414 M. C. Lea — Endothermic Decompositions by Pressure. 



matter. His views are so much to the point that I shall trans- 

 late a few sentences, putting in italics the statements to which 

 1 would specially refer. 



" We must consequently admit that through a rough mechan- 

 ical attack the molecular structure of certain chemical com- 

 pounds can be disrupted and destroyed. This will certainly 

 be possible only for compounds in whose molecules the arrange- 

 ment of the atoms does not correspond to a stable equilibrium 

 and in which therefore the chemical energies themselves are 

 already striving to form simpler and more stable compounds 

 out of the constituents of the existing substance. For it can- 

 not be admitted that actual chemical changes can be brought 

 about by a mechanical impulse? (1. c, p. 350). 



In another chapter he says with equal distinctness : 



" By mechanical means alone no reaction against the force 

 of chemical energy can be brought about. By a shock or blow 

 the molecular structure of chemical compounds can indeed be 

 so far loosened that free play is given to chemical forces ; but 

 against these forces we cannot by mechanical means separate 

 the atoms nor combine them in a definite way? (p. 594). 



These expressions of a distinguished chemist will sufficiently 

 indicate what has been up to the present time the opinion of 

 chemists as to the possibility of transforming mechanical 

 energy into chemical. 



♦ 



In the first part of this paper I believe I have been able to 

 show in a qualitative way the production of true endothermic 

 reactions by mechanical force. In the present part I hope to 

 show an increased number of such reactions and in one case to 

 exhibit actual' quantitative results, at least so far as to obtain 

 the product of the transformation in weighable quantities. 



In the first part decompositions were described that were 

 brought about by simple pressure. Compounds formed by 

 exothermic reactions, and therefore requiring expenditure of 

 energy to break them up, were decomposed. The investiga- 

 tion might probably have been made to include a still larger 

 range of substances. But it was found that the efficiency of 

 pressure was so enormously increased by the addition of shear- 

 ing motion, that decompositions requiring a force of hundreds 

 'of thousands of pounds with pressure alone, could be effected by 

 the mere strength of the hand when shearing stress was used. 

 More than this, decompositions which enormous pressures 

 failed to effect, readily took place under the action of shearing 

 stress.* 



* It would not have been difficult to obtain much greater pressures than those 

 described in the first part of this paper. This could be effected by means of the 

 differential screw. 1 had planned for a screw with threads of 40 turns in 10 inches 



