Chemical Action in the Crystalline State. 571 



permanganate respectively. Crystals containing only (VI 

 per cent, of potassium permanganate gave no measurable 

 evolution of oxygen under the same conditions. The solid 

 solution crystals were in each case fine and of uniform 

 grain. 



Fiff. 2. 









i 





?-r> 

















1 



6 











f 

 » 











i> 



! 

 i 



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fy/y 



-3~~ 



°^«— " ■ — 







80 



I. Large crystals KMn(\ at 239 s C. 



II. J Solid solution of KMn0 4 and KC10 t 

 I EI. ( (82 % KMnOJ. Small crystals at 239° C. 

 IV. Solid solution of KMn0 4 and KC10 4 



(26-8% KMnO,). Small crystals at 239° C. 



>(>0 MlfVUTES 



3. Decomposition of Ammonium Bichromate. 



Figure 4 shows the type of curve obtained with finely 

 ground ammonium bichromate at 219° 0. In connexion 

 with ammonium bichromate a further point of interest was 

 noticed. When a large crystal was heated at 212° 0. it did 

 not disintegrate, but the chromium oxide formed remained 

 as a coherent film, and when the whole surface was covered 

 the reaction ceased or became very slow indeed. The interior 

 of the crystal was unchanged. (Cf. an observation of Ball, 

 Trans. Chem. Soc. 1909, xcv. 87.) ' 



2 p 9 



