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BROWN ET AL.--ELECTROSTATIC PRECIPITATOR 201 center electrode was negative. This cannot be done by simply reversing the high voltage leads if one side is to be grounded. However, it can be accomplished by reversing the plate and filament connections to the high voltage rectifier so that the current passes through the circuit in the opposite direction, thereby reversing polarity. Further details concerning this change, as well as detailed information on the construction of the power supply can be obtained from us. All the necessary parts, except perhaps the coil, are readily available through local radio supply houses. The cost of the parts was approximately $35. The complete power supply can be assembled in the average laboratory in about two days and at a cost considerably less than the PS-10 or newer types of television high voltage power packs. Table 1.--Comparison of Material Collected by Electrostatic Precipitator Test 1 2 3 4 5 6 7 8 9 Totals.. 10 11 12 13 14 Totals.. 15 16 17 IS 19 20 21 22 23 24 25 26 27 1 28 Totals.. Material Used * Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Zinc oxide Zinc oxide Zinc oxide Zinc oxide Zinc oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Lead oxide Weight of Fume Collected, ..Mg., with Indicated Instrument and Polarity of Center Electrode Sampling Volume ,------------------------------------------------------- Operating Rate, Sampling of Air Old New Voltage, Cu. Pt. Time, Sampled, PHS-50 PS-10 M. S. A. M. S. A. Kv. per Min. Min. Cu. Ft. Pos. Neg. Neg. Neg. 13.5 3 14 42 21.5 22.6 12.0 u 13 39 500.2 456.5 12.0 3 30 90 101.1 103 .S , ,,, 12.2 3 25 75 3.1 3.4 12.4 O 37 111 10.4 8.3 12.4 3 15 45 62.9 50.7 11.4 3 40 120 21.2 19.2 12,2 3 30 90 32.2 28.9 11.5 3 30 90 12.2 , 12.2 11.8 3' 13.5 3 13.3 3 13.2 q 13.4 q 234 702 30 . 90 25 75 35 105 '35 105 35 105 764.8 ' 16.0 8.1 4.8 9.3 22.6 705.6 11.8 8.2 5.8 7.8 18.8 160 480 60.8 13.5 2.56 60 153.6 30.2 13.5 2.56 35 ~ 89.6 64.4 13.5 2.56 45 115.2 67.3 13.5 2.56 30 76.8 . ,11.7 13.5 2.56 35 89.6 30.7 13.6 2.56 50 128.0 .64.4 13.6 2.56 46 117.8 53.3 12.5 2.56 30 76.8 25.9 12.5 2.56 35 89.6 43.0 12.5 2.56 15 38.4 26.4 12.5 2.56 15 38.4 19.4 12.5 2.56 35 89.6 15.4 13.0 2.56' 30 76.8 31.2 13.0 2.56 10 25.6 .28.3 73 471 1,205.8 511.6 52.4 34.5 59.2 67.4 12.1 32.8 63.2 55.4 26.4 44.3 30.1 20.5 15.5 30.6 29.1 521.1 31.6 66-5 67.0 12.0 33.1 54.8 48.6 25.3 44.8 28.5 20.9 14.0 30.0 31.5 496.6 , 31.0 58.6 64.8 12.4 32.3 60.1 52.5 27.3 46.5 29.8 19.6 15.2 30.3 27.7 508.1 * Freshly formed lead and zinc oxides were prepared by means of a carbon arc inside the fume chamber. NEW POWER SUPPLY COMPARED WITH OTHER INSTRUMENTS The efficiency of'the PHS-50 power supply for the collection of lead and zinc oxide fume was compared with that of three Other instruments. These were (1) the PS-10 modification, (2) . the old M. S. A. and (3). the new M. S'. A. electrostatic, dust and fume sampler. These tests were conducted using a fume chamber which was approximately a 6 ft. (1.8 M.) cube. The four instruments were set up as shown in figure. 4 and were, operated simultaneously for the periods indicated. To minimize the effects of variation in the distribution of material inside the chamher, the positions of the precipitators were changed after each test. The air flow and the voltage were adjusted to the same value for each instrument before every test and checked at the conclusion of the test. The results of these tests are shown in table 1.