﻿182 C. Barus and V. Strouhal — Strain-effect of sudden 



Certain general properties of the Prince Rupert drop. 



It is well known that mere breakage of the tail of a P. 

 R. drop is sufficient to shatter it; that the splinters fly apart 

 with explosive violence. It is not so well if at all known, 

 that the same drop may be dissolved in hydrofluoric acid to a 

 mere spicule without exploding. This peculiar behavior calls 

 to mind certain properties of nitroglycerin, inasmuch as this 

 substance may be burned off quietly in a wick, but explodes 

 on percussion. It is in keeping, moreover, with a friend's* 

 ingenious suggestion that in the quenched globule we may pos- 

 sibly encounter a polymerization of the molecular structure of 

 the annealed globule. The fact that the strain in question is of 

 an ordinary mechanical kind seems proven, however, by the 

 observations of Table I, in which the behavior of P. R. drops 

 from which different thicknesses of shell have been removed 

 by solution, is described. Diameter refers to the mean trans- 

 verse thickness of the drops ; # and (j. to the thickness and the 

 mass, respectively, of the dissolved shells. After removing a 

 sufficient depth of shell, the residual explosive properties were 

 tested either by crushing the reduced drop, longitudinally, in 

 a vise, or by striking in the same direction with a hammer. 







Table I 



— Explosive tendency of P. R. Drops. 



No. 



Minutes 

 in HF. 



Diam- 

 eter. 



# 



f 1 



Remarks. 



12 

 10 

 11 



13 



3 

 5 



7 

 8 





 5 





 10 





 14 





 30 





 







"o 



cm 

 0-848 

 0835 



0-796 

 0-766 



0-795 

 0-760 



0-774 

 0-712 



0-795 

 0-688 

 0-825 

 0-720 

 0-763 

 0-539 

 0-791 

 0-557 



cm 

 0-006 



0-015 



0-017 



0-031 



0-054 

 0-053 



0-112 

 0-117 



0-291 



0-492 

 0-491 

 0-722 

 0-752 



( Shattered on breaking base of tail. 

 •< Explosive tendency diminished 

 ( in marked degree. 

 ( Shattered on being split longitudi- 



< nally. Fragments partially co- 

 ( here. 



1 Shattered on being split longitudi- 

 •< nally. Fragments partially co- 

 ( here. 

 ( Shattered on being split longitudi- 



< nally. Fragments more coher- 

 ( hag. 



j Is not shattered on splitting. Con- 



( choidal f rr oture. 



j Is not shattered on splitting. Con- 



\ choidal fracture. 



j Is not shattered on splitting. Con- 



] choidal fracture. 



j Is not shattered on splitting. Con- 



\ choidal fracture. 



The Table shows that the explosive tendency of the P. R 

 drop becomes rapidly less pronounced as the thickness of re- 

 moved shell increases ; that this tendency is very perceptibly 

 * A precautionary suggestion for which we are indebted to Dr. Gooch. 



