POLYMORPHIC TRANSFORMATIONS OF SOLIDS. 



105 



produced by mercury set free by decomposition, in the presence of 

 steel, either of the Hgl2 of this experiment, or of other mercury salts 

 used in previous experiments. ^: 



The Hglo was obtained from Eimer and Amend, "c. p." and was 

 used without further purification. For the first runs it was hammered 

 cold into a thin steel shell, and pressure transmitted directly to it by 

 kerosene. After this first run small transverse holes were drilled 

 through the sides of the shell to facilitate the reaction, and cut down 

 the width of the band of indifPerence, but no effect from this could be 

 observed. For the later runs, the Hglo was initially melted into the 

 steel shells and then the lateral holes drilled. Xo effect of the greater 

 initial compactness in increasing the reaction velocity was tobe 





.004 



-.002 



> 



.004^^ 



12345678 

 Pressure, kgm./cm.^ x 10 

 Mercuric Iodide 



9 10 



Figure 2.5. Mercuric Iodide. The observed differences of volume. 



observed. Three different samples were used, from 86 to 100 gm. in 

 amount, but each of these samples was used for a number of settings 

 up of the apparatus, and one was used for both high and low pressure 

 measurements. The effect of pressure is to compact the Hgl2 into a 

 mineral like mass, without the slightest tendency to dissolve in the 

 kerosene. After long use a slight amount of decomposition with 

 setting free of minute globules of metallic mercury could be detected 

 where the surface of the Hglo comes in contact with the steel. This 

 is to be expected, because iron will deposit mercury from mercury 

 salts, but the decomposition was too slight to produce a perceptible 

 change in the total volume of the reacting ciuantity of Hgl2. 



In view of the importance of the maximum temperature exhibited 

 by this substance, a detailed description of the experiment will be 

 given. When I started to investigate this substance, all that I knew 

 about it was that it had a transition at atmospheric pressure at 127°, 



