ISDCSTRIAL A S D ENGINEERISG CHEMISTRY
308
Hydrolysis of Oil
The use of alkali was suggested by the work of Fraps4 and was also deduced from the results of Experiment 9, Table I. After preliminary trials with calcium and sodium hydroxides, it was found that better results were obtained a t elevated temperature. It was decided to use lime since this substance is employed in the wood-distillation industry. METHOD-Hydrolysis was effected by placing the oil and an equal volume of water in a flask with a slight excess of lime. The amount of lime was determined by the saponification of a sample of the oil with standard alkali. The flask was provided with a reflux condenser and mechanical agitation, and the mixture was stirred vigorously and refluxed six hours. The oil and methanol were then steam-distilled from the resulting emulsion; the oil was separated and the methanol washed from it with water. The residue in the still was neutralized with sulfuric acid, water added as necessary, filtered hot, and washed with hot water. The solution was then evaporated and the lime salts dried.
The residual oil was light yellow and much improved in odor. The weak methanol was carefully redistilled through a column and evaluated on its specific gravity as determined by a Westphal balance. The calcium salts were ground and weighed and a sample analyzed by distillation with phosphoric acid.5 Figure 2 gives a comparison of the boiling range of the oil before and after hydrolysis. The curve shows that the oil above 165" C. is not greatly affected by the hydrolysis. Figure 3 outlines the treatment of a fraction of Betula oil, with the percentages of residual oil, methanol, and calcium acetate recovered. The experiments reported in Table I1 were conducted on different fractions of oils from various sources according to the method outlined above. The yields of residual oil, methanol, and calcium acetate are presented in each case. The lime salts formed varied in composition with the fraction of the oil from which they were obtained. The salt from the 55-70" C. fraction was almost entirely calcium acetate. The salt from the 70-160" C. fraction contained only 77 per cent as calcium acetate and was entirely free Am. Chem. J . , 25, 26 (1901). Griffin, "Technical Methods of Analysis," p. 32 (1921).
6
VOl. 19, KO. 2
from tar. It contained some calcium acetate, but was chiefly propionate and butyrate. The salt from the 160195" C. fraction contained only 56 per cent as calcium acetate and consisted of salts of higher acids. Table 11-Hydrolysis
of L i g h t Wood Oil
WOOD RESIDUAL 827, 80% ACETATE SOURCEBOILINGRANGE OIL OIL METHAXOL O F LIME O F OIL OF ORIGINAL OIL Lilers 0.60 0.90 1.10 1.00 3.80 8.80 5.20 0.70 0.50 1.20 0.40 0.70 0.50 1.60 a
Per cent 58 34 61 68 47 60 31 56 64 59 44 68 89 67
Per centa 16.1 29.6 12.3 2.7 39.5 12.5 0.6 6 9 6.3 6.6 33.0
1A.i
G.9"
Kg./liter 0.27 0.50 0.22 0.05 0.35 0.19 0.06 0.16 0.07 0.12 0.36 0.14 0.07 0.21
c. Betula Betula Betula Betula Betula Betula Betula Seargent Seargent Seargent Wells Wells Wells Wells
55-195 55-66 66-145 145-195 55-70 70-160 160-193 55-160 160-195 55-195 55-70 70-160 160-195 55-195
Per cent by volume of original oil
The methanol obtained contained appreciable amounts of methyl ketones, some acetone, but chiefly methylethylketone. The methanol was systematically investigated for higher alcohols, but no traces of any alcohol except methanol could be found. Evidently the oil contains considerable amounts of methyl esters. The results of the experiments on hydrolysis show that methanol and lime salts can be obtained by refluxing fractions of wood oil with milk of lime. The amounts of these products vary considerably with the source of the oil. The oil recovered from this treatment is much improved in odor and color. The lime salts vary in composition with the fraction from which they are obtained. Hydrolysis of t h e Oil R e m a i n i n g a f t e r NaHSOt Extraction
Aldehydes and methyl ketones are removed from wood oil by shaking with a strong sodium bisulfite solution. About 40 per cent of the volume of the oil was removed by this treatment. The remaining oil was hydrolyzed with lime in the usual manner. The yield of calcium salts was somewhat lower than was usually obtained.
Evaluation of Turbine Oils' By T. H. Rogers a n d C . E. Miller STANDARD OIL COMPANY (INDIANA), WHITING,IND.
