Relations in a chemistry text

[Mark A. Bell]

Special thanks to John Bateman for such a detailed and insightful analysis.
( http://listserv.linguistlist.org/cgi-bin/wa?
A2=ind0203&L=rstlist&D=1&F=&S=&P=1541 )

> (d) The data used to construct Fig 5.7. gives a straight line when we
> plot the pressure against 1/volume (Fig 5.8).
>
> (e) The linear plot implies that, for a fixed amount of gas at constant
> temperature, pressure is inversely proportional to volume, V:
>
> (f) this relation is known as Boyle's law.
>
> The evidence relationship between the linear plot and the
> inverse proportionality is actually buried in the "implies that", so
> there is an evidence (linear plot, pressure inversely proportional),

I had not considered the idea of a rhetorical relation burried inside a
grammatical metaphor. This explains my difficulty in deciding where to
segment the text.

> or maybe an interpretation relation is better.

In that case, how about:

Interpretation:
Sat (d) The data ... gives a straight line
Nuc (e) The linear plot implies that... pressure is inversely proportional
to volume

I also have trouble seeing an 'evidence' relation here, even though I
initially analysed it that way. It seems to me that the chain of reasoning
in the text (a graph of the data gives a straight line, pressure is
inversely proportional to vollume) is less like a 'claim' backed up with
evidence, than the steps of a syllogism or a mathematical proof.
R's 'belief' in the conclusion (P ~ 1/V) is not in doubt. What is
increased, is R's understanding of the chain of reasoning. Could (d) be a
kind of 'background' or 'preparation' to help R understand the logic of
(e)?

> As for (a) and (b), this is a projection (Halliday, 1994) and is
> not an RST relationship at all. (a) just sources (b). There may
> be texts which single out the projecting element rather than
> the projected element as "nucleus", but this probably isn't
> one of them.

That makes a lot of sense to me. Also, singling out the projecting clause
as a separate element makes the entire text an elaborating satelite
on "Boyle observed that". I see Robert Boyle and his observation as
background to the real subject which is the pressure - vollume relationship
in Boyle's law.

Thanks again to John Bateman for sharing his insight. FYI here's the
complete text.

Mark A. Bell
Sydney, Australia
http://www.users.bigpond.com/m487396

-------------------
Atkins, P. and Jones, L. (2000) Chemistry: Molecules, Matter and Change.
4th Ed. New York: W.H. Freeman and Company. Page 183.

Boyle observed that when he compressed a fixed amount of gas at constant
temperature,  the pressure of the gas increased in a certain way. A graph
of the dependence is shown in Fig. 5.7. The curve shown there is an
isotherm, which is a plot of a property at constant temperature. Scientists
often look for ways of plotting data in a manner that gives straight lines,
because such graphs are easier to analyze and interpret. The data used to
construct Fig 5.7. give a straight line when we plot the pressure against
1/volume (Fig 5.8). The linear plot implies that, for a fixed amount of gas
at constant temperature, pressure is inversely proportional to volume, V:

This relation is known as Boyle's Law. The law implies that, if we compress
a sample of a gas into half its initial volume - from 1 L to 0.5 L of from
10 mL to 5 mL, for instance - then the pressure of the gas will double.

The mathematical form of Boyle's law shows that the product of the pressure
and volume of a sample of gas at constant temperature is a constant. To
reach this conclusion, we multiply both sides of the last equation by V and
obtain [formula].

Our molecular model for gases is consistent with Boyle's law. As a gas is
compressed, its molecules are confined to a smaller volume. The interior of
the container becomes more crowded (Fig. 5.9) and molecules collide with
the walls more frequently. As a result, they exert a higher total force on
the walls.

Boyle's law states that the pressure of a fixed amount of gas at constant
temperature is inversely proportional to the volume.