the following non - limiting examples illustrate various preferred embodiments of the present invention . in each instance the starting material was γ fe 2 o 3 which had an average particle size of 1 . 0 micron by 0 . 15 micron . to 300 grams of the γ ferric oxide , there was added a solution consisting of 7 liters of pure water with 12 grams of sodium tripolyphosphate dissolved therein . this was placed in a mixer and mixed overnight . the resulting mixture was then filtered to produce a moist filter cake and this was dried by placing it in a drying oven at 100 ° c . overnight . the dried material was then mixed with the desiccant , if used , and placed in a porcelain combustion boat in an electric furnace , and hydrogen gas introduced into the tube . after the tube had been purged with hydrogen gas for ten minutes , the tube was heated to a temperature and for a time period as set forth in the examples . at the end of this time , the product is allowed to cool to room temperature and oxygen is slowly introduced in the presence of an inert gas ; this stabilizes the material . sodium tripolyphosphate treated γ - fe 2 o 3 reduced in h 2 . weight of sodium tripolyphosphate treated γ fe 2 o 3 = 4 . 2 gm sodium tripolyphosphate treated γ fe 3 o 3 reduced in the presence of cah 2 and hydrogen . weight of sodium tripolyphosphate treated γ fe 2 o 3 = 4 . 4 gm the above examples show that the hydrogen flow rate can be reduced by a factor of 8 and the reaction time reduced by employing calcium hydride . sodium tripolyphosphate treated γ fe 2 o 3 reduced in the presence of cah 2 and hydrogen . weight of sodium tripolyphosphate treated γ fe 2 o 3 = 250 gm as received γ fe 2 o 3 reduced in h 2 only . ratios of cah 2 / fe 2 o 3 from 0 . 65 to as much as 3 / 1 have been utilized and reduce the hydrogen consumption by 85 % to 90 %. further , the ideal ratio of cah 2 to γ fe 2 o 3 , which is 2 / 1 , allows for repeated use of cah 2 and has been successfully reused for up to three reductions . sodium tripolyphosphate treated γ fe 2 o 3 = 5 . 5 gm weight of sodium tripolyphosphate treated γ fe 2 o 3 = 5 . 3 gm same as example 5 using same cah 2 as in 6 ( third use ). the oxide was reduced to only 88 % of completion use . some operating condition as example 5 . complete reduction can be obtained using somewhat longer reduction times . the above examples show that the calcium hydride can be reused several times with little loss of efficiency . sodium tripolyphosphate treated γ fe 2 o 3 reduced in the presence of cah 2 and h 2 in a rotating kiln with counter - current flow of iron oxide and desiccant : kiln charge 5 kg cah 2 2 . 5 kg sodium tripolyphosphate γ fe 2 o 3 2 . 5 kg of γ ferric oxide was mixed with 3 . 15 kg of calcium hydride and 1 . 05 kg of calcium . the oxide was then reduced at 330 ° c . with hydrogen , flow rate 10 cfh , for 72 hours . the resulting product was cooled , stabilized and evaluated both as to the particles per se and magnetic tapes made from the particles . 2 . 5 kg of γ ferric oxide was mixed with 2 . 15 kg of calcium and 2 . 1 kg of calcium hydride . this material was reduced at 330 ° c . with hydrogen , flow rate 10 cfh , for 72 hours . the resulting product was cooled , stabilized and evaluated as in example 1 . 2 . 5 kg of γ ferric oxide was mixed with 3 . 15 kg of calcium and 1 . 05 kg of calcium hydride . the oxide was reduced at 330 ° c . using hydrogen gas , flow rate 10 cfh , for 51 hours . the resulting product was cooled , stabilized and evaluated as in example 1 . 2 . 5 kg of γ ferric oxide was mixed with 4 . 2 kg of calcium . this material was reduced at 330 ° c . with hydrogen , flow rate 10 cfh , for 73 hours . the resulting product was cooled , stabilized and evaluated as in example 1 . 2 . 5 kg of γ ferric oxide was mixed with 3 . 15 kg of calcium and 1 . 05 kg of calcium carbide . the oxide was reduced at 330 ° c . with hydrogen , flow rate 10 cfh , for 72 hours . the resulting product was cooled , stabilized and evaluated as in example 1 . the magnetic properties of the metallic iron particles made in accordance with the foregoing examples 9 - 13 were measured and also samples of the various iron particles were combined with a resin binder and used to make a magnetic tape . the properties of the tape were measured . the following results were obtained , both on the iron particles as made in accordance with the foregoing examples and also with practical magnetic tapes fabricated and utilizing these particles . ______________________________________magnetic resultsex - desiccant / * powder properties ** tapeam - reductant square - propertiesple ( weight σs ness hc square - no . ratio ) hc ( oe ) ( emu / g ) ( br / bs ) ( oe ) ness______________________________________ 9 cah . sub . 2 / ca 999 148 0 . 47 960 0 . 81 ( 3 / 1 ) 10 cah . sub . 2 / ca 966 138 0 . 45 917 0 . 80 ( 1 / 1 ) 11 cah . sub . 2 / ca 965 136 0 . 45 932 0 . 79 ( 1 / 3 ) 12 ca 1011 140 0 . 46 939 0 . 7913 ca / cac . sub . 2 999 148 0 . 47 960 0 . 81 ( 3 / 1 ) ______________________________________ * h . sub . app : 8koe d . c . ** h . sub . app : 5koe d . c .