58 A RESPIRATION CALORIMETER. 



to allow the hooks from the suspension wire to be readily slipped under 

 the handles of the absorber. By means of the wooden lever at the left- 

 hand side of the weighing closet, the movable platform on which the 

 absorber is placed can then be lowered slowly, thus gradually shifting 

 the weight to the wires. When the wooden handle is in an upright 

 position, the movable platform or elevator is at its lowest point, and the 

 object to be weighed swings freely above it. A simple clutch holds the 

 lever firmly when it is sustaining the weight of the absorber, and all 

 that is necessary to release the clutch is to push the handle forward a 

 short distance. 



The bracket- arm fastened to the lever has two chains attached to its 

 outer end ; these travel through pulleys in the top of the closet and are 

 so adjusted that both sides of the elevator are lowered to the same dis- 

 tance and simultaneously, thus making an even up-and-down motion. 

 The details of this apparatus are shown in figure 21. 



After weighing, the lever at the left of the balance is pushed for- 

 ward, thus taking the weight off the wire. The hooks can then be 

 unfastened and the absorber readily withdrawn. 



For weighing the carbon-dioxide absorbers, two copper loops act as 

 extensions to the steel hooks. A similar device serves for suspending 

 the oxygen cylinders. 



One of the most striking features of this balance is its great capacity 

 and extreme sensitiveness. In weighing the water-absorbers, some of 

 which weigh fully 18 kg., we have the greatest test on the sensitiveness 

 of the balance, and it is found that these absorbers may be weighed 

 so delicately that a difference of 20 mg. is readily detected a degree of 

 accuracy far beyond the ordinary requirements. 



A balance of the same type, but with one-half the capacity, z. <?., lokg. 

 in each pan, is employed for weighing food, feces, urine, and miscel- 

 laneous small articles used in connection with experiments on man. 

 This balance is so accurate and so sensitive that it can be used for 

 adjusting large weights, and by a method of double weighing we have 

 standardized with it all of our weights over 200 grams, and determined 

 the actual weight of the different counterpoises used on the water-meter 

 (see p. 126) and large balance. 



WEIGHTS. 



The accuracy of the determination of the balance of intake and out- 

 put of matter with the respiration calorimeter obviously depends on the 

 accurate weighing of the factors of income and outgo. The materials 

 of the income are weighed usually on a sensitive balance with one set of 

 weights, the samples for analyses weighed on an analytical balance with 



