Wood County reporter. [volume] (Grand Rapids [i.e. Wisconsin Rapids], Wis.) 1857-1923, 1884-01-10
GRADUATING THERMOMETERS
HOW the Mercury is Got Into The
TuDe-Extent OF the Defects in In
struments.

struments.
A New York reporter, with curl
oslty to learn how the mercury gets
into the tubes of thermometers, and
how the instruments are graduated.
recently visited a store in Williams
street, and was there instructed,
When thermometer is to be made. :"
sad manufacturer, ''the glass blow
er first blows bulb on the end of a
long tube. While this bulb IS hot the
end of the tube is inserted in mercury.
and as the bulb cools the mercury
rises and fills the bulb. This process is
repeated until the bulb and part of the
tube are filled. The bulb is then i'm
mersed in snow or Clipped ice, and
the mercury Settles to the freezing
point, which is marked on the tube as
81 degrees of Fahrenheit scale is to
be followed. Next the bulb is pat in
boiling water and the point to which
the mercury rises is marked on the
scale as 212 degrees. Ten degrees of
tue mercury are now detached from
the column by jarring, and the whole
length OF the tuoe is tested. The pro-
cess is repeated with five degrees of
the column, being measured all the
time by a standard thermometer to
see If the tube is conicai at any
point"
Are common thermometers usually
cQrTect?"
They generally varry about two or
three degrees, owing to the irregulari-
ty OF the opening in the tube, which
causes the mercury to rise slowly
where the opening is too large and
too fast where the opening is too mar
row. 1t requires great skill to blow a
tube with a uniform opening the
whole length"
Are thermometers ready for use
immediately after they are filed with
mercury?"
They should be allowed to stand
no less than one month-one year is
better-to allow the mercury to set
tie before the scale is made" ="
What are the different kinds that
are made.
The self registering thermometer
is used for marking the highest and
lowest points reached within a given
time. The bulb is filled with mercu-
ry, above which, in the tube, is inser-
ted fine piece Of steel spring; the
remainder Of the tube is filled with
(. rbolic acid or creos0te. The steel
spring rests at the highest point and
is pushed to by the mercury and is af-
terward drawn down by small mag
net. By a duplex arrangement and
revising the scale the lowest or cold
est point is indicated in the same
way. The deep-sea thermometer is of
the same pattern, and is encased in a
heavy copper tube to preserve it from
the pressure of water. It has besides,
a self regulating attachment. The
fever or clinical thermometers are
made with great nicely, and are used
for determining the temperature of
the human body.
What are used for filing bulbs of
thermometers"
Mercury is commonly used, it be-
IN g highly sensitive to heat and cold,
but for the. extreme northern climates
1t Will not answer, as it freezes at
40 degrees below zero. Where this
temperature is liable to be met, spirit
are used, being made
OF aIchohOl colored red and blue.
These spirit thermometers will not
answer for high Temperatures how
ever, as the alchohol volatililes too
readily"
is there government standard for
testing thermometers?
There is no government standard.
The slgnal-service uses the Fahren-
heit scale. The Winchester observa-
tory OF Yale college has established a
thermometric bureau for testing ther-
mometers either for dealers or other
interested in procuring exact instru-
ments. A small fee, ranging from 50
cents to 81, is charged, and Yale GER
tItlcate of correctness is furnished.
The observatory has elaborate appar-
atus for testing Thermometers and it's
services are of great value to physi-
clans IN testing clinical thermometers.
Ihe observatory has issued a circular
to physicians which contains the fol-
lowing statements: The competition
OF business, coupled with the entire
absence up to this time of any large
observatory in this country paying
special attention to thermometry, 10
which authoritative appeal could be
made, has so affected the manufacture
6rs of thermometers for medical
purposes, that it seems necessary to
issue card briefly indicating the
errors commonly found to exist, and
explain whyi in this case the representa-
tlon of the dealers may be at fault
through the want of a proper under
standing Of the subtle errors to which
medical thermometers are liable Too
great desire to economic time, good
material, and skilled labor has led, in
N the making of Thermometers to the
following faults: CD The graduation
IS sometimes started from one point of
the scale, near the normal, and the
SIZE OF the capillary tube is guessed at.
No upper point being fixed by the
maker, the higher graduates may be
to the extent of several de
grees. (2) Too much air separating
the index from the column Of mer-