66 



Dr. M. Wildernian. On Chemical Dynamics [Jan. 30, 



wrong in the water. And once the gills are affected, there is little 

 chance of the fish escaping. The whole habits of the salmon, in short, 

 render it peculiarly liable to this form of poisoning. 



Summary. 



Chemical analysis of the Spurge-extract shows that it contains 

 tannic acid. Experiments on the circulation in the lung and mesentery 

 of the frog reveal a close similarity between the action of the Spurge- 

 extract and of tannic acid. In the case of trout the similarity extends 

 to the non-recovery of the fish in fresh water, after they have come 

 under the influence of either Spurge-extract or tannic acid. The 

 power of the Spurge-extract to produce fatal effects persists for several 

 days without diminution. Twenty per cent, of the fresh extract is 

 fatal within 5 minutes, whilst 0*01 per cent, takes 4 to 6 hours, and 

 seems to be the smallest percentage which has fatal results. In the 

 case of fishes, death is considered to ensue from the inflammation 

 of the gills and consequent stasis of the circulation, set up by the 

 action of the tannic-acid component of the Spurge-extract. The fresh 

 extract is calculated roughly to contain about 1 per cent, of tannic 

 acid, but on this estimation the Spurge-extract is fatal within a shorter 

 period than the corresponding quantity of tannic acid. Hence, the 

 percentage of tannic acid has been under-estimated, or some other 

 substance or substances in the extract also aid in producing fatal 

 effects. 



" On Chemical Dynamics and Statics under the Action of Light." 

 By Meyer Wilderman, Ph.D., B.Sc. (Oxon.). Communi- 

 cated by Dr. Ludwig Mond, F.B.S. Keceived January 30, — 

 Eead February 13th, 1902. 



(Abstract.) 



Since the second half of the last century chemical statics and 

 dynamics have developed into a veritable science of their own. The 

 general law governing velocity of chemical reaction and chemical 

 equilibrium in homogeneous systems is now known as the law of 

 action of mass;* the law governing velocity of physical or molecular 

 transformations in heterogeneous systems proves also to be of a 

 general and simple nature : the velocity is directly proportional to the 

 surface of contact of the reacting parts and to the remoteness of the 

 system from the point of equilibrium ; f the velocity of chemical 



* Wilhelmy, Harcourt and Esson, Guldberg and Waage, Yan't Hoff. 

 f M. Wilderman, ' Zeitschrift fur Physikaliscke Cliemie,' 1899, and especially 

 ' Phil. Mag.,' July, 1901. 



