Presentation of the properties of ammonia-water solutions in liquid and,vapor phases is a formidable task because of the multifaceted nature of the constituent mixtures and the boundless number of combinations possible with them. In the mid 1930s the author and Francis P, Shannon became interested in water-ammonia solutions and, studied in-depth the publications and data which were then available. It appeared to them that a real contribution could be made if the most reliable data were selected and worked into a tabulation suitable for use by engineers and scientists. With the help of a team of workers such a tabulation was completed and published in 1938.

The authors, in the hope of making their tabulation convenient for users with minimum interpolation, created a voluminous, publication, so large that the magazine editor was forced to print, their paper in Refrigerating Engineering without including the tabulation itself. The complete publication appeared only in preprint and reprint form. The fact that the reprints were exhausted after a few years limited the extent to which the tables were used although the, complete paper can even now be obtained in reproduced form from ASHRAE.

There is still no clear answer as to whether aqua-ammonia data should be presented in graphical or in tabular form. A graphical presentation can give a picture of the whole liquid vapor spectrum of saturated water-ammonia but the numerical range required on one chart is so great that it is impossible to read values with suitable accuracy even when using a high-power reading glass. Moreover, determination of values of the vapor in equilibrium with the boiling liquid can only be found by graphical alignment and seldom can be read,with sufficient accuracy for the purposes desired.

Prior to the Jennings-Shannon Tabulation, Merkel and Bosnjakovic had written an exceptionally fine treatise on Absorption Refrigeration which included not one but many charts covering aqua-ammonia properties. Unfortunately, their presentation had been largely based on experimental work done in the first decade of this century which in the light of later investigations showed significant disagreements.