BRIDGMAN. — HIGH PRESSURE EXPERIMENTING. 635 



interior of the cylinder which will not be reached b\' the piston with a 

 core of brass or steel, thus reducing the volume and the compression 

 of the liquid. 



One must always be prepared for disappointment after constructing 

 one of these cylinders, for in spite of the greatest care of the manu- 

 facturer one cannot at the present day be sure that the steel will be 

 free from flaws. These flaws may develop during the preliminary 

 seasoning, but are much more likely not to show themsehes until the 

 piece has been reamed to the final size. For example, one cylinder 

 had been used for a year before finally a seam opened in a wall 2^ 

 inches thick, letting through a very fine stream of liquid. It is a 

 matter of pure chance whether a flaw will be found or not; of two 

 pieces from the same bar, one may have a flaw, and the other may be 

 sound. It has been my experience that about three out of every 

 four pieces are sound. 



Connecting Pipes. 



The proper construction of connections from one piece of appara- 

 tus to another has been until recently the most serious problem of all 

 this high pressure work, and the cause of almost every explosion. 

 The problem has at last, however, been satisfactorily solved. Dif- 

 erent types of connection may be used, depending on the pressure 

 to be carried. We begin with the connections for the lower pressures. 



For low pressure transmission, such as for the low pressure end of 

 the press up to 1000 kgm., the most convenient connection is copper 

 tubing. The size I have used is j of an inch outside diameter and Yt 

 of an inch inside diameter. This may be used either in its hard drawn 

 state or else annealed. It wull stand a single application of 1500 kgm. 

 and may be used almost indefinitely to 1000 kgm. For coupling 

 together two pieces of pipe, a cone coupling with right and left handed 

 thread will be found very convenient. (See Figure 7.) The hollow 

 cone may be best made of steel, since it is subjected to greater strain 

 than the other, which may be made of brass. The copper tubing is 

 attached to the cones by threading and soldering. The thread may 

 well be as long as | inch, and the unthreaded part another | inch. 

 If the soldered length at the end of the pipe is much less than 1 inch 

 long, solder will be slowly extruded through the threads by the pres- 

 sure, and there will eventually be leak. 



For making connections to the cylinder the coupling shown in 



