690
INDUSTRIAL AND ENGIiVEERING CHEMISTRY
compression is increased. This will cause an increase in the temperature of combustion, and hydrogen and carbon dioxide will disappear in equivalent quantities. The galvanometer deflection will then drop and will lie a t some point below the mean experimental relation shown in Figure 3. On the other hand, carbon dioxide and hydrogen will increase when the compression and combustion temperatures diminish, the air-fuel ratio being kept constant. From the foregoing considerations it can be seen that a simultaneous reading of the galvanometer and a determination of the percentage of carbon dioxide will suffice to give an indication not only of the air-fuel ratio, but, in a qualitative way the degree of compression and the maximum combustion temperature as well. I n order to make this clear a portion of the mean experimental relation in Figure 3 is reproduced in Figure 4. Lines
Vol. 17, No. 7
of equal concentration have been constructed in order to illustrate the method. A single reading of the galvanometer could mean almost anything within rather narrow limits, but determination of the carbon dioxide immediately places the reading where it belongs, and enables the air-fuel ratio to be determined. This method of exhaust gas analysis has proved useful in automotive research, particularly where the distribution of fuel to the various cylinders of a multicylinder engine is investigated. It is generally recognized that the most serious problem facing the automotive industry today is that of fuels, and it is hoped that the work outlined herein will prove a useful tool in the development of those refinements in the design of engines which must be made in order to cut down the enormous waste of gasoline taking place today.
An Explosion Method for Peroxide Fusions' By Walter F. Muehlberg NEWBURGH STEEL
T
WORKS, CLEVELAND, OHIO
HE fusion of ferrosilicons, chrome ore, and other difficultly fusible material with sodium peroxide in a nickel or iron crucible over a free flame is a thorough and efficient method of attack. It has, however, certain dis-
graphite and clay mixtures, clays, and many other substances which readily yield to this method of treatment. This explosion method has disadvantages, which, however, are not serious. From one and one-half to two times as much advantages. Large amounts of metal from the crucible are peroxide is used as when fusing over a free flame, and the solution of the melt is correintroduced into the melt spondingly greater in voland hinder subsequent deume. There is always an terminations. It is also This method of making sodium peroxide fusions has unfused residue, amounting, rather costly, for it is unsafe a wide range of application. Metal crucibles last inin finely ground ferrosilicon to use a nickel crucible for definitely. The fusion of a number of samples is pracand chrome ore, to from more than one thorough tically a simultaneous operation with a minimum 10 to 15 mg. When the fusion. The process of of effort. The cooled melt separates completely from amount of c o n s t i t u e n t leaching out the melt is more the crucible and its acidified solution is always clear. sought is small as in the case or less troublesome. There The expedient of computing the result from the of alumina in the Missabe are usually oxidized portions amount of sample actually fused is discussed and the iron ores, this residue may of the crucible in the acidiapplication of the method for ferrosilicon is outlined. be filtered off and disrefied solution of the melt, and garded. In most other inconsequently one is never stances it is sufficient to certain that the fusion has been complete. Fusion with alkali carbonates and niter weigh the ignited residue and subtract it from the weight in platinum is destructive to the platinum and, in the case of the sample used, making the necessary correction in the of much routine work of this nature, would be prohibi- final figure. Where the constituent sought is very considerative. Moreover, the acidified carbonate fusion of a ferro- ble, as in the case of silicon in ferrosilicon or chromic oxide silicon is never clear, even upon boiling, as the sodium sili- in chrome ore, it is advisable to re-fuse the residue in platicate formed during the fusion does not decompose readily, num with a small amount of alkali carbonate and add it to leaving one just as much in doubt about the complete solution the main solution. This takes only a few minutes and is only necessary as a precaution in case the unfused residue is of the sample as in the peroxide fusion mentioned above. To overcome some of the disadvantages of these two meth- quite large. ods, the writer has for the past ten years made use of a method If the unfused residue is considerable, any change undergone of fusion which is a modification of the well-known and widely during ignition, or any selective action which may have taken used sodium peroxide explosion method for sulfur in coal and place during the fusion would, of course, make computation of coke. The correct amount of sugar carbon is mixed with the the final figure from the portion actually fused impossible. sample and with the peroxide in a nickel crucible and ignited, If a ferrosilicon has been ground to pass through a linen handthe crucible being immersed in water during the ignition and kerchief and if a chrome ore is no coarser than 100 mesh, subsequent cooling. The method was a t first applied ex- the unfused residue should not weigh more than 10 to 15 mg., clusively to the determination of alumina in routine iron ore in which case the effect of such change or selective action apanalyses with a view toward speeding up the work. Since pears to be negligible, and re-fusion of the residue is unthen it has been used with success in the determination of necessary. sulfur in ores, fluxes, mill cinders, scales, and fluor spar, A ferrosilicon determination by this explosion method, in as well as getting into solution for the purpose of general which the residue was re-fused and added to the main portion, analysis such material as ferrosilicon, chrome ore, iron ores, indicated 54.30 per cent silicon. In a separate run, computing from the amount actually fused, the result was 54.35 per 1 Received March 30, 1925.
