62 Conductivity of Aqueous Solutions. Part III. 



removal of a long cylindrical platinum tube from a surrounding reinforc- 

 ing tube. 



The lower electrode is first removed from the bomb and replaced by the 

 steel piece shown in fig. 3, section 5, Part II, a gold washer being placed 

 under the V-shaped ridge to protect the lining and to make the joint 

 tight. A hardwood piece is then turned to fit the inside of the bomb as 

 closely as possible. The auxiliary cover shown in fig. 4 is next fastened on 

 in the usual way, and the bomb is then screwed into the cast-iron cup, fig. 

 10. A hydraulic pump is now connected with the bottom of this cup and 

 oil is forced into the space between the bomb and the cup. This oil flows 

 through the small holes in the steel shell and presses the lining on to the 

 hardwood piece within. A pressure of about 25 atmospheres, kept on for 

 two or three minutes, suffices. The bomb is then taken apart, and the 

 wooden plug with the lining on it may be readily removed. The lining is 

 then removed from the wood by heating it until the wood is slightly 

 charred. 



26. A MORE DELICATE LEAKAGE TEST. 



The original test of the lining with the hydraulic pump proved to be 

 insufficient, as the bomb may stand this test and yet permit the escape of 

 steam at high temperatures. The following has been found to be a much 

 more delicate and satisfactory test : 



The cover and lower part of the bomb are connected separately by 

 means of the auxiliary pieces, figs. 6 and 4, section 5, Part II, with a 

 cylinder of liquid carbonic acid, thus subjecting them to a gas pressure 

 of about 50 atmospheres. Before doing this the lining must be carefully 

 dried, best by rinsing with alcohol and ether, and it is well to insert in the 

 bomb cavities a little absorbent cotton, to take up any trace of liquid 

 which might be originally present in the tube connected with the carbonic 

 acid cylinder. The part being tested is then immersed in a glass jar of 

 xylene, or of some other colorless liquid which does not absorb carbonic 

 acid. The position of a leak is shown by the hole in the steel shell from 

 which the gas bubbles are seen to emerge. 



27. SOLID PLAT1NUM-IRIDIUM ELECTRODES. 



The platinum-covered steel electrodes originally used were somewhat 

 inconvenient because of the difficulty that attended their removal. After 

 a few experiments the brass nut, N, fig. 1, Part II, always got rusted 

 on so that it could not be taken off with the wrench. This difficulty has 



