a. Nail scrapings 

 OC-hydrate 



b. "Avg." pH<U.5 

 oC-hydrate 



"Avg." pH 6 - 7 

 Primarily y^-hydrate 



d. >^ hydrate 

 (BaTidisch) 



e. /^-hydrate (from 

 ferric chloride) 



Fig. 1 Ferric oxide mon ©hydrates X-ray dif- 

 fraction patterns identifying the rust on 

 iron nails as the o<-form and showing the 

 effect of the "average" pH range on the form 

 obtained in the oxidation of a ferrous pre- 

 cipitate. Pure *f- and ^ - forms are shovm 

 also as (d) and (e) respectively. 



