Mnemonics for Thermodynamic Equations The appearance of the Symposium on the Teaching of ThermoOctober, 1962) has prompted several dynamics (THISJOURNAL, readers to submit mnemonic devices found useful in helping the beginner to recall the symbolism which expresses the fundamental equations of thermodynamics. We have extracted the essentials from these communications and assume that the readers know both themeaning of the symbols and the equations. EDWARD T. RLDLEY,Northwestern State College, Natchitoches, La., suggests
Each term an the second line is the sum of the two above it; H i s the sum of d three on the first line. The connecting lines develop the differential equations, using the indicated signs, e.g.,
dA
=
-SdT - PdV or dH
=
TdS
+ VdP
BROTHERTHOUS MCCULLOUGH, CSC, St. Edward's h i versity, Austin, Tex., suggests the use of a triangular form:
The uppermost quantity is the Bum of the lower two an any line. Also the rectangle: The differentials of quantities in the quadrants is related to the quantities on the bounding axes, e.g.:
dG
=
-SdT
+ VdP
Tc
VdP dH
Also such relationships as:
follow consistently around the wheel
IRWIN COHEN,Youngstown University, Youngstorm, O., suggests the triangle:
relates the differentials so that the term on the midpoint of the eidrs is the u r n of the two t e r m on rhe adjawnt wrnere R~rrdrrslrmg fumiliur with TIII~ JOKRNAL will rerall d l e r einlilur devices u~rlrlishedabout l>20 sears a m . Fur cns~nple, see THIS J O U R N ~ L , 23, 587 (1946).
Volume 40, Number 5, May 1963
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261
