ABSTRACT
INTRODUCTION With the discovery by Bragg that one could use the angular dependence of scattering of X rays from a crystalline solid to determine the structure of that solid (1) , structural science has played a large role in the fi elds of chemistry and physics. Very early in the 19th century, it had become known that many compounds were capable of exhibiting the phenomenon of dimorphism , and could be crystallized into solids having different melting points and crystal habits. For example, the α - and β -forms of potassium ethyl sulfate were found to exhibit different solubilities and eutectic temperatures in their phase diagram (2) . The existence of a thermally induced phase transition between the anhydrous and monohydrate forms of 5-nitrosalicylic acid was deduced from the temperature dependence of its solubility (3) .
