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INDUSTRIAL AND ENGINEERING CHEMISTRY
tory, which would never logically be sold, even on paper, in New York, and which are produced in sufficient quantities to be quite independent of any price made in New York. Such a plan also fails to consider the necessity for spot stocks that must be carried to serve local consuming needs. An exchange in New York obviously could not deal in the bulk of the country's chemicals, and so could not control prices at distant points. To supply the New York market through an exchange and the rest of the United States by salesmen or through dealers is confusion worse confounded. It would complicate-not stabilize-chemical sales. Adjusting Supply to Demand
No manufactured goods have ever been successfully sold on exchanges because they do not meet the fifth requirement-namely, that supply must not be varied quickly by increased or decreased production. The stocks or bonds
Vol. 20, No. 12
corporations or a year's crop of wheat, cotton, or rubber do give a fixed maximum quantity for trading that cannot be quickly changed. Securities are retired, capitalization is increased, larger or smaller crops may be harvested from season t o season, but these changes are infrequent and their effect on supply is not quickly felt. The speculation, which discouraged Scottish iron producers from supporting the Glasgow and Tees Stores and finally led t o their abandonment, shows that even in iron, where i t is not easy t o vary production as a furnace once blown out is very expensive to restart, this factor is against the exchange. I n fact, since 1888, when the Berlin Bourse gave up its effort, begun in 1886, to trade in manufactured wares, no established exchange has ventured to extend its operations in this direction. Chemicals are manufactured goods, and, while i t is costly to vary the production, nevertheless none are so staple in this respect as iron, and most are very much less so.
Economical Recovery of Valuable Products from "Spent" Doctor and Caustic Solutions' F. J. Mechlin LOUISIANA OILREFINIXGCORPORATION, SHREVEPORT, LA.
ITHARGE and caustic soda are among the most expensive common reagents used in the refining of motor fuels. This paper describes briefly some experiments designed to reclaim valuable constituents of the spent caustic liquors. Reference to this type of investigation has been made by hlorrell and Faragher,2 although the work herein described was done independently.
L
Raw Materials
The raw material, "spent doctor,'' was found to contain caustic soda, sodium sulfate, tarry materials of the type ROH, and lead as plumbite ion, while suspended throughout the solution and floating on it were lead sulfide and organic lead compounds. The spent caustic liquor contained caustic soda, sodium sulfate, and dissolved tarry material. The original materials processed showed: doctor, 23" BB.; caustic, 8" BB. Obviously, the nature of the raw material charged will vary with the nature of the oil treated as well as the treating process itself. The spent liquors used in these experiments had been used in a continuous treating system operating on a pressure distillate derived mainly from Smackover and Urania crudes. Procedure
It was recalled that lead sulfide quite readily oxidizes to the sulfate, and that a concentrated caustic soda solution is a better solvent for litharge than a more dilute solution. Evaporation and oxidation by heating and air-blowing were thus suggested. Laboratory-scale experiments showed that lead sulfide was gradually oxidized and, as the concentration of the sodium hydroxide increased, the lead again entered solution as plumbite ion. The colloidal organic material gradually agglomerated and, on settling, floated on top of the specifically heavier caustic-plumbite layer. The sodium sulfate formed a disPresented before the Division of Petroleum Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. Received June 22, 1928. 9 IND.END.CHBM., 19, 1046 (1927).
tinct layer of crystals when the concentrated mixture was allowed to settle. It was found necessary to continue evaporation of the caustic and doctor solutions to a gravity of 42" to 45" BB. before a satisfactory separation could be secured. To accomplish this a submerged steam coil carrying 8 pounds exhaust steam was used for preliminary heating; low-pressure air heated by waste steam was delivered near the bottom of the vessel and allowed to bubble through the liquid layer. This arrangement is satisfactory for preliminary evaporation but a temperature of 270" F. (132" C.) is necessary in the liquid layer before the concentration is sufficient for the dissimilar materials to separate satisfactorily by settling. It was found that a layer of soapy material containing small amounts of caustic soda, sodium carbonate, and lead residues could be skimmed from the settled mixture when the concentration reached 35" BB. If the concentration continues without removal of the soap, the soap is converted to a tar. Iron equipment was found to be satisfactory for the operation. Experimental Results of Processing S p e n t Doctor a n d Caustic SoIutions-Batch Operation Run 1 2 3 hraterial charged Caustic Caustic Doctor 164 160 2 Ma&iai charied, liters Per cent of charge reclaimed 7.9 11.25 24.5 Heating surface, square meter 0.13 0 &13 270° F. 270 2ibh Maximum temperatureused, OF. (132.2' C.) (132.2O C.) (138' C.) BEFORE PROCESSING Specific gravity 1.059 1.06 1.19 (go Be.) (8" Be.) (23' Be.) 3.81 3.84 12.5 NaOH, per cent Sulfate, calcd. as NazSOa, per cent 0.52 0.52 0.3 .... 0.75 Lead, PbO ~~
....
AFTER PROCESSING
Specific gravity NaOH per cent Sulfate', calcd. as NazS01, per cent Lead, PbO, per cent NaOH recovered, per cent PbO recovered, per cent
1.414 (40° Be.) 33.2 0.426
....
94.7
....
1,383 (39.5O BC.) 23.0 0.236
. .. .
