NEW OBSERVATIONS IN CHEMISTRY AND MINERALOGY 



By George Augustus Koenig, Ph.D. 



Contents. 



1. A Sensitive Microchemical Reaction for Detecting Small Quantities op Cobalt along 



with Much Nickel 407 



2. Can Copper Ions Detach Themselves from Metallic Copper and Pass through Space at a 



Temperature Considerably Below the Melting Point of the Metal? 413 



3. The Action of Sulfurdioxyd on Cuprisulfate Solutions in a Sealed Tube at Different 



Temperatures 418 



4. On Sulfurdioxyd as an Oxydizing Agent by Preying upon its Own Oxygen 420 



5. On Aurobismuthinite spec, nov 423 



6. On Stibiobismuthinite 424 



7. On Crystallized Seladonite 424 



8. On Natrojarosite from New Locality 425 



9. On Mimetite from Santa Eulalia 426 



1. A Sensitive Microchemical Reaction for Detecting Small Quanti- 

 ties of Cobalt Along with Much Nickel. 



Basic Facts for the Method. — (a) In an ammoniacal solution of a cobalto- 

 salt in presence of sal ammoniac a green color develops upon the addition of 

 ammonium persulfate. The original solution being reddish-brown or brownish- 

 red, there may be a time when the solution looks dark gray or even black through 

 absorption-phenomena of light. Out of such a solution there soon falls a green 

 precipitate and the liquid clarifies. The green precipitate consists of an aggre- 

 gate of green crystals, rather olive-green mostly, but they may be any shade be- 

 tween bluish-green to emerald, to leek, to olive. The dimensions are microscopic ; 

 the shapes are various, but all conforming to monoclinic symmetry though fre- 

 quently, through twinning, forms develop of very bizarre outlines. These 

 crystals are not very soluble in pure water, nor in ammonia water. The precipi- 

 tate has sometimes a lavender color and under the microscope contains 

 granular, orange crystals. The latter may be obtained separately, as will be 

 described. The green crystals will prove to be " praseocobaltioctamino sul- 

 fate"; the orange crystals to be "luteo cobaltidecamino sulfate." The lavender 

 color is due to the presence of the isomeric " purpureocobaltioctamino sulfate." 



(6) In the blue ammoniacal solution of a niccolosalt the addition of am- 

 monium persulfate does not produce a change. Isometric, blue crystals may fall 

 from the concentrated solution; or green, isometric quadruplets; or after several 

 hours the crystals may turn brown-black, because they break up into mccohdi- 

 oxyhydroxyd, ammonia and ammonium salt. This change obscures the micro- 

 scopic field of vision, but since it only occurs in time, it does not interfere with 



407 



