234
ANALYTICAL EDITION
FIGURE3. BENZENE AND ACETIC ACID
FIGURE4. WATERAND FORMIC ACID
Vol. 4, No. 2
% WATER IN LIQUID
I n the previous paper (2) the constant-boiling mixture of benzene and acetic acid was not noted, since i t is higher in benzene than any of the points plotted. The portion of the curve near the azeotropic point, which is a t 98.5 per cent benzene, has been carefully plotted on an enlarged scale. Formic acid forms with water one of the comparatively few binary mixtures having a constant-boiling or azeotropic mixture of maximum boiling point. Bergstrom ( I ) has plotted the vapor composition curve for mixtures of the liquid higher in water content than the azeotropic mixture, and his curve falls just below that drawn in the upper loop,
FIGURE5. ACETICACIDAND ACETIC ANHYDRIDE
The acetic acid-acetic anhydride curve is typical of a normal binary mixture having no constant-boiling or azeotropic mixtures. LITERATURE CITED (1) Hausbrand, “Principles and Practice of Industrial Distillation,” Wiley, 1928. (2) Othmer, IND.ENQ.CHEM.,20, 743 (1928). (3) Othmer, Ibid., 22, 322 (1930). (4)Othmer, Ihid.,Anal. Ed., 1 , 9 7 (1929). RECEIVED September.8, 1931.
Potash Analyses Study of Methods for Eliminating Errors in Determination of Potash in Fertilizer Mixtures High in Phosphoric Acid C. M. BIBLE,Mellon Institute of Industrial Research, University of Pittsburgh, Pittsburgh, Pa.
I
N RECENT years it has been recognized by many
analysts that fertilizer mixtures high in phosphoric acid present difficulties in the determination of the potash content. Since 1925 reports have been published by Kerr (6),Bible ( I ) , Fraps (S), Haigh (4), and Lockhart (6). Workers on the problem attribute potash losses to the formation and attack of metaphosphates on silica, either the silica dishes used during evaporation and ignition, or soluble silica that may sometimes be present in amounts sufficient to cause trouble, even though evaporation and ignition may be carried out in platinum. The first four chemists mentioned have tried to solve the trouble by some method of removing the phosphoric acid before the ignition step, whereas Lockhart minimizes the metaphosphate attack by carefully controlling the ignition temperature. Removal of the phosphoric acid by any of the suggested methods prevents most of the attack on the silica dishes. I n 1926 the writer determined quantitatively the losses in the weight of silica dishes resulting by use of the official LindoGladding method and a modified method ( I ) in which the phosphoric acid was removed with magnesium oxide. Six new dishes were obtained for the tests from a leading manufacturer of silica ware. Three dishes were used by the official Lindo-Gladding method and three by the modified method on regular factory mixtures until each dish had been used seven times. The three dishes used in the official method lost in
weight 0.0339, 0.0427, and 0.0444 gram. The three used in the modified method lost in weight only 2.7 per cent as much. Much of the silica dissolved or loosened from the silica dish appears as an impurity in the potassium chloroplatinate, even if the dissolved residue is filtered prior to the addition of chloroplatinic acid. By dissolving the potassium chloroplatinate from the crucible with hot water, one can frequently find much insoluble impurity. I n some cases the silica is sufficient to make filtration very difficult. The modified methods providing for removal of the phosphoric acid, on the other hand, give precipitates of potassium chloroplatinate completely soluble in water. The ignited residue likewise dissolves in water much more readily. Removal of the phosphoric acid prior to ignition prevents losses of potash due to formation of insoluble potassium phosphosilicates or of potassium metaphosphate, which is soluble with difficulty. Results obtained by the modified methods usually do not fall far short of the theoretical potash content. The only objection to the use of any of the methods providing for the removal of the phosphate is that there appears to be a greater loss of potash due to occlusion, because of the additional precipitate that results, and there appears to be no practical way of recovering the occluded potash. Although the modifications contribute to refinement of the method, still the full potash values cannot be obtained.
