100 



CHEMISTRY. 



condition ; 2. Crystallized minerals developed in 

 a magma under pressure may lose their stabil- 

 ity and be dissolved in the same magma when 

 the pressure is removed: 3. In all those cases 

 where solution is accompanied by contraction the 

 solvent action of water and other liquids is in- 

 creased by pressure ; 4. Under great statical 

 pressures the whole substance of solid bodies may 

 be permeated by fluids, and chemical reactions be- 

 tween them be thus greatly facilitated ; 5. By such 

 intimate intermixture of solids and fluids the 

 properties of the former undergo great modifica- 

 tions ; 6. Mechanical stresses which tend to 

 overcome the attraction of the particles of a 

 a solid promote chemical action at those parts 

 of the mass which are in a condition of intense 

 strain; 7. Pressure may supply the conditions 

 for the renewal of the growth of crystals when 

 their development has been arrested for an in- 

 definite period, and even after they have suffered 

 mechanical injuries; 8. When solution under 

 pressure is going on in a crystalline body the 

 action is controlled and modified by its molecu- 

 lar structure ; 9. Under great pressures paramor- 

 phic changes take place in crystalline bodies 

 without any alteration of their chemical com- 

 position ; 10. Both solution and the formation of 

 new crystalline compounds may result from press- 

 ure, and the two may take place together ; in- 

 terchange of ingredients may take place between 

 the crystalline bodies, and pseudomorphs be 

 formed; 11. When the crystalline contents of 

 rocks are brought into close contact by dynamic 

 pressure, chemical affinity comes into play be- 

 tween them, and new mineral species may result ; 

 the operation is facilitated when, as a conse- 

 quence of internal strains, differential move- 

 ments are set up within the rock mass, and rub- 

 bing or sliding contacts between its particles are 

 brought about; 12. When internal strains and 

 differential movements affect a mass which is at 

 the same time undergoing recrystallization, the 

 forms and relations of the crystalline particles 

 that build up the new rock may be greatly modi- 

 fied by the action of the mechanical forces. 

 Statical pressure is not regarded as an agent of 

 change, like heat or electricity, but simply as a 

 condition under which these agents operate. 

 Such pressure, too, may produce great effects by 

 causing a closer contact and consequent chemi- 

 cal action between the molecules of a fluid made 

 to penetrate a solid, or between the molecules of 

 two solids forced into more perfect contact. 

 Statical pressure may further promote the es- 

 cape of volatile materials even under extreme 

 temperatures, and these substances may exercise 

 important influences on the solids and liquids 

 within which they are retained. Dynamical 

 pressure, especially when it results in differential 

 movements in a mass, can certainly do all that is 

 effected by statical pressure, and perhaps some- 

 thing more. 



Drs. Seubert and Pollard, of Tubingen, report 

 upon their experiments for determining the den- 

 sity and boiling point of cyanogen iodide, CNI, 

 a substance very difficult to deal with on account 

 of its extremely poisonous nature, which is made 

 more dangerous by its great volatility. It is 

 characterized as an' exceptionally beautiful sub- 

 stance, and has the property of subliming and 

 forming long, delicate, colorless, but highly re- 



fractive needles, bridging over from side to side 

 of the wide tube or flask in which the operation 

 is performed. These elongated prisms often at- 

 tain the length of six inches or more, and fre- 

 quently form an interlacing network, among 

 which may be seen an occasional star-shaped or 

 flower-like aggregation of smaller crystals. These 

 crystals have also the property of resubliming 

 from one side of the vessel to the other, accord- 

 ing as their position is varied as regards the di- 

 rection of the light which falls upon them. 



Experiments made by Carl Barus with a va- 

 riety of substances show that if temperature and 

 pressure vary linearly at a mean rate of about 

 11 C. per atmosphere, there will be no change 

 of volume. By judicious extrapolation, the prob- 

 able contours can be computed to 1,000 atmos- 

 pheres, with results accentuating this law. The 

 author has found, furthermore, that the pressure 

 necessary to solidify a substance is, other things 

 being equal, decidedly in excess of the pressure 

 at which it again liquefies. Making use of this 

 as a type of lag phenomenon, he is led to results 

 bearing directly on all lag phenomena, and be- 

 yond this on the molecular structure of matter 

 in general. Operating above 100 C., he observed 

 that (liquid) water at a pressure of 20 atmos- 

 pheres and a temperature pf 185 attacks ordi- 

 nary lead glass so rapidly that in very fine capil- 

 lary tubes the contents became opaque and solid 

 in about an hour. During thi time the com- 

 pressibility at 185 gradually and regularly in- 

 creased to a final value about three times the 

 original value. At the same time the isothermal 

 . volume of the silicated water decreased fully 13 

 per cent, of its original bulk. In the case of 

 mercury, the simultaneous decrements of elec- 

 trical resistance and volume were found to be 

 proportional to each other. The result indicates 

 a new method of attacking the thermo-dynamic 

 problems mentioned, and has already, according 

 to the author, led to conclusions of electrical in- 

 terest. 



The destruction of the passivity of iron in 

 nitric acid by magnetization has been the sub- 

 ject of continued studies by E. L. Nichols and 

 W. S. Franklin. The behavior of iron in nitric- 

 acid solutions varies with the temperature and 

 strength of the acid and with the molecular con- 

 dition of the metal. Increase of temperature 

 promotes the action of the acid. Time of ex- 

 posure operates to lower the temperature at 

 which passivity is lost. The authors found that 

 the action of the magnet is to lower the tempera- 

 ture of transition to the active state, and that 

 the intensity of the magnetic field necessary to 

 convert passive into active iron at a given tem- 

 perature increases rapidly with the concentra- 

 tion of the acid. 



In later papers respecting his investigations 

 of allotropic forms of silver, Mr. M. Carey Lea 

 observes that the three forms " the blue soluble 

 and the blue and yellow insoluble are not to be 

 understood as the only forms that exist, but as 

 only the best marked. The substance is pro- 

 tean, and exhibits other modifications not yet 

 studied. No other metal than silver appears to 

 be capable of assuming such a remarkable va- 

 riety of appearances. Every color is represented. 

 I have obtained metallic silver blue, green (many 

 shades of both), red, yellow, and purple. In 



