Chapter II: Preface: TO FIRST EDITION xi

CHAP.
I. INTRODUCTION 1

II. STANDARDS OF TEMPERATURE 9

Absolute or Thermodynamic Scale—Constant Volume
Gas Thermometer—Fixed Points for Calibration—National
Physical Laboratory Scale—Temperatures
above the Present Limit of the Gas Thermometer.

III. THERMO-ELECTRIC PYROMETERS 20

General Principles—Metals used for Thermal Junctions—
Changes in Thermal Junctions when constantly
used—Electromotive Force developed by
Typical Junctions—Practical Forms of Thermocouples—
Liquid Element Thermocouples—Indicators for
Thermo-electric Pyrometers—Special Features of
Indicators—Standardizingof Indicators to read
Temperatures directly—Standardization by Fixed Points—
Standardization by Measurement of E.M.F.—Cold-Junction
Compensators—Constant Temperature Cold Junctions—
Special-Range Indicators—PotentiometerIndicators—
Recorders for Thermo-electric Pyrometers—The Thread
Recorder—The Siemens Recorder—Foster’s Recorder—
Paul’s Recorder—The Leeds-Northrup Recorder—
Control of Furnace Temperatures—Contact-Pen Recorders—
Installations of Thermo-electric Pyrometers—Management
of Thermo-electric Pyrometers—Laboratory Uses of
Temperatures Thermo-electric Pyrometers—Measurement of
Lower by the Thermo-electric Method—Measurement of Surface
of Surface Temperatures—Measurement of Low Temperatures—
Temperature of Steam, Exhaust Gases—Measurement of
Differences of Temperature—Advantages of the
Thermo-electric Method of Measuring Temperatures.

IV. RESISTANCE PYROMETERS 101

General Principles—Measurement of Resistance by
the Differential Galvanometer—Measurement of Resistance
by the Wheatstone Bridge—Relation between
Resistance of Platinum and Temperature—Changes
in Resistance of Platinum when constantly Heated—Terms
used in Resistance Pyrometry—Practical Forms
of Resistance Pyrometers—Indicators—Siemens’
Indicator—Whipple’s Indicator—The Harris Indicator—
The Leeds-Northrup Indicator—Siemens’ Differential
Indicator—Recorders for Resistance Pyrometers—The
Leeds-Northrup Recorder—Paul’s Recorder—Installation
of Resistance Pyrometers—Management of Resistance
Pyrometers—Special Uses of Resistance Pyrometers.

V. RADIATION PYROMETERS 134

General Principles—Practical Forms of Radiation
Pyrometers—Féry’s Mirror Pyrometer—Féry’s Spiral
Radiation Pyrometer—Foster’s Fixed-Focus Radiation
Pyrometer—Paul’s Radiation Pyrometer—Indicators
for Radiation Pyrometers—Calibration of Indicators—
Recorders—Management of Radiation Pyrometers—Special
Uses of Radiation Pyrometers.

VI. OPTICAL PYROMETERS 167

General Principles—Wien’s Law—Practical Forms of
Optical Pyrometers—Féry’s Optical Pyrometer—Le
Chatelier’s Optical Pyrometer—Wanner’s Pyrometer—
Cambridge Optical Pyrometer—Holborn-Kurlbaum
Pyrometer—Lovibond’s Pyrometer—Mesuré and
Nouel’s Pyrometer—Colour-extinction Pyrometers—
Management of Optical Pyrometers—Special Uses of
Optical Pyrometers.

VII. CALORIMETRIC PYROMETERS 195

General Principles—Practical Forms—Siemens’
Calorimetric or “Water” Pyrometer—Special Uses.

VIII. FUSION PYROMETERS 204

General Principles—Seger Pyramids or “Cones”—
Watkin’s Heat Recorder—“Sentinel” Pyrometers—
Stone’s Pyrometer—Fusible Metals—Fusible Pastes.

IX. MISCELLANEOUS APPLIANCES 211

Expansion and Contraction Pyrometers—Wedgwood’s
Pyrometer—Daniell’s Pyrometer—Northrup’s Molten
Tin Pyrometer—Vapour-Pressure Pyrometers—Water-Jet
Pyrometers—Pneumatic Pyrometers—Conduction
Pyrometers—Gas Pyrometers—Wiborgh’s Thermophones—
Joly’s Meldometer—Brearley’s Curve Tracer.

INDEX 222

Preface to the Second Edition

Since the publication of the first edition in 1911, a great extension has been witnessed in the use of pyrometers in industrial processes and laboratory work, to which development the author hopes his book has contributed in some measure. During the stress occasioned by the war, pyrometers have proved invaluable in many processes, and British makers were fully able to meet the demands, owing to the status attained in pre-war days. The increasing use of pyrometric appliances renders necessary some book of reference which will provide the user with information to enable him to get the best results out of his instruments, and it is hoped that the present treatise meets this need. In preparing the second edition, certain parts have been revised in conformity with modern practice, and the later developments included. The scope of the book remains as before.

The author desires to acknowledge the assistance he has received from the British makers of pyrometers, all of whom have liberally provided him with information of a most useful kind, of which he has availed himself in the production of the present edition.

CHAS. R. DARLING.
WOOLWICH, 1920.

Preface to the First Edition

The present treatise has been founded on a course of Cantor Lectures on “Industrial Pyrometry,” delivered by the author before the Royal Society of Arts in the autumn of 1910. The practice of pyrometry in recent years has progressed at a greater rate than the literature bearing upon it; and the author is not aware of the existence of any other book written in English which treats the subject from the standpoint of the actual daily use of the instruments. In the succeeding pages the exact measurement of temperature, as an end in itself, is made subordinate to the practical utility of pyrometers in controlling various operations; and consequently descriptions of appliances of interest only theoretically have either been omitted, or at the most briefly described. Nevertheless, the fundamental principles are in all cases fully explained, as an understanding of these is essential to the intelligent use of the appliances dealt with in the book. When necessary, numerical examples are given to illustrate the applications of the principles; and the reader who finds any difficulty in following the various explanations—which of necessity involve an understanding of many portions of the subject of heat—is referred to the author’s treatise on “Heat for Engineers,” issued by the publishers of the present volume.

With regard to temperature scales, the author has in the main employed Centigrade degrees, but has recognised that the Fahrenheit degree is still largely used, and has therefore frequently expressed temperatures in terms of both scales.

The number of those who find it an advantage in their calling to measure and control high temperatures is constantly increasing; and the manufacture of pyrometric appliances now gives employment to considerable numbers. The author trusts that the present treatise will prove of service to all thus concerned, and also to those who pursue the fascinating study of high temperature measurement from the purely scientific standpoint.

In conclusion, the author expresses his thanks to the various firms, mentioned in the text, who have loaned blocks for the purpose of illustration, and who have furnished him with much valuable information.

CHAS. R. DARLING.
WOOLWICH, 1920.

PYROMETRY