INDUSTRIAL AND ENGIiVEERING CHEMISTRY
302
Samples for test were placed under 30 mm. or less pressure for 24 hours a t 140" to 150" F. (60" to 65.6" C.) and cooled a t room temperature in the same vacuum. The characteristic whiteness of refined wax disappears with this treatment. Airfree samples are of a blue-gray color and somewhat translucent. After this treatment carefully cut samples were weighed on the Nicholson in air at 60" F. (15.56" C.), then placed in the lower pan and weighed in water a t the same temperature. Results
Table I shows specific gravities a t 60" F. of several semirefined waxes. The last sample is from a tar still stock. The next to the last column gives the specific gravity a t 130" F. The last column gives the value at 60" F., which would be ordinarily determined from the apparent specific gravity a t 130" F. and the usual petroleum conversion table.5 Table I-Specific ~
Gravity of Semirefined Waxes
NICHOLSON A T 60 F.
AT 60" F6 130
SPINDLE
HYDROM-F.
MELTING POINT
AND P E TROLEUM CONVER-
F,
Average
Checks
SION
TABLE
I
a
F.
O
103
c.
39.4
109 42.8 115.1 4 6 . 2 1 1 8 . 5 48 123.2 50.7 127.2 52.9
l
I 0.8799 0.8797 0.8805 0.8804 O.SS$0.8844 0.8955 0.8973 0.9057 0.9048 0.9045 0.9056 0.907 0.9067 0,925 0.915
I
0.0008 0.8801
0.778
0.8053
0 , 0 0 0 4 0.8842 0.0018 0.8964 0.0011 0.9053
0.777 0.780
0,8044 0.8072
0.0003 0.01
0,784
0.811
0.9068 0,920
0.782
...
0.8091
...
I n an attempt to determine where the break comes in the expansion coefficient, the specific gravities of several waxes 6
Bur. Standards, Circ. 07.
VOl. 19, Yo. 2
were taken with the Kicholson every 10" F. (5.56" C . ) from 60" to 110" F. (15.56"to 43.3" C.) and every 5" F. (2.8" C.) from 110" to 130" F. (43.3" to 54.4" C.), compared with water at 60" F. Table 11-Specific Gravity of Three Paraffin Waxes from 60° to 130° F. Melting Point
TEJIPERATVRE
F. 60 70 80 90 100 110 115 120 125 130
0
118.5' F. (48' C . )
123.2' F. (50.7' C.)
127.2' F. (52.9" C . )
0.906 0.899 0.885 0.882 0.874 0.858 0.841 0,801 0.802 0.780
0.907 0.903 0.890
0.920 0.913 0.905 0.893
c.
15.56 21.1 26.7 32.2 37.8 43.3 46.1 48.9 :1.7 a4.4
0,887
0.868 0.856 0.830 0.802 0.801
0.785
0.878 0.876 0,870
0.848 0.818 0.803
The results, shown in Table 11, are the average of two or three determinations, none varying more than 0.005. Probably the complex nature of the material had something to do with the slight discrepancies. This is shown better graphically in Figure 1. The 118.5" F. (48" C.) melting point sample is representative of wax made from neutral wax distillate; the 127.2" F. (52.9" C.) melting point sample from tar wax distillate. I n the 118.5" F. (48" C.) wax there is a break between the 100" F. (37.8" C.) and 120" F. (48.9" C.) where probably most of the hydrocarbons composing this sample melt. The significance of the flat spot between 120" F. (48.9" C.) and 130" F. has not been determined. It occurred in every wax of this nature examined. There is a flat spot 20" to 30" F. (11.1" to 16.7" C.) below the melting point on each wax, which of course is not accounted for. Incidentally, the Nicholson, checked on one was a t 130" F. with an ordinary spindle hydrometer and with a pycnometer, gave the same figure within a reasonable error.
Effect of Moisture on Electrical Properties of Insulating Waxes, Resins, and Bitumens' By James A. Lee and Homer H. Lowry BELLTELZPXONB LABORATORIES, INC.. NEW YORP,N. Y.
