INDUSTRIAL AND ENGINEERING CHEMISTRY
September, 1924
from typical crude oils from Pennsylvania, Wyoming, Oklahoma, California, and Texas. 2-The Pennsylvania fractions show the least rapid change in viscosity for a given change in temperature; the California, Oklahoma, and Wyoming oils are intermediate in this respect; while the fractions from the Texas crude show the greatest change of viscosity for a given temperature increment. The temperature viscosity curves for the Oklahoma and Wyoming oils exhibit characteristics intermediate between those of the Pennsylvania and California fractions, but they resemble the former most closely. &-The most impressive viscosity differences appear in the higher fractions; the curves representing the characteristics of the lighter oils are quite similar. &The data of Table I1 show that the viscosity-temperature rela tionship of the undistilled residuum from the Pennsylvania crude is of the same general type as the curves for the distilled fractions. The change of viscosity with temperature
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entirely feasible to plot @ as a function of the gravity at 15.6" C. (60' F.). Hence, for lubricating fractions distilled from ft given crude, a single determination of viscosity a t a suitable temperature, together with the gravity at 15.8" C. (60" F.),is sufficient to define the viscosity-temperature relationship over a wide temperature range. 9-The possibility of extending the method described in Conclusion 8 to the determination of the viscosity-temperature relationship for lubricants produced from different crudes is discussed. It is pointed out that if the viscosity at 40" C. (104OF.) and the gravity at 15.6" C. (60OF.) are known for any of the lubricating distillates derived from any of the five typical crude oils by the Bureau of Mines analytical method, the change of viscosity from 20" to 100" C. (68" to 212" F.) can be predicted with considerable accuracy. Preliminary trials seem to indicate that this method cannot be used with entire success on commercial lubricants.
Combustion of Petroleum Hydrocarbons' By C. F. Mabery CASESCHOOL OF APPLIEDSCIENCE, CLEVELAND, OHIO
ECAUSE of frequent inquiries for information concerning the details of hydrocarbon analysis, probably due to the increasing interest in the composition of petroleum, which must include analysis of its constituents, JEUFfC GRAWTY AT 60.K and having made some essential improvements that greatly FIG.6 - - R E L A T I O N S H I P B E T W E E N T H E V A L U E OF 6 AND THE S P E C I F I C facilitate the large amount of work now on hand, it seems GRAVITY AT 60' 5 '. FOR BOTHT H E HEAVIER AND LIGHTER DISTILLATES worth while to present the method as it is now in use. I n FROM THE TYPICAL CALIFORNIA CRUDEOIL two papers presented many years ago2 were set forth the for a mixture of the Pennsylvania residuum and Pennsyl- errors in the analysis of organic compounds in general. It vania distillate may be represented by a curve which is simi- has recently appeared, however, that elimination of other lar to those for the unblended Pennsylvania distillates. sources of error, and a great reduction in the time required Furthermore, the temperature-viscosity characteristics for a are made possible by certain changes in manipulation. mixture of Pennsylvania residuum and California distillate The details requiring particular attention in this analysis represents an average between the characteristics of the in- are as follows: dividual components. These points were fully discussed and 1-Instant and complete control of the initial rate of comillustrated in the previous paper. 5-With certain exceptions already indicated, the tempera- bustion. 2-An excess of hot oxygen in front of the oil. ture-viscosity curves for the kerosene fractions from the 3-Duplicate absorption bulbs filled with oxygen, and kept various crude oils studied show the same qualitative relation- overnight or longer in large desiccators also filled with oxygen. 4-A second safety tube filled with soda lime and phosphorus ships as those for the lubricating fractions. in front of the 50 per cent potassium hydroxide bulb. 6-Viscosity-temperature data can be represented by equa- pentoxide 5-Copper oxide heated t o the full extent of a gas-heated tions of the general form: furnace, a temperature that only the most infusible Bohemian
"= K
I
+ At + Bt2
+
V' = c ( t P)" The constants K , A , and B were discussed in the previous paper. 7-The logarithmic form of the second equation is log VI, = log c 1z log (t P) When @ is suitably chosen for each oil, the relationship between log VI,and log (t @)for all fractions, including gasoline, kerosene, gas oil, and lubricants, may be represented by a series of straight lines. In the case of the lubricating fractions derived from any one of the typical crude oils, these straight lines converge practically to a single point. The location of the common point varies somewhat with the crude. 8-It follows from Conclusion 7 that, for lubricating oils derived from a known crude by the Bureau of Mines analytical method, the relation between temperature and viscosity may be determined when the viscosity et one suitable temperature and the value of @ are available. It appears to be
or by
+
+
+
glass or its equivalent can withstand. 6-The combustion train relieved from pressure or suction. Every one is familiar with the difficulty of obtaining tight joints with cork connections.
