NBSIR 78-1476

Precision Laboratory Standards

of Mass and Laboratory Weights

A reprint of NBS Circular 547, Section 1 by Lashof and Macurdy, Aug. 1954

October 1978

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
PREFACE

National Bureau of Standards, Circular 547, Section 1, "Precision Laboratory

Standards of Mass and Laboratory Weights," served for many years as a defining

authority for various classes of weights and associated adjustment tolerances.

Technological and organizational changes which occurred within a few years after

the issuanca gradually led to its obsolescence and consequently, it has been

out of print for some time. In the interim, a new standard ASTM E617-78, "Lab

Weights Precision Mass Standards," has been issued updating the same subject

matter. There are still numerous requests for Circular 547 since it is widely

referenced in the literature. While the document is reprinted in its entirety

in NBS Handbook 77, this source is also out of print and available only at

certain repository libraries. Because of technical content and historical value

of Circular 547, it is being issued in the NBSIR series* of documents, to be

available through NTIS. It should be noted, however, that for matters

concerning calibration, one should refer to the latest copy of NBS SP-250,

"Calibration and Test Services of the National Bureau of Standards", available

from the Office of Measurement Services.

^Sections 5, 6, and 7, which refer to obsolete procedures, have been deleted.

October 1978

i
NBSIR 78-1476

PRECISION LABORATORY STANDARDS

OF MASS AND LABORATORY WEIGHTS

A reprint of NBS Circular 547, Section 1 by Lashof and Macurdy, Aug. 1954

October 1978

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Director

FOREWORD

National Bureau of Standards Circular 3, Design and Test of Standards of

Mass, has been a basic reference on mass standards and weighing since its

publication in 1918. The expanding needs of science, industry, and commerce

call for the replacement of Circular 3 by a larger and more comprehensive

document. Because of the time required to prepare a single large document,

it is planned instead to prepare a series of publications covering the subject

i matter of Circular 3 and issue each as it is completed.

This first publication presents the specifications of the National

Bureau of Standards for precision laboratory standards and other laboratory

weights. It also presents the regulations governing the submission of these

weights to the Bureau for test, and outlines the weight-calibration service

of the Bureau. It supersedes chapters VI, VII, and XI and related portions of

other chapters of Circular 3.

Other publications will present specifications for commercial standards of

mass, methods of weighing, tests for sets of weights, a discussion of fundamental

standards and concepts, and the design and test of balances and scales.

The material presented here is based not only on the third (1918) edition

of Circular 3, prepared by A.T. Pienkowsky, but also on Mr. Pienkowsky’s 1941

manuscript for a fourth edition. It also is based on suggestions and assistance

received from manufacturers and suppliers of weights for scientific use at the

1952 Annual Meeting of the Scientific Apparatus Makers Association.

A.V. Astin, Director

1954

ERRATA TO CIRCULAR 547 SECTION 1, PRECISION LABORATORY STANDARDS

OF MASS AND LABORATORY WEIGHTS

Page 10, Table 7, Acceptance tolerances 1 for class M weights is revised

as follows:

1. The acceptance tolerance applies to both Class M and Class J weights.

2. The individual tolerances below 1 gram is changed to 0.010 mg.

3. The group tolerance for each group of weights in a particular decade below

1 gram is changed to 0.020 mg.

!a11 paragraphs referring to this table shall be revised to reflect these

changes, in particular, the tolerance of 0.003 mg for Class J weights has been

changed to 0.010 mg.

April 10, 1962

ii

CONTENTS

Page

Preface..... i Foreword ii

1. Introduction 1 2. Classification of weights 2 3. Requirements for precision laboratory standards

of mass — Classes J, M, S, and S-l 3

3.1 Material 3

3.2 Design 4

3.3 Surface 4

3.4 Denominations 4

3.5 Marking of weights 6

3.6 Lifters 7 3.7 Case 7 3.8 Tolerances 7 3.9 Constancy under variations in humidity 11

3.10 Packaging 11

4. Requirements for laboratory weights

Classes P, Q, and T 12

4.1 Material 12

4.2 Design 13

4.3 Surface...... 13

4.4 Denominations.... 13

4.5 Marking of weights 13

4.6 Lifters 14

4.7 Case 15

4.8 Tolerances 15

4.9 Packaging 15

Appendix 1. Conversion factors for

units of mass 20

Appendix 2. Units and abbreviations for

marking weights 21
'

'
Precision Laboratory Standards of Mass and

Laboratory Weights

T. W. Lashof and L. B. Macurdy

This is the first part of the revision of National Bureau of Standards Circular 3 Design and Test of Standards of Mass, last revised in 1918. Laboratory standards of mass ’in order

of decreasing precision are classes J, M, S, and S-l. The newly introduced class J weights with a tolerance of 0.003 milligram for each weight, may be used for the calibration of equipment for ultramicroanalysis. Class M weights are reference standards for highprecision work and work demanding high constancy. Class S weights arr> laboratory working standards. Maintenance tolerances start at 0.0054 milligram fur class M frac- tional weights and 0.014 milligram for the smallest class S weights, and decrease to 5 parts per million for the larger weights of both classes. Class S-l are for use in routine analytical work with quick-weighing balances and are the most precise weights available in nonmetric

units. Tolerances vary from 0.025 milligram for the smallest weights to 10 parts per million

for the larger weights.

Classified for the first time are class P laboratory weights for routine analytical work

class Q for technical and student use, and class T for rough weighing operations. Maintenance tolerances for these weights start at 0.1 milligram for classes P and Q and 0 8 milli- gram for class T and decrease to 40, 100, and 300 parts per million, respectively, for the

larger weights of these classes. In addition to the tolerances, the denominations, composition, construction, marking

packing, and performance of weights of each class are fully described. Also described are

the nature and precision of the tests available and other features of the Bureau’s weightcalibration service. In general, the calibration service is intended primarily to provide

standard weights for the calibration of other weights, for legal use, and for use in scientific work where the highest precision is required.

1. Introduction

The National Bureau of Standards throughout

its history has been the center in the United States

for the calibration of precision standards of mass. Because of its position, which stems from its custody of the national standards of mass, the

Bureau has been the logical source of a system of

classification for both commercial and scientific weights. Although the National Bureau of Standards is not invested with the authority to impose

mandatory classifications and tolerances for weights, the classifications and tolerances that

have been recommended by the Bureau have met

with almost universal acceptance in this country.

The first classification issued by the National

Bureau of Standards was given in Circular 3, in

1903. This was revised in 1907 and again in 1918. The 1918 revision of the Circular (although

out of print for 25 years or more) has continued

as a basic reference on mass standards up to the

present time, even though additional classes of

weights have been added to supplement the original ones. During the 35 years that have passed since the

publication of the third edition of Circular 3,

a great expansion of scientific, technical, and

commercial activity has taken place, bringing with

it the need for new classes of weights and demands

for improved constancy and accuracy in certain

ranges of the established classes of weights. The

major changes that have been made to meet these

needs are:

1. The introduction of a new class J for very

accurately adjusted microweights.

2. The use of tighter tolerances for classes M

and S, especially for the smaller weights, in order

that in semimicro and analytical work the cor- rections for these weights normally may be

neglected.

3. The introduction of “group” tolerances in classes M and S, for the above purpose, and in

order to prevent accumulation of errors when

many small weights are used.

