194 Prof. J. P. Cooke on the Variation of Constitution of a 
Arr, XVIII—Crystalline form not necessarily an indication of 
definite Chemical Composition: or, on the possible variation of 
constitution in a mineral species independent of the Phenomena of 
Isomorphism. By Jostan P. Cooxg, Jr., A.A.S., Professor of 
Chemistry and Mineralogy in Harvard College.* 
of zine and antimony which I named stibiobizincyle and stilnotn- 
ing proportions of zine and <i differing very a 
nite proportions; a 
in order to render myself intelligible, it will be necessary 
recapitulate very briefly the facts in question, referring to we 
original memoir for the full details, 
The erystals both Sb Zn? and SbZn? can be obtained with 
great readiness, It is only necessary to melt together the two 
i rf when the metals are ful 
alloyed, to proceed exactly as in crystallizing sulphur. >%° 
melted mass is allowed to cool until a crust forms on the surface, 
which then is broken, and the liquid metal remaining 10 = 
interior poured out. On subsequently breaking the crucible, the 
interior 1s found lined with magnificent metallic crystals, which, 
when not tarnished by oxydation have a silver-white lustre. fn 
the course of my investigations on these compounds, crystal 
tions were made, or attempted, of alloys, differing in composition 
by one half to five per cent, according to cireumstances, he 
the alloy Porat 95 per cent of zinc, to that containing 95 
per cent of antimony; but only two crystalline forms were 0% 
ved, that of Sb Zn? nad that of Sb Zn, he enystals shot 
~ , 
Pemmmicated by the Author. New Series 
ransactions of the American Academy of Arts and Sciences, 
vol, v, p. 387, This Jour, [2], xx, 222, : 
es ee 
