Wadsworth — Determination of Specific Heat, etc. 265 



Art. XXX. — On the Conditions required for attaining Maxi- 

 ■ mum Accuracy in the Determination of Specific Heat by 

 the Method of Mixtures ; by F. L. O. Wadsworth. 



Introductory Note. — In the last volume of the Proceedings 

 of the American Academy, which has just been received at the 

 Observatory, I find a paper by Professor Holman* discussing 

 methods of making the "cooling corrections" in determining 

 specific heat by the method of mixtures. In this paper the 

 author has suggested that this correction may be simplified by 

 a modification of the usual method which "is supposed to be 

 new." This suggestion is of the same nature as one which I 

 made some years ago and embodied in a paper which formed 

 part of my report in laboratory work at the Ohio State Uni- 

 versity for 1888-89, but which was never published. The 

 investigation was undertaken as preliminary to an accurate 

 determination of the specific heat of the metal of one of 

 Professor Rogers' standard bars, a sample of which had been 

 sent to Professor Thomas for that purpose. No opportunity 

 was given at that time to put the suggested method to actual 

 test, as it was subsequently decided to use the ice calorimeter 

 instead. 



The method differs from that suggested by Professor Holman 

 in that it goes further and eliminates the necessity for the cool- 

 ing correction entirely. Except for that part of the paper 

 (pp. 274-277) which deals with the conditions for securing thi© 

 result, there is nothing novel or particularly original in the 

 treatment. But as the whole discussion is more or less linked 

 together and as it will serve to supplement to some extent 

 Professor Holman's paper, which deals only with the cooling 

 correction (the most important but not the only source of error 

 in calorimetric determinations), it has been decided to let the 

 paper stand as it was first written (except for a slight rearrange- 

 ment of the order of the paragraphs), supplementing the orig- 

 inal text with footnotes where it seemed necessary. At the 

 end will be found a few general notes relative to the arrange- 

 ment and use of apparatus in the determination of specific heat 

 by both the method of mixtures and the method of the ice 

 calorimeter. These notes did not form part of the original 

 paper, but have been added from time to time as suggested 

 in my laboratory experience. The method of " discharging the 

 hot body from the heating vessel and receiving it in the calori- 

 meter, and of maintaining the jacket of the latter at a con- 



* " Calorimetry : Methods of Cooling Correction," Proc. Amer. Acad., vol. xxiii, 

 p. 245, 1896. 