4. The separation of class S into an improved

class S and a new class S-l, the latter being almost

the equivalent of the class S of Circular 3, third

edition, and these two classes conforming to the

trade practice of double- and single-checked

weights.

5. The provision of nonmetric denominations

under class S-l, to meet the need for laboratory

standards in these denominations.

6. The introduction of three classes, P, Q, and

T, of rough laboratory weights, essentially equivalent to the classes of weights now available from

the laboratory supply houses, in order to provide

the standardization desired by the industry.

7. The use of a double tolerance scheme (acceptance tolerances for new or newly adjusted

1
weights and maintenance tolerances for weights

that have been in use), which recognizes that

weights of certain denominations and classes can and should be adjusted .very closely so that they

will remain within useful tolerances for a reasonable length of time.

8. A more detailed statement of the requirements, particularly with regard to material,

design, and surface finish, and other factors that

affect the constancy of weights, with a tightening

of these requirements for classes M and S. Several manufacturers are now making weights

that meet the closer tolerances and other requirements for classes M and S mentioned above. As

a matter of fact, the Bureau in 1951 increased the

accuracy and precision with which it certified

these weights. Modern research and the new

quick-weighing devices demand the improved

constancy and accuracy.

The Bureau will accept weights for certification

under these new requirements, beginning 3 months

after the date of this publication. For a period

of a year after the date of this publication, the

I

Bureau will continue to certify weights under tin

' previous requirements of Circular 3. After tin'll end of the 1-year period, noncommercial weights, i will be tested on the basis of these new requirements, and will be certified under one of the

classes J, M, S, S—1 , P, Q, and T, only when they

meet all the requirements contained herein for the class for which they are submitted.

Although every effort has been made to meet

present needs and to anticipate future needs for scientific mass standards and other laboratory

weights, situations undoubtedly will arise that

will indicate the need for amendments and additions to the material contained in this publication.

The staff of the National Bureau of Standards

wall consider suggestions for modifications of these i specifications. Recommendations for changes

j should be submitted to the National Bureau of

j Standards in waiting, with sufficient detail and ; with the information, research documents, etc., I necessary to establish the need for the recom- mended changes.

2. Classification of Weights

Weights may be divided into four groups according to their use, namely, precision laboratory

standards, laboratory weights, commercial standards, and trade weights. Precision laboratory

standards include weights used in scientific and

technical laboratories as standards of mass for the

calibration of other weights and weighing equipment or as precision laboratory weights for analytical work. Laboratory weights include weights

used for rough analytical work and for general

laboratory and technical work. Commercial

standards include the State, office, and working

standards used in law enforcement. Trade

weights include weights used in the purchase and

sale of goods both by the Government and in

ordinary trade. Table 1 lists the classes of weights under each

of these groups except the trade group. The

classification, specifications, and regulations for trade weights (as adopted by the National Conference of Weights and Measures and recom- mended by the National Bureau of Standards for promulgation by the several States) are covered

in NBS Handbook 44, 1 revised to date, or its successor. The intended use or purpose of weights of each

of the laboratory classes is given at the beginning

of chapters 3 and 4; that for each of the commercial classes (A, B, and C) is given in Circular 3. 2

1 NBS Handbook 44, Specifications, tolerances, and regulations for commercial weights and measures, and weighing and measuring devices, for sale by the Superintendent of Documents, U. 8. Government Printing Office. Washington 25, D. C., $1.25. •NBS Circular 3, 3d cd., Design and test pf standards of mass (1918.) Out of print, but available in many libraries.

Table 1. National Bureau of Sta)tdards classification of weights

Class Application

Precision Laboratory Standards

JM

S

S-l

Microweight standards (microbalance work).

High-precision scientific standards (reference, high-precision, and high-constancv work).

Scientific standards (reference, calibration, and

precision analytical work).

Laboratory standards (routine analytical and

precision noninetric work).

Laboratory Weights

.. P » Q

T

Analytical and precise technical weights. General laboratory, technical, and student

weights.

Utility weights.

Commercial Standards (reference, working, and

field standards used in law enforcement)

A 3 B 3 C 3

State primary standards. State working standards. Test weights.

Trade Weights (weights used in the sale of commodities and services)

See classes listed in NBS Handbook 44.

1 Formerly class 5-2.

• This classification is being revised. 2
3. Requirements for Precision Laboratory Standards of Mass

Classes J, M, S, and S-l

Class J. These are metric weights designed

primarily as standards for the calibration of

weighing equipment used in the precise determination of very small masses in ultramicroanalysis.

The effect of changes in relative humidity will be small for properly constructed class J weights.

Class M. These are metric weights designed

for use as reference standards, for work of the

highest precision, and for investigations demanding

a high degree of constancy over a period of time.

Tolerances for class M weights up to 5 g have been

so selected that for most semimicro and microchemical work the corrections for the individual

weights may be neglected.

When used with care, properly constructed

class M weights will be constant within considerably less than the prescribed tolerances. As a group, these weights should be constant for several

years within the indicated accuracy of the highprecision class M calibration (see 5.1, class M (a)). Class S. These are metric weights designed as working standards for the calibration or other

weights or as high-precision analytical weights for the more precise weighings in physical and

chemical laboratories and in assay work. The

tolerances for class S weights are such that the

weights may be used without corrections, other

than allowance for air buoyancy, for most analytical work and as keyboard or dial-controlled

weights in quick-weighing analytical balances

having a 200-g capacity.

Class S weights may be used also as reference

standards. However, they may not be expected

to remain as constant as class M weights.

Class S-l

These are designed for use as

precision laboratory weights in routine analytical

work with balances using quick-weighing devices,

such as a chain. Class S-l weights bridge the

area between the best laboratory weights (class P)

and the precision laboratory standards. Class S-l

includes weights in avoirdupois, apothecary, troy,

and certain other units (see table 4), as well as those in metric units. Weights that meet class S-l specifications are the most precise laboratory

working standards currently available in nonmetric units.

3.1. Material

3.1.1. Hardness

Class J. Weights shall be constructed of hard,

nonporous material, resistant to abrasion, and not

likely to chip or spall in use. The Knoop hardness

number of this material when determined at a

test load of 100 g shall be 165 or greater (e. g., platinum-iridium or tantalum).

Classes M, S, and S-l. The hardness requirement shall apply to the material of which the

body (including knob) of the weight is constructed

and also to the plating of a plated weight, except

as noted below under 3. 1.1.1. The Knoop hardness number shall be as follows: (a) 125 or greater

at a test load of 200 g for weights above 30 mg or equivalent (brass and harder materials, such as

stainless steel) ; (b) 55 or greater at a test load

of 100 g for weights 30 mg and below (aluminum

and harder materials).

3. 1.1.1. Option

Classes M and S. At the option of the purchaser, if class M or S weights are to be used as reference standards, the surface of weights 1 g

and above may be protected with gold.

3.1.2. Corrosion Resistance

Classes J, M, S, and S-l. Weights shall be

constructed of material that is resistant to oxidation or corrosion, except as follows: Classes M, S, and S-l. Brass and materials

similarly susceptible to oxidation and corrosion

may be used for weights 1 g and above, provided

that the surface is suitably protected in accordance

with 3.3.3. Aluminum, aluminum alloys, and

other metals that have resistance to oxidation

and corrosion, depending largely on the surface

condition of the metal, may be used only when

the surface will take and hold a high polish.

