84 INTERESTING CRYSTi^LLINE ALLOTS. 



If it were possible to attack the Bi by some acid tbat is not 

 oxidizing, we should unquestionably obtain crystals of the alloy 

 of Pt and Bi, or Pt and Cu, or perhaps Pt, Bi, and Cu ; but on 

 using nitric acid as the solvent, we have to be content with 

 pseudomorphs of PtOg after the alloy. 



In order to avoid the use of nitric acid, an experiment was 

 made by substituting Zn for Bi, in the hope that crystals would 

 be formed that could be separated by dissolving out the Zn with 

 Hj,S04. A black powder was obtained in this way, showing, 

 however, no evidence of crystallization. On treating the black 

 powder with nitric acid, Cu was dissolved to the extent of 20 per 

 cent., and a grayish-black residue was obtained, which, when 

 dried, possessed highly oxidizing properties (No 14). It instantly 

 ignited a drop of alcohol and exploded a mixture of hydrogen 

 and air. What the exact nature of this substance is, I have not 

 determined ; but it diflPers materially from the crystalline black 

 substance prepared from the Bi alloy. Prom the loss sustained 

 on ignition (less than one-half required for PtOj.) it would appear 

 to be finely divided platinum intimately mixed with PtOg. Its 

 oxidizing properties are, however, far more energetic' than were 

 shown by the previous compound. 



These experiments that I have drawn attention to may be 

 regarded as being af a preliminary character. They offer, how- 

 ever, a field for further investigation that would, in all probabil- 

 ity, lead to some interesting facts connected with the composition 

 of alloys. 



