A Double-Tube Combustion Furnace CHARLES B. DEWITT,~ University of Tennessee, Memphis, Tenn. 3HE furnace here described was designed to shorten the time required for combustion analysis of organic compounds. It carries two tubes but permits the temperature of either to be regulated a t will without affecting the other. This is accomplished by use of wide-topped burners mounted on a frame movable in any horizontal position, together with a flame spreader and a partition between the tube compartments. I n addition to this principal feature, the furnace is lighter than the usual gas models, has no breakable clay tiles, and radiates less heat into the room with consequent economy of gas and increased comfort to the operator. The end of this furnace is shown in Figure 1. Rivets are indicated by solid dots, and bolt holes by circles. The uprights A and the crosspieces B and D are made from 3.2 by 25.4 mm. (0.125 by 1 inch) iron bar, C of 3.2 by 50.8 mm. (0.125 by 2 inch), and E of 3.2 by 12.2 mm. (0.125 by 0.5 inch) stock. Pieces of transite board which line the heating chamber are shown by broken lines. Two of these are slotted to form sliding gates to permit easy removal of the combustion tubes. The ends are held together at I I by 12.2-mm. (0.5inch) rods provided with nuts on each side of the upright. As in the Bunsen furnace, the upper rods support the tiles in the open position. The burner unit rests on B but is not fastened, and may be moved as desired. The modified V grooves, F,G, and H , carry angle irons which in the order named spread the flame, serve as troughs for the tubes, and support the sides and cower tiles. The end of each angle iron is cut away so it 1 Present
address, Iowa State College, Ames, Iowa.
will rest in the flattened notch with a shoulder indicated by the dotted lines a t F which bears against the crosspiece and prevents the angle slipping out of position.
OF BURNER ASSEMBLY FIGURE2. CONSTRUCTION
A, base; B, holder
Figure 2 shows the construction of the burner assembly. Twelve Fisher burners with bases tapped for screwing into pipelines are used. The pipe and fittings required are: No. 2 2
2
2 2 2 1 1 1 12
DIMENSIONS 19.2 X 838 mm. (0.75 X 33 inch) extra heavy gas pipe 19.2-mm. (0.76-inch) ells 19.2 X 50.8 mm. (0.75 X 2 inch). niuoles iG.2-mm. close nipples 19.2-mm. unions 19.2-mm. tees 19.2-mm. plug 19.2- t o 9.6-mm. (0.75- t o 0.376-inch) bushing 9.6-mm. (0.375-inch) hose connection to attach 8-mm. rubber tubing 3.2-mm. (0.125-inch) close nipples (brass)
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The construction of this unit is the most exacting operation in building the furnace, for the holes in the pipe must be in exact alignment so that the burner tops will be in a straight line. This was accomplished by use of a holder about a meter long made of three pieces of hardwood, as shown in Figure 2-B. The pipe is driven into this holder, and a straight line is marked on it by using the face of the holder as a guide for the scriber. The pipe is then turned so that the line is on top, and the positions of the holes are deeply punch-marked 11.43 cm. (4.5 inches) apart. A straight board is clamped to the drill table so that when the pipe holder is moved along against it
VIEW OF TILE FIGURE3. SECTIONAL
FIGURE1. DIAGRAM OF ENDOF FURNACE
the point of the drill is directly over the line. Small holes, 3.2 mm., are first drilled to serve as guides for the larger bit, 8.1 mm., which is the proper size for the tap. The holes are threaded by placing the tap in the drill chuck and turning it by hand. The pipe must not be moved in the holder a t any time during the drilling and threading operations. The burners, which are not shown in the figure, must be taken apart for connection. Metal-clad asbestos board is used for the top and sides instead of the usual clay tiles. A sectional view of one of these “tiles” is shown in Figure 3. The inner layer is of 6.4-mm. transite, the middle one of 6.4-mm. soft asbestos board, and the backing of 26-gage black sheet iron. This is superior to clay in insulating qualities and is practically unbreakable. A small eye bolt inserted through a hole near the top of each tile affords a convenient means for lifting it either with a wire hook or with tongs. 225
226
ANALYTICAL EDITION