3. 1.2.1. Adjusting Material

Classes S and S-l. Tantalum, copper, aluminum, tin, or material equally resistant to oxidation

and corrosion shall be used if adjusting material

is required. Materials that readily oxidize and

corrode (lead, dirt, powdered materials, organic

materials, such as paper and oil, etc.) shall not be used in adjusting cavities.

3. 1.2. 2. Contamination

Classes J, M, S, and S-l. All surfaces, exterior

and interior (including the adjusting cavity and

threads of the knob) shall be free of deposits,

residues, and other contaminating substances,

such as residues from electroplating and cleaning

solutions.

.3.1.3. Magnetic Properties

Classes J, M, S, and S-l. Weights shall be

constructed of nonmagnetic material. Neither

ferromagnetic nor strongly paramagnetic materials

may be used.

Classes S and S-l

Nonmagnetic stainless-steel

alloys (including type 18-8) may be used, provided

the nickel content is at least 50 percent by weight

of the chromium content.

3.1.4. Density

Classes J and M. No requirements.

Classes S emd S-l

The total volume, including

any air-tight cavity, shall be such that the average

density is within the ranges shown in table 2.

3
Table 2. Density for class S and S-l weights

Weights Allowed density

tlcm • Greater than 1 g (or equivalent) 7.8 to 0.1

1 g to 50 mg, inclusive (or equivalent) — 4.5 and up

Less than 50 mg .. 2.6 and up

3.2.

Design

3.2.1. General Shape

Classes J, M, S, and S-l . A weight may have

any shape that does not introduce features that reauce the reliability of the weight. All weights

shall be free of ragged or sharp edges or ends.

Wire weights shall not be excessively long and

shall not be tightly coiled or otherwise shaped

so as to have a tendency to catch and hold lint or dust. Both sheet-metal and wire weights

shall be free from cracks such as may be formed

in bending.

3.2.2. Thickness

Classes J, M, S, and S-l. Sheet-metal weights

shall not be unnecessarily thin. In particular,

the weights shall not be so thin that the surface

tension of water will bend them out of shape.

Class J. The nominal thicknesses of the material from which sheet-metal weights are formed

shall be equal to or greater than the values in table 3. The actual thickness shall be not less than 90 percent of the nominal thickness.

3.2.3. Number of Pieces

Classes J, M, S, and S-l. • The entire weight

shall be a single piece and homogeneous, except

as follows:

Class M. Surface protection in accordance

with 3.3.3; gold adjusting material fused on the

upper surface of sheet-metal weights.

Classes S and S-l. Surface protection (3.3.3); means of adjustment (such as a screw knob covering an adjusting cavity); adjusting material in adjusting cavity; gold adjusting material fused on the upper surface of sheet-metal weights.

Table 3. Nominal thickness for class J sheet-metal weights

(.Minimum values)

Weight Thickness Weight Thickness

mg in. mg in. 50 0. 0050 i 0. 0009

30 . 0047 0. 5 . 0006

20 . 0042 . 3 . 00045

10 . 0031 2 . 00037

5 . 0023 j . i . 00026

3 . 0015 . 05 . 00019

2 . 0013 j

1

3.3. Surface

3.3.1. Irregularities

Classes J and M. The entiro surface of the* weight shall be smooth, except for such markings

as are allowed under 3.5, and shall be highly

polished.

Classes S and S-l. The entire surfaco of the

weights shall be smooth, except for such markings

as are required under 3.5, and shall be carefully

polished or have equivalent finish.

3.3.2. Porosity

Classes J, M, S, and S-l. When subjected to unaided visual inspection, the surface shall appear

free from pits and pores and shall show no effects of porosity.

3.3.3. Protection

(a) Larger Weights (i. e., weights other than

sheet-metal or wire weights)

Class M. Weights of brass, bronze, or other

metals that tarnish on exposure to the atmosphere

shall be plated with platinum, rhodium, or other

suitable metal. Gold plating may be used at option of purchaser (3. 1.1.1). There shall be no darkening of the surface and no formation of

spots of any kind when the weights are boiled for 3 half-hour periods in distilled water and cooled in

distilled water between boilings, or when the

weights are subsequently dried at a temperature

of 110° C for 1 hour.

Classes S and S-l. Unless the surface material

is at least as resistant to atmospheric corrosion as aluminum, it shall be plated with metals such as platinum or rhodium, or shall be lacquered.

Lacquer, if used, shall be hard, of only moderate ' thickness, transparent, and not easily chipped.

Lacquer shall not be used, however, on weights

that are made of, or are plated with, a material

that normally need not be protected against oxidation or corrosion. Gold plating shall not be

used as the final coating, except that class S

weights that are to be used as reference standards

may be gold plated at option of purchaser (3. 1.1.1).

(b) Sheet-Metal and Wire Weights

Classes J, M, S, and S-l

.

Sheet-metal and wire

weights shall be made of a material that requires no surface protection. If these weights arc adjusted by fusing or plating, the adjusting material

shall require no surface protection. Lacquer or other coatings, other than electroplating, shall not

be used.

3.4.

Denominations

3.4.1. System in Which Denominations Are

Expressed.

Classes J, M, and S. The system shall bo

metne.

4
Class S-l. The system shall be metric, avoirdupois, apothecary, troy, or certain other units

as set forth in table 4. 3.4.2. Individual Weights.

Classes J, M, S, and S-l. The denominations

shall be selected from table 4, except when weights

are intended for a special application.

3.4.3. Sets of Weights.

Classes J, M, S, and S-l

The weights included in a set shall be sufficient for each weight of the set to be compared directly with another weight of the set or with a summation of other weights of the set.

3.4. 3.1. Optional Series.

Classes J, M, S, and S-l. The weights of a set may be arranged in one or more of the following

series: 5-2-1 -1-1; 5—2—2—1—1 ; 5-3-2-1-1; or 8-4-2-1-1; or equivalent as specified in 3.4.3. The unit in boldface represents a summation of

smaller weights of the set. When there are no

smaller weights in the set, the unit in boldface

represents an additional weight that is required

by 3.4.3 in the 5-2-1-1-1 and 8—4-2-1-1 series,

but which may be omitted in the 5-2-2-1-1 or 5-3-2-1-1 series.

Table 4. Preferred denominations for precision laboratory standards of mass —

' - —

Classes

J M 8 s-l 8-1 (nonmetrlo)

Metric Avoirdupois Apothecary Troy Grain

1 Carat

mg *0 *0 *0 lb oz oz ap OZ t Grain c 50 25 50 50 100 10 12 1 , 000 j 10, 000 2, 500

30 20 25 25 50 8 10 500 5,000 2, 000

20 10 20 20 25 5 8 300 3,000 1, 000

10 5 10 10 20 4 6 200 2,000 500

5 3 5 5 10 3 5 100 | 1,000 300

3 2 3 3 8 2 4 50 500 200

2 1 2 2 5 1 3 30 300 100

1 1 1 4 Vs 2 20 200 50

0. 5 0 3 v* 1 10 100 30 .3 500 0 0 2 y; 5 50 20 .2 300 500 500 1 Me dr ap 3 30 10

. 1 200 300 300 0. 5 M2 6 2 20 5

. 05 100 200 200 . 3 %4 5 1 10 3 50 100 100 . 2 0.

