M. C. Lea— Chemical Energy, etc. 877 



Art. XLIII. — Transformations of Mechanical into Chemical 

 Energy. Third Pajper. Action of Shearing Stress con- 

 tinued ; by M. Carey Lea. 



That mechanical energy may be transformed into chemical, 

 has been, I believe I may say, well proved by the reactions 

 described in the previous papers of this series. But the mat- 

 ter is one of sufficient importance to make it desirable to accu- 

 mulate evidence and to obtain a solid foundation of fact on 

 which to rest the argument. 



In the paper which described the effects of shearing stress 

 (this Journal, Dec. 1893), I was able to cite one instance only 

 in which the decomposition product was obtained in easily 

 weighable quantities. More lately others have been obtained, 

 among them one, mercuric oxide, in which it can be deter- 

 mined how many units (gram-meters) of mechanical energy 

 have been transformed into chemical. 



Silver-oxide precipitated and dried in the absence of day- 

 light is soluble without residue in ammonia. After tritura- 

 tion therefore, the unchanged portion is easily removed by that 

 solvent. 



1. Half a gram of silver-oxide wholly soluble in ammonia 

 was triturated for 20 minutes in a porcelain mortar the un- 

 changed portion was removed by ammonia, the residue was 

 treated with nitric acid, filtered, and the silver thrown down 

 by hydrochloric. 



Silver chloride obtained '0402 



Corresponding to metallic silver . # 0303 



The use of a porcelain mortar is attended with the disadvan- 

 tage that during the prolonged and forcible grinding necessary, 

 a very appreciable amount of material is removed from the 

 mortar and pestle, which must be separated from the product 

 subsequently. I have therefore made some comparative ex- 

 periments with a large agate mortar and an agate pestle pro- 

 vided with a stout wooden handle adapted for the use of as 

 much force as with a porcelain mortar. But even under the 

 most favorable conditions, the efficiency of such a mortar is (as 

 will be seen) only one-fifth to one-tenth that of a porcelain 

 mortar of the same size. This is largely due I think, to the 

 high polish which is very unnecessarily given to the inside of 

 agate mortars. 



It is therefore better to make use of a porcelain mortar, tak- 

 ing adequate means afterwards to separate the material abraded. 



