OF ARTS AND SCIENCES. 245 



When litmus paper gave the neutral reaction, the liquid was filtered 

 hot, evaporated, crystallized, and dried, the mother liquor being evap- 

 orated to dryness, and the salt dried. This gave a white product with 

 very little loss. 2500 grams of calcium benzoate were subject to 

 dry distillation, and 820 grams of the crude product were obtained. 

 This liquid was of a dark red color, and 608 grams of it boiled 

 above 200°. The result of fractionation was a straw-colored liquid, 

 which would not solidify by cooling even to — 15° C. ; but on the 

 addition of a very minute crystal of benzophenone the whole solidified 

 suddenly. This product was again fractionated, and all below 280° 

 rejected. After three recrystallizations from a mixture of alcohol and 

 ether, 500 grams of pure benzophenone were obtained, which, after 

 being dried, melted at 46°. 74 to 47°. 72 ; a recrystallization gave the 

 same ; but after carrying the benzophenone through the entire series 

 of observations in the boiling-point apparatus, the melting point was 

 47°. 62 to 48°. 02, and it solidified at 47°.7, indicating that the initial 

 melting points were probably lowered by presence of alcohol or 

 ether. 



Benzol. — The Kahlbaum product was tested for thiophene with isa- 

 tine, and was shaken with P 2 5 and distilled. This product melted at 

 4°.22, and was used in the measurements. 



Results. 



The direct results obtained will be now given, with deduced formulae 

 and tables. On page 247 is a table interpolated for each 2 cm. pressure 

 for each substance. In the interpolation for these an application of 

 the method of residual curves greatly facilitated the work. Each table 

 of observations contains two or more series. Columns headed p give 

 measured pressures in millimeters within the boiler ; those headed 

 t give the corresponding temperatures measured by the air thermom- 

 eter. The correction to reduce the air thermometer to absolute scale 

 is beyond the limits of accuracy of this work, and has therefore been 

 omitted. 