T
HE oxidation and evaluation of turbine oils becomes
a problem of increasing importance with the growing use of steam turbines as prime movers. Two years ago Funk2 presented the problem from the standpoint of the user, stating that further improvement in turbine design, affecting the stability of the oil, could not be expected, and that improvement in quality of turbine oils was therefore a problem for the refiners. However, the first step toward such development has hardly been accomplished, inasmuch as no method of evaluating the quality of turbine oil has been generally accepted. Emulsion tests are worth while for determining the initial quality of an oil, but, aside from indicating the care used in refining, they are not a measure of the stability of an oil in service. Turbine oils in service are maintained at elevated temperatures (varying from about 115' to 170" F. in different in1 Received August 28. 1926. Presented before the Division of Petroleum Chemistry at the 72nd Meeting of the American Chemical Society, Philadelphia, P a , September 5 to 11, 1926. 2 THIS JOURNAL, 16, 1080 (1924).
stallations) in the presence of air. The undesirable changes which take place in the oil are formation of insoluble material and, in the presence of water, very persistent emulsions. These changes are undoubtedly due to oxidation, as it has been found that in the absence of oxygen mineral oils are perfectly stable. From laboratory experiments it has been found that with oils of turbine grade oxidation is characterized by gradual formation of asphaltenes, free acids, and saponifiable material, the latter probably being lactones or anhydrides. Asphaltenes are very slightly soluble in turbine oils a t ordinary temperatures and are strong emulsifying agents of the water-in-oil type. The acids apparently are emulsifying agents of the opposite type, but this effect is very mild. Acids are particularIy harmful because they form soaps by action on the metal surfaces, particularly iron and copper. These heavy metal soaps, like asphaltenes, are slightly soluble in the oil at elevated temperatures, and deposition of both materials takes place in cooling coils or settling tanks when the temperature of the oil is lowered. These soaps are, of course, powerful emulsifying agents, and are of the same
I S D USTRIAL A S D ENGINEERING CHEMISTRY
February, 1927
type as asphaltenes. Therefore if water is present, which cannot be prevented in many installations, an emulsion is produced, the stability of which depends largely on the amount of the emulsifying agents present. After serious oxidation there may be formed thick emulsions, further stabilized by the presence of finely divided solids, which are almost impossible of resolution. It seems prob:ible that in the absence of water precipitated materials are not markedly deleterious until large amounts are formed.
Beunng
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Brus rad
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309
Although the acids formed by oxidation are quite weak, it is certain that, a t least in the presence of water, their action on metals is appreciable. I n fact, examination of a large number of deposits from turbines shows that, excluding iron rust and casual impurities, the greater part consists of healy metal soaps.'O The actual percentage of naphthainsoluble material in the oil is quite small. However, this is the cause of one of the characteristic difficulties in turbine practice-the formation in large amount of thick emulsions. These consist largely of water emulsified in oil, with generally less than one per cent of material insoluble in naphtha but soluble in chloroform. This material consists of the asphaltenes and heavy metal soaps described above; as determined by ash values and solubility in ether, the latter generally constitute 60 or 80 per cent of the chloroform-soluble portion. Examination of used oils also shows that high ash, deposition of sludge, and formation of persistent emulsions are more pronounced as the acidity increases. Stability Test
Figure 1-Herschel
Demulsibility Apparatus
The foregoing considerations have served as a basis for the development of a laboratory stability test. I n accordance with the most authoritative work on oxidation tests, the temperature chosen is moderately low, 100" C. Recognizing (I) the importance of acidity development, ( 2 ) the significance of emulsion tests as an index of the practical effect of oxidation on the oil, and (3) the difficulties attendant on quantitative determination of small amounts of asphaltenes, this test involves determinations a t various stages of the oxidation of (a) acidity and (b) Herschel demulsibility, and (c) observations as to the time required for first formation of precipitate.
