Abstract: The automatic determination of the total rare earths in the aluminium-rare earth alloys was studied by using our recently designed automated flow injection device and the high sensitive and selective rare earth reagent-DBC-CPA (2 -(2-phosphono-4-chlorophen-ylazo)-7-(2,,6-dibromo-4-chlorophenylazo)-1,8-dihydroxy-3, 6 - dis-ulfonaphthalene). The automated flow injection device consists of an Apple Ⅱ microcomputer, two peristaltic pumps and a spectrophoto-meter. It has good automatic degree and high producibility, the sampling volume and rotation velocity of the pumps can be changed continuously and automatically. The total rare earths in aluminium-rare earth alloys were automatically determined at 645nm wavelength in the medium of 1.Omol/L HC1 and 1% H₂C₂O₄ . Fe Cu, Al, Mg, Ni, Zn and Cr don't interfere with the determination and temperature has no effect on the sensitivity in the range of 10～49℃ above zero. The calibration curves for cerium group and yttrium group rare earths are close to each other. The relative standard deviation of repetitive detection of 7 times for various types of aluminium-rare earth alloys is in 1% or so with a sampling frequency of 200 samples per hour. The results correspond to that of the manual spectrophotometric method well. This simple, rapid and exact method is best suited to the analysis in batches of the total rare earths in all aluminium-rare earth alloys.

Key words: Flow injection analysis, automatic determination DBC-chlorophenylazo, Aluminium alloy, Rare earths, Microcomputer.