26 A RESPIRATION CALORIMETER. 



dehydration is very complete, even though the depth of acid through 

 which the air passes is not great. 



The absorbers are constructed to withstand increased pressure, and 

 consequently in testing for tightness a water manometer is attached 

 and air forced in. If a leak is indicated by the manometer it can be 

 located by either coating the joints with soap solution or immersing 

 the whole absorber in a vessel of water and noting any escape of air 

 in the form of bubbles. 



For connecting the absorbers to each other and to the valve, metal 

 couplings are used, but the desired flexibility of the parts is secured 

 by means of a specially made elbow of rubber. 1 The simple form of 

 coupling shown in figure n, when used with a soft rubber gasket 

 2 mm. thick, has invariably resulted in a perfectly tight closure. 



Durability of the water-absorbers. When the absorbers were first 

 obtained they gave excellent satisfaction in every way. After about 

 three months' use, however, it was noted that the acid had penetrated the 

 earthenware and was collecting in drops on the outside of the absorber. 

 As a result of a number of tests it was found that after thoroughly 

 washing the absorbers to free them from acid and then drying at 

 1 00 in a water-oven until thoroughly dry, boiling- hot paraffin could 

 be forced into the porous material and thus prevent leaking. The 

 hot dry absorber was removed from the water-oven, a pint of boiling 

 paraffin poured into it and well shaken about so as to insure contact 

 with all portions of the interior, and then the excess of paraffin poured 

 out. The openings in the top of the absorber were then carefully 

 corked and a pressure of 10 or 15 pounds applied by forcing air into 

 the absorber with a bicycle pump. As the absorber cooled, the paraffin 

 solidified, filling the porous portions of the absorber. This treatment 

 has thus far given excellent satisfaction. 



Efficiency of the water-absorbers. The greater the efficiency of the 

 water-absorbers the fewer required in series and the longer they can be 

 used. It was found that with a current of air passing at the rate of 75 

 liters per minute an absorber freshly charged with sulphuric acid would 

 remove 500 grams of water vapor from the air current before allowing 

 any water vapor to pass through unabsorbed. As the system is now 

 arranged, one absorber is used to remove the water from the air cur- 

 rent and another to collect the water taken up by the air current in 

 its passage through the carbon-dioxide absorbers. In practice, a record 

 is kept of the weight of each absorber, and when a gain of 400 grams 



1 These elbows were furnished upon specifications by the Davol Rubber Co., 

 Providence, Rhode Island. 



