GB1229328A - - Google Patents

Abstract

1,229,328. Sampling using electric arc. APPLIED RESEARCH LABORATORIES Inc. 7 June, 1968 [9 June, 1967; 20 May, 1968], No. 27278/68. Heading B1X. [Also in Divisions C7 and H5] To obtain homogeneous samples, e.g. for chemical analysis, an aerosol 10 is produced by passing an electric arc between a counter electrode 14, 40, and an electrically conductive source material 12, 28, 44, with the net current flow being in the direction from the counter electrode to the source material a gas introduced through an inlet 20 in a surrounding enclosure 18, 24, 41, flowing through the arc to form an aerosol of the gas and droplets ejected from the source material, and the aerosol being withdrawn through an exhaust tube 14, 40 provided by the counter electrode. The source material is either a solid body 12 or may be molten material 28 in a cooled crucible 26, an induction coil 32 and the crucible providing heating and stirring of the source material 28. Tube 14 is of copper and is watercooled to prevent sputtering from it, and has an apertured cap 17 of refractory, corrosionresistant, insulating material which helps to restrict and stabilise the arc. A tangential motion may be imparted to the gas as it enters the aperture 19, the gas being argon, helium or nitrogen. For continuous or intermittent sampling of molten source material 44, a lance including an exhaust tube 40, insulating element 36 and a contact electrode 41 is lowered into the melt in an open berth furnace. The aerosol droplets emulsify and are analysed spectrometrically or otherwise. Powdered metals, e.g. iron powder, with particles of very small size (<1Á diameter) or of very uniform composition may be produced with the apparatus by suitable control of arcing current and gas flow rate.