I I j j j j I The foregoing conclusions as to the nature of the oxidative changes are supported by many statements in the literature, and this interpretation of the effects in turbine service has been substantiated by examination of used turbine oils and of turbine deposits. I n 1913 Schwartz and Marcusson3 pointed out that turbine deposits contain heavy metal soaps and determined the Kissling tar number as well as the coke number of various oils. The important work of Staeger4 2+ on trzinsformer oils has added much to our knowledge of the 3 oxidation of oils. He emphasizes the claim that oxidation 3 tests a t temperatures above 115" C. do not parallel the behavior of oils a t lower temperatures, stating carbenes and lower molecular weight acids begin to form above that temperature. The writers have found that, with certain classes of oils, sludge tests a t 162 O C. do not agree with those a t 120" C. Considering for a moment the general problem of oxidation tests for oils, including transformer, turbine, and motor oils, Figure 2-Effect of Iron and Copper on the Oxidation of a Turbine Oil a lack of agreement exists largely because different end products are emphasized. The Kissling test!' measures This test consists in subjecting 500 cc. of the oil to the acmainly the acids formed; the Waters,6 Michie,' Sligh,s and tion of oxygen a t 100" C. Demulsibility tests and acidity the life testg consider only the asphaltenes; while the B. B. C. determinations are made on samples (approximately 50 cc.) test3 measures both. The Funk test,2 one of the few tests which are taken every 48 hours. Oxygen is used instead of designed particularly for turbine oils, involves determinations air in order to accelerate the test. It is passed through a wash of the volume of sludge and emulsion produced after 50 or bottle containing water and bubbles through the oil in a slow 100 hours, agitation of the oil with air and water in an iron stream (two or three bubbles per second). Consumption vessel a t 100" C. It seemed to the writers that a more of oxygen is relatively slow, so that the rate of oxidation is quantitative turbine oil test is desirable, as well as one that not a function of the oxygen supply, which is thus greatly considers the effect of the various oxidation products as shown in excess. by examination of used turbine oils. The apparatus which has been found convenient for this 8 Z. angew. Chem , 26, 355 (1913). test is as follows: A one-liter round-bottom flask with a 4 THIS JOURNAL, 17, 1272 (1925). long neck is supported in a bath of boiling water. A ther6 Chem -Ztg., 33, 531 (1909); Proc. A m . Scc. Testing .ldaterials, 23, mometer and a delivery tube for the oxygen, which reaches 454 (1923) 6 THISJOURNAL, 3, 512 (1911) to the bottom of the flask, pass through a stopper in the 7 J . Insl Elec. Eng. ( L o n d o n ) ,51, 213 (1913). neck of the flask. A 10-pound pail, or better, a copper vessel J
y1
8
9
Proc A m Soc TeqLing Materials, 24, 964 (1924) , 24, 973 (1924).
Ibzd
10
Cf Blakeley, THISJOURSAL,17, 250 (1925).
ISDCSTRIAL AND ENGINEERIYG CHEMISTRY
310
of the same size, provided with a constant-level device for water supply, serves as the bath, the flask being immersed so that the oil level is well below that of the water. With a layer of asbestos paper for insulation and a cover fashioned around the neck of the flask the water can be maintained at
lW
EQc H O U R S
Figure 3-Stability
300
400
500
Teats of Several Turbine Oils
boiling temperature by means of an ordinary round laboratory hot plate. The samples are filtered through paper in order to remove any suspended material. This obviates the necessity of obtaining a representative sample of any precipitated material which may be in the flask, and conforms with modern plant practice where the oils are filtered in the circulation system. Demulsibility tests should be made immediately thereafter. The Herschelll demulsibility test was chosen for several reasons: i t requires only 27 cc. of oil; with welldesigned apparatus i t is the writers' experience that more reproducible results over a wide range can be obtained than with other tests; and the method of agitation perhaps approximates more closely the conditions in a turbine than a steam test. The apparatus was built very sturdily, as shown in Figure 1, in order to avoid the difficulties sometimes experienced in getting reproducible stirring conditions and results. Acidities are determined by titration of a naphtha solution of the oil with 0.1 N potassium hydroxide, using 95 per cent alcohol and phenolphthalein as the indicator. The mixture of 75 CC. of alcohol and 200 cc. of "cleaners' naphtha" is brought to a faint pi&, after which 10 grams of the oil are added and titration made to the same shade. With very dark oils it is often advisable to draw the alcohol layer up in a pipet for observation; in this case the blank should be titrated to the same end point. A special flask consisting of an Erlenmeyer into the bottom of which is sealed a wide cylindrical tube about 2 inches long has been found useful. This lower chamber facilitates both settling of the oil and observation of color. EFFECT OF METALS-These tests, then, afford comparative results on the oxidation of oils, as measured by the acidity, as well as the effect of this oxidation on the demulsibility of the oil. Figure 2 shows the results of tests of the same oil when tested without metal present, in the presence of iron, and in the presence of copper. It can be seen that oxidation is catalyzed somewhat by iron and still more by copper. The demulsibility values drop rapidly and present a rather confusing aspect after 60 or 75 hours. It is difficult to explain these results quantitatively, although the suggestion may be made that irregularity is to be expected as a result of the production of different emulsifying agents, and to some extent emulsifying agents of opposing types. From what has 11
