68 



CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



It is highly desirable to determine the oxygen to within 0.1 gram, and 

 we are fortunate in having a balance of the type used frequently in this 



Fig. 31.— Diagram of oxygen balance and cylinder. At the top is the balance 

 arrangement, and at the center its support. At the left is the oxygen 

 cylinder, with reducing valve A, rubber tube D leading from it, F the 

 electro-magnet which opens and closes D, K the hanger of the cylinder and 

 support for the magnet, R the lever which operates the supports for the 

 cylinder and its counterpoise S, T' a box which is raised and lowered by 

 R, and T its surrounding box. 



laboratory which will enable us to weigh this cylinder accurately with a 

 sensitiveness of less than 0.1 gram. Since 1 liter of oxygen weighs 1.43 

 grams, it can be seen that the amount of oxygen introduced into the cham- 



