1 % ^ STATE OF ILLINOIS STATE HIGHWAY DEPARTMENT BULLETIN NO. 13 The Testing of Road Oils Including Character of Oils and Methods of Examination. Prepared by F. L. ROMAN Testing Engineer, Illinois State Highway Department £ ' f t 1 '■ Springfield, Illinois, December, 1916 [Printed by authority of the State of Illinois.] STATE OF ILLINOIS STATE HIGHWAY DEPARTMENT BULLETIN NO. 13 The Testing of Road Oils Prepared by F. L. ROMAN Testing Engineer, Illinois State Highway Department COMMISSION. A. D. Gash, President. S. E. Bradt, Secretary. James P. Wilson. Wm. W. Marr, Chief State Highway Engineer. BUREAU CHIEFS. Clifford Older, Bridge Engineer. H. E. Bilger, Road Engineer. B. H. Piepmeier, Maintenance Engineer. F. L. Roman, Testing Engineer. J. M. McCoy, Chief Clerk. Springfield, Illinois. December, 1916. Schnepp & Barnes, State Printers Springfield, III. 1917. P5543 — 1M CONTENTS. PAGE. Preface 5 Introduction 7 Source and Character of Road Oils 7 Chemical Composition of Road Oils 8 Methods of Testing 10 Specific Gravity 10 Specific Viscosity 13 Volatilization Loss 16 Solid Risidue 19 Flash and Burning Points 21 Total Bitumen 23 Bitumen Insoluble in Paraffin Naphtha 25 Fixed Carbon 26 Paraffin Scale 27 Miscellaneous Tests 29' References 29 ILLUSTRATIONS. PAGE. Westphal Balance, Figure 1 12 Hydrometer, Figure 2 12 Pycnometer, Figure 3 12 Engler Viscosimeter, Figure 4 14 New York Testing Laboratory Oven, Figure 5 17 Dow Penetration Machine, Figure 6 19 Open Cup Oil Tester, Figure 7 22 Apparatus for Determining Soluble Bitumen, Figure 8 24 Apparatus for Determining Fixed Carbon, Figure 9 24 Freezing Apparatus for Determining Paraffin Scale, Figure 10 28 PREFACE. The increasing use of road oils in highway work, especially in the surface treatment of earth roads, has made it necessary for high- way engineers and road oil manufacturers to have a clear under- standing of the specifications involved, and consequently of the nature and character of these oils and of the methods of testing. Jn preparing the following treatise, an effort has been made to give this information in readily available form. This bulletin is necessarily of a technical character, and is not intended for general distribution among the public. It is assumed that engineers and manufacturers who will have occasion to refer to this publication have at least an elementary knowledge of chemistry. Digitized by the Internet Archive in 2017 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/testingofroadoilOOroma INTRODUCTION. The study of the nature and character of road oils has become a subject of special importance in the Middle West where these oils are being used extensively in the surface treatment of earth roads. It is estimated that in Illinois alone, approximately two hundred thousand dollars ($200,000) were spent for road oils applied during 1915, and that this amount has been more than doubled in 1916. A large per cent of the road oils used in the past was pur- chased by townships and often the only requirement made has been that the product should have a certain gravity or a certain per cent of “asphaltum.” No temperature at which the gravity of the oil was to be taken was given, and the consistency of the “asphaltum” or residue to be obtained was not specified. The absurdity of such specifications will be shown further, by the fact that road oils having the same gravity at a given temperature, or having the same per cent of residue or “asphaltum” of a given consistency, may be of entirely different character. It has been a source of gratification to note, however, that the number of oils purchased in the past year under suitable specifica- tions has increased considerably and that the character of the oils used has been in general much better than in past years. SOURCE AND CHARACTER OF ROAD OILS. Road oils are either crude petroleum or petroleum products. It should be noted, however, that a few of the heavier oils consist mainly of asphalts which have been fluxed with light oils. It is not the purpose of the writer to enter into a discussion of the origin of petroleum, but in order to understand the character of the various types of road oils, it is necessary to say a few words concerning the source of the petroleums and the petroleum products used in Illinois. With the exception of a small amount of Mexican and Trinidad products, the petroleums and petroleum products used in Illinois are obtained almost entirely in the United States. The main oil fields are generally divided as follows : (1) Appalachian field; (2) Ohio-Indiana-Illinois field; (.3) Mid-Continent field ; (4) Gulf field ; (5) California field. Petroleum from different parts of the same field may vary con- siderably and may show greater variations than oils from different fields. The petroleums high in paraffins are obtained in the Appala- chian, the Ohio-Indiana-Illinois and the Mid-Continent fields. The Ohio-Indiana-Illinois oils are somewhat heavier than the Pennsyl- vania oils (Appalachian field) and contain much larger quantities 8 of sulphur compounds. Some of the southern Illinois oils contain a fairly large per cent of asphaltic hydrocarbons, and for road build- ing purposes resemble closely the best Kansas and Oklahoma oils. The Mid-Continent field comprising Oklahoma and Kansas, pro- duces petroleums which vary rather widely, but which as a rule contain less paraffins and more asphaltic hydrocarbons than the oils from the Appalachian and Ohio-Indiana-Illinois fields. The petroleums from the Gulf field, comprising Texas and Louisiana, leave a fairly heavy residue and contain only a small per cent of solid paraffins. For road purposes they may be con- sidered as intermediary products between the paraffin petroleums described and the asphaltic petroleums of California and Mexico. The California field produces petroleums which consist mainly of asphaltic hydrocarbons. They leave heavy residuums which show good binding qualities and which are generally superior for road purposes to all the other petroleum residuums of the United States. It will be seen that from the standpoint of road oils alone, the five petroleum fields described produce three types of oils, the paraffin, the semi-asphaltic, and the asphaltic products represented by the Pennsylvania, Texas and California oils respectively. The crude oils of each type may vary widely in consistency from light liquids which flow freely to heavy liquids so viscous that they can be pumped only with great difficulty. Some crude petro- leums are available which as such are satisfactory for road pur- poses, while others may require refining or fluxing. A small amount of refining rapidly increases the price of road oils on account of the cost of handling, and it has therefore