Bur Mtnes. Tech P a p e r 3!23A, Method 320 31
Vol. 19, No. 2
been said earlier in this article, it follows that the acidity values are of greatest importance. (It may be noted that any heavy metal soaps present will titrate as free acid.) Other indications of deterioration may be obtained by examination of the samples, after standing, for precipitated material, or by a determination of the naphtha-insoluble on the final residue of the oil. TESTSI N PRESEXCE OF IRoX-The test with iron present has been tentatively chosen as sufficiently comprehensive for most purposes. The results do not differ so markedly from those with copper, and from information in the literature3>l2it would not be expected that other metals would introduce widely different results. Furthermore, contact with iron is invariable in all turbine service and contact with other metals varies widely. For the sake of ease of reproduction, a length of 40 inches of 18-gage iron wire is used for this purpose. Figure 3 shows the results of tests of several oils, in the presence of iron. These are all turbine oils with viscosities of 140 to 160 seconds at 100" F. Tests AI and Az were made on the same oil a considerable period apart. The oil suffered a marked drop in demulsibility due to exposure, which accounts for the widely different initial portions of the demulsibility curves of A i and Az. The acidity curves are practically identical, however. This illustrates very well the fact that initial demulsibility cannot be taken as a measure of the stability of an oil. Additional oxidation tests on oil A when fresh have substantially confirmed the initial portion of the demulsibility curve AI. Oil B is also a turbine oil of excellent grade. The acidity development was somewhat greater than that for oil A and the demulsibility curi-e in general lies below that of oil A . Oil C developed acidity more rapidly, its drop in demulsibility is sharper than that for oil A, and after 300 hours this
'
Li-
1
I IW
TURBINE TEST
Bo
- MONTHS
m
STABILITY TEST-
4
HOURS
,
4 0
0
3cd
of Stability Tests and Turbine Test Runs, Using 0118 A and B Average temperature of stability test, oils A and B, 99.6O C. Average
Figure 4-Comparison
temperature of oil A in turbine test, 63.9O C. B in turbine test, 63.5" C.
Average temperature of oil
x-alue remained between 50 and 60. This is apparently a rough minimum value for all oils, and increasing formation of asphalt seems to have no further effect. Oil C developed more acidity but the demulsibility values lie between those for oils d and B. DEPOSITION OF SLUDGE-A third means of comparing the behavior of the oils in this test is afforded by observations as to the deposition of sludge in the samples. Oil A did not deposite sludge after 500 hours, while oil B began to show a precipitate a t 300 hours. Unfortunately, record was not kept of the behavior of oil C in this regard. It is not believed that the time required for sludge precipitation (comparable 1'
Heyden and Typke, Pelroleurn Z , S O , 320 (1924).
I S D U S T R I A L A N D ENGINEERING CHEMIXTRY
February, 1927
with the life test for transformer oils) will necessarily parallel acidity development, so that such observations give supplementary information. This should be valuable, for instance, in eliminating an oil of low quality which would deposit asphaltic sludge very soon but which might not develop high acidity. Turbine Test Runs
The stability tests are on oils having a relatively high degree of refinement, and it is noteworthy that a definite difference between them is brought out. Almost any test will serve to throw out oils of very poor quality, but it is admittedly difficult to differentiate between oils of good quality. However, the absolute value of the test depends, not on the reproducibility or on the definiteness of the results afforded, but on the correctness of the viewpoint adopted in developing the test. To this end carefully controlled test runs with two of the oils reported above have been made in 1000kilowatt turbines. Two General Electric 1000-kilowatt (3600 r. p. m.) T S.C. turbines, running side by side under almost identical conditions, were used for test runs on the better two of the oils mentioned above ( A and B ) . The cooling water of the bearings of the turbines was regulated so that the average temperatures, taken at the three bearings every 8 hours, check within 0.4"C. Oil replacement has been made exactly the same for both oils. Xeither of these turbines leaks water. Data and results of the tests are shown in Table I. Table I- Data on Turbine Test Runs HERSCHEL A s T M T~~~ ACIDITY DEMULSI-STEAX
TIME
BILITY
J l g . K O H / g . oil
2 hours 1 week 1 month 2 months 3 months 4 months 4 . 7 months 6 months 7 months
0.01 0.01 0.05 0.08 0.11 0.14 0.18 0.25 0.26
1470 660 273 137 201 100 107 91 84
EMULSION Seconds Oil A 80 164 143 267
ALERi G E TURE
' C. 6 7.4 16 33 47 86 100 132 176
OIL
RE-
TEMPERAPLACE-
...