4 0. 5 5 2 30 50 50 . 1 . 3 3 . 3 3 1 20 30 30 . 05 . 2 2 O 2 0. 5 10 20 20 . 03 . 1 1 . 1 1 . 3 5 10 10 . 02 . 05 Vs . 05 0. 5 • 2 3 5 5 . 01 . 03 . 03 . 3 • 1 2 3 3 . 005 . 02 8 ap . 02 . 2 . 05

1 2 2 . 003 . 01 2 . 01 . 1 . 03

1 1 . 002 . 005 1 . 005 . 05 . 02

mg . 001 . 003 . 003 . 03 . 01 500 mg mg . 0005 . 002 . 002 . 02 300 500 500 . 0003 . 001 . 001 . 01 200 300 300 . 0002 . 0005 . 0005 . 005

100 200 200 . 0001 . 0003 . 0003

50 100 100 . 00005 . 0002 . 0002 A.T. 30 50 50 . 00003 . 0001 . 0001j 4 20 30 30 . 00002 2

10 20 20 . 00001 1 dwt 1 5 10 10 10, 000 0. 5 3 5 5 5, 000 . 2

2 3 3 3, 000 . 1

1 2 2 2, 000 . 05

0. 5 1 1 1, 000

. 3 0. 5 0. 5 500 Factor weights

. 2 . 3 . 3 300

. 1 . 2 . 2 200 0

. 05 . 1 . 1 100 Carbon 2. 7273

. 05 . 05 50 Yi carbon 1. 3636

30 silicon 1. 1680 I 20 V10 silicon 0. 4672 : 10

K Phosphorus 1. 630

3 Sugar 52

2 26

1 13

294607°—54 2 5
Table 5. Maximum and minimum denominations of commonly used sets of precision laboratory standards of mass

Class ami purpose From maximum

i To minimum

Class J: Microbalance 50 mg 0.05 mg

Classes M and S: GENERAL PURPOSE

Analytical balance 100 g 1 mg

Semimicro-balance . . .. 50 ft 1 mg

Microanalytical balance - - 20 g 1 nig

Assay balance. . ... . 1 g 1 mg

BALANCE WITH BUILT-IN WEIGHTS (100 mg tO 1 mg)

Analytical balance . 100 g 100 mg

Semimicro balance. . _ . .. . 50 g 100 mg

Microanalytical balance 20 g 100 mg

Class S-l:

general purpose (metric) i Large-capacity balance . . _ _

' 20, 5, 2, or 1 kg 1 g or 5 mg

Large-capacity analytical balance. ... .. . ... 500 or 200 g 5 mg

Analytical balance .. .. .. 100 g 5 mg

ANALYTICAL BALANCE

With chain . 100 g 100 mg

With chain and rider or with chain and built-in weights 100 g 1 g general purpose (customary)

Avoirdupois.. . .. .. .. 50, 10, 5, 2, or 1 lb or 8 oz

50, 10, 5, 2, or 1 lb

‘•32 oz Do 0.001 lb Do 10 02 0.001 oz Apothecary .. 12 oz ap or 4 dr ap 0.1 grain Trov. . _ . ._ .. . 500 oz t 0.1 grain

Do 500 oz t 0.00 1 oz t. Drain... . ...... .... .. . . . 1,000 grain 0.1 grain Carat .. .. .. . (with two 200-c weights) 200 c 0.01 c Assay ton. . 4 or 1 A.T. Hu A.T.

1

3. 4. 3. 2. Optional Maximum and Minimum Denominations.

Classes J, M, S, and S-l. Maximum and

minimum denominations of commonly used sets of laboratory standards of mass are given in

table 5.

3.5. Marking of Weights

3.5.1. Denomination

Classes J, A I, S, and S-l. Weights shall be

marked with the number and unit, as specified

in 3.5.1 .1 and 3. 5. 1.2

3. 5. 1.1. Number

By “number” is meant the number representing

the nominal mass or “value” of each weight as expressed in terms of some acceptable unit.

Class J. If the shape or size of a weight does

not distinguish it from other weights of the set, it may be marked with small shallow dots or other

distinguishing marks. The numbers may be

marked on the larger weights, and, if marked,

shall be expressed in milligrams.

Class M. The numbers may be marked on the

weights, and if marked, shall be expressed in kilo- grams, grams, or milligrams.

Class S. The number shall be plainly marked

upon each weight, except in the case of riders and

other wire weights, and shall be expressed in kilo- grams, grams, or milligrams.

Class S-l

.

The number shall be plainly marked

upon each weight, except in the case of riders and

other wire weights, and shall be expressed in terms of one of the units listed in appendix 2.

3. 5. 1.2. Unit

Classes J, AI, S, and S-l. The unit (in terms

of which the nominal value of each weight is ex- pressed) shall be as specified in 3. 5. 1.1 for each

class. The name of the unit, if abbreviated, shall be abbreviated in accordance with appendix 2. The abbreviation shall not include a period.

Classes J and AI. The unit shall not be marked

on weights less than 100 g. Classes S and S-l (metric). The unit may be

marked on the larger sheet-metal and cylindrical

weights.

6
Class S—l (nonmetric). The markings shall in- clude the name of the unit or its accepted abbreviation in accordance with appendix 2, except that

j on cylindrical weights below. )i oz or equivalent

j and on sheet-metal weights below 1 grain or

eouivalent, the name of the unit may be omitted

when space does not permit its inclusion in legible

form.

3.5.2. Duplicate Weights

Classes J, M, S, and S-l

Duplicate weights

shall each dc marked with one or more distinguishing marks.

3.5.3. Unnecessary Markings

Classes J, M, S, and S-l. Markings other than

those required or allowed in 3. 5. 1.1, 3. 5. 1.2, and

3.5.2 shall not be used.

3.5.4. Depth of Markings

Classes J, M, S, and S-l. Markings shall be

shallow, relatively broad, and free from burrs

and sharp angles. The markings shall not perforate or crack sheet-metal weights.

3.6.

Lifters

Classes J, M, S, and S-l. Special lifters or

forceps shall be provided for sets of weights.

Lifters or forceps shall be provided for individual

weights when specified by the purchaser.

3.6.1. Design of Lifters

('/asses J, A/, S, and S-l

The lifters or forceps

shall hold securely the weights for which they are designed. Additional pressure shall not cause the

dropping of small weights or the forceful ejection

of large weights.

(a) For weights 500 g and larger the parts of

the lifters that may come into contact with the

weights shall be covered with some material softer than the surface of the weight, such as plastic,

velvet, or chamois skin from which the grease has

been removed.

(b) For smaller weights the lifters may be of

the same design, where practicable, or may be of

a material softer than the weights, such as ivory,

close-grained wood, or plastics that are not affect ed by alcohol. When the parts of the lifters or forceps that come in contact with the weights

are not covered with a soft material, they shall be smooth and polished and the edges on which

weights may be partially or wholly lifted shall be

well rounded.

(c) If forceps are used solely for lifting slieet- metal weights, steel forceps with gold-plated tips

may be used.

3.6.2. Warping of Lifters

Classes J, A/, S, and S-l. Forceps shall be so constructed that with use or with storage in a

closed position they will not warp enough to interfere with their performance.

3.7.

Case

Classes J, M, S, and S—l

One or more suitable cases shall be provided with each set, of weights.

The case shall be so designed that, as long as the

lid remains closed, the weights cannot get out of

their pockets (3.7.1). The hinges and locks shall be adequate to hold the lid closed with any reasonable handling. There shall be no discoloration of

the weights due to the lining or the case, such as might result from long storage in a warm or damp

location.

Class J. The case shall be dustproof.