been the tendency to sell as road oils many crude petroleums which are entirely un- satisfactory for road building purposes. Before taking up the methods of examining these products it is necessary to say a few words in regard to the chemical composition of road oils. CHEMICAL COMPOSITION OF ROAD OILS. Road oils consist mainly of hydrocarbons with generally some sulphur compounds and small amounts of nitrogen and oxygen deriva- tives of some of the hydrocarbons. As stated previously, the road oils from the eastern field consist mainly of hydrocarbons of the paraffin series (C n H 2n+2 ). These hydrocarbons are also found in large quantities in the Ohio, Indiana, Illinois, Kansas and Oklahoma petro- leums, but the best road oils from these states contain also saturated hydrocarbons of the C n H 2n _ 2 and C n H 2a _ 4 series and also some unsaturated hydrocarbons. The California road oils consist largely of unstable polymethylene hydrocarbons and leave residues showing a large per cent of unsaturated hydrocarbons. The Texas road oils consist mainly of paraffin and of stable polymethylene hydrocarbons. Hydrocarbons of the olefine or ethylene series C n H 2n and some aromatic hydrocarbons are present in most of the road oils. The naphthenes or monocyclic poly methylene hydrocarbons mainly of the 9 hexamethylene series are found in most of the semi-asphaltic and asphaltic road oils. As will be seen from the above outline, road oils are extremely complex mixtures of various hydrocarbons belonging to a number of different series. That it would be an impracticable task to isolate the hydrocarbons in road oils can be readily understood when it is stated that according to Hubbard (Dust Preventives and Road Binders), the lowest member of the paraffin series which might be found in road oils is pentane C 5 H 12 and that the known normal paraffins run as high as C 60 H 122 . Each member of this series has a number of isomers and their number increases rapidly with the increase of carbon atoms, hexane, (C 6 H 14 ) having six isomers while tridecane (C 13 H 28 ) has 802 isomers. The number of paraffin hydrocarbons alone which might exist in road oils is therefore enormous. As each series of hydrocarbons which may be present in a road oil usually imparts some special property to the oil, it is necessary to say a few words of some of the characteristics of the most important series. The paraffins give a greasy appearance to road oils and their presence in large quantities, especially of the solid paraffins, indicate that the oil has poor binding qualities. The higher members of the paraffin series which are solid at room temperature dissolve readily in the lower members of the series which are liquid. This fact is used as a means of separating from the paraffins and other saturated com- pounds the heavy unsaturated hydrocarbons which are insoluble in paraffin naphtha. The lower members of the paraffin series are readily soluble in alcohol and ether, but the higher members which are solid at room temperature are much less soluble, and are practically insoluble at low temperatures. This property of the paraffins has been made the basis of a method for determining the solid paraffins or the so-called paraffin scale. The paraffins are probably the most stable hydrocarbons, and are not attacked by sulphuric or nitric acid. The cylic hydrocarbons of the naphthene or monocyclic poly- methylene series and of the polycyclic polymethylene series are not attacked by sulphuric acid, but are not as stable as the paraffins. The polycyclic polymethylenes, a number of which have probably very com- plex structures, are less stable than the monocyclic polymethylenes. They are found mainly in asphaltic and semi -asphaltic road oils; and, in oils which show very little paraffin scale, they constitute probably a large per cent of the portion of oil which is not removed by concen- trated sulphuric acid. The unsaturated hydrocarbons comprising the olefines, the camphan group of terpenes and a number of aromatic and straight chain compounds which occur more or less frequently in road oils, probably do not all have the same value in road oils, but it has been noted that in general the higher is the per cent of bitumen removed by sulphuric acid, the better are the binding qualities of various road oils. Some of these unsaturated hydrocarbons appear, therefore, to give adhesiveness to the oils and to the residual asphalts obtained from 10 road oils showing large percentages of bitumen removed by sulphuric acid. METHODS OF TESTING. In general, the methods described in the following pages are not new, and a number of them have been used in asphalt testing for a number of years. Nearly 800 samples of road oils have been examined in the laboratory of the Illinois State Highway Department during the past four years, and- some of the methods have been somewhat modi- fied in order to make them suitable for the testing of road oils. Most of the comments and suggestions which are found in the following description of these tests represent the results of the experience of the laboratory in the examination of oils, and of observations of the results obtained with these oils in the field, mainly on earth roads. SPECIFIC GRAVITY. The specific gravity of road oils is generally taken at 25 °C. (77°F.) as compared with water at the same temperature. This is about the average temperature at which road oils are handled. It has been found to be more convenient, therefore, to determine their gravity at 25°C. than at 15.5°C. (60°F.), the temperature at which the specific gravity of most oils is generally taken. The specific gravity of the thin fluid road oils is determined usually by means of either a hydrometer or a Westphal balance, but it may be determined also by the pycnometer method. Hydrometers and Westphal balances are generally calibrated to give specific gravity readings at 15.5°C. With such instruments the determination is car- ried on at 25 °C. as usual and a correction applied to the specific gravity reading. For ordinary practical work this reading may be cor- rected to water at 25°C., considered as unity, by multiplying by 1.002 as follows : Specific gravity at 25°C./25°C. = specific gravity at 25°C./15.5°C. X 1-002. In practical field work the gravity of road oils is often expressed by means of the Beaume scale. The specific gravity at 25°C. of road oils commonly used being in general less than unity, their gravity in degrees Beaume may be obtained from their specific gravity by means of the following tables or by means of the formula: 140 Degrees Beaume = 130 at 15.5°C. specific gravity COMPARISON OF DEGREES BEAUME AND SPECIFIC GRAVITY. (Liquids lighter than water.) °B. Sp. Gr. °B. Sp. Gr. °B. Sp. Gr. 