Show Pre preparation i on of fuller s earth COMPILED compilli BY W C the bleaching action of fullers earth is independent of its chemical composition but depends entirely upon its selective power of absorption or capillary action therefore the slight variations in the analysis of the earth bear no relation to its bleaching powers As is well known the main use of fullers earth is for the bleaching of oils and the gravity method is used in preference to agitation the main object sought is to get the lightest t possible color with the most prolonged use of the earth the renewal of which is accomplished by burning in a recent article by C R siegfried national petroleum news august 20 1919 p 38 it is pointed out that the blame for poor filtering is often placed on the earth whereas it is due to improper manipulation it is important to bear the following in mind 1 the longer the column of earth the better the bleach and the li lighter 6 liter the color of the oil other conditions being equal 2 the coarser the earth the more rapid the flow and the poorer the bleach other conditions being equal 3 the higher the temperature the faster the flow and the poorer the bleach other conditions being equal 4 As a corollary filtration should take place at the lowest temperature at which the oil works well 5 the oil which is bein being t filtered must be fluid enough to be acted on mechanically by the internal structure or pores of the earth for it is in these pores that the coloring ingredients of the oil are retained and not lot in the spaces between the grains themselves each particle of the earth there fore re has its own work to do independent of the others the preparation of the earth prior to its going to the filtration plant is of great im Pera ture of 1050 1050 to 1100 deg P in suase firing a burner for fullers earth is the party who breaks or makes the life of the earth in the filter the preparation is done by burning and the first burning is the most important por tant of all all fullers earth is hygroscopic that is it absorbs moisture from the air during the e first burning it is essential to get rid of 01 this absorbed moisture and also the cheral chemically cally combined water the quantity of t water varies from 10 to to 15 per cent and this ws must be expelled before the earth goes to the filter organic and volatile salts are also 0 expelled during the first burning and cale jun lime carbonate is converted to caustic it has been best bes found by experiment pediment Peri ment that the deg dee temperature for r the initial burn is jio to deg P at this temperature all ratton otis of monthly ly reports on minerals invests the the interior insert bureau of mines department of ger of fusion or incipient fusion whereby the particles are glazed the pores closed moisture is expelled and there is no dan and the absorptive power lost the second burning is almost as important as the first as there is a greater tendency for the grains to fuse and stick together than in any subsequent burnings it is therefore run more slowly than the first or subsequent burnings and at a temperature pera ture of 1050 to 1100 deg F in subsequent burns with florida earth the proper temperature has been found to vary from 1100 to 1200 deg F any temperature above 1200 deg caused a loss of filtering power it was found on the fourth burning of two samples of earth from the same filter that or of two samples the one burned at 1100 deg F and the other at 1400 deg F the of deg F caused a loss of filtering nf power of 30 per cent |