July, 1925
INDUSTRIAL A-VD ENGINEERING CHE;MISTRY
cent silicon, the residue in the latter case weighing 0.0135 gram. Still another ferrosilicon yielded 49.50 per cent silicon by re-fusing the residue and adding it to the main portion, as against 49.57 per cent by fusing in platinum with sodium carbonate. By this explosion method the average of two closely agreeing results on a chrome ore obtained by re-fusing the residue in porcelain with a small amount of sodium peroxide over a free flame and adding it to the main portion was 47.19 per cent chromic oxide, and upon computing the result from the amount actually fused the figure was 47.25 per cent. The weights of the residues were 0.0365 and 0.0225 gram, respectively. One-half gram samples were taken in all the cases cited above. I n the determination of chromic oxide by means of this explosion method the sulfuric acid solution of the melt is oxidized with ammonium persulfate in the presence of silver nitrate, as is customary, for the chromium is partially reduced by the peroxide in acid solution. The alumina results on Bureau of Standards Magnetite Ore, Sample 29, obtained by means of this explosion method, were in close agreement with the average figure given on the certificate of analysis. From these data it appears that this explosion method, if properly performed, is as accurate as fusing with peroxide over a free flame or with alkali carbonate in platinum. It is, moreover, very simple and can be quickly performed. A dozen samples, once they are in the cooling pan, can be ignited and fused in about 2 minutes by passing the ignitor to each crucible in succession. The melt shrinks from the crucible when cool, or at most requires only a slight tap against the table to loosen it entirely. There is practically no metal from the crucible in the melt, the crucibles appearing bright and burnished after years of use. It conserves platinum ware and saves nickel crucibles. There is no danger of the fusion going through the bottom of the crucible, as is often the case with peroxide fusions made over a free flame. The acidified solution of the melt is always crystal clear, even in the fusion of a ferrosilicon; the small amount of unfused residue settles quickly, permitting decantation before bringing the residue on the filter. The following method for ferrosilicon may be changed or amended to suit conditions encountered with other material. Method for Ferrosilicon
Transfer 0.5000 gram of the finely ground sample and 0.5 to 0.7 gram of sugar carbon (prepared by igniting granulated sugar in a covered porcelain crucible) to a nickel crucible. A convenient size of nickel crucible is one about 52 mm. high and 44 mm. in diameter, having a capacity of about 60 cc. (Although no accidental explosions have ever occurred in this laboratory, it is advisable to wear goggles whenever peroxide fusions are being made.) Counterpoise the crucible on the pan of a solution balance and transfer 15 grams of sodium peroxide to the crucible. Mix well by turning the crucible with the left hand against a spatula held a t an angle, and finally brush adhering particles of the charge into the crucible (Note 1). Tamp the charge firmly, using a glass stopper with a round, flat head; cover the crucible and insert it into one of the holes of the cooling pan previously filled almost to the under side of the cover with water (Note 2). Grip about 10 cm. (4 inches) of cotton string in the end of a crucible tongs, light the end of the string and insert it through the hole in the center of the crucible cover. This hole should be from 5 to 6 mm. in diameter. Ignition should take place promptly and easily. When cool, tap the crucible sharply against the table if the melt has not already loosened, and transfer the contents to a dry, covered, 600-cc beaker. Fill the crucible with water and empty the solution into the beaker which is then immediately covered. When the action has
691
