72 sosman: problems of the oxides of iron 



re-dispersed (peptonized) by pure water, simply through the 

 leaching out of the salts carried down by them from the strong 

 precipitating solution. A method of secondary concentration js 

 thereby suggested. It is evident that from studies in colloid 

 chemistry we may expect considerable advances in our knowl- 

 edge of the sedimentary ores. 



I have presented a rather varied list of problems, some of 

 which may seem remote from pure chemistry, but I may possibly 

 find an excuse in the fact that this meeting has been held as a 

 joint meeting of the Chemical Society and the Washington 

 Academy of Sciences. As soon as we begin to consider them in 

 detail, we find that the problems of the oxides of iron are but 

 phases of some of the greater problems of chemistry, physics, 

 biology, and geology. And they can not be solved by taking 

 thought about them; new facts, to be yielded by new experi- 

 ments and new observations, are demanded. Nor are the 

 problems as simple as some of them may have appeared from 

 my statement of them. The chemist is amazed by the facile 

 transformations of iron from ferrous to ferric, beholding the two 

 states of oxidation acting like two absolutely different elements. 

 The physicist stands appalled before the spectrum of iron, 

 realizing the many unknown quantities hidden behind its thou- 

 sands upon thousands of lines. Even the layman can get a 

 vivid realization of the complexity of the problems involved; 

 he has but to walk out through the country round about Wash- 

 ington and note the bewildering play of inorganic colors every- 

 where about him, ranging from deep brown-black through various 

 shades of drab, brown, purple, and maroon, and through the 

 many tints of pink, ocher, and rose, to the most brilliant of reds 

 and orange-yellows, and then realize that almost every one of 

 these hundreds of colors is due to an oxide or hydrated oxide 

 of iron; he will begin to realize then that our chemical knowledge 

 of these oxides is almost infinitesimal. One thing only is clear 

 to us, and that is that we are only skirting around the edges of 

 that vast body of knowledge about iron and its oxides which 

 is, as the mining geologist says, "in sight," not to mention the 

 unsuspected problems that lie "in depth," far beyond our farthest 

 plans for research. 



