A RESPIRATION CALORIMETER., PARTLY AUTOMATIC, 

 FOR THE STUDY OF METABOLIC ACTIVITY OF SMALL 

 MAGNITUDE 



By C. F. Langworthy, Chief, and R. D. MiLNER, Assistant Chief, Office of Home 

 Economics, States Relations Service 



INTRODUCTION 



A respiration calorimeter of the type of that described in a previous 

 number of the Journal oe Agricultural Research, 1 which is employed 

 in the laboratory of the Office of Home Economics of the Department 

 of Agriculture for the study of the metabolism of matter and energy in 

 the human organism, is easily adapted to inquiries of similar character 

 with other organisms. An apparatus much smaller than the one referred 

 to has been developed in the same laboratory for use in the study of 

 gaseous exchange and energy transformations of small magnitude and 

 has been employed in investigations on the ripening of fruits and the 

 wintering of bees. In fundamental principle this small respiration calo- 

 rimeter is similar to the larger one mentioned above in that it combines 

 a closed-circuit respiration apparatus and a continuous-flow water calorim- 

 eter. However, it differs from it in construction, having been modi- 

 fied in ways which make for ease of operation and for greater accuracy. 

 Important changes have also been made in details, particularly with 

 reference to its calorimetric features, the use of special devices for con- 

 trolling and recording temperatures rendering it quite largely automatic 

 in this respect. Brief accounts of this apparatus and of experimental 

 work with it have been published, 2 but the details of construction and 

 operation are given for the first time in the present article. A general 

 view of the small respiration calorimeter is shown in Plate XCII. 



CONSTRUCTION OF THE RESPIRATION CHAMBER 



The apparatus is devised so that chambers of different size or shape, 

 constructed according to the varying needs of different investigations, 

 can be substituted for each other. The chamber at present employed 

 (PI. XCIII) is 45 cm. square and 91 cm. deep, and has a total capacity 

 of close to 185 liters. It was designed to accommodate a quantity of 



1 Langworthy, C. F., and Milner, R. D. An improved respiration calorimeter for use in experiments 

 with man. In Jour. Agr. Research, v. 5, no. 8, p. 299-347, pi. 30-36. 1915. 



2 An improved form of respiration calorimeter for the study of problems of vegetable physi- 

 ology. In Orig. Com. 8th Internat. Cong. Appl. Chem., v. 18, sect, viiic, p. 229-236, 1 pi. [1912.] 



A new respiration calorimeter for use in the study of problems of vegetable physiology. 



In U. S. Dept. Agr. Yearbook 1911, p. 491-504, pi. 65-67. 1912. 



Some results obtained in studying ripening bananas with the respiration calorimeter. In 



U. S. Dept. Agr. Yearbook 1912, p. 293-308. 1913. 



Journal of Agricultural Research, Vol. VI, No. 18 



Dept. of Agriculture, Washington, D. C. July 31, 1916 



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