10 1.0000 22 .9210 34 .8536 11 .9929 23 .9150 35 .8484 12 .9859 24 .9090 36 .8433 13 .9790 25 .9032 37 .8383 11 °B. Sp. Gr. °B Sp. Gr. °B. Sp. Gr. 14 .9722 26 .8974 38 .8333 15 .9655 27 .8917 39 .8284 16 .9589 28 .8860 40 .8235 17 .9523 29 .8805 41 .8187 18 .9459 30 .8750 42 .8139 19 .9395 31 .8695 43 .8092 20 .9333 32 .8641 44 .8045 21 .9271 33 .8588 Either the hydrometer or the Westphal balance may be used for making a rapid determination of the gravity of thin fluid products, the Westphal balance being more satisfactory for accurate work. Neither apparatus is suitable, however, for the determination of the gravity of viscous oils. Figure 1 shows a type of Westphal balance satisfac- tory for road oil testing, and Figure 2 shows a hydrometer and hydrometer jar. When using hydrometers with road oils, care should be taken to let the instrument sink slowly in the oil until it has come to rest. The reading obtained should be checked by raising the hydrometer a few degrees and letting it sink again. The hydrometer should not be pushed below the point at which it comes to rest until the readings have been completed. To judge if the oil is too viscous for a satisfactory determination of the gravity, the hydrometer should be sunk in the oil 3 or 4 degrees below its resting point. If it should not begin to rise at once, the oil is too viscous for the hydrometer method, and the pycnometer must be used. The Hubbard type of pycnometer is used for the determination of the gravity of almost all heavy viscous road oils, and is suitable also for the lighter oils. This type of pycnometer is shown in Figure 3 and consists of a straight walled glass tube,. 70 milli- meters in length and 22 millimeters in diameter, with a heavy ground glass stopper bored with a hole 1.6 millimeters in diameter. When stoppered the pycnometer has a Capacity of about 24 cubic centimeters. With fluid oils the specific gravity determination using this type of pyncometer is similar to the determination with the ordinary pycnometers. The weight of the oil which will fill the pycnometer at 25° C. is divided by the weight of the same volume of water afi the same temperature. With the viscous road oils the following method of determin- ing their specific gravity is used, all weighings being made with the stopper in place on the pycnometer. The weights of the empty pycnometer and of the pycnometer filled with water at 25° C. are determined as usual and called “a” and “b” respectively. The road oil is heated until it pours readily and the pycnometer is filled to about three-fourths of its volume, taking care that no oil comes in contact with the stopper. After cooling, the pycnometer and contents are weighed and the weight called “c.” Enough dis- tilled water is then poured on top of the oil to fill the pycnometer, which is then immersed for at least 20 minutes in a beaker of dis- tilled water at 25° C. Although their gravity is less than that of 12 water, the heavy viscous oils will give no trouble in this operation. Less viscous oils show, however, a lower gravity and less adhesive- ness, and will tend to float on the water. The specific gravity of these oils may often, however, be determined by this method by taking care to add the water slowly around the sides of the pycno- m /yy t/ydron? e ter Method F/y.J-Pyenom efer (/tub bard Type) meter. Should this fail to keep the oil from floating, some other method of determining its gravity must be adopted. The pycnometer with the oil and water at 25° C. are weighed and this weight is called “d.” All the values necessary to calculate the specific gravity are now available, and the following formula which will be readily understood is obtained : c — a Specific gravity at 25°C./25°C. = . (b — a) — (d — c) “a” and “b” are constants and after being determined once they need to be checked only from time to time. The specific gravity at 25° C.^(77° F.) of light fluid road oils of a paraffin nature for cold application vary from about 0.890 to 0.930, while the specific gravity of the corresponding asphaltic oils is slightly higher from about 0.910 to 0.950. The heavy viscous asphaltic oils which are applied hot have a specific gravity at 25° C. (77° F.) varying from about 0.950 to unity. As a rule the determination of the specific gravity alone is of little value in the examination of road oils, but if taken in connec- tion with other tests, it is of value to check the nature and source of these oils. It should be noted in connection with this test that the volume of road oils increases when their temperature is raised, and that their gravity shows a corresponding decrease. A specification requiring a given gravity for an oil without stating the temperature at which the gravity is to be determined is, therefore, worthless. The coefficient of expansion of road oils, that is the ratio between the increase in volume of the oils when their temperature is raised one degree and the original volume of these oils, varies somewhat with the nature and character of the oils and the tem- perature at which this coefficient of expansion is measured. For most practical purposes the coefficient of expansion of road oils, when their volume at 25° C. (77° F.) is taken as unity, may be assumed to be 0.0007 per degree centigrade, and 0.0004 per degree Fahrenheit. Thus if V is the original volume of the oil, its volume V 1 when the temperature has been raised 20 degrees centigrade will be V (1 -f~ (20 X 0.0007) or V (1 + 0.014) or V X 1.014. This should be taken into consideration in the measurements of road oils by volume. An oil measured hot at a temperature of 177° F. would show a decrease per unit of volume when cooled to a temperature of 77°F. of (177 — 77) X 0.0004 = 0.04 or in other words, a decrease of 4 per cent by volume. SPECIFIC VISCOSITY. The Engler viscosimeter is generally used for this determination. Other types of viscosimeters will undoubtedly give satisfactory results, but on account of the ease with which it can be cleaned, the Engler type has been generally adopted. It is shown in Figure 4, and consists of a brass vessel “a” with gold plated interior for holding the road oil. This vessel has a cover “b” and is fitted with an outflow tube “c,” exactly 20 mm. in length with a diameter of 2.9 mm. at the top and 2.8 mm. at the bottom. The tube can be closed with the wooden plug “ d 14 Three metallic projections are placed in “a” at equal distances from the bottom and serve to measure the charge of 240 cubic centi- meters. The thermometer “e” shows the temperature of the road oil, while the thermometer “f” gives the temperature of the heating bath. The thermometer “e” is made especially for this apparatus and is graduated either to 50°C., 100°C., or 150°C. The brass