3.7.1. Pockets

Classes J, S, and S-l. A separate pocket shall be provided for lifters or forceps and for each

weight, and all pockets shall be large enough so that no appreciable frictional force will be en- countered in inserting or removing weights. If the cover is not lined, the individual holes in the cover for the knobs of the weights shall be smooth

or lined. Pockets for weights 1 g or equivalent

and larger shall be lined with some soft material,

such as velvet.

Class M. Either a lined pocket shall be provided, as specified for classes J, S, and S-l, or the

position of the weight may be determined by a

shallow ring or plate. If a guard ring or plate is used, the diameter of the unlined pocket or opening shall be at least 10 percent larger (and in all instances at least 2 mm larger) than the diameter

of the weight, and all parts of the case shall be

designed so that the weights can be inserted or removed without danger of rubbing on any part

of the case.

3.7.2. Marking of Case

Classes J, M, S, and S-l. The class and the

unit or system of units shall be marked conspicuously on the case. In addition, denominations shall be marked as follows: Class J. Each pocket of the case shall be

marked with the denomination of the weight to be kept in the pocket.

Class M. If the denomination is not marked

on the weight (3.5.1), it shall be marked beside

the pocket in which the weight is kept.

Classes S and S-l. The denominations may be

marked beside the pockets in which the weights

are kept.

3.8.

Tolerances

The tolerance of a weight is the maximum

allowable departure of the weight from its nominal

value.

3.8.1. Basis For Adjustment

Classes J, M, S, and S-l. Ordinarily, weights

shall be adjusted according to their “apparent mass versus brass” values. However, in those

cases in which the larger weights of a set are of

7
Table

6.

Tolerances

for

class

S-I

weights ) 8
Tabi.k

6.

Tolerances

fur

class

S-l

weights

—

Continued

8 8 O T O O 10 N a N — 00 g g'N 1- -r CO ^ ^ CO **-« ^ _

6

CD ^ N

’

— d 0

i- t- 2

a

£3

_C£ CO O O N V 0 co 00

>* c* N CD O O CO c l_ a co cd N CD CO $ 0 .... N H

< C3 _c iONh 05 § 03 .3 N ' *-H O i-H - fl C G •§

Ih

a3 50

a> %NH d

' s0

a® £ 0 0 0 u 2^5.0 0 £

fcJD 3m

Q aj 7 m to Q* 0

0

§

iO o

N »D iCOW ONO .OOO O O CO N hh ^ O O

OOO OMC O ^ CO CO N N OOO OOO

O <N ON ^ OOO

OOO OOO OOO O <N OOO ON*-H OOO O (N

00 O CO o OOOO (N 00 O O oor^oo rr co co co OOOO OOOO

00000 OOOO

<N(N<N<N N N N N OOOO OOOO

xO OOO OOOO

O CO <N 1 OWMH ©

^O OOO OOOO Soooo OCO(N H O (N (N ' OOOO

iD CO N *-< O iD iD *d O rt< CON

O iO O O 10 N NiOCCNh OOOO

lOCON^

OOOO O CON *h

Oraiu 0.

10

.

050

.

020

.

Oil

.

0074

.

0043

.

0031

.

0023

.

0017

.

0013

.

0011

.

00083

.

00070

.

00060

.

00050

.

00043

.

00040

.

00038

.

00038

.

00038

O n *d O N X CD lO O ID N 00 X 0 iD — X MOt X X N N N N N

<d*tO N CON 'f N N -H — O OOO OOO OOO O

^ CD «hO

-

ID

iD N —

O iONh OOO O

OOO OOO OOO iONh d

' •|o OOO OOO OM-h

, £0 lO N —

! O .

! 0 CNh

9
some material having a density markedly different

from brass, all the weights of the set may be

adjusted (at the option of the purchaser) according

to the apparent mass vs. platinum, tantalum,

gold, or whatever is the material ot the larger

weights.

“Apparent mass vs. brass” values are those that the weights would be assigned on the basis of a comparison

at 20° C in normal air against normal brass standards. “Apparent mass vs. other material” values are those that the weights would be assigned on the basis of a comparison at 20° C in normal air against the true mass

of standards of this other material. In both cases, no corrections would be applied for the buoyant

effect of the “normal air” (defined as air having a density of 1.2 mg/cm3 ), and values would be derived from the true mass of the standards (normal brass standards being defined as standards composed of brass having a density of 8.4 g/cm3 at 0° C and a

coefficient of cubical expansion of 0.000054 per deg

Celsius (centigrade)). 3.8.2. Acceptance Tolerances

Classes J, M, S, and S-l. New and newly

adjusted weights shall meet the tolerance re- quirements specified in 3.8.2. 1 and 3. 8. 2. 2. 3.8.2. 1 . Tolerances For Individual Weights

Class J. For weights that can be intercompared readily in a series (i. e., weights of the

preferred denominations listed in table 4), the

tolerance for each weight shall be 0.003 mg.

For weights the denominations of which are of

irregular amounts not readily intercomparable in a series, the tolerance for each weight shall be

specified by the purchaser, but normally shall be

not loss than the tolerances for the class M weights

nearest it in value.

Class M. Individual weights shall be correct within the tolerances prescribed in table 7 in

the column marked “Individual.”

Class S. Individual weights shall be correct within the tolerances prescribed in table 8 in the

column marked “Individual.”

Class S-l. Weights shall be correct within

the tolerances prescribed in table 6, and, in addition, not more than one-third of the weights

of a set of new or newly adjusted weights may be

in error by more than one-half of these prescribed tolerances.

Classes M, S, and S-l. For an individual

weight of a denomination not listed in the tables,

the tolerance shall be determined by proportional

interpolation between tolerances given for weights

of the next larger and next smaller amounts.

3. 8. 2. 2. Group Tolerances

Classes M and S. The corrections of the in- dividual weights shall be such that no combination of weights that is intended to be used in a weighing shall differ from the sum of the nominal

values by more than the amount listed under the

group tolerance. The group tolerances and the

weights to which they apply are as follows: Class M. Weights of a set that include weights

less than 10 g shall conform to the group tolerances

prescribed in table 7 in the column marked

“Group.”

Class S. Weights of a set that include weights

smaller than 50 g shall conform to the group

-tolerances prescribed in table 8 in the column

marked “Group.”

3.8.3. Maintenance Tolerances

Classes J, M, S, and S-l. Weights that have

been in use shall meet the tolerance requirements

specified in 3.8.2. 1. and 3. 8.2. 2., except as follows: Class M. Maintenance tolerances for weights

from 500 mg to 100 mg shall be 0.0105 mg for individual weights and 0.020 mg for the group.

Class S. Maintenance tolerances for weights

100 mg and larger shall be twice the acceptance

tolerances for these weights, as shown in table 8 both for individual weights and for decade groups.

Table 7. Acceptance tolerances 1 for class .1/ weights

Denomination Individual Group

mg mg 25 125 20 100

10 50

5 25

3 15

2 10

1 5. 0

9 500 2. 5 300 1. 5 200 1. 0

100 0. 50

50 . 25 30 . 15 20 . 10 10 . 050

5 . 034 i 32

. 034

. 034 > 0.065

1 . 034 1 mg 500 . 0054

300 | 200

. 0054

. 0054 i 0.0105

100 . 0054 1 50 . 0054

30 ] 20

. 0054

. 0054 i 0. 0105

10 . 0054 J

5 . 0054

| 3

2

. 0054

. 0054 1 0. 0105

1 . 0054 J

| 0. 5 . 0054

]

. 3

. 2

. 0054 i

. 0054 i 0. 0105

. 1 . 0054 ]

. 05 . 0054 0. 0105

1 Maintenance tolerances are the same as acceptance tolerances, except

that the maintenance tolerances for weights from 500 mg to 100 mg arc 0.0105 mg for individual weights and 0.020 mg for the group.

