

THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.! 



Art. LY. — On Endothermic Decompositions obtained by 

 Pressure. Second Part. Transformations of Energy by 

 Shearing Stress / by M. Carey Lea. 



Of the relations which exist between two forms of energy, 

 mechanical and chemical, very little if anything is known. In 

 the second volume of his Lehrbuch, Ostwald remarks that as 

 to these relations "almost nothing" is known.* 



There are certain familiar cases in which mechanical energy 

 may seem at first sight to be converted into chemical energy. 

 The fulminates, iodimide, and other substances explode by 

 shock. But it is hardly necessary to remark that ail such reac- 

 tions are exothermic and need an external impulse only, to 

 start them — if this impulse were not needed such compounds 

 could not exist at all. Were such reactions taken as true trans- 

 formations of energy an absence of due relation between cause^ 

 and effect would be involved. For the shock that suffices to 

 explode a grain of fulminate will equally explode a ton. The 

 faint spark that will explode a grain of gunpowder will also 

 explode a magazine. 



Present opinion holds undoubtedly that no true transforma^ 

 tion of mechanical into chemical energy is known. Most text 

 books do not consider the question at all. But Dr. Horstmann 

 in the volume of theoretical chemistry which forms part of the 

 last German edition of Graham Otto's Chemistry, discusses the 



* ; Andererseits i?t von der Verhaltnis zwischen mechanischer unci chemischer 

 Etiergie. fast nichts bekannt." A few lines below, this remark is repeated with 

 emphasis. Lehrbuch, 2d German ed., vol. ii, p. 12. 



Am. Jour. Sci.— Third Series, Vol. XLYI, No. 276.— Dec, 1893. 

 29 



