JULY 15, 1940
I
43
ANALYTICAL EDITION
I
I
63
83 GRAPIS
I /03 PRESSURE
I
/23
I e3
OF PRESSVRE ON ABRASIOS Loss FIGURE 2 . EFFECT
of Mines built a similar machine in order to continue the investigation. Describing this n-ork, Sheppard anti Dasher wrote ( 9 ) : After Fonie use, t,wo other possibilities of the machine were realized: (1) the specimen holder’s radius arms could be pivoted so that the tangential reaction force between the specimen and sample could be measured; and (2) a roller could be substituted for the sled and the grindability of coal measured. The combination of the two possibilities resulted in the development of that which, to our knowledge, is the only machine capable of direct measurement of the net power required to grind coal or other material. Abrasiveness testing mas discontinued and development of the new grindability method begun.
Conclusions After numerous changes in design, the present machine under standard test conditions is apparently not easily affected by any operation or manipulation conditions except variations in the abrasive characteristic of the material being tested. An essential part of the design i s the elimination of vibration b y separating the drive motor from the machine and using a light rubber belt drive. Other essentials are: removable test pan, cutting tool for producing a true wax surface, accurately precisioned specimen holders, method of holding specimens, proportions of specimen holders, dimensions and
423
preparation of specimens, method of preparing wax surface, sample spreader, revolut,ion counter, and all-rustless material. Antimony and silver test specimens mere decided upon for dentifrice testing. The sample slurry consistency is determined by a simple absorption test, and the machine’s test results are not affected by thinner or thicker slurry. Although the machine was developed primarily for simple research and control tests on precipitated calcium carbonate, it also works satisfactorily on dental powders and creams. It is sensitive to minute quanitites of very hard pulverized abrasives (silica anti emery) when mixed in a standard lowabrasive Carbonate sample. Variations in don-nward pressure on specimens cause only mild changes in test results, maximum loss occurring with 83 grams’ pressure. This machine suggested an idea which was developed by the U.S. Bureau of Mines into a grindability machine for coal and other materials.
Literature Cited (1) Am. Dental Assoc., “Accepted Dental Remedies”, pp. 88, 108, 1937. (2) Bierbaum, C. H . , “ A Study of Bearing Metals”, Am. Inst. Mining Met. Engrs., Bull. 1216-N1-16 (E’eb., 1923). (3) Bierbaum, C. H., Capp, J . A., and Diedcrichs, H., Am. SOC. Mech. Engrs., Progress Report, pp. 3-15 (Dec. 7-10, 1920). (4) Brady, E. P., paper read before North St. Louis Dental Society, Jan. 27, 1937. and Du Four, E. B., Hygeia., 15,315-16,398-401, (5) Gordon, S.M., 714-16 (1937). (6) Hodge, H. C., J . Dental Research, 15, No. 5 , 271-9 (Sept., 1936). (7) Hodge, H. C., and McKay, J. H., Ibid., 16, No. 5, 453-61 (October, 1937). (8) Ray, K. W., and Chaden, H. C.. Dental Cosmos, 75, 1070 (Nov., 1933). (9) Sheppard, IT. A , , and Dasher, John, U. S Bur. Mines, typewritten report, 1939. (10) Smith, M ,L., ISD.ENG.CHEM.,Anal. Ed., 11, 155-8 (1939). Chem. Ind., 54, 269-75T (1935). (11) Smith, M. L., J . SOC. (12) Souder, W. C., and Schoonover, I. C., J . Am. Dental Assoc., 24, NO. 11, 1817-21 (Nov., 1937). (13) Wright, I€. N., and Fenske, E. L., I b i d . , 24, No. 11, 1889-95 (Nov., 1937).
An Asphalt Gloss- and Stain Meter .A. P. ANDERSON
4ND
T. E. REAhIEH, Shell Development Company, Emeryville, Calif.
A photoelectric device is described that permits a quantitative determination of the gloss of asphaltic bitumen. A procedure for determining quantitatively the degree to which asphalts stain absorbent materials is outlined.
T
HE gloss of an asphalt and its tendency to stain surrounding absorbent material are two properties which have hitherto been evaluated by visual observation and consequently hare been subject to the interpretation of the individual observer. A dull surface may be an indication of the presence of excessive wax, which often results in lowered ductility, decreased weathering stability, and poor adhesive properties. The tendency of asphalt, particularly roofing asphalt, to stain surrounding material is detrimental to the appearance of the finished roof
Apparatus An instrument of the type designed for use on hard surfaces, such as paints and varnishes, has been modified for use with plastic asphaltic bitumen. A general view of the instrument
with auxiliary equipment is shon-n in Figure 1, and a schematic cross section in Figure 2. The unmodified instrument was purchased from the Research and Development Company, S e w York, N. Y.
