236 KOENIG—ARTIFICIAL PRODUCTION OF CRYSTALS. [Junel, 
0.005 mg., was dissolved in H NO, and evaporated to dryness. The 
dry mass dissolves in water, to which a drop of dilute H,SO, has 
been added. Solution is without opalescence. Hence antimony 
can only be present in traces. Then 2.78 mg. of fine copper wire 
was dissolved in H NO,, this being just seventy per cent. of the 
arsenide. Both solutions made ammoniacal were compared in 
proper dilution of 50 cc. on the colorimeter. The color of the 
solution from the pure copper is slightly lighter and by adjustment 
brings the percentage 
Cu 72 
The crystals are thus proven to be domeykite and not stibiodo- 
meykite. The strange habitus of the crystals, so unlike that of the 
prevalent habitus,.must be looked for in the influence of the anti- 
mony, though the latter does not itself enter the composition. 
6. ACTION oF ARSENIC VAPORS UPON ZINC. 
Experiment of March 2, r90z.—A piece of chemically pure 
zinc, broken from a stick, was exposed for twenty hours, The sur-* 
face is covered by a crust which is developed into mamillary groups, 
somewhat like psilomelane. The crust detaches itself by a blow 
from the hammer and breaks into flaky pieces resembling graphite. 
Analysis gives (0.222 gram): 
Zno = 0.1720 = 0.1381 Zn 
Hence 
; Zn =-62:20 
(By difference) As = 37.80 
100.00 
Zn : As = 959 : 504 = 1.902: 1 
Zn,As 
Zinc acts toward arsenic vapors like nickel; the ratio 2/1 seems 
to be the normal. 
7. ACTION OF ARSENIC VAPORS UPON LEAD. 
The lead melts. Exposure for twenty hours. Product is:still 
Peeteata + « 