T
HAT most materials absorb water from an atmosphere containing water vapor has been generally recognized for many years. Further, the occasional lack of agreement between the results of electrical measurements on insulating materials made by different investigators, as well as the wide range of electrical values sometimes assigned to a given material by any one investigator, has been attributed to an undetermined effect of the water content of the material. However, there are few records of systematic efforts to relate the electrical properties of insulating materials definitely to their water content. Evershed2 has published an elaborate investigation of the effect of moisture on the volume resistivity of very porous materials, such as paper and cloth. Similarly, A. Schwaiger3 studied the rate of decrease of insulation resistance of unimpregnated paper when exposed to high humidity. cur ti^,^ in a comprehensive study of the "Insulating Properties of Solid Dielectrics," includes a brief account of the effect on volume resistivity of drying a number of materials, including f
Received September 21, 1926.
* J . Inst. Elec. Eng. (London), 2,
51 (1914). :Arch. Elektrofech.,3, 332 (1915). 4 Bur. Standards, Bull. 11, 359 (1914-1915).
.
Bakelite, marble, slate, shellac, and several molding compounds. More recently, Kujirai and collaborators5 have published work on the effect of humidity on the insulation resistances of fibrous materials. showing that the change in resistance could be quantitatively related to change in humidity. It may be observed that the investigations cited above have been very largely limited to fibrous materials. I n order to obtain similar information about the various waxes. resins, and bitumens which are used for insulating purposes. the work reported in this paper was undertaken. The scope of the work was broadened, however, so as to include not only a study of the relation of insulation resistance, or volume resistivity, to the moisture content of the materials, but also to include a similar relation for the dielectric constant and the effective conductivity a t 1000 cycles. A list of the materials studied is given in Table I, together with their grade, source, and physical constants. Attention has been directed to a comparison of the insulating properties of a large variety of materials when initially free from moisture and at intervals after immersion in 3.5 per cent sodium chloride solution, which is equivalent to exposiire to 9 s per cent relative humidity, except for the Sci. Papers Inst. Phys. Chem. Research ( T o k y o ) , 1, 79 (1923).
February, 1927
IA$’DUSTRIdL A N D ENGINEERING CHEMISTRY
effect due to porosity and possible solvent action of the water on impurities in the materials. For a preliminary study, this method offers the advantage of easy duplication and ready control of conditions for the different waxes, since close temperature regulation and good circulation are relatively unimportant factors as compared to actual exposure to correspondingly high humidities. It is felt that the results obtained in this way may have their greatest value in providing data for an intelligent selection of these materials for purposes of insulation in electrical apparatus! particularly that type which may be subjected to high humidities. Preparation of Materials
303
and hot pressed. Spermaceti was cold pressed in the steel mold, but in this caselonly a small amount of pressure was necessary. Before pressing onion-skin paper was placed on both sides of the disks to prevent sticking to the mold and the paper was easily removed without harming the specimen. Methods of Determining Electrical Properties
Capacitance and conductance measurements were made a t 1000 cycles per second on a shielded bridge of the type described by G. A. CampbelL6 Those samples which had been machined were measured between a 9 X 14 inch tool maker’s surface plate and a brass electrode 3 inches in diameter, while mercury electrodes were used for others. The mercury upon which the sample floated served as the lower electrode Preliminary tests showed that disks 3.5 inches in diameter and a brass ring filled with mercury was used as the upper and 50 mils thick were of suitable dimensions so that the electrode. Precautions were taken to eliminate entrapped measured values of their electrical properties would be air between the mercury and the surfaces of the sample. No guard ring was used in makwithin the range of the existing the A-C measurements, ing measuring a p p a r a t u s the error caused by fringand yet be thick enough Measurements of dielectric constant and effective coning of the electrostatic field that the very fragile speciductivity at 1000 cycles, and resistivity have been m a d e over the edge of the sample mens could be handled with on thirty-one waxes, resins, a n d bitumens. These being corrected for by the safety. Several m e t h o d s materials include n o t only naturally occurring products method described by Hoch.? had to be used in the prepab u t commercial dielectrics and mixtures. The measI n s u l ation resistance r a t i o n of the disks since urements are given for the initial thoroughly dry measurements were made