The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1901-04-21
SCIENCE OF PYRoMETRY
EXPERIMENTS IN THE NEW SCIENCE
OF HEAT MEASUREMENT.
Temperature Too High tn he Record
ed by Any known Method-In-
dustriaI Value of Tests.

trial methods. Millions OF dollars are being
saved annually as the result of information
derived from the researches of the technical
laboratories. Recent experiments in the
laboratory of physics at the Massachusetts
Institute OF Technology, for example, I'M
Ger the direction OF Prof. c. L. Norton are
particularly instructive opening up new
occupations for men of technical training
in field OF great Importance, since heat is
now the almost universal source of indus
trial energy, and have. indeed, developed
what ray almost be called new science
''pyrometry," or heat measurement.
An ordinary thermometer. the instru-
ment which records the temperatures Of
everyday use seems like a child's toy
when placed in comparison with the py-
rometer. the scientific device for measuring
temperatures which mount into thousands
Of degrees And, although with the py-
rometer scientists can measure cold which
is hundreds OF degrees below zero and
heat which is thousands of degrees above.
yet the same instrument fails as COM
pletely in recording the extreme heat of
which an electric furnace is capable, as an
ordinary house thermometer would fail in
recording the heat of a blast furnace. Tenn
peratures are possible TO the electric fur
mace which have never been measured. and
will not be, until new devices are discov-
cred. As the present standards of heat
measurement range from the boiling point
Of water TO the melting point of platinum,
so the new standards may begin at the
boiling point OF substances which become
liquefied only when subjected to the great
est amount of heat which can be measured
by the pyrometer and include temperatures
so high as to be almost inconceivable to
the ordinary mind.
SCHOOL FOR MANUFACTURERS
But while physicists find in these high
temperatures an attractive field for inves-
tigation they are still chiefly employed in
heat experiments within the range of pos
sible measurement, in the interest of their
application to certain technical industries.
Methods familiar to the scientist i'll his
workroom are often comparatively unfa-
milar to the practical manufacturer For
example, manufacturer came TO the Tech
nology laboratory some time ago for advice
as to method of ascertairing the tempera-
ture of his tempering and annealing ovens
At Professor Nortons suggestion he pur-
chaser a pyromter and has since reported
that by means of il he has been able to
save many thousand dollars every year. A
case has been recently reported of retort
used for gas making which, If not over
heated, will last about ten weeks, but which
can rarely be made TO last three, because
the only method that has been used to
judge of excessive heating has been the
very uncertain but very common one Of the
eye-it Cooked too hot" The indicator of a
good pyromter. il faithfully read, would
have guarded completely against any pos
sible overheating, and. moreover, the cost
of a pyromter would not have exceeded
that of a single retort. With examples like
this constantly brought TO its attention the
Institute of Technology started about ten
years ago a regular course of laboratory
instruction in the science of heat measure
ment. or pyrometry.
1t will surprise most persons TO learn that
in measuring temperatures to 932 degrees
Fahrenheit 600 Centgrade) mercury Their
mometers can be used, since the develop
ment i'm delicacy of manufacture during
the past five years makes them satisfactory
technical instruments up to that limit. Such
thermometers may be standardized occa-
sionaly by being immersed in boiling iq-
uids whose boiling points have been care
at 212 degrees Fahrenheit. of naphthaline
at 42i degrees. and Of sulphur at S32 degrees
are we'll established and the substances
are cheap and may be easily procured in
large quantities and of the necessary pur-
ity. The melting points of tin at 450 de-
grees, of lead at 622 degrees, and of zine
at 7s6 degrees give other reference points
by which these high-grade mercury Their
mometers may be tested still further.
ORDINARY MEASUREMENTS.
The range of the mercury thermometer
must have been passed before one enters
the region of pure pyrometry though the
instrument of the science, the pyrometer
is ordinarily used from 600 degrees or there
abouts. In measuring temperatures lying
between this and the upper limit of the
electric furnace, whatever that may be,
it is possible to make use of many different
forms of pyrometer. For most technical
work in the region below 200 degrees the
thermo-electric pyrometer of lie Chatelier
Is generally used. This pyrometer consists
of three working parts-a pair of wires,
commonly called a Junction of suitable
metals, preferably platinum and platinum
alloy, with united ends TO be subjected
inclosed, TO prevent mechanical injury. in
porcelain or tube iron-to the temperature
to be measured; a set of insulated connect
ing wires and a galvanometer. When heat
ed the end Of the junction becomes the seat
of an electro-metive force which grows
greater with the increase of temperature.
the result being recorded on the dial Of
the galvanometer.
For occasional work. where the expense
OF such an instrument may not be war
ranted, simpler. though less accurate
methods of making pyrometric measure
ments have been worked out One which
is specially recommended on account of
its simplicity is the calorimeter. A SUBJ
stance is first heated in the furnace, then
dropped into a vessel of water The rise
in the temperature Of the water is easily
obtained from a thermometer, and from
this the temperature of the furnace is cal
culated. In this way Professor Norton
says he has, with an old hammer head, an
empty tomato can and common thermome-
ter. taken the temperature OF a red-hot
muffie furnace with precision which was
within at least 30 degrees. With ball of