MBNT
Gallons
..
311
oils as shown in the turbine tests. A possible explanation of the latter difference is the fact that, while the average temperatures of the two turbines were the same, one bearing of the turbine containing oil A ran consistently 3 or 4 degrees warmer than the corresponding bearing for oil B, which difference was compensated by somewhat lower temperatures in the other two bearings. Furthermore, the necessity of oil replacements in the turbine tests constitutes a difference from the procedure of the stability tests, which may have some effect. On the whole the agreement between stability and turbine tests is about as good as can reasonably be expected for the conduct of a reaction under conditions which differ so widely in scale and detail. It is indicated that 9 hours in the turbine is equivalent to 1 hour in the stability test. Inasmuch as the temperature difference is 36" C., this ratio is smaller than might be expected. This corresponds to a doubling of the rate for every
1 1 i 1 h I
Figure 5-A.
I
I
I
2
I
,
a 4 M O N T H S SERVICE
I
5
I
6
l I
7
S. T. M. Steam Emulsion Tests of Oils A and B in Turbine Tests Runs
11.5' C. Furthermore, the use of oxygen instead of air for the stability test should further accelerate the reaction a t the elevated temperature, so that a much higher ratio than 295 297 5 9: 1was anticipated. 235 3 238 0 In addition to the usual tests, the color and the A. S. T. M. 239 0 steam emulsion values of the samples from the turbine runs Oil B were determined. Oil B showed a much more rapid increase 2 in color than oil A , probably in line with the fact that it forms 4 5 asphaltic sludge more rapidly. After 7 months in the tur3 bine neither oil showed a precipitate when hot, but oil B 3 precipitated asphaltenes after standing 48 hours. Oil A 0 0 showed no precipitate after similar standing. It will be observed that, with respect to asphaltene formation, the time R o g e r s , Grimm, a n d Lemmon, THIS JOWRNAL, 18, 164 (1926) ratio of the turbine run to stability test is much greater than At the start the turbines were carefully cleaned and flushed the 9: 1 cited above, which is based largely on acidity values. The A. S. T. M. steam emulsion values are shown in Figure with the new oil. Samples taken 2 hours after the test started showed a very slight difference in color from fresh oil 5 , where the points are connected by straight lines without and only slightly lower demulsibility. Samples taken each attempting to draw a smooth curve. These values are the month thereafter were tested as in the stability test, the re- result of two or more determinations on each sample. Good sults being shown by the points and the full curves in Figure 4. agreement was obtained; the average error was - 9 per cent For comparison the. curves, omitting the points, for the as compared with -6 per cent for the Herschel determinalaboratory stability tests of the same two oils are shown in tions. It is manifestly difficult to interpret these results. dotted lines in the same figure. The value of the time co- The behavior hardly seems rational as on the fifth month and ordinate for the turbine test run has been chosen so that the thereafter both oils show an improvement. The results are acidity curves agree equally well for both oils. It will be in a general way like those of the Herschel tests in that there observed that the stability test curve lies above that for the is the initial rapid decrease in quality, without any very turbine test run in the case of oil B and below it for oil A. great change thereafter. However, owing to the crossing of The turbine test runs in a general way substantially dupli- the curves, no clean-cut decision as to which is the better oil cate the behavior of the oils in the stability test. The indi- can be made. cated superiority of oil A is confirmed by the turbine tests. Discussion There is some lack of quantitative agreement, as shown by the sharper drop in demulsibility of both oils in the turbine tests It should be clearly brought out that this stability test and by the smaller difference in acidity between the two measures the oxidizability of the oil under turbine conditions, ...