the mechanical properties of condition, after six months’ immersion in a salt solubetween the same types of the materials varied over a tion corresponding qualitatively to exposure to 98 per electrodes used in the case wide range. cent relative humidity, a n d after having been redried. of the A-C measurements All the insulating materials studied absorbed water ~\IETHOD I-The method but with the use of suitable under the conditions of experiment. The absorption found suitable for the prepaguard rings. Measurements ration of the disks from matewas least with the hydrocarbons and greatest with were made by the direct derials 1 to 21, inclusive, was to shellac and bayberry wax. melt and pour them into a flection method, a well inIn general, the greatest increase in capacity and conbrass mold which consisted of sulated battery of 350 volts ductivity a n d the greatest decrease in resistivity were a lower flat plate about 5 being placed in series with inches square and an upper shown by t h e materials which absorbed t h e most water. a resistance of a megohm, flat plate about 5 inches The percentage change was m u c h greater in t h e consquare and approximately 90 the sample under test and ductivity a n d resistivity than i n the dielectric constant, mils thick, from the center of the galvanometer. A high as was to be expected. which was cut a circle 3.5 s e n s i t i v i t y L e e d s and inches in diameter. In some Northrup galvanometer was cases it was necessary to free the molded disks from enused having a current sensitrapped air. This was done by use of vacuum or by flashing tivity of 7.8 X amperes per millimeter, with a scale the surface with a flame. These molded disks were turned down distance of 2 meters, so that resistances up to 4.5 X 1013 to approximately 50 mils on a machine specially designed for surohms could be measured. facing wax disks. The thickness of each sample was taken as the average Each variety of wax required slightly different treatment in molding to avoid warping and cracking and to allow removal of a t least six micrometer readings at different locations. from the mold. Carnauba had to be cooled very slowly. This material caused more trouble than any other because of the Using these thickness values the dielectric constant, the tendency to warp and crack. The mold was warmed in an oven effective A-C conductivity, and the volume resistivity were to within a few degrees of the melting point of the wax, which obtained by calculation from the capacitance, conductance, was then poured into the mold a& the whole allowed to cool and insulation resistance values, and are given in Tables 11, over a period of 3 to 4 hours. Slower cooling caused crystalliza- 111, and IV. I n general. each value represents the average of tion in the specimens. In order to easily remove the disks of montan pitch from the determinations made on four different samples. I n some mold and to prevent the decomposition of the stearates, these cases, as a result of breakage and warping, the values are materials could not be heated with a higher temperature than averages of less than four samples. necessary to pour smoothly into the mold. When molding materials 10, 11, 12, 13, and 17, the bottoms of the molds were Table I cooled under the water faucet, as soon as the wax was plastic, I-Candeldla W a x . Innes Speiden Co. Melting point (capillary to prevent sticking. On the other hand, in order to remove materials 8, 14, 15, and 16, the bottoms of the molds were care- tube method), 65O C . ; specific gravity, 0.972; saponification value, 56.0, acid value, 16.0. fully heated over a flame after the wax had hardened, 2-Cavnauba W a z . (No. 2 North Country) Innes Speidrn Co. ~IETHO IT-Specimens D made from materials 22 to 27, inclusive, were molded as in Method I to approximately 50 mils in thick- Congealing point, 78’ C . ; saponification value, 50.4; acid value, 2.8; ioness. This was necessary since the first three were too sticky dine value. 12.7; ash content, 0.27 per c e n t ; insoluble in carbon tetrachloride, 0.36 per cent. and the last three too brittle to be reduced in thickness. 8-ikfonlUn Pi!ch. (Crude) Elbert & Co. Saponification value. METHOD 111-Neither of these methods was adapted to make disks of the remaining materials, since materials 23, 30, and 31 6 ; acid value, 3 ; ester number, 3; soluble in ether, 15 per cent; ash, 1.7 per cent. tend to form very large crystals with air spaces between them, 4-Montan W a x . (Crude) Innes Speiden Co. Melting point, and shellac cannot be heated to the melting point without decomposition. Stearic acid and halowax were made into disks 80-82’ C.; specific gravity, 1.0; saponification value, 58; acid value, 2 5 ; of about 60 mils in thickness in the usual manner of pouring ester number, 33; soluble in ether, 15 per cent; insoluble in benzene, 0.3 melted wax into the molds at room temperature. After cooling per cent; ash, 0.5 per cent. the disks were removed and placed in a steel mold of the same diameter, and hydrostatic pressure was applied. I n the case of 6 Eke. w d d , 43, 647 (1904). orange shellac the material was ground and put into a steel mold ’ Bell System Tech. J . , 1, 110 (19221.
