A Convenient Multiple-Unit Calorimeter Installation Page: 3
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A CONVENIENT MULTIPLE-UNIT CALORIMETER INSTALLATION.
By J. D. DAVIs and E. L. WAIICE.
INTRODUCTION.
Within the past ten years most purchasers of large quantities of
coal have adopted the heat-unit basis of evaluation. The calorific
value of a fuel, although it does not give all the information that
could be desired as to quality, furnishes a more reliable specific indi-
cation than any other test that can be conveniently applied in the
laboratory. The amount of heat a coal can produce on combustion
is a main consideration in its purchase, and the heating value as
determined in the laboratory is a direct and logical measure of that
ability. Notwithstanding the fact that other important factors enter
into the problem of coal evaluation, such as the use of coal suited to
the equipment at hand or the character of heating desired, the
calorific value is the best general expression of value, irrespective of
the proposed use of the coal. It is therefore the most important
factor to be considered in coal specifications. The Government early
recognized this fact and is now buying the greater part of its fuel
supply under specifications based on heating value.
The actual determination of the calorific value of a fuel should
be carried out as cheaply as possible (as the price of coal limits the
justifiable expense) and with a high-degree of accuracy, in order to
facilitate comparisons of coals not differing greatly in value. Here
it may be said that as the sampling of coal is subject to an error
of at least 1 per cent, it is useless to strive for higher accuracy in
calorimetry. This objection, however, is not pertinent when the
heating value is computed on the basis of coal free from moisture or
ash, that is, the "coal substance." In other words, the chief cause
of error in sampling is the taking of a sample that includes too small
or too large a quantity of impurities to be correctly representative
of the coal sampled, the sampling error as regards the character of
the coal substance itself being small. Consequently, if the ash per-
centage is eliminated in computing the value of the coal as based on
the calorimeter test, the sampling error is negligible. It is desirable
that the accuracy attainable with a coal calorimeter be such that
variations in determinations with duplicate samples shall not exceed
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Davis, J. D. & Wallace, E. L. A Convenient Multiple-Unit Calorimeter Installation, report, 1918; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc66440/m1/5/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.