14 A RESPIRATION CALORIMETER. 



against the metal shoulder and is held in place and made airtight by 

 being thoroughly cemented with a wax prepared by melting together 9 

 parts of beeswax and 2 parts of Venice turpentine. The wax is first 

 crowded around in the space between the edge of the glass and the 

 metal, and then by means of a soldering iron it is melted and pressed 

 into every crevice. A pin-hole through the wax is disastrous to accu- 

 rate work. As the result of a number of tests, we have found that this 

 method of closing the window is very satisfactory. 



Food aperture. For passing smaller objects, e.g., food containers, 

 etc. , into and out of the respiration chamber during the progress of 

 an experiment, it is necessary to provide an opening which can be 

 opened and closed without leakage of air. The arrangement adopted 

 consists practically of a brass tube through the walls, with a hinged 

 port at each end, such as is used on vessels. (Figs. 8 and 33.) 



The inner port is soldered directly to the copper wall and to a metal 

 ring which in turn is soldered between the zinc and the copper wall. 

 The door closes on a rubber gasket making an airtight joint. The 

 outer port is tightly soldered to a brass tube 24.3 cm. long and 15.2 cm. 

 in diameter, which extends into the food aperture to within 5 mm. of 

 the door on the inside. This brass tube has a smaller diameter than 

 that of the metal tube soldered between the metal walls, and there is 

 accordingly an annular space between these metal tubes. Since the 

 inside port is soldered to the ring forming the outer boundary of this 

 annular space and the outside port is soldered to the tube forming the 

 inner boundary, it is only necessary to fill this space completely to make 

 an airtight joint. After considerable experimenting with solid-rubber 

 rings, cement, wax, etc., a flat rubber tube with a smaller tube and 

 valve attached to it in such a manner that it could be inflated like a 

 bicycle tire was utilized. (See D, fig. 8.) 



The smaller tube and valve project through the outer wall of the 

 calorimeter just below the opening for the food aperture. The large 

 rubber tube is held in place between the two metal tubes by a thick 

 coating of shellac, and when once put in place and well inflated a tight 

 closure is maintained. 



Air-pipe openings. The openings for the pipes conducting the air 

 into and out of the chamber are placed on the right of the front end 

 of the chamber (see V, figs. 8 and 30) a little above the center line. 

 The two round openings in a rectangular box (see fig. 30) are the air- 

 pipe connections. The construction of the box, the connection of the 

 pipes, and the method of attaching and securing tight closure to the 

 copper wall are shown in detail in figures 32 and 33. Two heavy brass 

 flanges, threaded on the inside, are well soldered to the copper wall, the 