jacket “g” is nearly filled either with water or a high boiling oil acting as a heating bath. The apparatus is supported on a tripod “h” to which is attached a ringburner “i” for heating the bath. The oil is received in a 50 cc. 15 cylinder “j” which has been found most satisfactory for all practical work. Special care should be taken to keep the vessel “a” and the outflow tube “c” perfectly clean. It is also sometimes necessary to remove impurities from the road oil by straining it through a cheesecloth before performing the viscosity test. The viscosity determinations are made at various temperatures, 25°C, 50°C., and 100°C. being generally adopted. As all viscosity determinations should be compared with water at 25 °C. the apparatus should first be calibrated with water, after it has been thoroughly cleaned. With the required charge of 240 cc. an Engler viscosimeter will deliver the first 50 cc. in about 11 seconds and the first 100 cc. in about 23 seconds. The time of flow is measured with a stop watch which is started at the same time that the plug “d” is removed and is stopped when the oil has reached the required mark on the receiving cylinder. With proper care of the apparatus, the time of flow of water at 25 °C. should remain a constant and will require checking only at long intervals. It is essential that all the oil of the charge be at the required temperature when its viscosity is determined. The fluid oils should remain at the temperature chosen for a least 3 minutes, and the heavy viscous road oils for at least 5 minutes just previous to the time of measuring their viscosity. With a little experience the temperature of the heating bath may be regulated so as to keep the temperature of the oil in the inner vessel practically constant. The specific viscosity of the oil compared with water at 25 °C. is obtained by dividing the time of flow of a certain number of cubic centimeters of the oil by the time of flow of the same number of cubic centimeters of water at 25 °C. Thus : ~ ~ Time of flow of 50 cc. of oil at X°C. Specific viscosity at X C./25 C. Time of flow of 50 cc. of water at 25°C. The determination of the specific viscosity of a road oil is of great value in determining whether the oil may or may not be applied cold, and if heating is required, the temperature at which it should be applied. It permits also to judge if an oil is of the proper consistency for certain types of road construction. The viscosity of oils which are to be applied cold is generally taken at 50°C. The viscosity of oils which are to be applied cold from gravity distributors is often taken also at a lower temperature, preferably 25°C. The viscosity of road oils which will be heated with steam coils, should be taken at 50°C. and 100°C, while the viscosity of the heavy asphaltic oils, which will require heating to temperatures above steam heat before application, should be taken at temperatures of 100°C. and possibly 150°C. An oil with a specific viscosity of more than 60 at 25°C. and more than 15 at 50°C. can not always be applied cold from gravity distributors. Pressure distributors will not always handle properly cold oils having a specific viscosity at 50°C. of more than 20, although in hot summer weather an oil with a specific viscosity as high at 70 at 16 50°C.. has been applied without heating. It is difficult, under certain conditions, to heat with steam to a satisfactory fluidity an oil having a specific viscosity at 100°C. of more than 15, but on hot summer days it is possible to heat with steam, to a satisfactory fluidity, an oil show- ing a specific viscosity at 100°C. as high as 30. It should be noted that it has been the tendency within the past years to heat road oils which might have been applied cold. The appli- cation of the oil after heating instead of cold, appears to give some- what better results on earth roads, as the oil being somewhat more fluid will be distributed somewhat more uniformly over the road surface, and on cold days the danger of having the oil “cake” on the surface of the road is eliminated. VOLATILIZATION LOSS. The purpose of this test is to determine the per cent of the oil which will volatilize when a given quantity of the oil in a standard size container is maintained at a certain temperature for a given number of hours. The volatilization test which has been considered as a standard test for asphalts and road oils in the past years (See 1915 Year Book of the American .Society for Testing Materials) is to heat 20 grams of the material contained in a seamless tin box 2 y 2 inches in diameter and 24 inches deep (about 6 cm. in diameter and 2 cm. deep) for 5 hours at a temperature of 163°C. (325°F.) in a New York Testing Laboratory oven. This type of oven is shown in Figure 5, and has been most commonly used, although other types of ovens which can be regulated to give uniform temperature will undoubtedly give satis- factory results. The New York Testing Laboratory Oven is made either of iron or copper, covered on the outside with asbestos. It is constructed in such a way that it provides a uniform circulation of air. It is heated with gas by means of the ring burner “a,” and the gas supply is regulated by means of the mercury thermostat “b.” With a fairly uniform gas presssure this attachment will permit to regulate the heat in the oven within one or two degrees of the temperature desired. When a road oil is heated the two thermometers “c” and “d” are used. The bulb of the thermometer “c” is immersed in a non-volatile oil and shows the temperature of the road oil during the volatilization test. The thermometer “d” is kept in air at about the 'same level as “c” and is used to give warning of any sudden change in the temper- ature of the air in the oven due to possible irregularities in the gas. •supply, “e” is the top of the oven and shows the openings which per- mit a satisfactory circulation of air. The oven should be brought to the required temperature before the cup containing the oil to be tested is inserted. When the oil has been heated for the required length of time, it should be removed to a desiccator and allowed to cool before weighing. The original weight of the oil taken should be within 0.2 gms. of 20 gms, and the weighings should be accurate to the third decimal place. 