
 ---pagebreak--- 1.3. Prefixes and their symbols used to designate certain decimal multiples and submultiples
          Factor        I      Prcfix    |    Symbol            Factor               Prcfix
                                                                                               |
                                                                                               i
                                                                                                     Symbol
     10»              1      exa             E                 10-1                 deci            d
     10"                      peta           Ρ                 10-1                 centi      i    c
                                                                                               i
     101*             j      tera            τ                 10-                  milli
                                                                                               I m
     10*                     g'ga            G                 10_#                 micro           μ
     10»                      mega            M                iO-»                 nano            Π
     10»                      kilo           le                io-"                 pico            ρ
     10»                     hccto            h                io-"                 femto           f
     101                     deca
                                              da         J | 10-1'            | atto                a
     The names and symbols of the decimal multiples and submultiples of the unit of mass
     are formed by attaching prefixes to the word 'gramme' and their symbols to the symbol
     V-
     Where a derived unit is expressed as a fraction, its decimal multiples and submultiples
     may be designated by attaching a prefix to units in the numerator or the denominator,
     or in both these parts.
     Compound prefixes, that is to say prefixes formed by. the juxtaposition of several of the
     above prefixes, may not be used.
1.4. Special authorized names and symbols
     1.4.1 . Special names and symbols of decimal multiples and submultiples of SI units
                                                                           Unît
                           Quantity
                                                   Name            Symbol         |           Value
             Volume                             litre            H1),                 1 1 = 1 dm* = 10-» m3
             Mass                               metric ton       ■                    1 t = 1 Mg = 103 kg
             Pressure, stress              | bar                 bar                  1 bar = 105 Pa
             (1 ) For the symbol for litre , where there is a risk of confusion between the letter 1 and
                  the number 1, one may use the abbreviation "ltr" or write "litre " in full (CIPM , 1976).
             Special names and symbols of decimal multiples and submultiples of SI units
             which may be used only in specialized fields
                                                                           Unit
                           Quantity
                                                   Namc            Symbol       H             Value
             Area of farmland and
             building land                      are              a                    1 a = 102 ma
             Mass per unit length of
             textile yarns and threads          tex* (')         tex*                 1 tex = \0~* kg • m-1
             Note: The prefixes and their symbols listed in 1.3 may be used in conjunction
                          with the units and' symbols contained in Tables 1.4.1 and 1.4.2.
                          The multiple 10* a is, however, called a 'hectare*.
              0) The character • after a unit name or symbol indicates that these do not appear in the lists drawn
                  up by the CGPM, CIPM, or BIPM. This applies to the whole of this Annex.
 ---pagebreak--- 2. UNITS WHICH ARE DEFINED ON THE BASIS OF SI UNITS BUT ARE NOT DECIMAL
    MULTIPLES OR SUBMULTIPLES THEREOF
                              !                                   Unie
           Quantity
                              |       Name                 Symbol                    Value
    Plane angle                 revolution* (a)                            1 revolution = 2 * rad
                                grade* or gon*       gon »                 1 8°n == 25Ô rad
                                degree               e                     1° = -2- rad
                                                                                  180
                                minute of angle      t
                                                                           1,= ïôîôô rad
                                second of angle      *
                                                                           v = 6Wm tid
                                                   i
    Time                        minute               min                   1 min ■- 60 s
                                hour                 H                     1 h = 3 600 s
                                day                [ d                  | 1 d =»= 86 400 s
    (a) No international symbol extsrs.
    Note : The prefixes listed in 1.3 may only be used in conjunction with the names 'grade* or
            'gon' and the symbols only with the symbol *gon\
 3. UNITS DEFINED INDEPENDENTLY OF THE SEVEN SI BASE UNITS
     The unified atomic mass unit is one-twelfth of the mass of an atom of the nuclide "C.
     The electronvolr is the kinetic energy acquired by an electron passing in a vacuum from one
     point to another whose potential is one volt higher.
                      I|                                       Unit
         Quantity |                Name                   Symbol                      Value
     Mass                unified atomic mass unit      u               1 u « 1 -6605655x10-" kg
     Energy              electronvolt                  eV    ,         leV »» 1-6021 892X10-" J
     The value of these units, expressed in SI units , is not exactly known.
     The above values are taken from CODATA Bulletin No 11 of December 1973 of the Inter­
     national Council of Scientific Unions.
     Note : The prefixes and their symbols listed in 1.3 may be used in conjunction with these two
             units and with their symbols.
  4. UNITS AND NAMES OF UNITS PERM1TIED IN SPECIALIZED FIELDS ONLY
                           '              I
                                                                        Unit
                    Quantity              |          Name                             Value
      Vergency of optical systems           dioptre*                      1 dioptre = 1 m-1
      Mass of precious stones               metric carat                  1 metric carat = 2X IO-4 kg
      Note : The prefixes listed in 1.3 may be used in conjunction with the above units.
 ---pagebreak---                                            CHAPTER II
         LEGAL UNITS OF MEASUREMENT REFERRED TO IN ARTICLE 1 b
Quantities, names of units, symbols and values
                                                              Unit
            Quantity
                                      Name             Symbol                    Value
 Blood pressure                 millimeter of      mm Hg             1 mm Hg = 133,322 Pa
                                mercury
Plane angle                                       JL* 0              1--= 205 rad
Activity ( of a radio­
nuclide )                        curie             Ci                1 Ci = 3-7 X 10,# Bq
Absorbed dose                    rad             ; rad(2)            1 rad = 10-1 Gy
Equivalent dose                  rem *             rem *             lrem = 10~2 Sv
Exposure (X and y
rays )                           rontgen           R                 1 R = 2-58 X10"4 C ■ kg "1
( 1 ) Symbol for "grade ".
(2 ) when there is risk of confusion with the symbol for radian, rd may be used as symbol for rad.
Note: The prefixes and their symbols listed in 1.3 may be used in conjunction with the units
         and symbols contained in this section, with the exception of 'g'.
 ---pagebreak---                                    CHAPTER III
                                                                     I
     LEGAL UNITS OF MEASUREMENT REFERRED TO IN ARTICLE 1 c
Quantities, names of units, symbols and approximate values
Lcngtn                                                                        ^ _
.     ,                                                1 in - 2*54 X 10-* m
                                                       1 ft = 0-3048 m
     Lm
fathom c)
                                                       1: fm = 1-829* r;™
                                                                          m
            ''                                          1 mile = 1 609 m
 Arca                                                                                     .
square foot
           . .                                          1J sqM ft =„ 0-929_...X 10-1 m1
                                                         lac - 4 047 m51
  acre
  Volume                                                                          „       •
       ..                                                1* fl" OK « 28-41 X 10-°        m1
  fluid ounce
  flm /i nnnrr
                                                         j iU = 0.142i x 10~» m*   _ _ -
  e.                                                      1 Dt = 0-5683 X 10-' m*
  p                                                       1 qt = 1-137 X 10"* m3
  gallon                                                  1 gal ^ 4-546 X 10- m'
  Mass            .
  ounce (avoirdupois)                                     11 oz  = 28-35 v
                                                             oi. tr = 31-10 :
   potmd                                                   11b = 0-4536 kg
   (*) Pot marine navigation only.