304
INDUSTRIAL AND ENGINEERING CHEMISTRY
5-Jafian Wax. A. Klipstein Co. Melting point (capillary tube method), 50' C . ; specific gravity, 0.984; saponification value, 229; iodine value, 11.6. 6-Chinese Wax. Lehn & Fink. Melting point, 65' C. (drip-point method); saponification value, 92.9; acid value, 13.0: iodine value, 15.2. 7-Baybevry Wax. Supplier unknown. Melting point, 60' C. (drip-point method) ; saponification value, 206.5; acid value, 21.0; iodine value, 1.6. 8-Beeswax. (Crude) Klipstein & Co. Specific gravity at 25' C., 0.976; saponification value, 93.5; acid value, 20.3; ester value, 75.7; ester ratio, 3.8. 9-Ozokerite. (Black) Innes Speiden Co. Melting point, 79.5O C. (drip-point method) ; saponification value, 0; acid value, 0 ; iodine value, 7.8; odor of kerosene present. 10-Ceuesin. (Yellow) Innes Speiden Co. Congealing point, 7073O C . ; specific gravity at 23' C., 0.883; Saponification value 290 60-120 > 290 >290
>110 0.3-4 75-160 >270-0.40-0.10 0.03-0.16 0.0005& 0.8-1.1
6-7
1-2 2-5 5-12 30-40 > 290 >290 >290 >460 >610 >490
7-4
400-5 600 150 18 > 560 2.6 0.00031
140- > 290 20-27
Paraffin-beeswax Paraffin-rosin-rosin oil-carnauba > 450 18 Paraffin-rosin-hydrated lime >910 640 19 Zinc stearate 20 Aluminum stearate 400- >900 21 Blown gilsonite and residual petroleum oil > 290 22 Cumar resin > 300 23 Rosin 5.50 ~. 24 Manila copal >410 25 Stearin pitch 14-18 26 Soft blown petroleum asphalt 50-72 27 Soft blown petroleum asphaltrosin-rosin oil 14-18 28 Spermaceti wax 3-4 29 Shellac > 360 4-9 30 Halowax 31 Stearic acid 3-7
< O.OOO31 8-10
100- > 500 > 740 0.000:1 4-12 50-95
640 300-700 720 6,6-7.0 40-52
7.9 0 ,00059-0.00031 < 0.00031 0.4 < 0.00031
-
T a b l e V-Physical SO.
1 2 3 4 5 6
7
8 9 10 lln l i- b .
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
>630 270 > 1200 >610 21 1-2 0.96 7-8
36-20 > 900 > 900 >660
> 1000 > 1000 60-90
130-1 50 31-33
> ,500 > 900 > 1000 > 560
> 1000 > 800 39 1000
26-33 9-15
> 1000
0.1-0.7 1-6
After drying over calcium chloride. After 6-months’ immersion in 3.5 per cent sodium chloride solution. c After redrying. b
With the exception of the bayberry and spermaceti wax and shellac, the change in dielectric constant on immersion in water of the naturally occurring waxes, resins, and bitumens is not very great and quite generally those showing the largest change have absorbed the most moisture, as shown in Table Y. I t should be noted that the above three exceptions Kahlenburg and Anthony, J . chim. p h y s . , 4, 359 (1906).
