BRIDGMAN. — HIGH PRESSURE EXPERIMENTING. 



637 



able. This may stand as much as 9000 kgm. on the first appHcation 

 of pressure. The tubing should not be softened, but left hard drawn. 

 It is likely to have flaws in it, but these can be usually detected by a 

 careful examination of the outside of the tubing. For pressures up to 

 4000 kgm. it is safe to use with this tubing a connection like that 

 shown above (in Figure 8) for the copper tubing. But the right and 

 left hand thread connection (of Figure 7) cannot be used, since for 

 one thing a soldered joint will not stand the pressure, the solder being 

 eventually pushed out. The washers, of course, should be of steel, 

 and it pays to cup the upper steel washer, filling the groove of the cup 

 with solder. At pressures in excess of 4000 kgm. the tube is likely to 

 fail by the " pinching-off " effect, if the rubber type of packing is 

 used. This "pinching-off" effect almost invariably takes place at 

 the bottom of the thread, the weakest part of the tube. 



For higher pressures than 4000, up to 6000 or 7000, a connection 

 must be used which prevents the packing from coming into contact 

 with the thread. The cone packing of Figure 9 

 answers this purpose. The cone. A, screwing 

 over the end of the tube is of hardened nickel 

 steel. The liquid is kept from coming into con- 

 tact with the thread by a ring, B, of soft steel, 

 protected by solder, C, above. A hollow cone 

 of soft steel, D, cut at a slightly more acute 

 angle than the solid cone is the packing. To 

 ensure initial tightness, before pressure has been 

 pushed high enough to make the cones conform 

 to each other, a thin piece of rubber, or a ring of 

 copper may be placed between the cones. This 

 packing has never been quite satisfactory, since 

 often rupture did ultimately occur at the base 

 of the threads. At the Geophysical Laboratory 

 in Washington a method has been developed by 

 Dr. John Johnston for packing commercial steel 

 tubing that will doubtless be found more con- 

 venient than the above. ^ He has tested the 

 method to 8000 kgm., but whether the tubing 

 will stand the continued application of 8000 I 

 do not know. 



For continued use to pressures higher than 7000 I have not been 



Figure 9. Coned 

 packing for use with 

 tubing up to 7000 

 kgm. The purpo.se 

 is to keep the pres- 

 sure from the threads 

 on the outside of the 

 tubing, where rup- 

 ture is particularly 

 likely to occur. The 

 scale of the diagram 

 is * actual size. 



2 John Johnston and L. H. Adams, Amer. Jour. Sci., 31, 50.5 (1911). 



