CHEMISTRY. 



301 



7. Solubility of Pure Salts as a Means of Fixing Points on the Thermometric Scale . 



Of course any definite property of material possessing a marked tem- 

 perature coefficient may be used to determine the thermometric scale. 

 The solubilities of pure salts furnish suitable data, but since their 

 changes with changing temperature are usually not linear, but are 

 rather represented by curves, many solubilities must be determined 

 in relation to the international standard in order to use these data for 

 calibrating thermometers. Since no determinations of sufficient accu- 

 racy for this purpose seem ever to have been made, it appeared to 

 be worth while to make a practical test by careful study of a typical 

 case. Sodium sulphate was selected as one of the most suitable salts, 

 for many reasons; and the work was carried out by Dr. Victor Yngve, 

 whose work on transition temperatures had led to the suggestion. 



It was found that the solubility of sodium sulphate is easily adjusted 

 to exact saturation and is capable of precise estimation. Determina- 

 tions of its magnitude at about 15°, 17.5°, 20°, 22.5°, and 25° were 

 made w4th an accuracy which has perhaps never before been attained, 

 referring the data to the Parisian hydrogen scale and to the platinum 

 resistance scale. A fairly adequate empirical equation was derived, 

 connecting temperature and solubility over this range, and the solu- 

 bility values at degree intervals were computed. Although this was 

 only a beginning, the results afforded a hope that in the future, when 

 more data have been obtained, the method may be of real use to those 

 who possess no accurate thermometer, by affording them a convenient 

 standard of reference. 



The experimental results, together with the extreme variations from 

 the mean, recorded in terms of the temperature readings of two 

 Baudin thermometers, carefully standardized at the Bureau des Poids 

 et de Mesures, were as follows: 



Sherman, H. C, Columbia University, New York, New York. Continu- 

 ation of the chemical investigation of the amylases. (For previous reports 

 see Year Books Nos. 11-15.) 



During the past year the investigations, referred to in previous 

 reports, upon the chemical properties of pancreatic and malt amylases 

 and also the amylase of Aspergillus oryzcB, have been continued. 