The apparatus shown in the figure, simple in construction and durable in operation, eliminates these sources of error. I n hundreds of analyses the oxygen purifying train has been in use without change for more than two years. The oxygen supply is better regulated from an independent reservoir under slight water pressure than directly from a tank. It passes from a 6-liter bottle, regulated by an overflow, through two bottles containing a 50 per cent solution of potassium hydroxide on either side of which is a mercury safety seal, and then through a Iarge U tube containing sulfuric acid. Two small U tubes containing sulfuric acid follow, one of which delivers oxygen just within the cork of the combustion tube, and the other in front of the boat Received July 7, 1924. Mabery, J . A m . Chcm. Soc., 21, 510 (1899); Mabery and Clymer, Zbid., Pa, 213 (1900). 1
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I N D U S T R I A L A N D ENGINEERING CHEMTBTRY
containing the oil and near the copper oxide, at a rate of a bubble in 2 or 3 seconds. This arrangement avoids the possibility of an accident from excess of pressure, or coming together of the acid and potassium hydroxide by a large depression in temperature in cold weather, or by careless operation. It is, in fact, “foolproof.”
Vol. 16, No. 9
other, or, if longer time intervenes between analyses, the corrections are only a few tenths of a milligram. If kept in the open air they may be filled in a few minutes. By weighing the bulbs filled with oxygen a loss of time in replacing oxygen with air after sweeping out carbon dioxide is avoided. On account of the instability of petroleum hydro-
The only combustion tube that will withstand the requisite carbons and the resistance of the escaping gases to oxidation, high temperature, without vitrification, is the most infusible even a t high temperatures, unless the progress of the oxiBohemian glass. The oil is as clearly visible in the boat dation is rigidly controlled in the beginning, there is danger after fifty analyses as in the first analysis. Of course, a t of loss. Such control is only possible in the gas furnace. such temperatures copper oxide easily fuses into quartz. It That the even heat of the electrically heated furnace cannot is best to use a mixture of finely granulated and powdered be varied to meet these requirements was shown by the failure copper oxide. in this laboratory to obtain concordant results in the analysis Since the absorption bulbs may be used in at least twenty of hydrocarbons in an electric furnace, when closely agreeing analyses, the carbon dioxide held back in the acid, as shown results were obtained in the gas furnace. A solution of in one of the earlier papers, does not affect the percentage palladium chloride is not needed, since the oxidation is comof carbon. A 50 per cent solution of potassium hydroxide plete under the conditions herein described. endures longer use without refilling. But even with the safety So much has been claimed for the aid of catalyzers in general tube of the potash bulb filled with soda lime and phosphorus organic analysis, it seemed advisable to test their efficiency pentoxide, unless it is followed by another longer tube likewise in hydrocarbon analysis. A layer of pumice saturated with filled, which invariably increases in weight of moisture 1 cerium oxide, which has been recommended as the best or 2 mg., there is a corresponding loss in carbon dioxide. catalyzer, was placed in front of the oil, which was volatilized This tube needs refilling only once in one hundred or more with ordinary rapidity. Several analyses showed loss of analyses. volatile hydrocarbons to the extent of 1.5 to 2 per cent. It Unless the combustion train is completely relieved from pres- appears, therefore, that, besides slow initial volatilization sure or suction, there is danger of slight loss by leakage of car- only hot oxygen delivered in front of the oil and an extremely bon dioxide. This is of less consequence if other elements are high temperature of the copper oxide can prevent loss by present in the substances analyzed, but with only carbon and incomplete oxidation of the volatile hydrocarbons. hydrogen such loss is prohibitive; it is easily avoided by the By this method four or more analyses are possible in a day, use of an aspirator with just sufficient length of siphon, as instead of two, which formerly were considered a daily task. shown in the figure, to equalize the back pressure in the As an example of the time required, two perfect consecutive bulbs. With the bulbs filled as described much time is saved analyses were made in 1 hour and 50 minutes, which inin replenishing, since aluminium oxide, calcium chloride, and cluded 70 minutes in sweeping out the carbon dioxide. soda lime are difficult to clean out, and none of these absorI n most of the lines of work with which the writer has been bents can be used more than two to five times. Besides their occupied during the last fifty years, he has had to study longer use, potassium hydroxide and sulfuric acid are much substances that involved combustions, and has always reeasier to manipulate. gretted the loss of time. Of all the different forms of apBy weighing duplicate bulbs filled with oxygen and keeping paratus he has used, the one herein described is the simplest them in large desiccators also filled with oxygen, much time is and most efficient. When once started its oversight intersaved by carrying the weights forward from one day to an- feres very little with other continuous work.