17 Because of the fact that the residues obtained after submitting 20 grams of the oil to the volatilization test are often too small to per- mit their examination in a satisfactory manner, many of the labora- tories have adopted the use of a 50-gram sample for the volatization test. The container for the 50-gram sample should be a tin seamless box similar to a 3-ounce gill style ointment box, deep pattern. It should have a flat bottom and vertical sides and should be 5)4 cm. in diameter and 3 ]/ 2 cm. deep (approximately 2-3/16 inches in diameter and 1 y% inches in depth). The American Society for Testing Materials recommends in their 1916 revised “Standard Tests for Loss on Heating of Oil and Asphaltic Compounds” (A. S. T. M. Standards, 1916) that in addi- tion to the adoption of a 50-gram sample a special type of oven be used. This oven may be either of circular or retangular form, and the source of heat may be either gas or electricity. The most impor- tant feature of this type of oven is that the shelf which carries the samples is suspended by a vertical shaft midway in the oven, and is revolved by means of a motor at a speed of 5 to 6 revolutions per minute. This shelf which is perforated, has a diameter of 24.8 cm. (9^4 inches), and the samples all rest in the same relative position in a circular row. It should be noted in connection with the volatilization of a num- ber of samples of oils at one time in the same oven, that this procedure is not to be recommended when the samples represent materials of different -character. It has been noted repeatedly that when a heavy asphalt consisting exclusively of high boiling hydrocarbons is heated in an oven containing an oil rich in low boiling hydrocarbons, the asphalt having the high flash point will show less loss than when it is heated alone in the oven, and in some cases will show a slight increase in weight due probably to the absorption of some of the volatile pro- ducts of the oil having the low flash point. It is, therefore, probable that when a number of road oils which have different flash points are heated together in an oven, the volatilization losses will not be the same as those obtained when each oil is heated alone, and in some cases an appreciable error may be noted. This is especially true when ovens of the New York Testing Laboratory type are used, but prob- ably to a much lesser degree when ovens with a revolving shaft of the Frease Electric type are used. As the volatilization loss depends to some extent of the ratio of the exposed surface of oil to the volume of the oil and also of the shape, size and depth of the container, it is essential that the tin boxes which have been described above and which have been generally adopted, be used in all cases if comparative results are to be obtained. It should be noted that the 20 gram and 50 gram samples may show volatilization losses which vary materially. The volatilization test is sometimes undertaken at various temper- atures other than 163°C., generally at 105°C. or 110°C., and at 205°C. or 210°C., and the length of heating is sometimes varied from 1 to 7 hours. Specifications requiring a volatilization test should, therefore, contain statements as to the temperature at which the oil is to be heated, the length of time of volatilization, the type of oven used, and the quantity of oil taken for the test. This test is mainly of value in determining the “setting” or hard- ening properties of the heavier oils. An examination of the residue obtained by this test will sometimes give information also as to the nature of the oil. The volatilization test is of very little value, how- ever, when used in the examination of many of the light oils which are used on earth roads. 19 SOLID RESIDUE. The purpose of this test is to determine the per cent of solid residue or so-called “asphaltum” which may be obtained from an oil. A‘ given quantity of the road oil, generally 20 grams or 50 grams is kept at temperatures only high enough to produce volatilization of the lower boiling compounds, until the residue will become solid on cooling and show the consistency desired. The apparatus used to measure the consistency of this residue is the same as the one used to determine the consistency of asphalts. A Dow penetration machine is generally 20 used, but a New York Testing Laboratory penetrometer, or a similar type of machine will give satisfactory results. All these machines measure the distance which a standard No. 2 cambric needle (or a steel needle having a diameter of 0.040 inch and tapered *4 inch to a sharp point) will penetrate, under a certain weight and during a given length of time, a bituminous material maintained at a given temperature. The Dow penetration machine (Figure 6) con- sists of a No. 2 cambric needle “a” inserted in a brass rod fitting in the aluminum rod “b.” The aluminum rod is a part of an aluminum frame work “c” weighing with the brass rod and needle exactly 50 grams. It is held at “d” by means of a clamp which may be held open by means of a button. Additional weights of 50 or 150 grams are added at “e” when the penetration is taken under weights of 100 or 200 grams. The penetration is measured by means of the rack “f” and dial “g.” The rack is connected with a pinion to which is attached the hand of the dial, and penetration may be measured by this arrange- ment to an accuracy of 0.1 mm. The tin box “h” containing the bituminous material is kept in water at the desired temperature and when tested is placed on the shelf “i.” The time of penetration is generally indicated by a metronome, although various electrical attach- ments have been devised for the purpose of regulating accurately the time of penetration. Road oils are generally heated until a residue is obtained which has a penetration in 5 seconds at 25°C. under a weight of 100 grams of 10 mm. Road oils may be heated, however, until softer or harder residues are obtained, and the rather indefinite term “asphaltum” is commonly given to all of these residues. The chemical composition of these residues may vary widely, the paraffin road oils leaving a greasy residue rich in solid paraffins, while some of the best road oils leave an adhesive residue consisting mainly of asphaltic hydrocarbons. It will be readily understood, therefore, that a guarantee, such as some oil companies give, of furnishing an oil with a certain per cent of asphal- turn has no definite meaning and is worthless. Furthermore the heating of road oils at temperatures above 200°C., during the evaporation tends to produce “cracking,” that is the decomposition of some of the hydrocarbons and the formation of new compounds. Thus a paraffin might decompose into a paraffin and an olefine as follows : C n (-heat paraffin Thorpe and Young state (Ber. des Deutch Chem. Gesellsch., 1872, p. 536) that the products obtained in cracking paraffin petroleums are mixtures of several paraffins and olefines. As it is practically impos- sible to obtain a residue of suitable consistency from many oils, especially those rich in paraffins of high boiling point, within a reason- able length of time without heating them at a temperature above 200 °C., it is probable that some “cracking” often takes place in this test. Furthermore an increase in the rate of evaporation corresponds to a decrease in the amount of residue of a given consistency which is C ( n _a) H 2 ( n _ a ) +2 + C a H s paraffin olefine 21 obtained, due to the fact that when the rate of evaporation is rather high some high-boiling hydrocarbons are driven off which remain in the residue when the rate of evaporation is very slow. The per cent of residue of a given consistency which is obtained from an oil may, therefore, vary materially. It is difficult also to judge if a residue has the proper consistency. A few minutes of heating may often change a residue from a product which is too soft to a product which is too hard, and it has been the experience of the laboratory of the State Highway Department that it is often necessary to heat two or three samples of the same oil before a residue of the proper penetration can be secured. The determination of the per cent of solid residue in road oils is of value in the examination of new products, but it should be remem- bered that this test is inaccurate and often misleading as to the quality of an oil. It should not, therefore, be considered a standard test, and specifications for the purchase of road oils should never be based solely on a given per cent of solid residue or “asphaltum.” It is, however, the only test of which many township highway commissioners have any knowledge, mainly because of the practice of oil manufacturers of selling oils with a guarantee of a given asphaltum content. For this reason a test for asphaltum has been retained in some of the specifica- tions for road oils used on earth roads, although it would be generally better practice to eliminate this test from these specifications and to require only tests for gravity, viscosity, bitumen insoluble in naphtha, etc. It is to be noted that the word “asphaltum” as used in connection with road oils is generally misunderstood by the public. A 40% asphaltum oil is generally taken to mean that the oil contains 40% of a definite material called “asphaltum.” It is a very difficult matter to make the average township commissioner understand that the so-called “asphaltum’.’ in an oil is not a definite substance and that the pro- portion of residue or asphaltum obtained from an oil does not neces- sarily indicate the quality of this oil. FLASH AND BURNING POINTS. The purpose of these tests is mainly to determine the highest temperature at which an oil may be heated, without danger of burning. They serve also to indicate the presence or absence of the low-boiling oils. The tests may be performed either in one of the various types of closed testers or by the open cup method. The closed testers give more accurate results, but for practical work with road oils some form of open cup oil tester is generally used. A convenient form of open cup flash and burning point apparatus is shown in Figure 7. The cup “a” having a capacity of about 100 cc., contains the oil to be tested, while the other vessel “b” acts as an air jacket heated by means of a spirit lamp or a gas burner “c.” The thermometer “d” is placed so that the entire bulb is immersed in the oil, but that it does not touch the bottom or sides of the cup. In the determination of the flash point 22 the oil is heated so that its temperature will be raised at the rate of 5°C., per minute. A test flame is brought from time to time almost in contact with the surface of the oil. The most suitable test flame is a jet of gas from a piece of glass tubing drawn to a point with an open- ing about 1 mm. in diameter, the flow of the gas being regulated so as to give a flame between 5 and 10 mm. in length. The temperature at which the test flame will produce the first distinct flash over the entire surface of the oil is taken as the flash point of the oil. If the 23 temperature of the oil is raised further until the oil will ignite and burn when tested in the manner described above, the burning point of the oil is obtained. The metal cover “e” is used to extinguish the flame. It should be remembered that the closed types of oil tester give lower results in the determination of the flash and burning points than the open cup testers. As stated previously the open cup method is accurate enough for most practical work, and it is probable that the conditions under which the flash and burning point determinations are performed in the open cup tester are very similar to the working conditions in the field. The determination of flash and burning points should be made on all road oils which will require heating before application. These tests should be performed also on light oils which it is intended to apply cold, but which are likely to contain some hydrocarbons volatile at ordinary temperature, and might easily become accidentally ignited. TOTAL BITUMEN. The test consists in determining the per cent of organic matter in the oil which is soluble in chemically pure carbon disulphide at room temperature. The amount of oil taken for the determination will vary with the per cent of impurities, but with most road oils about 10 grams may be used. The oil is weighed in a 150 cc. Erlenmeyer flask and 50 cc. of carbon disulphide are added. The contents of the flask are now agitated and given a whirling motion until no more oil adheres to the bottom or sides of the flask. After letting the corked flask stand about 10 minutes, its contents are filtered through a Gooch crucible which contains a mat of coarse asbestos fiber and which has been ignited and weighed. The usual filtering arrangement is shown in Figure 8. The Gooch crucible “a” fits tightly in the rubber tubing “b” which makes also an air-tight connection with the funnel “c.” The stem of the funnel is fitted to the filtering flask “e” by means of the one hole rubber stopper “d.” At “f” is attached a section of pressure tubing which can be connected to a suction pump when desired. With most road oils the carbon disulphide solution can be filtered without difficulty and the suction is applied only to remove the greater part of the carbon disulphide remaining in the mat, after the contents of the Erlenmeyer flask have been transferred to the Gooch crucible and the flask and crucible washed several times with fresh carbon disulphide. Any material which tends to adhere to the bottom or sides of the Erlenmeyer flask should be removed to the Gooch crucible either by means of a policeman or by washing with carbon disulphide. After the filtration is completed the crucible is dried at 110°C., and weighed, and the quantity of material insoluble in carbon disulphide is calcu- lated. The crucible is then ignited, and the loss on ignition is taken as the weight of organic matter insoluble in