Physical and Chemical Behavior of Solids. 247 



alloys. In those systems in which the metals crystallize out 

 from the melt as pure components, there is no essential differ- 

 ence between the conglomerate produced by compression and 

 that obtained by fusion. In all other systems the immediate 

 effect of compression is slight and consists solely in the fact 

 that compression brings about very intimate contact between 

 the particles, the result of which, in turn, is the formation 

 at the contact of a compound (if such be possible) or the pro- 

 motion of diffusion (when the metals can form mix-cryst 



The Work of G. Spezia. 



Spezia has performed a number of experiments on the effect 

 of pressure on chemical reactions and transformations ; and has 

 reached conclusions in harmony with those presented in this 

 paper. 



In 1898 he noted that opal from Baldassero, treated for 

 seven days at a temperature of 280-290° with a dilute solution 

 of sodium silicate, was transformed into quartz. On the other 

 hand a prism of the same opal immersed for eight years in the 

 same solution at a temperature never above 30° and under a 

 pressure of 1600 atmospheres, showed no evidence of such 

 transformation.* 



He has lately published an accountf of similar work, under- 

 taken chiefly to disprove certain assertions made by Van Hise;j: 

 with regard to the effect of pressure in bringing about silicifica- 

 tion, dehydration and deoxidation. These experiments are 

 presented in summary form below. 



Table VII. — Spezia 's Experiments on the Influence of Compression on 

 Certain Reactions at Ordinary Temperature. 





Compression 





System 



Amount -p, , . 



, ' Duration 

 in atm. 



Result 



I. Hydrated silica + CaC0 3 --. 



II. Alum (K 2 A1 2 (S0 4 )4.24H 2 0) + 



powdered quartz 



Alabaster + powdered quartz 



Limonite + Powdered quartz 



III. Gothite 4- quartz . 



6000 

 1 



^8000 



i 



9500 

 9500 

 9500 

 7000 

 7000 



1 year 



8 months 



26 days 



30 days 



30 days 



6 months 



6 months 



No trace of reaction 



f Absolutely no 

 J dehydration of the 



j first named 



[substances 

 No dehydration 

 No trace of reaction 

 No trace of reaction 

 Absolutely no change 

 Absolutely no change 



IV. CuO (powder) + Mg (filings). 



CuO (powder) + K 



V. Calcite 



Aragonite _ __ 





*Rivista Min. Ital., xxxr, 62-64, 1908. 

 t Atti Accad. Sci. Torino, xlvi, 1, 1911. 

 J'' Treatise on Metamorphism " (U. S. Geol. Survey, Monograph No. 47). 