MATERIAL
Candelilla wax Carnauba wax Montan pitch Montan wax Japan wax Chinese wax Bayberry wax Beeswax Ozokerite Ceresin Paraffin PaFaffin - ..“Superla wax” “Xaudella wax” Zinsser’s insulating wax Zinsser’s insulating wax-beeswax Paraffin-beeswax Paraffin-rosin-rosin oil-carnauba Paraffin-rosin-hydrated lime Zinc stearate Aluminum stearate Blown gilsonite and residual petroleum oil Cumar resin Rosin Manila copal Stearin pitch Soft blown netroleurn asohalt Soft blown’petroleum aiphalt-rosinrosin oil Spermaceti wax Shellac Halowax Stearic acid
Changes
FINAL DIFFERENCE HnO IK IYITIAL A N D COXTENT FINAL WEIGHTS Peu cent 0.13-0.20 0.72-0.90 0.09-0.11 0.62-0.87 0.26-0.58 0.75-1.16 6.1 0.42-0.43 0.85-1.20 0,04-0.05 0 04-0.06 oa-0.11
Per cent 0.00 0.00 0.22- +0 .27 -0.02 -1.02--1.4
+
0.50 1.72-2 21 1 . 5 -2.4 0.11-0.54 0.32-0.33 0.17 3.0 2.7
-0.59--0.81 -0.50 -0.13--0.20 - 1 . 0 --1.3 0.00--0.05 -0.43--0.66 - 0 ..6 6.- - 0 . 7 1 -0.02 +O.l5 -0.030.00 -1.4 2.4 -0.18--0.31 -0.42--0.48 +0.50 +0.45 io.20
3.3 0.41 0.46 0.41-0.60 1.23-1.40 0.47-0.52
+ O . 63 0.00 -0.28 0.00 +0.30-+0.48 -0.020.00
0.44-0.56 1.27-2.11 4 . 3 -5.1 0.20-0.28 3 . 2 -4.0
-0.05-
n
0.60-0.oa
-
-0.04-
-1.9
-0.2
0.00 -0.37 0.00 -0.15 --0.4
-
FINALC
a
8
all absorb relatively very large amounts of water. Halowax which is free from physical imperfections behaves much like these natural waxes. “Blown gilsonite fluxed with residual petroleum oil” is peculiar in its behavior, since in spite of a large absorption of water the increase in dielectric constant is less than 20 per cent. This is also true to a lesser extent in the case of montan wax. Stearic acid and the stearates absorb relatively large quantities of water and also increase in dielectric constant more than most of the natural waxes.
28 29 30 31
T a b l e IV-Volume Resistivity (Unit = 1018 ohms c m )
305
I n general it is not possible to explain satisfactorily the differences between the initial and final values of the dielectric constants. As mentioned previously, the explanation in the case of “Zinsser’s insulating wax” was obvious. I n certain cases the difference is quite probably due to extraction of water-soluble matter, as indicated in Table V. Other possible causes include evaporation of volatile constituents, such as kerosene which is generally present in small amounts in ozokerite and ceresin, oxidation or hydrolysis as is indicated in Table V for the stearates, “Naudella wax,” montan pitch, “blown gilsonite fluxed with residual petroleum oil,” etc., which gave a final weight greater than the initial weight. While the effective A-C conductivity of the waxes, resins, and bitumens covers a wider range of values than does the dielectric constant, in general there is good correlation between high dielectric constant and high A-C conductivity as is t o be expected. The wider range of conductivity values is to be attributed to the larger influence of small amounts of “impurities” on the conductivity than on the dielectric constant as previously shown by Granier.g With this fact in mind, a direct comparison of the changes in dielectric constant and effective A-C conductivity may be made The data in Table IV show that, with very few exceptions, the initial resistivity of all these materials is very high, many being too high to obtain more than a lower limit. The fact that this limit is different with different materials is due to the circumstances that the measurements were not all made a t the same time or with the same galvanometer, and to certain small variations in thickness of the various samples. The changes in resistivity of the materials studied parallel those in the dielectric constant and conductivity, though naturally in this case the changes are decreases in resistivity. J. phys., [61 6, 51 (1924).
I-VDUSTRIAL A S D ENGINEERING CHEMISTRY
306
Attention should be called t o the considerable amount of water absorbed by some of the waxes. Even the hydrocarbons, paraffin, ceresin, and “Superla” wax, absorb measurable amounts, while certain of the natural waxes which contain fatty acids and esters, which as a rule have a greater affinity for water, absorb from 0.5 to 6.0 per cent. Shellac,
VOl. 19,
XO.
2
which is widely used as an insulating material in electrical apparatus, absorbs 4.3 to 5.1 per cent of water under the conditions of these experiments and loses its insulating properties to a greater extent than any of the other naturally occurring waxes, resins, or bitumens which have been tested.
