712
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
0 second reading would have been about 60, corresponding to a hardness of 720,000,000 (7.2 X lo8) dynes per cc., or (dividing by 27,500) 26,000 Ibs. per cu. in. Substituting in the above formulas we get: 3 X 6000
"' =
24 %
= 2 d 2 0 X 0.004 = 0.56 in.
If the force be increased 8-fold, the depression d will be increased 4-fold to 0.016 in., hence the maximum pressure will be increased 4-fold1 while the width of contact will double. In the above, it has been assumed that the metal body or roll is absolutely rigid. Such cannot be the case. Assuming the load to be distributed uniformly, the deflection midway between the ends (at 1/2L) can be expressed in terms of the total force F, the external diameter D, and the internal diameter DOof the metal portion, and E the modulus of elasticity of the metal (assume 30,000,000 Ibs. per sq. in. for iron). From applied mechanics the maximum deflection f is: F L8 f=- 5 384
where
I =
To take a specific example, let DI, -18 in., Do=14 in. and let F be 3 and 24 tons. If F is tons or 6000 lbs:
0.004in.
= ( 4 X 26,000 X 150\/20) H d = 26,000 X 0.004 = 104 Ibs. per sq. in. X 26,000 X 0.004 = 70 Ibs. per sq. in. '/8 H d =
.
E1 (D14- Do4) 64
Vol. 13, No. 8
=
6X6OOOX15OX15OX15OX64 x384x30,000,000xm4--144)
=
0.0027
7r
If F is 24 tons or 48,000 Ibs.: f = 8 X 0.0027 = 0.022in.
I n order to compensate for this deflection, as well as to vary the maximum pressure with respect to the length if the process warrants it, a crown or convex curvature is applied to the surface of the roll. This crown may be so designed that the pressure will be distributed in any predetermined manner. Under these conditions, the relation between depression, force per unit length, and distance along the roll will not be constant. dF/dL cannot be considered constant, but will be determined by the equation : 4HdaI2
dFdL,=
3dF
I n this equation d may vary. It would be necessary under such conditions to develop equations for the deflection of the metal body. Enough has been adduced to show the value of a hardness constant and the possibilities of its application to the design of rubber-covered rolls.
The Examination of Sugar Crystals by Projection' By George P. Meade CENTRAL CONTROL LABORATORY, CUBAN-AMERICAN
Daily samples of raw sugar from a number of factories are received at the laboratory for examination of various physical characteristics, among which size and regularity of crystal are important. For convenience in reporting the size to the factories a scale of ten is used, No. 1being very small, No. 10 very large, and No. 5 the medium size desired. Examination under a small tripod lens (2.5 to 3 diameters) and comparison with photographic standards proved fairly reliable in the hands of a trained observer, but the method was tedious and hard on the eyes, and did not admit of ready use by different operators. A method was needed which would be rapid, simple, and accurate, which would give a magnification of a t least ten diameters, and which a t the same time would show a sufficiently large number of crystals a t one time to be representative of the sample. It occurred to the writer that magnification by projection would fulfil all of these requirements. The apparatus selected for the purpose is a Bausch & Lomb Balopticon, Model C, with lens of 8-in. focus, one and five-eighths-inch diameter projection lens, and 400-watt incandescent Mazda lamp. The Balopticon is fitted with a vertical attachment in order that the object to be projected may be placed in a horizontal position. Experiment has shown that the apparatus magnifies ten diameters when placed 'with the center line of the projection lens exactly 7 ft. from the screen. To cut off the greater portion of the daylight, a black curtain made in the form of a tube or tunnel, about 3 ft. across, is hung on a frame of light iron rods, with the screen at one end of the tube and the projection apparatus a t the other. The curtain can be drawn back when the apparatus is not in use, leaving the greater portion of the table which the apparatus occupies free for other work.
*
Presented before the Section of Sugar Chemistry and Technology at the Blst Meeting of the American Chemical Society, Rochester, N. Y., April 26 to 29. 1921.
SUGAR
CO., CARDENAS, CUBA
A small amount of the sugar to be examined is placed in a 40-mm. petri dish, a few cubic centimeters of sugar-saturated alcohol are added, and the crystals are separated by rolling them gently under the finger. The dish is then placed on a metal stage on the horizontal condenser, and the image focused on the screen. Various methods of comparison were tried, but the one described below proved the most satisfactory. The screen is a smooth plaque of plaster of Paris, about 18 in. square and 0.5 in. thick. On the surface of the screen are drawn five squares, 3.5 to 4 in. on a side, subdivided as described below, and arranged so as to be distributed over the circle of light thrown by the projection apparatus. The lowest square is subdivided into 4-mm. squares, the next square into 6-mm. squares, the middle square into 8-mm. squares, and the other two into 10-mm. and 12-mm. squares, respectively. As our No. 5 sugar is about 0.8 mm. on a side, these sets of squares represent the sizes 3, 4, 5, 6, and 7, allowing for the magnification, and cover practically all of the range of sugars we receive. The observer compares the projected image of the sugar crystals with the variously sized sets of squares and determines which size the majority of the crystals most closely approximate. This he can easily do to the nearest whole number of our scale, which is the full accuracy required for the purposes of our control. The form and regularity of the crystals are also noted, and in case these are abnormal the fact is reported to the factories for correction. i
Licenses were granted during July for the importation of 253,687.4 lbs. of dyestuffs from Germany by the dye and chemical section, division of customs, of the Treasury Department, according to the monthly report of the American Dyes Institute. In the same month licenses were granted for the importation of 145,848 lbs. from Switzerland, and 21,232 from England. The only license granted for French dyestuffs was for 12 Ibs. of Victoria green.
