| 摘要 |
PURPOSE:To produce Fe3O4 magnetic fine particles narrow in the distribution width of particle size by adding NaOH of the amount according to the change of color of an aq. soln. at one time in case of producing magnetic fine particles by adding an NaOH aq. soln. to the mixed aq. soln. of ferrous salt and ferric salt. CONSTITUTION:An aq. soln. of ferrous salt such as ferrous chloride and ferrous sulfate and the aq. soln. of ferric salt such as ferric chloride and ferric sulfate are mixed and an NaOh aq. soln. is added to this mixedliquid to produce Fe3O4 fine particles. In this case, when the pH value of this aq. soln. becomes to 1.8-2.0 and color of the liquid becomes brown, pH is once regulated to 6 and thereafter raised to 6.25 and furthermore raised to 7, and when color of the liquid becomes dark brown, the pH value is regulated to 9-12 and color of the liquid is made black. NaOH to be added in these respective stages is added at one time and thereby color of the aq. soln. is changed, and fine power of Fe3 is deposited, heated at 100 deg.C and aged. This is filtered, washed by water and dried to produce Fe3O4 magnetic fine particles narrow in the distribution width of particle size which are used for a magnetic fluid.
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