April 15, 1932
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INDUSTRIAL AND ENGINEERING CHEMISTRY
The writer has attempted to prevent metaphosphate formation and attack in another way, without removing the pliosphates, by having present a t the time of ignition sufficient combined sodium and potassium to give the orthophosphate. I n practice, it requires only the addition of a little potash-free sodium hydroxide to the aliquot during evaporation. AB early as 1903, Carpenter (Z), acting as referee on fertilizers, suggested “the use of a little hydrochloric acid to liberate occluded potash and neutralization with sodium hydroxide instead of ammonium hydroxide to prevent occlusion of potash, which is usually found when using ammonia and ammonium oxalate.’’ He reported that the results were promising. However, no method involving the use of sodium hydroxide was adopted. It is unfortunate that the work was not continued, for neutralization with sodium hydroxide instead of with ammonia results in more nonvolatile bases to combine with the phosphate, and tends to keep the phosphate from going to the meta form. I n trying out the effectiveness of sodium hydroxide in preventing metaphosphate attack, the phosphatic compounds diammonium phosphate, treble superphosphate, and nitrophoska were used. The potash determinations were carried out only to the point where the ignited residue could be examined for form and amount of phosphorus, and the insolubility of the ignited residue in water acidified with a little hydrochloric acid. The official Lindo-Gladding method in silica dishes gave residues which left much white waterinsoluble material after long digestion with water acidified with hydrochloric acid. About one-third of the phosphorus was volatilized, both from platinum and silica dishes. When 2 cc. of normal sodium hydroxide were added to a solution of diammonium phosphate containing 0.1140 gram of phosphorus pentoxide, evaporated and ignited in silica, the solution was almost clear, and no phosphorus was volatilized. When the sodium hydroxide was increased to 4 cc., the solution was perfectly clear, and no phosphorus was volatilized. These tests show the benefit of sodium hydroxide additions in the presence of enough phosphorus to form much metaphosphate. A comparison of methods on a mixture of potassium chloride and superphosphate, with 0.0730 gram of phosphorus pentoxide in the aliquot used for analysis, gave: METHOD Official Lindo-Gladding Phosphorus removed with MgClz Phosphorus removed with MgO Normal NaOH, 3 ac., used Normal NaOH, 6 cc., used
Kz0 COR. FOR
IMPURITY
% 5.82 5.84 5.88 5.81 5.86
METHOD Official Phosphorua removed with MgO Normal NaOH, 6 cc., used
0.02 0.03
5.80 5.80 6.89
0.03 0.02
5.96 6.89 6.88
0.11 0.07 0.05
0.11
KzO COR. FOR
IMPURITY
% 5.40 5.27 5.40
IMPURITY
% 0.17
None None
Several other mixtures of ammoniated superphosphate with from 0,0370 to 0.0420 gram of phosphorus pentoxide in the aliquots taken were tested by the official method and also by adding 1 cc. of normal sodium hydroxide during evaporation. The residues by the official method would not burn white, would not dissolve completely, and silica retarded filtration. The use of sodium hydroxide gave white residues easily soluble in water, and the potassium chloroplatinate was free from silica. Analyses were also carried out on preparations with known potash content. A solution of pure potassium chloride was made, containing 0.25 gram to 50 ml. of solution. That amount was put into each of three 250-ml. volumetric flasks. Into two of the flasks was leached the water-soluble portion of , 2.25 grams treble superphosphate. To the third flask no phosphate was added. With the volume in each flask a p proximately 200 ml., ammonia and ammonium oxalate were added. To one of the flasks containing phosphate, about 1 gram of magnesium oxide powder was added. All three were then finished as in the Lindo-Gladding method. Two aliquots were taken from the flask containing phosphate but no magnesium oxide. One was used following strictly the official Lindo-Gladding method. To the other aliquot was added 0.09 gram of sodium hydroxide in solution, and the experiment was then finished in the same way. The only difference in the methods employed was the use of sodium hydroxide in the one. The potash contained in equivalent amounts of the treble superphosphate and in the reagents was determined and deducted from the final results. The potash recovery by the method using magnesium oxide was 99.03 per cent. The official Lindo-Gladding method gave 97.9 per cent recovery, whereas the combination of the Lindo-Cladding method with a little sodium hydroxide gave the best recovery, 99.36 per cent. LITERATURE CITED
%
PROPER FRACTIONATION WILL REDUCECOST OR MANCFACGASOLINE.The cost of manufacturing gasoline from high-sulfur crude oils may be reduced by proper fractionation , methods is indicated as the result of a study made by the United hates Bureau of MineB, Department of Commerce. The importance of proper fractionation in the manufacture of gasoline from crude petroleum is evidenced when gasoline is being made from crude oils containing relatively large proportions of sulfur. Such gasolines usually require considerable chemical treatment after distillation from the crude oil to meet trade re uirements as motor fuels. %he cost of the treatment necessary to prepare an acceptable motor fuel is generally the major difference between the cost of manufacturing gasolines from different crudes. The actual cost of distilling equal amounts of gasoline from different crudes TURINQ
A mixture of potassium chloride and superphosphate, ammoniated with aqua ammonia, with 0.0592 gram of phosphoric pentoxide in the aliquot used for analysis, gave:
IMPURITY
0.40 0.28 0.36
235
(1) Bible, J . Am. Oficial Agr. Chem., 8, 420 (1925). (2) Carpenter, Ibid., 7, 390 (1923-1924). (3) Fraps, Ibid., 9, 192 (1926). (4) Haigh, Ibid., 10, 220 (1927). (5) Kerr, Ibid., 8, 419 (1925). (6) Lockhart, IND.ENG.CHEM.,Anal. Ed., 3 407 (1931). RECEIVEDSeptember 12, 1931. Resubmitted December 24, 1931. Presented before the Division of Fertiliaer Chemistry at the 82nd Meeting of the American Chemioal Society, Buffalo, N. Y., August 31 to September
4, 1931.
varies little, for the amount of heat required to vaporize a gallon of gasoline of the same gravity from different. crudes is nearly constant. It must be recognized, however, that depreciation of the distillation equipment is greater with some crildes than others. An investigation has therefore been conducted by the Petroleum Experiment Station at Bartlesville, Okla., which is maintained by the Bureau of Mines and the State of Oklahoma, to determine the effect good fractionation would have on the manufacture of gasoline from crude oil rontaining sulfur, for, if highsulfur crudes caa be distilled so that the cost of preparing gasoline suitable for motor fuel will be reduced by eliminating some of the chemical treating costs, the commercial value of these crudes will be increased proportionally. Preliminary results of the investigation are regarded as quite encouraging.
