Chemistry Reference
In-Depth Information
its knowledge -
that which is
- but rather one of
that is,
what can be
.
Objectivity is not given from the beginning, but rather produced in a
realisation,
'
'
process of
'
objectification,
of the world
and human intelligence. With Bachelard again, we consider that the sciences them-
selves must be assessed as particular and concrete forms of life with different
'
the provisional result of which is a
double instruction
'
'
'
addressing quite different sets of problems and surrounding
conditions, and which have their own awkwardness:
microrationalities
'
Each interesting problem,
each experiment, or even each equation requires a philosophical reflection of its
own
'
(Bachelard
1940
, p. 14). This is the reason why it is of paramount importance
for us to investigate chemical practices in order to study the
local
meaning, if any, of
the
ceteris paribus
clause in the
'
canton
of chemistry. Without the multiplication
'
'
of perspectives, there is no objectivity.
Because precision is sensitive to the way it is determined some specific types of
precision should be distinguished.
Reproducibility
is the measure of agreement
between results obtained with the same method on identical test or reference
material under different conditions, executions by different persons, in different
laboratories, with different equipment and at different times. The measure of
reproducibility is the standard deviation of these results.
Repeatability
is the
measure of agreement between results obtained with the same method on identical
test or reference material under the same conditions, the job done by one person,
in the same laboratory, with the same equipment, at the same time or with only a
short time interval. Repeatability corresponds to the
ceteris paribus
clause as it is
usually defined by logicians in domains different from chemistry. At this point of
our enquiry, we understand that what is considered to be the meaning of the
ceteris
paribus
clause in many contexts only corresponds to a single step among many
others belonging to a long chain of procedures carried out for stabilizing what we
call the complex {apparatus-methods-bodies-associated milieu-devices} in the
framework of chemistry.
Chemists then resort to the study of the
within
-
laboratory reproducibility
which
is the agreement between results obtained with the same method on identical test
material under different conditions, execution by different persons, with the same
or different equipment, in the same laboratory, at different times. This is a more
realistic type of precision for a method over a longer span of time when conditions
are more variable than defined for repeatability. Last but not the least along our
non-exhaustive list, they have to ensure the
robustness
/
ruggedness
of an analytical
procedure which is defined as a measure of its capacity to remain unaffected by
small, but deliberate variations in method parameters and provides an indication of
its reliability during normal usage. Such conditions can be temperature, extraction
or shaking time, shaking technique, pH, purity of reagents, and sample size, among
many factors. The ruggedness test is conveniently done with the so-called “Youden
and Steiner partial factorial design” thanks to which analyses seven factors can be
varied and analyzed in only eight replications. This test corresponds to another
practice of modeling which holds probability, metrology, and chemistry together.
Each step of the co-stabilization of the whole complex reveals a certain amount
of repetitions and holds a wide range of multifarious tools together. Concomitant
