6o 



Conductivity of Aqueous Solutions. Part III. 



due to the spreading of the large nut when the pressure came on within 



the bomb and when, at any stage of the heating, the large nut was 



heated faster than the lower part of the bomb. 



A second screw-thread of exactly 



the same size as the first is also cut 



below the hexagonal part of the steel 



shell, as shown in the same figure. 



This screws into the special chuck 



described in section 23, and so helps in 



the construction of the bomb and in 



the removal of the platinum lining 



from the shell. (See section 25.) 

 Fig. 10. 



Fig. 9. 



23. SPECIAL LATHE-CHUCK USED IN THE CONSTRUCTION OF THE BOMB. 



The construction work has been greatly facilitated by the use of a 

 special lathe-chuck. This is shown in vertical section in fig. 10. It is 

 a cup-shaped piece of cast iron which at the lower end screws on to the 

 spindle of the lathe. The upper end is made to take the thread on 

 the shell of the bomb. All of the finishing of the shell, both at the top 

 and bottom, is done with the latter screwed into this chuck, with the result 

 that the bomb can at any time be brought into the lathe so as to run 

 perfectly true. 



24. A NEW COMPOSITE LINING FOR THE BOMB. 



The original form of the platinum lining of the lower part of the 

 bomb was, when once in place, perfectly satisfactory for work up to 

 306. But for higher temperatures the lining always leaked at the curved 

 portion near the bottom. This was doubtless due to the unequal 

 expansion upon heating of the shell and lining. These were fastened 

 together by the screws and packing-ring at the upper end and by the 

 electrode at the lower end. Upon heating there was a tendency for the 

 steel, which expands more than platinum, to draw away from the latter, 

 leaving it unsupported at the bend. The effect of this was not evident 

 up to 306, but at higher temperatures it caused a very bad leak, for at 

 these temperatures water passes freely through the pores of the platinum 

 at any unsupported place. Moreover, there was always a great deal of 

 difficulty in originally fitting the lining to the curved portion of the 

 bottom, so that upon first applying the hydraulic pressure the lining 

 often tore at this point. 



These difficulties are entirely obviated by doing away with the curved 

 portion, thus making the bottom flat, and by using a lining made in 