62.9 62.;3 63.1 64.13 65.4 64.7 64.0
3 6 2 3
312
INDUSTRIAL AND E,VGIiWEERING CHEMISTRY
but does not attempt actually to duplicate the behavior of the oil in a “wet” turbine. Liquid water is not present, and, under these conditions, there seems to be practically no action of the acids on iron. There is no evidence of soap formation in the stability test and likewise in the turbine test runs neither oil showed a trace of ash after 7 months’ use. Acidity determinations are used as an index of the tendency of the oil to form soaps in the presence of water, and the assumption is explicitly made that the amount of soap formed will be proportional to the acid concentration. The turbine test runs therefore confirm the laboratory experiments as tests of the oxidizability of the oils. Unfortunately, no turbines which leak water were available for similar careful test runs. However, the evidence obtained from examination of used oils as well as laboratory experiments, in which it has been found that the acids formed by oxidation will attack iron in the presence of water, serves to indicate the validity of the above assumption. It might be proposed that the stability test be carried out with water as well as oil in the flask. However, in view of the recognized difficulty of obtaining satisfactory emulsion tests of oils under the simplest conditions, it hardly seems practicable to combine emulsion and oxidation tests. It is the belief of the writers that fundamental information on the rate of oxidation
VOl. 19, No. 2
of the oil, interpreted in terms of its effect on the behavior of the oil in the turbine, is the best means of evaluating turbine oils. Summary
The deterioration which turbine oils undergo in zervice is due to oxidation. Two types of oxidation products are formed: (1) asphaltic material, insoluble in the oil; ( 2 ) free acids, soluble in the oil. The latter, in the presence of water, form insoluble soaps in contact with metals such as iron and copper. A stability test has been developed in which moist oxygen is passed through the oil a t 100” C. in the presence of iron. Determinations of the acidity and demulsibility of samples taken periodically, along with the sludging time, serve as a measure of the degree of oxidation and its effect on turbine service. By comparative turbine test runs it has been established that this stability test substantially duplicates the behavior of oils in a dry turbine. Acknowledgment
The writers wish to acknowledge thanks for advice and suggestions to F. W. Sullivan, Jr., in whose department this work was carried out.
Acids in Automobile Crank Cases’ A Few Observations By A. F. Meston MOTOR IMPROVEMENTS. INC.,NEWARK, N. J,
An acid condition is always present in an automobile HE oil and vapors in cars were equipped with oil crank case. I t is shown that acids are present in the an automobile c r a n k filters. The gasoline used in lubricating oil, in the diluents in the oil, and in the case a r e always acid. the cars was, for the most. vapors escaping from the crank case. Some of the Corroded or “etched” wrist part, a n extensively adveracids are more soluble in water than in oil. Some of pins are occasionally found tised brand enjoying broad them are corrosive. Positive tests for naphthenic distribution. The oils used in automobile engines and acids are obtained with oils, diluents, and condensed are advertised as “100 per furnish striking evidence of water vapors. cent Pennsylvania.” It i s this acid condition. The The neutralization value of a crank-case oil apbelieved the conditions set seriousness of the condition parently reaches a maximum after the oil has been up by these oils and fuels. is apparently a matter of exin service for several hundred miles of car operation. were as favorable as those perience and of opinion. The The presence of sulfur is noted and data relating to under which the average car average car owner is blissits distribution in the various liquids and vapors are operates. No attempt was fully ignorant of its possipresented. made t o analyze the problems bilities and fortunately selthat sometimes arise when dom has reason to be otherwise. Superintendents in charge of fleets, who have noted blended fuels or special lubricants are used. Figure 1 shows graphically the increase in neutralization corrosion within the crank cases of their cars and trucks, have had considerable success in eliminating the trouble value or so-called “acidity” of the crank-case oil in a 1925 by providing crank-case ventilation. There is little in the model of a six-cylinder car, used by the owner in driving literature to show that the subject has been systematically about Kewark, N. J. The test started with new oil (desigstudied, but the efforts of automobile manufacturers to fur- nated as L-1) April 22, when the weather was quite cool, and nish ventilated crank cases indicate that they have appre- continued until August, a t which time very warm weather and unusually high humidity existed. No oil except samples ciated the advantages of this practice. The observations herein described were compiled, not for was removed during the test and make-up oil averaged 1 the purpose of explaining wrist-pin corrosion in particular, quart per 250 miles (1 liter per 380 km.). The acidity inbut to furnish additional information on the general subject creased quite evenly until a value of 0.35 mg. KOH per gram of of crank-case acidity, its extent and distribution. The data oil was reached, which appears to approximate an equilibrium were obtained from block test runs with a Chalmers Six value for this particular oil in this car. Figure 1 also shows engine and fromexperimental and routine runs of a number of the dilution present in the oil during the test. I n 400 miles the better known four-cylinder and six-cylinder cars. All (644 km.)the dilution reached an equilibrium for the operating conditions existing a t about 19 per cent. As the xeather 1 Received August 30, 1926. Presented before the Division of Pebecame warmer the dilution decreased, and throughout the troleum Chemistry a t the 72nd Meeting of the American Chemical Society, summer it remained quite constant, a t 8 per cent. The Philadelphia, P a , September 5 to 11, 1026
T