Oxidation and Hydrolysis of Light Wood Oil’.’ By P. 0. Powers with A. Lowy and W. A. Hamor UNIVERSITY OF PITTSBURGH, PITTSBURGH, PA.
A n investigation has been made of the methods for and the method of distillation, IGHT wood oil is obconverting light wood oil, a by-product in the disbut also to the method of tained from three printillation of hardwood, into possibly useful products. storage before shipment of cipal sources in the inSamples of the oils from various plants have been exthe sample. dustrial distillation of hardamined and the effects of treatment with oxidizing The low-boiling fractiors wood: (1) the distillate on agents and alkalies have been studied. Among the distilled over slightly colored. steaming the settled tar, (2) oxidizing agents tried, nitric acid has been found to The odor of the first 10 per the refined pyroligneous acid give the best results, and research attention has been cent of the distillate was pleasin the copper stills, and (3) accorded to effect of conditions on the yield of organic ant, but thencefrom it became the weak methanol distillate acids. Of the alkalies, lime has been shown to afford strong and pungent. The from the lime lee still. The satisfactory results and these products have been exfractions on distillation oils from these sources are amined. Hydrolysis gave the best results and a method ranged from pale yellow to s o m e t i m e s separated but for the treatment of the oil by this method has been deep red and darkened to more often collected together. devisedd e e p b r o w n o n standing. The oil is usually a-darkS o m e f r a c t i o n s darkened c o 1o r e d , flammable liquid with an exceedingly disagreeable odor. Its vapors irritate much more readily than others, but in general the higher the eyes and throat. Practically all the wood oil produced boiling fractions were much more deeply colored. The wood oil possessed a sharp characteristic odor, which is consumed as fuel, although the higher fractions have found some uses. For this reason the work of the authors was was especially evident in the fraction from 65” to 150’ C. confined to the fractions boiling below 195” C. A large num- The vapors had a lachrymatory action. Neither nitrogen. sulfur, nor halogen was found in the ber of various types of organic compounds have been isolated oil when elementary tests were applied. Group tests showed from certain wood oils and tars.3 the presence of aldehydes, ketones, esters, acids, furfurDistillation aldehyde, phenols, and unsaturated compounds. Samples of light wood oil were obtained from wooddistilling plants a t Smethport, Betula, and Seargent in Pennsylvania, and Wells, Michigan. Most of the investigational work was done with the sample from Betula. An estimate of the wood used a t this plant showed the following distribution as to varieties: maple, 55 per cent; beech, 35 per cent; birch, 5 per cent; ash, 3 per cent; and oak, 2 per cent. Samples of the oils were distilled from a 3-liter flask through a Clark and Rahr’s column. The following fractions were obtained:
L
FRACTIONSSMETHPORT BETULA SEARGENT WELLS
c.
Per cent
70
2.0 33.2
Residue
33.6
O
-
- 160 - 195
66.4
P w cent 22.3 52.6 74.9 25.1
P e r cent 1.0 57.0 77.0 23.0
Per cent 14.5 47.0 65.0 35.0 PERCENTAGE
Distillation curves for such oils are given in Figure 1. It will be noticed that the boiling range of these oils varied considerably. .This was due not only to the wood used 1
Received September 29, 1926.
* The research described in this paper was carried out while Dr. Powers was the junior incumbent of the Multiple Industrial Fellowship sustained in Mellon Institute by the National Wood Chemical Association (1923-51, to which organization the authors are grateful for this support and also for the release of the work for publication. The present contribution is an abstract of a thesis presented by Dr. Powers t o the Graduate School of the University of Pittsburgh in partial fulfilment of the requirements for the degree of Ph.D. * Bunbury, “The Destructive Distillation of Wood,” p. 106 (1923).
Figure I-Boiling
DISTILLED
Range of Light Wood 011
Oxidation of the Oil
Preliminary experimentation showed that wood oil gave a good yield of organic acids when treated with oxidizing agents. After several experiments with chlorine, bromine, bleaching powder, and chromic and nitric acids, it was found that nitric acid gave the best results. The oxidation with nitric acid was then investigated in more detail. METHOD-The fraction to 195’ c. of the Betula oil was used in all this work. Seventy per cent nitric acid was diluted with water
