58 



BRIDOaUN. 



^— A 



parts of the mass. It might at first thought seem that the steel shell 

 would produce irregularities by tending to hinder the change of 

 volume accompanying the reaction, but no irregularities of this nature 

 were ever found. Sometimes, when the substance could be melted 

 without danger of decomposition, it was melted, instead of hammered, 

 into the shell. Under these conditions the shell was, of course, closed 

 at the bottom end. If the substance were one soluble in kerosene, 

 two slightly different methods were used. By the first method, the 

 salt was formed into a cylinder of suitable dimensions, either by ram- 

 ming into a split mound or by melting into a form, and then sub- 

 merged under mercury in a steel shell, being prevented from rising 

 by a clip at the upper end. Or it might be hammered or melted into a 

 steel cylinder, which was then inverted below the surface of mercury 

 as shown in Figure 1. This method is applicable if the substance 

 melts somewhere within the range of the experi- 

 ment, and was used in all such cases. The air, of 

 course, was exhausted in this case. The chief 

 trouble with this method of the inverted cup is 

 that the cup is very likely to be ruptured by the 

 change of volume during either melting or the 

 change from one solid to another. Substances are 

 strikingly different in their rigidity and the readi- 

 ness with which they rupture the cylinder. It is 

 significant that the shell was never ruptured while 

 determining transitions in the low pressure appa- 

 ratus; this is another bit of evidence showing the 

 greatly increased rigidity, or better, viscosity, pro- 

 duced by high pressures. The shells finally had to 

 be made of hardened chrome nickel steel of the 

 dimensions shown, and even then they were some- 

 times broken. The dimensions of the free space 

 allowed for the mercury are of importance, since 

 the kerosene must not come in contact with the 

 substance in consequence of the changes of volume 

 brought about by the transitions or the compres- 

 sibility. The proportions shown sufficed for all sub- 

 stances investigated here up to 12000 kgm. 



In other respects the apparatus was of the same 

 design as that previously used, but accidents necessitated the renewal 

 of various parts. Three lower cylinders were ruptured, two by amal- 

 gamation, and one by a violent explosion. This explosion also ruined 



Figure 1. The 

 modified form of 

 container for those 

 substances which 

 melt within the 

 range of the exper- 

 iments. 



