Chemistry and Physics. 187 



with that of an) 7 member of the humite group to which leuco- 

 phoenicite is related chemically. 



The presence at Franklin Furnace or at Stirling Hill of the 

 following minerals, not hitherto recorded, has been established: 

 Marcasite, millerite, pyrrhotite, aurichalcite, hyclrozincite, 

 psilomelane, gothite, albite, chlorite, ganophyllite, manganese 

 pectolite, descloizite, anglesite and native silver. 



With these additions and the omission of a number of spe- 

 cies of the older lists which could not be verified, the number 

 of minerals recorded for this locality becomes ninety-three. 



Harvard University, October, 1909. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistey and Physics. 



1 . The Formation of Colloidal Solutions by the Action of Ultra- 

 violet light upon Metals. — It was observed by Lenard and Wolf 

 in 1 889 that certain substances, particularly metals, were resolved 

 to dust by the action of ultra-violet light. This effect was detected 

 both by the roughening of the surfaces and the detection of 

 the detached particles in the adjacent layers of air. It was found 

 that different metals gave different degrees of this action, that 

 the electrical condition of the metallic plate exerted a pronounced 

 influence upon the action, as did also the nature of the source of 

 light employed. These investigators did not attempt the pre- 

 paration of colloidal solutions by this means, but they observed, 

 when experimenting with a zinc plate, that a layer of water held 

 back the zinc dust. Svjedberg has now made use of this 

 phenomenon in preparing colloidal solutions of various metals in 

 various liquids. He placed the metal, the surface of which must 

 be (reed from layers of oxide, in a shallow dish, placed the liquid 

 upon it, and exposed it to the rays of a Heraeus' quartz-mercury 

 arc lamp at a distance of a few centimeters. After a few minutes 

 the liquid when examined by the ultra-microscope showed the 

 characteristic appearance of a colloidal solution. Different metals 

 and different liquids behaved veiy differently. Silver, copper, 

 tin and lead gave colloidal solutions easily, while platinum, 

 aluminium and cadmium showed little or no effect. The action 

 with lead was particularly strong. When w T ater was used this 

 metal gave a milky liquid in five minutes, probably colloidal 

 hydroxide, while with ethyl alcohol the same metal gave a 

 colloidal metallic solution. Further experiments with lead and 

 silver in water and six different organic liquids indicated that 