10
Table 8. Acceptance tolerances 1 for class <S weights

Denomination Individual Group

*0 mg mg

25 62

20 60

10 25

5 12

3 7. 5 2 5. 0

1 2. 5

9 500 1. 2 300 0. 75 200 . 50

100 . 25

50 . 12

30 . 074

} 20 . 074 0. 154 10 . 074 1

5 . 054

] 32

. 054

. 054 i 0. 105

1 . 054 J mg 500 . 025

300 ] 200

. 025

. 025 l 0. 055

100 . 025 J 50 . 014

| 30

20

. 014

. 014 i 0. 034

10 . 014 J 5 . 014

] 3

2

. 014

. 014 l 0. 034

1 . 014 J

0. 5 . 014

]

. 3

. 2

. 014

. 014 i 0. 034

. 1 . 014 J

. 05 . 014 0; 034

' Maintenance tolerances for weights below 100 mg are the same as the acceptance tolerances. For weights 100 mg and above the maintenance

tolerances are twice the acceptance tolerances.

3.9. Constancy Under Variations in

Humidity

Classes S and S-l

When the relative humidity

of the surrounding atmosphere is kept at 30 per- cent for 3 days, raised to 70 percent and kept

there for 4 days, and then brought back to 30

percent and kept there for 2 days, neither the mean variation nor the net gain shall be more

than the amounts specified or calculated in ac- cordance with table 9.

Table 9. Tolerances on variability and net gain caused by

variations in atmospheric humidity from 30 percent to 70

percent for weights of classes S arid S-l

Denomination

1 Maximum allowable variation and ! net gain for—

Class S Class S-l

9 mg mg 2221 0. 22 0. 65 2200 . 20 . 60 2121 . 15 . 44 2100 . 13 . 38 250 . 085 . 25

100 . 070 . 21 50 . 050 . 14 30 . 030 . 090

20 . 025 . 075

10 . 016 . 048

5 . 011 . 032

3 . 009 . 028

2 . 007 . 020

1 . 005 . 015

The “mean variation” is defined as the average of the quantities B-A and C-D, and t he "net gain” is defined as the quantity D-A, where A, B, O, and D

are the measured masses (corrected for the buoyant

effect of the air) of the weights under the following

conditions: (A) After the first '3 days at 30 percent

relative humidity, (B) after 1 day at 70 percent, (C)

after 4 days at 70 percent, and (b) after again being

at 30 percent fox 2 days.

For individual weights of denominations listed

in table 9, the allowable variation and net gain

shall be as listed in the table. For individual

weights of denominations not listed in the table,

the allowable variations and net gain shall be determined by proportional interpolation between

values given for weights of the next larger and

next smaller amounts.

For all ordinary sets and for groups the sum of

which does not exceed 250 g or equivalent, the

allowable variation and net gain shall be applied

to the sum of the weights. Larger groups shall be divided in any appropriate manner into groups

of 250 g or smaller. For sets or groups of weights

listed in table 9, the allowable variation and net gain shall be as listed. For sets or groups of

weights not listed in the table, the allowable variation and net gam shall be equal to the sum of

the amounts allowable on weights of the denominations actually in the group.

3.10. Packaging

This section applies to new or newly adjusted

weights.

3.10.1. Separate Package

Classes J, M, S, and S-l. Each set of weights

11
and each individual weight not part of a set shall be packaged separately.

3.10.2. Seal

Classes J, M, S, and S-l. The package shall be sealed by the manufacturer or adjuster so that the weights cannot be removed from the

package without destroying the seal. The weights

shall be packed in accordance with 6.4 before

sealing. 3.10.3. Marking

Classes J, M, S, and S-l. The sealed package

shall be marked with the class of weight, the

maximum and minimum denominations contained

therein, the unit or system of units, the name of

the manufacturer, the manufacturer’s type number, a caution against breaking the seal, and any

other appropriate information.

3.10.4. Manufacturer’s Information Sheet

Classes J, M, S, and S-l. A manufacturer’s

information sheet shall be packaged with new

weights. It shall list the density to two or three

significant figures and also the composition of

the allov, commercial grade, or accepted trade

name of the material of which the weights are composed. (See 3.1 for specifications as to density and composition.) The nature of the

surface protection (3.3.3) and the construction

(one-piece, screw-knobs, screw-knob pinned, driven

knob, etc.) shall also be described on the information sheet.

4. Requirements for Laboratory Weights—Classes P, Q, and T

Class P (formerly class S-2). These weights

are designed for routine analytical work in the

scientific or technical laboratory.

Class Q. These weights are designed for use with precision pressure gages and for the technical

work of commercial and student laboratories.

Weights of this class are suitable for the laboratory

dispensing of chemicals and pharmaceuticals,

rough determination of mass in the elementary

physics laboratory, etc. Class T. These weights are designed for rough

weighing operations in the physical and chemical laboratories, such as with force-measuring

apparatus.

4.1. Material

4.1.1. Hardness

Classes P, Q, and T. The Knoop hardness

number shall be as follows: (a) 125 or greater at a

test load of 200 g for weights above 5 g or % oz or equivalent (brass and harder materials) ; (b) 55 or greater at a test load of 100 g for weights of 5 g or equivalent and below (aluminum and harder

materials)

.

4. 1.1.1. Option

Classes P, Q, and T. If the weights are to receive rough use, the hardness requirement may

be changed at the option of the purchaser to read:

The Knoop hardness number shall be 225 or greater at a test load of 500 g for all weights (cast

iron and stainless or dense steel).

4.1.2.

Corrosion Resistance

Classes P, Q, and T. Weights shall be constructed of material that is resistant to oxidation

or corrosion. Lead shall not be used. Cast iron

and other metals with similar rates of oxidation

may be used for weights of class T but shall not be used for weights of the other classes. Iron and

steel shall not be used for weights of 5 g or % oz or equivalent and below, except that stainless steel may be used for weights of all denominations.

4. 1.2.1. Adjusting Material

Classes P, Q, and T. Brass, copper, aluminum,

tin, or material equally resistant to oxidation and

corrosion shall be used if adjusting material is required.

Classes P arid Q. Lead shall not be used.

4. 1.2.2. Contamination

Classes P, Q, and T. All surfaces, exterior and

interior (including the adjusting cavity and

threads of the knob) shall be free of deposits,

residues, and other contaminating substances,

such as cutting oil and residues from electroplating and cleaning solutions.

4.1.3. Magnetic Properties

Class P. Weights shall be constructed of non- magnetic material, with the following exceptions

or provisions:

(a) Nickel may be used for surface protection.

(b) Nonmagnetic stainless steel alloys may be

used, provided the nickel content is at least 50

percent by weight of the chromium content.

(c) Dense steel, rolled or otherwise worked,

may be used for weights of 10 kg or 20 lb or equivalent and above.

Class Q. Class P specifications apply except

that dense steel, rolled or otherwise worked, may

be used for weights above 5 g or % oz or equivalent.

12
Class T. Class Q specifications apply except

that cast iron may be used for weights of 100 g or

4 oz or equivalent and above.

