SPECIFIC HEAT OF AMMONIA. 405 



hoped for, the average deviation of — and ^7-"" from the curves taken 



8d 86 



to represent them, being of the order of O.o%. Xo considerable 

 amount of time was spent in checking these values, it being considered 

 more profitable to spend the time improving the method so as to avoid 

 the principal sources of error, and at the same time retain the essen- 

 tial idea, which is the measurement of the specific heat at a point. 



These results are now published because there have hitherto been 

 no data above 70° C, and the values of Drewes are not wholly reliable 

 even to that temperature. 



It is unfortunate that while these measurements of Cv extend to 

 125° C. or within 8° of the critical point, the values of Cs2 and Cs^, 

 can only be computed up to 100° C. owing to the lack of data on Vi 

 above that temperature. 



Acknowledgments. 



The writer is under great obligations to ^Yilliam H. Gran, and 

 Frederick L. Brown for their careful and conscientious work in taking 

 observations during the final measurements. 



To Mr. F. Kiing, Departmental ^Mechanician, is due the mechanical 

 excellence of the apparatus. The writer owes much to his continued 

 interest in the investigation. 



Throughout the course of the investigation. Dr. George V. McCauley 

 has offered many suggestions of great value, and to him the writer's 

 best thanks are due for his very material assistance. 



To Professor Henry Crew, under whose direction the work was 



carried on, the writer offers his sincere thanks for his advice and 



assistance, as well as for the generous manner in which the facilities 



of the laboratory have been placed at his disposal, and special appara- 



~tus and equipment purchased. 



Acknowledgment is made of a generous grant from the Rumford 

 Fund of the American Academy of Arts and Sciences, which made 

 possible the purchase of the Calorimetric AYheatstone Bridge. 



IX. Appendix. 

 1. summary of notation. 



dll Any increment of energy added to the calorimetric system 



through the heating coil. 

 8H1 An increment of energy added to the calorimetric system 



through the heating coil, container filled with ammonia. 