Gloss Measurement The structure, size, and rate of formation of wax crystals in an asphalt, which influence the degree of light reflection, are controlled as far as possible by the treatment of the sample previous to gloss measurement. The asphalt is heated to at least 60” c‘. (140’ F.) and poured into shallow trays which are placed in an air thermostat at 26” C. (77” F.). A sealed container immersed in a water bath is also convenient for this purpose. iifter 24 hours, the tray is laid upon a flat surface under the glossmeter and the legs are adjusted for height until the deflection of the microammeter is at the maximum. In the case of the asphalt whose gloss is chosen as the standard (a 40-50 penetration Mexican as,phalt), the deflection is adjusted to correspond to 100 scale divisions. Hence, the greatest deflection produced by the sample under test mill indicate the percentage gloss. An example of an application of the glossmeter is given in Table I, in which are listed the properties of a number of fract,ionated cuts from a residue. When the gloss evaluations by visual inspection are compared with those obtained with the glossmeter, the glossmeter values may vary from 107 to
VOL. 12, NO.7
INDUSTRIAL .4ND ENGINEERING CHEhIISTRY
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POLISHED
BLACK P L A T E 7
/
T A B L E 111. VIsU.AL, SCHTVEYER A S D HOWELL, AND IKSTRUMEST EVALUATIOS O F STAIS FOR BLOTWASPHALTS
Asphalt Sample
Visual Stain Estimation
Stain-IIeter Schneyer and Values Howell Method
70 A B
C D
. WATER BATH-’
- -
/CONSTAG VOLTAGE
GLOSS AND
TRANSFORMER
STAiN METER’
VIEW FIGURE 1. GENERAL
OF
METERWITH ACCESSORIES
TABLE I. COMPARISON OF GLOSSMETER MEASUREMEKTS WITH VISUAL CLASSIFICATION AND WAXCONTENT ON FRACTIONS FROM RESIDUE A Saybolt Furol
CFt ho.
Penetration a t 25” C. (77O F.)
Softening Point (Ring and Ball)
C.
TABLE 11.
Cut
KO.
Untreated Stock Gloss measureVisual ment appearance
2 3
4 5
6
7 8
91 84
79 77 67 66 62 57
a t QS.Qo C. Holde (210° F.) Wax (1)
Measurements
Wt. %
F.
SURFACE GLOSS AS AX INDICATION O F OF PROCESSIXG
70 1
Gloss
Viscosity
First Processing Gloss T‘isual measurement appearance
% Hazy Hazy Dull Dull Dull Dull Dull Dull
103 101 90 84 80 74 72
67
Visual Appearance
%
EFFECTIVENESS Second Processing Gloss Visual measurement appearance
Very slight stain Slight stain Definite stain Dark stain
73
1 2
61
50 B5
:i J
the instrument described herein directly on the paper with the photoelectric cell in the top position, one can read the degree of staining in terms of the amount of light diffused from the sample, the standard (no stain, 100 per cent reading) being obtained by adjusting the instrument so that a deflection of 100 scale divisions results when an unused Whatman No. 5 filter paper is placed on a glossy black surface.
A comparison of visual and instrument evaluation of the staining characteristics of several blown asphalts from various sources is given in Table 111. The visual method is, of course, subjective, and liable to personal errors of estimation which are eliminated in the quantitative instrument method. The staining characteristics of asphalt may also be evaluated by the method of Schweyer and Howell ( 2 ) which depends upon the number of sheets of cigaret paper discolored when in contact with the asphalt sample. The results of this method and the instrument evaluation method on the same asphalts are also compared in Table 111. The values obtained by the Schweyer and Howell method are to some extent quantitative but do not give the range of values, and consequently the degree of accuracy, given by the proposed stain meter method. Moreover, variations in the quality of the cigaret paper affect the reproducibility of the test.
% Bright Bright Hazy Hazy Dull Dull Dull Dull
89 per cent, yet the asphalts appear “bright” to the eve. I n the range from 85 to 81 Der cent the gloss is rapidly lost; below 84 per cknt the only subjective term available is “dull”. The use of the glossmeter in gaging the effectiveness of a particular type of processing to remove wax is indicated in Table 11. The effect of the treatment is clearly shown in the improvement in gloss.
111 111 101 88
85 78 77
Bright Bright Bright Hazy Hazy Dull Dull
TO 8 VOLT SOURCE I
Literature Cited (1) Holde, D., “Untersuchung der Xohlenwasserstoffole und Fette”, p. 45, Berlin, Julius Springer, 1913. (2) Schweyer, H. E., and Howell, H. C., IND.ENG. CHEM.,Anal. Ed., 9, 563 (1937).
POSITION OF PHOTOELECTRIC CELL
LEADS TO
Stain Measurement In one test used by the roofing industry to determine the tendency of an asphalt to stain absorbent materials the asphalt is placed in the lid of an 0.089-liter (3-ounce) seamless can and covered with a Whatman No. 5 filter paper, cut to fit the lid, and weighted with a 5-gram iron washer. Heretofore the extent to which the asphalt st,ains the filter paper after contact with it for 32 hours at 79.4’ C. (175” F.) has been estimated by visual observation. By placing
TRAY OFASPHALT FOR GLOSS MEASUREMENTS
1 1
LENSES
LABOUT I MM.
FIGURE 2. DIAGRAM OF METER
CLEARANCE
