6 NEW HAMPSHIRE EXPERIMENT STATION [Bull. 261 



eaten. The iiniformitj' in the sampling of mixed meals was controlled 

 by combustions on two samples of the same meal collected in separate 

 containers. Although undoubtedly a certain degree of approximation 

 entered into the planning of this research, nevertheless the various fac- 

 tors studied do logically dovetail together and present a more complete 

 picture than would be the case if any one factor alone had been studied. 

 The fraternity and the sorority dining rooms in which the food 

 samples were collected were in well-ordered college houses where special 

 attention was given to the studj' of supply and waste, to caloric values, 

 and the economics of the proper preparation of food. We are deeply 

 appreciative of the courtesies extended by the committees responsible 

 for these houses, in permitting these observations to be made. 



THE OXY-CALORIMETER, ITS 

 MODIFICATIONS AND ITS USE 



An effort to develop an instrument of simple construction that could 

 be used for measui-ing accurately the energy value of foods, excreta, and 

 organic compounds in general, and that might in many instances supplant 

 the expensive and complicated bomb calorimeter has resulted in the oxy- 

 calorimeter. Since the laboratory at the New Hampshire Agricultural 

 Experiment Station has made extensive use of the oxy-calorimeter, since 

 the experience there gained has indicated the advantage of making cer- 

 tain modifications for the betterment of the apparatus, and since it is 

 desired to stress the practical use of this instrument, it has seemed fitting 

 to restate in this report the fundamental principle underlying the oxy- 

 calorimeter, to give a short description of the modifications that have 

 been made in it, and to discuss briefly its use. In the original detailed 

 description of all its technical niceties, emphasis was laid upon the im- 

 portance of adjusting the final temperature of the apparatus so that it 

 would be the same as the initial temperature.^ In the description of the 

 somewhat less accurate form," designed primarily for use with existing 

 models of respiration apparatus and suggested chiefly for the study of 

 the energy values of foods and excreta, the question of temperature con- 

 trol was not emphasized, for it was believed that the error inherent in 

 the sampling of most mixed foods and excreta would be much larger 

 than the probable error arising from less perfect control of the tempera- 

 ture of the apiiaratus. In a subsequent German description' of the ap- 

 paratus the temperature control, although mentioned, was by no means 

 adeciuatel}' stressed. Later experience* has shown that the temperature 

 control is not only desirable but practically imperative, and it is the 



^Benedict, F. G., and E. L. Fox, Indus, and Eng. Cheni., 1925, 17, p. 912. 

 A slightly modified form was briefly described by us in a previous bulletin. 

 (Univ. New Hampshire, Agric. Expt. Sta., Bull. 242, 1929). 



-Benedict, F. G.. and E. L. Fox, Journ. Biol. Chem., 1925, 66, p. 783. 



'Benedict, F. G., Abderhalden's Handb. d. biolog. Arbeitsmethoden, 1929, 

 Abt. IV, Tail 13, p. 51. 



*Dr. J. M. Petfik (Professor of Physiology at the Masaryk University at 

 Brno, Czechoslovakia) spent several months at the Nutrition Laboratory in 1930 

 as a visiting Fellow of the Rockefeller Foundation, and made many observations 

 with the oxy-calorimeter, which led to the special study of temperature control. 



