354 



iPROCEEDINGS OF THE NATIONAL MUSEUM 



apparent, though in places there are faint remnant gamma boundaries 

 along which phosphide particles are disposed. 



At numerous points the phosphide particles are thickly crowded 

 in round areas, which appear to the eye as dim lighter spots on the 

 etched surface and at moderate magnification suggest galaxies in a 

 photograph of the stars. At high magnification the phosphide par- 

 ticles appear irregular in shape, fairly uniform in size, and without 

 orientation. In places these groups or "galaxies" of phosphide par- 

 ticles inclose small irregular black inclusions of unusual character — 

 a dense aggregate of phosphide particles in a phosphide-poor ground- 

 mass. At low magnification they resemble areas of black gamma- 

 alpha aggregate, but they are definitely proved to be phosphide. 



On a thin slice cut from the base of the jDyramidal mass the specific 

 gravity was determined and a chemical analysis made, after all fused 

 material from the outer edge of the slice had been removed. The 

 sample was placed in a flask and covered with dilute hydrochloric 

 acid, and the gas given off was passed through a train of lead-acetate 

 solution to precip)itate any sulphide gas as lead sulphide. There was a 

 small residue in the flask after it had stood in contact with the acid 

 for 20 hours. This insoluble material was filtered off and washed 

 several times with dilute hydrochloric acid to make certain that it 

 was free from kamacite. The residue was then taken up in aqua 

 regia, diluted to volume, and analyzed separately from the portion 

 soluble in hydrochloric acid. 



The weight of the material soluble in hydrochloric acid and called 

 kamacite, and that of the material insoluble in hydrochloric acid and 



ANALYSIS OF PIMA COUNTY METEORITE 

 (E. P. Henderson, Analyst) 



' The molecular ratios are obtained by dividing the percentage of each element found by the atomic 

 weight of the element. 



