the followinrf substances formed successively: Ferrous hydroxide r^- 



ferrous oxide ?■ magnetite --- > -ferric oxide monohydrate 



- - .-i-ferric oxide monohydrate. There may very well be departures 



from this schematic arrangement, but under the conditions ' Ith which this 

 v/ork is concerned, the limited oxygen supply and the 7.U - 8.5 pH range of 

 sea vrater (h) '.rould be expected to favor this mode of chemical change. In 

 X-ray diffraction studies made by Fr, \ L. Starr o^ this Laboratory the 

 major ultimate product was identified as the ^^ -monohydrate in scrapings 

 taken from iron nails which had been immersed in sea ?fater for several 

 months (see Fi.^ure la). This being knovm, it vrould b3 very desirable to 

 precipitate this form in the wood for test purposes, but unfortunately, the 

 information available concerning its synthesis is insufficient to devise 

 a method to accomplish such treatment viith certainty. Hovfever, it has been 

 possible to precipitate the intermediates in v/ood v;hich may very well achieve 

 the same purpose, T^e transformation of the intermediates to the ultimate 

 condition of form and particle size r:.ay be someT/hat slow because of the 

 small energy differences {S) and loyi solubilities. M effort has been 

 made to form all the other types in wood, as well, in order that the in- 

 vestigation be as complete as possible. 



Hydrous ferric oxide (R','"drous Fe^O-j or Fe(OH)., ) 



In the first tests made a ferric salt v/as precipitated by ammonium hydroxide 

 in wood. The protection afforded by this particular treatment was insuf- 

 ficient to be of practical value.. This method precipitates a hydrophilic 

 sol usually referred to as "hydrous ferric oxide," The particles are too 

 small to give an X-ray diffraction ^^ at tern until aged for many months at 

 ro'^m temperature. The aged gel produces the anhydrous <3< -ferric oxide 

 X-ray diffraction pattern. Prior to this change the hydrous oxide is much 

 more soluble and readily subject to colloidal dispersion and, therefore, 

 may very well undergo serious leaching. Phase rule studies by .feiser and 

 Liilligan (6) indicate that the initial form is a simple oxide or hydroxide, 

 and the eventual product, as mentioned above, is the anhydrous X-form, 

 both forms being^ very different from that identified in rust scrapings both 

 as to crystal type and particle size. 



Anhydrous -^-ferric o'/ide ( -:^'. -FepOr)) 



The conversion of the hjrdrous ferric oxide gel to the anhydrous •;:*. -f orm 

 takes place rapidly at 600^0 . or above. The product is a fine, very hard, 

 brick red crystalline material identical to mineral hematite and commercial 

 red rouge. It was found that this conversion temperature could be lowered 

 to 120°C. by use of saturated steam (15 psi) v/hich is known to reduce the 

 temperature required in the dehydration of this as T;ell as many similar 

 hydrates. Under these conditions this tr.aisition vjould involve a time- 

 pressure relationship in which pressure is a parameter of temperature, 

 and it is possible that the change fould take place rapidly at a slightly 

 lower pressure. However it could not be reduced to as low as atmospheric 

 pressure, because the boiling of a suspension has been found to be very 

 slow in bringing about the conversion to particles large enough to produce 



K - 2 