4.1.4 Density

Classes P, Q, and T. Weights shall be constructed of materials having densities within the

ranges shown in table 10.

Table 10. Density for laboratory weights

Class Weights Allowed density

P, Q

T

12 g or Me oz or 30 grains

1 and greater.

[Less than 2 g or He oz ^100 g or 4 oz and greater. Less than 100 g or 4 oz

< and greater than 30 g

or 1 oz [30 g or 1 oz and smaller..

ff/em*

7.2 to 10.0

2.6 and up

7.0 to 10.0

2.6 and up

1.0 and up

4.2. Design

4.2.1. Edges and Corners

Classes P, Q, and T. A weight shall have no

sharp edges or corners or other features, such as perforations or cracks, that introduce danger of

excessive change with ordinary use. Sheet-metal

weights shall not be unnecessarily thin.

4.2.2. Rings

Classes P, Q, and T. A weight shall have no movable parts, except as follows: Class T. A weight of this class may have a

ring provided that the ring is not split or removable.

4.2.3. Knobs

Classes P, Q, and T. A knob shall be held in place tightly enough to prevent its working loose

with ordinary handling.

4.2.4. Shape

Classes P, Q, and T. A weight shall be shaped

so as not to be susceptible to undue variability,

in particular:

Classes P and Q. A weight of these classes

shall not have a coin shape, unless the weight

meets the hardness requirement for rough use as

specified in 4. 1.1.1. 4.2.5. Adjusting Material

Classes P, Q, and T. Adjusting material shall be securely contained and shall not project beyond

the surface of the weight.

4.3. Surface

4.3.1.

Irregularities

Classes P, Q, and T. Any irregularities of the

surface shall be slight and not of sharp contour. The surface shall be free from pits or pores visible

to the unaided eye.

4.3.2. Protection

Classes P, Q, and T. A weight shall be resistant

to corrosion or tarnishing by the air or by handling

with the bare hands. When the base metal is of

such material that protection is required, a plating

such as nickel or a thin coating of transparent

paint or lacquer shall be used. If transparent

paint or lacquer is used, it shall be hard and not

likely to chip. No lacquer or paint of any kind

shall be used on sheet-metal weights or on weights

composed of a material needing no surface protection. If sheet-metal weights are adjusted by

fusing or plating, the adjusting material shall require no surface protection. Opaque paint

may be used as follows:

Classes P and Q. On weights above 50 kg or 100 1b. Class T. On all weights, except as noted above.

4.4.

Denominations

4.4.1. Individual Weights

Classes P, Q, and T. Except when weights are intended for a special application, the denominations of the weights shall be selected from table 11.

4.4.2 Sets of Weights

Classes P, Q, and T. A set of weights shall in- clude the duplicates necessary to permit weighing

of any load within the range of the set.

4.4. 2.1. Optional Maximum and Minimum Denominations

Classes P, Q, and T. Maximum and minimum

denominations of commonly used sets of laboratory weights are given in table 12.

4.5.

Marking of Weights

4.5.1. Designation of Value

Classes P, Q, and T. The nominal mass or “value” of each weight shall be plainly marked

upon it, except in the case of riders and other wire

weights. Wire weights shall be bent in such

forms as to suggest the denomination, unless they

are to be used as riders or for other purposes that

demand special forms. Nominal values shall be

expressed in terms of one of the units listed in appendix 2.

4.5.2. Designation of Unit

Classes P, Q, and T. The marking shall include

the name of the unit or its accepted abbreviation

in accordance with appendix 1, except that on knob weights below 10 g or K oz or equivalent and on sheet-metal weights below 100 mg or 1 grain or equivalent the name of the unit may be omitted

when space does not permit its inclusion in legible

form. The abbreviation shall not include a

period. In the case of weights of the troy or ap.othecary systems for which the nominal values

13
Tabus 11. Preferred denominations for laboratory weights

Classes P, Q, and T Classes P and Q Class P |

Metric A voirdupols Apothecary Troy Orain Carat

kq lb oz oz ap OZ t iwt Grain

! c 1, 000 2, 500 10 12 1,000 10, 000 10, 000 2, 500 500 2, 000 8 10 500 5, 000 5, 000 2, 000 200 1, 000 5 8 300 3, 000 3, 000 1,000

100 500 4 6 200 2, 000 2, 000 500 50 200 3 5 100 1, 000 1, 000 300

25 100 2 4 50 500 500 200

20 50 1 3 30 300 300 100

10 25 Yi 2 20 200 200 50

5 20 y* 1 10 100 100 30

3 10 % 5 50 50 20

2 8 Me dr ap 3 30 30 10

1 5 H2 6 2 20 20 5 4 Ysa 5 1 10 10 3

0 3 4 0. 5 5 5 2 500 2 0.

5

3 . 3 3 3 1 300 1 . 3 2 . 2 2 2 0. 5 I 200 . 2 1 . 1 1 1 .3 1 100 0. 5 .1 K . 05 0. 5

0 50 . 3 . 05 . 03 . 3 . T 30 . 2 . 03 i * ap . 02 . 2 . 05

20 . 1 . 02 2 . 01 • 1 . 03

10 . 05 . 01 1 . 005 . 05 . 02

5 . 03 . 005 . 003 . 03 . 01

3 . 02 . 003 . 002 . 02

2 . 01 . 002 . 001 . 01

1 . 005 . 001 . 0005 . 005

. 003 . 0005 . 0003 • mo . 002 . 0003 . 0002 1 500 . 001 . 0002 . 0001 300 . 0005 . 0001 200 . 0003

100 . 0002

50 . 0001 30 . 00005 ;l 20 . 00003

10 . 00002 1 5 . 00001

32

10. 5

. 3

. 2

. 1

. 05

are expressed in pounds, ounces, drams, or scruples,

the identification letter “t” or “ap” shall be used

in addition to the name or abbreviation of the

unit.

4.5.3. Unnecessary Markings

Classes P, Q, and T. Markings other than those

required or allowed in 4.5.1 and 4.5.2 shall not be

used, except as follows: (a) On weights of 25 kg or 50 lb or equivalent and above, unnecessary markings such as the name or the trade mark of maker

or dealer shall be limited to no more than the

shortest name by which the firm commonly is known, and the numbers or letters composing the

marking shall be no larger than those of the denomination. (b) On weights less than 25 kg or 50 lb or equivalent, unnecessary markings shall be

relatively inconspicuous as compared with the

denomination.

4.5.4. Depth of Marking

Classes P, Q, and T. Raised or depressed letters or figures shall not be deeper than 0.04 inch

(1 mm).

4.6. Lifters

Class P. Special lifters or forceps shall be pro- vided for weights of a set. All parts of the lifters that come in contact with the weights shall be

smooth, and shall have no sharp or rough edges.

Forceps shall be so constructed that with use or with storage in a closed position they will not

warp so as to interfere with their performance.