87.8
....
1.47 (46'Be.) 36.1 0.35 2.1 87.3 84.7
Yields
1
Laboratory and semi-plant yields of caustic based on the analyses of the liquid charged show a recovery of 80 to 90 per
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1928
cent. Lead recoveries of 84 per cent have been secured. The results obtained experimentally are s h o r n in the accomDanying - - - table. Properties of Soapy Layer
The soapy layer contains sodium carbonate, caustic soda, and organic compounds of the type RONa. The gravities
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of the samples obtained varied from 35" to 38" Be. The material is miscible with water in all proportions and somewhat soluble in commercial gasolines. Other properties of the soapy material are being investigated. Considerable amounts of caustic were converted to carbonates and varying amounts were lost in the tar layer as well as in the mass of crystals.
Ignition of Mixtures of Air with Natural Gas and w i t h Methane by Induction Coil Sparks' E. G. Meiter PITTSBUROH
EXPERIMENT STATION,
u. s. BUREAUOF
A
KNOWLEDGE of the relative inflammabilities of various mixtures of air with Pittsburgh natural gas and with methane is important, because the United States Bureau of Nines uses natural gas rather than methane for producing explosive atmospheres for its investigations of the safety of mining equipment and of explosives, and for explosion tests in its experimental mine. Natural gas is preferred because i t is available in large quantities and methane is not. Purpose of Investigation
Owing to the high methane content of the natural gas used in the Pittsburgh district it has been customary to assume that its flame properties are similar to those of methane. It is known2 that the ignition temperature of natural gas, as determined in a quartz tube, is somewhat lower than that of methane. This evidence is not, however, conclusive as regards the propriety of the use of natural gas in testing the safety of mine electrical equipment. The purpose of the tests described in this paper was therefore t o determine this relation under constant experimental conditions when an electric spark is the igniting agent. A careful comparison of the ignitibility of natural gas and methane under the same experimental conditions was therefore made.
Received July 16, 1928. Published by permission of the Director, (Not subject to copyright.) * Coward, Jones, Dunkle, and Hess, Carncgie Inst. Tech., Bnll. SO (1926). * J. Chcm. SOC.109, 523 (1916). 1 Ibid., 117,903 (1920). 8 U.S. Bur. Mines, Bull. 16, 63 (1912). 1
U.S. Bureau of Mines.
PA.
used, and therefore, in the present research, the same apparatus was used throughout for determining the relative igniting currents for mixtures of air with methane and with natural gas. Storage and Analysis of Gases
All gases and mixtures of gases were prepared and stored in glass gas-holders over mixtures of glycerol and water. The analyses of all hydrocarbon-air mixtures were made over mercury in a Bone and Wheeler6 apparatus having an accuracy of about 0.02 per cent. Composition of Gases Used
~ T E T H S S E - T ~methane ~ was obtained from a me11 whose gas contained less than 2 per cent impurity. It was purified by liquefaction and fractional distillation. The product contained no other hydrocarbons according to combustion analyses on the Bone and Wheeler apparatus. N-~TURAL GAS-A large sample of the natural gas used a t the Pittsburgh Experiment Station was drawn from the gas mains and stored over glycerol and water. An analysis of this gas by W. P. Yant and F. E. Frey, of the Bureau of hiines, gave the following: CH,, 88.9; C2He,7.4; CaHs, 2.4; C&, 0.8; higher hydrocarbons, 0.1; and nitrogen, 0.4 per cent.
Previous Investigations
Sastry3 and Wheeler4 have determined the relative ignitibility of a series of methane-air mixtures by measuring the current that had t o be broken in the primary circuit of an induction coil to give a t the spark gap in the ignition vessel a secondary discharge just capable of igniting the mixture. Wheeler found that the most easily ignitible mixtures of methane and air are those which contain about 8.3 per cent methane. Burrel16 a t Pittsburgh found by other methods that the most sensitive mixture of natural gas and air contained between 8.5 and 9 per cent gas. A direct comparison between the ignitibility of methane and natural gas cannot be drawn from these experiments. The igniting currents as determined by the method of Sastry and Wheeler are not absolute measures of the energy required to cause ignition. They depend upon the apparatus
MINES,PITTSBURGH,
Experimental
The apparatus 'and method of experimentation were similar to those described by Sastry3 and Wheeler.4 The measure of the ignitibility of n given mixture was the amount of electric current that had to be broken in the primary circuit of the induction coil to give a t the spark gap in the ignition vessel a secondary discharge just capable of igniting the mixture. APPARATUS-The apparatus used was the same as that previously described by Coward and Meiter.' (Figure 1) The ignition vessel was made of glass, with electrodes of bluntly pointed platinum wire. The one electrode was mounted on a micrometer head, graduated to 0.01 mm., so that the width of the spark gap could be accurately adjusted. The second electrode was fixed in position. For the present experiments a spark gap of 1 mm. was used. The volume of the ignition vessel was about 38 cc. A 15-em. (6-inch) induction coil was used with a motor-driven mechanical break in the primary circuit, similar to that described by Wheeler.8 0
7 8
Grice and Payman, Fuel Science Practice, 3, 236 (1924). J . Am. Chem. SOC.,49,396 (1927). J. Chem. SOC.111, 132 (1917).
