Mnemonics for Thermodynamic Equations

The appearance of the Symposium on the Teaching of Thermo- dynamics (THIS JOURNAL, October, 1962) has prompted several 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, Natch- itoches, La., suggests

The differentials of quantities in the quadrants is related to the quantities on the bounding axes, e.g.:

dG = -SdT + VdP Also such relationships as:

follow consistently around the wheel

IRWIN COHEN, Youngstown University, Youngstorm, O., suggests the triangle:

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 BROTHER THOUS 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:

VdP Tc dH

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~rrdrrs lrmg fumiliur with TIII~ JOKRNAL will rerall d l e r einlilur devices u~rlrlished about l>20 sears am. Fur cns~nple, see THIS J O U R N ~ L , 23, 587 (1946).

Volume 40, Number 5, May 1963 / 261