moderated somewhat, wash any particles from the crucible and cover into the beaker with a jet of water and dilute the solution to about 300 cc. Add a distinct excess of concentrated hydrochloric acid while stirring vigorously, being careful to add the acid very slowly as the neutral point is neared, to prevent excessive foaming. If the work has been properly carried out, the sodium silicate will be completely decomposed and the silicic acid will be entirely in solution. When the unfused residue has settled, decant all but a few cubic centimeters of the solution into a large dish or beaker (Note 3) and transfer the residue to a small filter by the use of a jet of water. Use suction and wash successively with hot water, a hot, 10 per cent solution of sodium carbonate, hot, dilute hydrochloric acid (1: l), and finally, again with hot water. Combine the washings with the main solution and ignite and weigh the residue. If this residue does not weigh much over 15 mg. the final result may be computed from the amount of sample actually fused. If it weighs considerably more than 15 mg., re-fuse it in platinum with about 1 gram of sodium carbonate, and leach out the melt in the filtrate and washings of the first fusion, which should then be taken to dryness twice with intermediate filtration. The solution may be evaporated rapidly over a flame until the first indication of bumping, when it should be transferred to the steamplate. I n filtering, use suction and wash with 5 per cent (by volume) hydrochloric acid until the salts of iron have been removed, and then with hot water. Ignite in platinum and weigh. Add sufficient water to moisten the silica and treat with three drops of sulfuric acid (1:l) and a slight excess of hydrofluoric acid. Evaporate, ignite, and weigh. The loss in weight multiplied by 0.4672:is silicon. A blank run for silica should be made on each lot of sodium peroxide, taking it through all the steps outlined above. Notes 1-For infusible material such as chrome ore, or, ferrosilicon, 0.5-gram samples are taken. For more easily fusible material 1-gram samples may be used. I n either case, 0.7 gram of sugar carbon and 15 grams of sodium peroxide are used. Certain kinds of ferrosilicon will make a more satisfactory button with only 0.6 gram of carbon, and if a sample is known already to contain available carbon, such as graphite or coal ash, the amount of carbon to be added may be correspondingly decreased. Crucible, spatula, charge, etc., should be perfectly dry, as the peroxide absorbs any available moisture, which tends to slow down the action or t o inhibit it altogether. 2-A serviceable cooling pan is made of galvanized iron, about 23 X 17 X 6 cm. (9 X 6.5 X 2.5 inches) with a loose fitting, removable cover having holes cut into it so that the crucibles will fit snugly when resting on the bottom of the pan. This cover rests on lugs riveted to the inside of the pan and is such a distance from the bottom of the pan that the crucibles, resting on the bottom, protrude through the hole about 1 cm. (0.5 inch). This size pan will accommodate six crucibles of the slze described above. 3-In this laboratory a 600-cc. beaker is used. If a dish is Dreferred, it will be found that if this dish rests on the periphery of k section of wrought iron pipe, the inside diameter of which is about 2.5 cm. (1inch) less than that of the dish, and the depth of which is such that the bottom of the dish comes to within about 6 mm. ( l / d inch) from the top of the hot plate, the solution will go to dryness without bumping and without much creeping of salts even if the temperature of the hot plate is considerably ,above 100' C. These advantages are still more noticeable if a disk of asbestos from 3 to 6 mm. ( l / 8 to l / d inch) thick is placed under the bottom of the dish. Guggenheim Foundation Award in Chemistry-Chemistry has received a share in the fellowship appointments recently made under the John Simon Guggenheim LMemorial Foundation in the award to Dr. Gerhard Krohn Rollefson, of the University of California, for work on the application of methods of physics to the study of chemical phenonema, principally with Professor Franck, of the University of Gottingen.
