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IS0
I N T ER N AT1 O N A L ORGAN I Z AT I ON FOR S TA N DARD I ZATl O N
IS0 RECOMMENDATION
R 652
ENCLOSED-SCALE CALORIMETER
THERMOMETERS
1st EDITION
February 1968
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The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 652, Enclosed-scale calorimeter thermometers, was drawn
up by Technical Committee ISO/TC 48, Laboratory glassware and related apparatus, the Secre-
tariat of which is held by the British Standards Institution (BSI).
Work on this question by the Technical Committee began in 1957 and led, in 1961, to the
adoption of a Draft IS0 Recommendation.
In December 1963, this Draft IS0 Recommendation (No. 716) was circulated to all the
IS0 Member Bodies for enquiry. It was approved by the following Member Bodies :
Argentina Czechoslovakia New Zealand
France Poland
Australia
Austria Greece Spain
Belgium Hungary Switzerland
Brazil India Turkey
Bulgaria Italy U.A.R.
Canada Japan United Kingdom
Chile Korea Rep. of U.S.A.
Colombia Netherlands Yugoslavia
One Member Body opposed the approval of the Draft:
Germany
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in February 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 652 - 1968 (E)
IS0 Recommendation R 652 February 1968
ENCLOSED-SCALE CALORIMETER
THERMOMETERS
1. SCOPE
This IS0 Recommendation specifies requirements for a series of short-range enclosed-scale
thermometers for use in bomb calorimetry and for other purposes where an accurate measurement
of a change of temperature is required. The thermometers are not provided with auxiliary
scales at O “C and are therefore not suited to the absolute measurement of temperature (which
is not normally required in calorimetry), unless they are checked against a standard thermometer
immediately before use.
2. TYPE OF THERMOMETER
The thermometers should be of the mercury-in-glass enclosed-scale type.
3. TEMPERATURE SCALE
The temperature scale to which the thermometers refer is the International Practical Scale of
Temperature, adopted by the Conference Générale des Poids et Mesures in 1960 as the revised
edition of the International Temperature Scale of 1948.
4. IMMERSION
The thermometers should in general be adjusted for use at total immersion (i.e. the reading
should be correct when the thermometer is immersed at least to the end of the liquid column
in the medium whose temperature is required to be measured) in a vertical position, but adjustment
for use at partial immersion should be optional at the request of the user. On partial immersion
thermometers, a line should be etched at least half way round the sheath of the thermometer,
at the level to which it is intended to be immersed, which should preferably be the junction of
the “saddle” and the sheath (marked E in Fig. 1, page 4).
5. GLASS
The glass should be selected so that the finished thermometer shows the following characteristics :
Strain in the glass should be reduced to a level sufficient to minimize the possibility of
5.1
fracture due to thermal or mechanical shock.
5.2 The correction of the thermometer reading at the lowest temperature of the nominal range
should not change by more than 0.02 degree Celsius immediately after the thermometer
has been heated for 15 minutes at a temperature 30 degrees Celsius higher than the lowest
temperature and allowed to cool naturally in air.
5.3 The accuracy of the reading should not be impaired by devitrifying or clouding during
manufacture.
5.4 The meniscus should be distorted as little as possible by defects or impurities in the glass.
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ISO/R 652 - 1968 (E)
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FIG. 1. - Enclosed-scale calorimeter thermometer
Dimensions in millimetres
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ISO/R 652 - 1968 (E)
6. GAS FILLING
Above the thermometric liquid, thermometers may be either vacuous or gas-filled; in the latter
case, only a dry, inert gas should be used. The indication of a gas-filled thermometer, when the
meniscus is at the top of the scale, should not change by more than 0.01 degree Celsius, when the
temperature of the gas above the mercury is changed by 30 degrees Celsius.
NOTE. - If the bulb is sufficiently rigid for the thermometer to comply with clause 7.4, this requirement should
be satisfied, if the internal gas pressure does not exceed '/z atm (normal atmosphere), when the thermometer is
registering its highest temperature.
7. CONSTRUCTION
7.1 Shape
The thermometers should be straight and their external cross-section approximately circular.
7.2 Top finish
The top of the sheath should be sealed by fusing and should be covered by a metal cap.
7.3 Strip bearing the scale
The strip bearing the scale should be of translucent material suitable to the temperature to
be measured. It should be placed tightly against the capillary tube inside the sheath and
should be firmly and securely fastened at the top of the thermometer, in such a way that
it can freely expand in length
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