14
Tahi.k 12 . Maximum and minimum denominations of commonlij used sets of lulion/loii/ in ii/hts

Class ami sysliini From maximum

-To minimum

Class 1' (formerly S2):

Metric. 100 or 50 g 1 g or 5 mg

500 mg 5 mg

Avoirdupois . 50, 10, 5, or 2 lb 1x2 OZ Apothecary . __ 12 oz ap or 4 fir ap 0.1 grain

drain 10 grain 0.1 grain

Troy 5 oz t 0.1 grain Carat. _ (with two 200-c weights) 200 e 0.01 c

Class Q:

Metric 5, 2, or 1 kg 1 K

500, 200, or 100 g > K

2 or 1 kg, 500, 200, or 100 g 10 mg

50, 10, or 1 g, or 500 mg 10 mg

Avoirdupois .. . . 8, 4, 2, or 1 lb, or 8 oz He oz Apothecary . . 8, 4, or 2 dr ap ui grain

(train. .. 20 grain 1 grain

Troy 50, 20, or 5 oz t y> grain

Class T: Metric . .. .. . . . 20, 5, 2, or 1 kg 10 g Avoirdupois _ 50, 8, 4, 2, or 1 lb oz

4.7.

Case

Classes P, Q, and T. When a closed case is re- quired or provided, it shall be so designed that as long as the lid remains closed the weights cannot

get out of their pockets (4.7.1). The hinges and

locks shall he adequate to hold the lid closed with

any reasonable handling.

( 'lass P. A closed case or box shall be provided

with each set of weights.

Classes Q and T. A closed or an open case may

be provided for weights of these classes.

4.7.1. Pockets

Classes P, Q, and T. When a case is provided,

it shall contain a separate pocket for lifters or forceps and for each weight, and all pockets shall he large enough so that no appreciable frictional force will be encountered in inserting or removing

the weights. Deep pockets either shall be lined

with some soft material, such as velvet, or shall be

smooth, free from grit or hard specks or streaks,

and of fine-grained wood or other material not

likely to scratch the weights.

4.7.2. Marking of Case

Classes P, Q, and T. The name of the class and

the name of the unit or system of units shall be

conspicuously marked on the case.

4.8.

Tolerances

4.8.1. Basis for Adjustment

Classes P, Q, and T. The weights shall be adjusted on the basis of 'their apparent mass as determined by comparison with brass standards in

air.

4.8.2. Acceptance Tolerances

Classes P, Q, and, T. New and newly adjusted

weights shall be correct within the tolerances pre- scribed in table 13. The tolerance for a weight

less than those listed in table 13 shall be 5 percent

of the nominal value of the weight. The tolerance

for other weights not listed in the table shall he

determined by proportional interpolation between

tolerances given for weights of the next larger and

the next smaller denomination.

4.8.3. Maintenance Tolerances

Classes P, Q, and T. Weights that have been

in use shall be correct within twice the acceptance

tolerances prescribed in table 13.

4.9.

Packaging

This section applies to new or newly adjusted

weights.

4.9.1. Separate Package

Classes P, Q, and T. Each set of weights and

each individual weight not part of a set shall be

packaged separately.

Classes P and Q. For weights of these classes,

the package shall be sealed by the manufacturer

or adjuster so that the weights cannot be removed

from the package without destroying the seal. The weights shall be packed in accordance with

6.4 before sealing.

4.9.2. Marking

Classes P, Q, and T. The package shall be

marked with the class of weight, the maximum

and minimum denominations contained therein,

the unit or system of units, the name of the manufacturer, the manufacturer’s type number, and

any other appropriate information.

15
Table

13.

Acceptance

tolerances

1

for

laboratory

weights

16

t

» /
Table

13.

Acceptance

tolerances 1

for

laboratory

weights —

Continued

17
Table

13.

Acceptance

tolerances

1

for

laboratory

weights—

Continued

18
Table

13.

Acceptance

tolerances

1

for

laboratory

weights

—

Continued

Carat

Denomination

|

P mg 10 8.0

4.02.0

1.0

0.

70

. 50. 33. 26. 20

. 15. 12

. 10.

080

.

070

.

060

.

053

.

050

2,

500 2,

000

1,000 500 200 100 50 20 10 5 2 1 0.5 . 2 . 1

. 05

. 02

. 01

Metric

E-1

till

< 1 1 1 xi<©«o ©noon ! ! I ! ?n tw - eccSt^-*** eict h h ©'** !!!! S<o4«N -h i,ii 1 1 1 1

1 1 1 1

1 1 1 1

a

© © © © 10*0© 00©©© © N © 00t^-©*0 © © © © cc©r^© coconn —< —i ©©©©

ftui ^ CO N -< ©

PH

*0 000 ICMOO OOO ^OCO 00r>-t^<0 lOiOiOO

cocc<nc4 ^ oooo oooo

^ *-i O

Denomination OOOO oO OOO OOOO *0 CO <N *-< g © © © © lOCOC^^H

iO CO c*

0

150 75 30 15 7.5

4.53.82.2

1.4

1.0

mg750 470 300 210 160 100

<y 050 25 10 5.0

2.5

1.2

1

. 0

mg

500 250 150 100 50 30 20 15

9.0

<3 20 10

4.0

2.0

1

. 0

mg 500 400 200 100 60 40 20 10

6.0 4.0

2.0

Denomination kg 1,

000 500 200 100 50 25 20 10 5 3 2 1

0

500 300 200 100

19
coCOa§O

CO -M

fl faU

.0

CO

t-l O

•w

<y faCo

co

Ui

o>>CoU

*5

**< a>aa<

20
Appendix 2. Units and Abbreviations for Marking Weights

Name of unit Accepted

abbreviation

Assay ton (29.1667 g) _ Carat (200 mg) _ _ AT « c dr ap

GN 1

kg

mg

oz ap

oz

oz t dwt

lb

s ap

Dram, apothecaries’ - - Grain

Gram _ _ Kilogram

Milligram

Ounce, apothecaries’ (480 grain)

Ounce, avoirdupois (437.5 grain)

Ounce, troy (480 grain)

Pennyweight - Pound, avoirdupois _ Scruple, apothecaries’ . - - --

i In descriptive material the abbreviation for "assay ton” should be written A. T., and ‘’grain” should be spelled out.

i

21

V I f ntft rn mcH'i -rMir#
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR '78-14762. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Precision Laboratory Standards of Mass and Laboratory Weights

5. Publication Date 8-20-54

6. Performing Organization Code 1 732

7. AUTHOR(S)

T. W. Lashof and L. B. Macurdy

8. Performing Organ. Report No. 1

' 9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 7320190

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less lactual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) National Bureau of Standards, Circular 547, Section 1, "Precision Laboratory

Standards of Mass and Laboratory Weights," served for many years as a defining

authority for various classes of weights and associated adjustment tolerances.

Technological and organizational changes which occurred within a few years after

the issuance gradually led to its obsolescence and consequently, it has been

out of print for some time. In the interim, a new standard ASTM E617-78, "Lab

Weights Precision Mass Standards," has been issued updating the same subject

matter. There are still numerous requests for Circular 547 since it is widely

referenced in the literature. While the document is reprinted in its entirety

in NBS Handbook 77, this source is also out of print and available only at

certain repository libraries. Because of technical content and historical value

of Circular 547, it is being issued in the NBSIR series* of

documents, to be available through NTIS. It should be noted, however, that for

matters concerning calibration, one should refer to the latest copy of NBS SP250,

"Calibration and Test Services of the National Bureau of Standards," available

from. the Office of Measurement Services.

Sections 5, 6 and 7, which refer to obsolete procedures, have been deleted

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Laboratory weights; mass standards; precision laboratory weights; precision mass standards; weights

18. AVAILABILITY 31 Unlimited

F or Otficial Distrib ution. Do Not Release to NTIS

CZ Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. C 1 3

X

Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY C LASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAC.l S

25

22. Price

$4.00

use omm. c