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An end view of the top and the partition is shown in Figure 4. The top is made in the same manner as the tiles. It rests on 3.2 by 12.7 mm. bars set in the notches J J (Figure l ) , and is held above these bars by transite blocks which thus provide a vent for hot gases from the burners. The partition is made of a single sheet of transite bound on the edges and held to the top by sheet-iron straps and stove bolts through the support blocks. The top and partition should be made in two sections, each half the length of the furnace, and all bolt holes should be appreciably larger than the bolts used to prevent warping and cracking of the asbestos. The iron bars which support the top extend about 40 cm. beyond the end of
FIGURE5. SECTIONAL VIEW
FIGURE 4. END VIEW OF TOP AND PARTITION
the furnace, so that absorption bulbs may be hung from them. The lower edge of the partition rests in the angle-iron flame spreader which is protected by transite strips held in place by metal straps. A sectional view of the sides and bottom is given in Figure 5. The center piece A is drilled with 28.6-mm. holes, which fit the tops of the burners. A few of the burners are almost certain to be sufficiently out of line to hold it in place by friction. It is not fastened to the other part of the casing, but is movable with
OF
SIDESA N D BOTTOM
the burner rack. A transverse partition of transite on each side of the region near the boats aids regulation of temperature in this section. An extra tile of small size that fits between these partitions and rests against the flame spreader and the bottom of the furnace permits cutting the heat entirely off from under one boat while the rest of the tube and the entire length of the other are kept a t maximum temperature. The burners may also be shifted so that they are entirely under one tube, or so that the flame is under only one tube a t one end but divided between both a t the other. The furnace has proved entirely satisfactory on a series of test runs. The only defect noted was a tendency of the iron troughs and flame spreader to sag. This could evidently be corrected by making these parts of nickel. RECEIVED July 17, 1931
Determination of Mercury in Oil Preparations of Organo-Mercurials E. E. MOOREAND E. F. SHELBERG, Abbott Laboratories, North Chicago, Ill.
ITu’
THE determination of mercury in medicinal preparations of organo-mercurials in oil, it is impracticable to attempt to destroy the organic matter (1) because of the relatively large sample which must be taken in order to have sufficient mercury for an accurate assay. The following method is based on the ability of strong mineral acids to decompose many organo-mercurials to compounds which, when treated with hydrogen sulfide, give mercury sulfide (2). The procedure was evolved for the assay of a preparation containing 0.040 per cent 4-nitroanhydrohydroxymercuri-ocresol in mineral oil. It is presented in the hope that it may aid those who have similar preparations to assay. The method cannot be applied to those compounds whose mercury is not completely split off by concentrated hydrochloric acid. A 100-gram sample is diluted with 100 cc. of petroleum ether, and 50 cc. of concentrated hydrochloric acid are added. The flask is placed in a shaking machine where it is shaken vigorously for 2 hours, or the contents may be stirred for the same length of time with a mechanical stirrer. The contents of the flask are transferred to a separatory funnel. The flask is rinsed with three 10-cc. portions of water and the rinsings added to the contents of the funnel. The acid layer is
drawn off through wet filter paper into the precipitation flask, the wet paper retaining any oil. The funnel and filter paper are washed with three 10-cc. portions of water and the washings are added to the contents of the precipitation flask. The solution is neutralized with gaseous ammonia, rendered acid with hydrochloric acid, and the mercury precipitated as mercury sulfide. The precipitate is transferred to a weighed Gooch crucible and washed with water, alcohol, carbon disulfide, and ether. It is dried at 100’ C., cooled, and weighed as mercury sulfide. Two 100-gram samples containing 0.04 gram each of 4-nitroanhydrohydroxymercuri-o-cresolanalyzed by this method gave results from 1 to 3 per cent high. Dyes do not interfere with the assay, which gives satisfactory results with solutions containing as little as. 0.02 pkr cent mercury.
LITERATURE CITED (1) Scott, “ S t a n d a r d Methods of Chemical Analysis,” p. 312B, Van Nostrand. 1927. (2) Whitemore, “Organic Compounds of Mercury,” pp. 41, 50, Chemical Catalog, 1921. RECEIVED December 7, 1931.