carbon disulphide, and its per cent of the oil calculated. As some of the inorganic material in the oil is often carried through the mat by the carbon disulphide solu- tion, the per cent of inorganic material in the oil is not determined from the residue remaining on the Gooch crucible, but is obtained from a separate sample. It may be determined directly by igniting 1 gram of 24 the oil in a platinum crucible. When a fixed carbon determination is performed, the per cent of mineral matter is calculated from the amount of ash obtained. When the amount of carbonates in the ash is large, the percentage of mineral matter is obtained accurately by moistening the ash with a few drops of a solution of ammonium car- bonate, drying and igniting again at a low heat. The crucible is then cooled in a desiccator and weighed. One hundred minus the percent- ages of organic matter insoluble in carbon disulphide and of mineral 25 matter is taken as the per cent of total bitumen. The mineral matter and insoluble organic matter are generally reported separately. Most of the road oils show very small percentages of impurities, but as the results of a number of the tests are calculated in per cent of the total bitumen, the percentages of mineral matter and of organic matter insoluble in carbon disulphide are determined in all road oils. BITUMEN INSOLUBLE IN- PARAFFIN NAPHTHA. The purpose of this test is to separate from the oils some of the heavier hydrocarbons of an asphaltic nature. The test is based on the fact that these heavy asphaltic hydrocarbons, largely unsaturated com- pounds do not dissolve readily in light paraffin naphthas in which the remaining portion of the oil is soluble. These asphaltic hydrocarbons are less soluble in the light naphthas than in naphthas from asphaltic petroleums. Care should be taken, therefore, to secure a suitable naphtha for testing purposes and its nature and gravity should always be indicated in reports of tests. The solvent used for this determina- tion in most laboratories is a distillate from a paraffin petroleum pur- chased under the name of 86 degrees Beaume, paraffin naphtha. It distills between 35°C., and 75°C., and has a specific gravity at 15.5°C, of about 0.650. The method of determining the naphtha insoluble bitumen or so-called “asphaltenes” is practically the same as the method used in determining the inorganic matter insoluble in carbon disulphide, except that 86°B. paraffin naphtha is used as the solvent instead of carbon disulphide. About 10 grams of the light paraffin road oils may be taken for the test, but only about 2 grams of the heavy asphaltic oils should be used. In order that the very viscous road oils may be attacked readily by the naphtha, it is sometimes advisable to heat the oil slightly after it has been weighed in the Erlenmeyer flask, and let it cool in a thin layer at the bottom and around the lower half of the flask. The filtration is carried on in the same manner as with the carbon disulphide solution. It is not generally possible to transfer all the insoluble material to the crucible, and the Erlenmeyer flask is dried with the crucible at 110°C., and weighed. The total weight of the residues in the flask and in the crucible are calculated in per cent of the weight of oil taken. It is assumed that all the material insoluble in carbon disulphide is also insoluble in naphtha, and the difference in per cent between the material insoluble in carbon disulphide and in a given grade of naphtha is the bitumen insoluble in the naphtha. Thus if the oil shows 0.5% insoluble in carbon disulphide and 12.1% insol- uble in 86°B. paraffin naphtha, the bitumen insoluble in the naphtha would be 12.1 — 0.5 or 11.6 per cent of the oil. The bitumen insoluble in- the naphtha is not generally expressed in per cent of the oil, but in per cent of the total bitumen in the oil. Thus assuming that the oil con- sidered above shows 99.4% of total bitumen, the bitumen insoluble in 11.6 X 100 86 °B. paraffin naphtha would be the total bitumen. 99.4 or about 11.7 per cent of 26 The determination of the per cent of total bitumen insoluble in paraffin naphtha is of much value in determining the nature of road oils. It should be remembered, however, that the bitumen insoluble in naphtha does not represent any definite compound or any definite series of compounds, but merely indicates that the oil contains more or less heavy hydrocarbons of an asphaltic nature. The light paraffin road oils show generally less than one per cent of bitumen insoluble in 86°B. paraffin naphtha while the very viscous oils of an asphaltic nature may show as high as 15 to 20% of bitumen insoluble in the same grade of naphtha. FIXED CARBON. This test is based on the fact that when they are heated in a cov- ered platinum crucible in the full flame of a gas burner, asphaltic oils leave a greater amount of residual carbon than the corresponding paraffin oils. This fixed carbon is due mainly to the decomposition of the heavier asphaltic hydrocarbons and to a smaller extent to the decomposition of the heavy paraffins. The method of testing is derived from the method used in coal analysis, as described in the Journal of the American Chemical Society, 1899 Vol. 21, page 1116. The plati- num crucible used weighs about 25 gms. with the cover. For road oil testing the cover of the form of crucible generally used is made with a flange about 4 mm. wide, fitting tightly over the outside of the crucible. A sample of the oil within two milligrams of 1 gram is weighed into the crucible and the covered crucible is then heated for seven minutes over the full flame of a Bunsen burner as shown in Figure 9. The crucible is held in a platinum triangle supported by a tripod of suitable height. Care should be taken that the burner gives a satisfactory flame and that the determination is made in a place free from drafts. With road oils the outside of the crucible and upper side of the cover should burn clean without difficulty if the test is per- formed under proper conditions. After heating for the required length of time the crucible is placed in a desiccator to cool. It is then weighed, the cover is removed and the fixed carbon attached to the crucible and cover is ignited until nothing but ash remains. If necessary the ash is moistened with a few drops of a solution of ammonium carbonate as described under total bitumen. The crucible and cover are cooled and weighed, and the per cent of ash determined. The difference between the weights of the crucible with the fixed carbon and of the crucible with the ash is the weight of the fixed carbon. This weight is generally reported in per cent of the weight of oil, exclusive of the mineral matter. There has been much discussion as to the value of the fixed car- bon determination. It is contended that as the carbon obtained in this test is not present as such in the oil, it can not properly be called fixed carbon and that the determination is useless. The fixed carbon test for road oils gives valuable information, however, as to their nature, and to a certain extent corroborates the results obtained from the determination of the naphtha insoluble bitumen. If used with the understanding that the results obtained merely serve to indicate the 27 nature of the road oils, there can be no objections to this test except when it is used with oils which foam badly or which contain rather large quantities of impurities. In order to obtain uniform results it is necessary, however, to follow closely the method of testing described and to work under conditions as uniform as possible. The light paraffin road oils' show only a small per cent of fixed carbon, generally less than two per cent, while the corresponding asphaltic oils show a higher per cent of fixed carbon, the very viscous asphaltic oils showing as high as 15 per cent of fixed carbon. PARAFFIN SCALE. This determination is based on the property of the solid paraffins of being practically insoluble in a mixture of equal parts of alcohol and ether at low temperatures. In order that the paraffins may not be contaminated with the impurities in the oil and some of the heavier asphaltic hydrocarbons which are insoluble in the ether and alcohol mixture, the oil is generally distilled and the distillate taken for the paraffin determination. With light paraffin road oils, practically free of impurities it may not always be necessary to perform the distilla- tion, but the following method may be applied to all cases. One hundred grams of the oil are weighed in a 250 cc. iron or glass retort and distilled as rapidly as possible to dry coke. The distillate is received in a weighed Erlenmeyer flask, and when the distillation has been completed, the weight of the total distillate is determined. From 2 to 5 grams of the distillate which has been well mixed are weighed accurately in a 100 cc. Erlenmeyer flask and dissolved in 25 cc. of Squibb ether. Twenty-five cc. of absolute alcohol are then added and the flask is packed in a freezing mixture of 3 parts of finely chipped ice and 1 part of salt, and the oil mixture is maintained at a temperature of — 20°C. for 10 minutes. It is then filtered through the apparatus shown in Figure 10. This apparatus consists of a Gooch filter tube “a” with a long stem. The filter tube contains a layer of absorbent cotton “b” tightly packed and a layer of asbestos wool “c” covered with an asbestos mat. The filter tube is surrounded by the freezing mixture in the container “d” made from the upper half of an acid bottle. The tube “e” serves to remove bv means of suction the salt solution produced by the melting of the freezing mixture. As far as possible the filter tube should be kept loosely cov- ered and the freezing mixture container should be wrapped in towels, or provided with a jacket of felt and suitable cover. When the oil mixture and the apparatus of Figure 10 have been cooled to a suitable temperature, the oil mixture is transferred to the filter tube and filtered as quickly as possible bv means of suction. The Erlenmever flask and filter are then washed twice with 25 cc. of a mixture of 1 part of Scmibb ether and 1 part absolute alcohol, cooled to a temperature of — 20°C. The filter tube is then taken out of the anoaratus and is fitted over a suction flask in a way such that the stem of the filter tube will drain into a test tube or sample tube of suitable size. Warm 86°B. naphtha is then added to the filter tube and when the paraffin scale has dissolved, suction is applied. The filter is 28 washed twice with about 25 cc. of naphtha, and the test tube, or weighing tube, containing the naphtha and paraffin scale is removed and its contents transferred to a weighed platinum dish. Some paraffin scale may adhere to the Erlenmeyer flask in which the precipitation of the paraffin scale was made, and if necessary this flask is washed two or three times with small amounts of naphtha which are transferred to the platinum dish containing the naphtha and the paraffin scale. The naphtha is then evaporated off on the steam bath and the platinum dish and paraffin scale are brought to constant weight by heating for a few 29 minutes in an oven at 110°C. The weight of paraffin scale divided by the weight of distillate taken and multiplied by the per cent of total distillate in the oil gives the per Cent of paraffin scale in the oil. Even when performed under the best conditions, the determina- tion of the paraffin scale is not accurate, due largely to the fact that some decomposition takes place during the distillation of the oil. Furthermore, the liquid paraffins are probably just as injurious to the binding qualities of road oils as the solid paraffins, and the determina- tion of the solid paraffins appears to be, therefore, of small value, and is generally omitted. MISCELLANEOUS TESTS. Road oils are sometimes submitted also to the following tests: Distillation, bitumen removed by sulphuric acid, bitumen insoluble in carbon tetrachloride and in various other solvents. While some of these tests may give at times valuable information, they are not generally applied to road oils, and the methods used have not been described in this publication. Descriptions of these tests together with discussions of some of the special topics which have been taken up in this bulletin, may be found in some of the publications listed below. REFERENCES. Prof. Dr. D. Holde. The Examination of Hydrocarbon Oils, 1915. John Wiley & Sons, New York. F. W. Clarke. The Data of Geochemistry, 1916. Bulletin 616, United States Geological Survey, Department of the Interior, Washington, D. C. L. Ubbelohde. Handbuch der Chemie, Analyse und Technologie der Oele und Fette, 1908. S. Hirzel, Leipzig, Germany. Clifford Richardson. The Modern Asphalt Pavement, 1914. John Wiley & Sons, New York. Prevost Hubbard. Dust Preventives & Road Binders, 1910. John Wiley & Sons, New York. Prevost Hubbard. Laboratory Manual of Bituminous Materials, 1916. John Wiley & Sons, New York. Prevost Hubbard and Charles S. Reeve. Methods for the Examination of Bituminous Road Materials, 1915. Bulletin No. 314, United States Department of Agriculture, Washington, D. C. American Society for Testing Materials, Year Book, 1915. Published by the Society, Secretary-Treasurer, University of Pennsylvania, Philadelphia, Pennsylvania. American Society for Testing Materials, A. S. T. M. Standards, 1916. Pub- lished by the Society, Secretary-Treasurer, University of Pennsylvania, Philadelphia, Pennsylvania. N