I N D U S T R I A L A N D ENGINEERING CHEMISTRY
July 15, 1929
But despite these corrections for the source of the oils, Equation 1yields low values a t high temperatures. The experimental data obtained in the present investigation indicate that the specific heats of mineral oils a t elevated temperatures can be calculated with the aid of Equation 2 sufficiently accurately to fulfil engineering requirements.
151
Literature Cited (1) Cragoe, International Critical Tables, Vol. 11, 151 (1927). (2) Fortsch and Whitman, IND.END.CHEW,18, 795 (1926); contains a review of earlier work. (3) ill and Coats, Ibid., 20, 641 (1928). (4) Keyes and Beattie, J . Ant. Chem. S O L , 46, 1753 (1924).
The Color of Wheat Flour' Arthur C. Hardy, Prentiss I.Gole, and Charles W. Ricker, Jr. DEPARTMENT OF PHYSICS, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE, MASS.
Pure W h i t e
Pure W h t e JMqC03
(w~coJ\ 1
6
5
5-
E
G
.r
3
SoSt W \ n t e r W h e a t No. 1 Patent No. 2 S t r a i g h t
No. 3 b a k e v S
e
$ qr
2 0
'
I
l
l
I
;
799
l
8%
were obtained with a sample of hard spring wheat of a patent grade. Curve 1represents the unbleached flour and curve 2 the same flour after bleaching. It will be noticed that the unbleached flour has a lower reflecting power in the blue region of the spectrum, which gives it a yellowish cast. The principal effect of bleaching is to raise the curve in this region of the spectrum, which causes the flour to occupy a slightly higher position
VOl. 1, No. 3
ANALYTICAL EDITION
152
experience is necessary before the appearance of a sample can be estimated exactly from the shape of the spectrophotometric curve. This difficulty will soon be solved by an attachment to the color analyzer which will compute mechanically the three primary sensations produced by a given sample. As the usual method of performing this computation is extremely tedious ahd unsuitable as a routine procedure, the writers have devised a much simpler one to fit the present case in an attempt to correlate their results with the other known properties of the many grades of flour. Since the maximum sensitivity of the normal human eye occurs a t 556 mp in the green, this point in the spectrum was selected as the basis for estimating the position of a specimen on a scale of grays. Thus the reflecting power of Sample 3 in Figure 2 at 556 mp is 88 per cent. Consequently, by definition, the brilliance score of this sample is 88. The yellowness of a sample depends principally on the degree of excitation of the primary blue sensation which has a maximum at 440 mp, If the height of the curve representing Sample 3 were 88 per cent a t this point, it would probably appear to be a neutral gray in color. The actual height is 79.7 per cent and the difference between this value and 88 per cent is arbitrarily taken as the yellow score. This method of deducing the value of the color sensation from the spectrophotometric curve is only approximate, but it is satisfactory whenever all the curves have the same general shape, as was found to be true in this case. For example, Figure 2 shows a curve for a representative sample of a patent, straight, and bakers’ grade of wheat flour. The curves for all thirty-five samples were found to be of this general form and corresponded closely to the designated grade for samples obtained from mills which maintain color standards carefully. Although these results are of a preliminary character, the writers have attempted to correlate the computed color values with the other known properties of the samples. The results for thirty samples obtained from nine mills are given in the accompanying table.
Experimental DaIta MILL
ASH^
GRADE
BRILLIANCE Y ~ L L O W SCORE SCORE
Per cent VI11 VI IX VI1 I1 VI11
,
0.334 0.345 0.404 0.380 0.394 0.441 IX 0.404 VI1 0.400 VI 0.442 I 0.392 111 0,460 I 0.447 VI1 0.620 I1 0.386 I11 0.395 111 0.395 0.450 IV IV 0.410 V 0.393 I1 0.433 0.418 V I 0.668 111 0.659 111 0.460 0.536 VI 0.588 V I1 0.534 IX 0.659 IX 0.659 111 0.650 a 15 per cent moisture basis. b Unbleached.
Patent Patent Patent Patent Patentb Straight Straight b Straight Straight Patent Straight b Straight Bakers’ Patent Patentb Patent Straight Patent Patent Straight Straight Bakers’ Bakers’b Straight Bakers’ Bakers’ Bakers’b Bakers’b Bakers’ Bakers’
94.8 93.7 93.4 92.8 92.8 92.7 92.7 91.8 91.6 91.4 91.3 90.9 90.7 90.5 90.5 90.5 90.2 89.4 89.4 89.4 89.1 88.8 88.8 88.2 88.0 87.7 87.6 87.4 87.4 85.8
3.8 5.6 6.3 6.2 11.3 4.5 11.0 6.4 6.0 5.8 14.2 5.8 12.5 6.2 7.2 13.9 6.9 9.5 6.4 8.4 8.9 6.0 13.7 8.5 8.3 8.3 9.8 11.6 9.8 7.6
Although curves were run on the other samples, the results were not included because the data as to ash or moisture content were incomplete. These samples were classified into patent, straight, and bakers’ grade according to the miller’s designation when that was furnished, or according to the recommendation of Alway and Clark when the miller’s designation was lacking. It will be seen from this table that the brilliance score tends to decrease with an increasing ash content and the yellow score to increase. This is better illustrated by Figures 3 and 4. It is expected that more work along this line will be undertaken when a commercial model of the color analyzer is available for routine purposes.
Rapid Calibration of Pipets and Burets’ Alfred T.Shohl BABIES’AND CHILDREN’S HOSPITAL, DEPARTMENT OF PEDIATRICS OF SCHOOL OF MEDICINE, WESTERNRESERVEUNIVERSITY, CLEVELAND, OHIO
HE method proposed is rapid and accurate and invdlves no special apparatus. It depends upon the specific gravity of mercury. The required weights and one of a pair of tared flasks are placed upon the right pan of a rough balance. The other tared flask is placed upon the left pan. Mercury, covered by a layer of water, is deIivered from the apparatus to be calibrated into the second flask until the balance just turns. Delivery of the known weight of mercury measures the desired volume. The pipet must be standardized between marks. The upper graduation is first marked and etched. A narrow strip of paper is then gummed lengthwise along the lower stem at the point where the lower calibration is to be made, and a stopcock attached to the tip of the pipet with heavy-walled rubber tubing. Into the pipet is introduced, by suction, first a little water and then mercury to a point somewhat above the upper mark. The stopcock is manipulated so that the water meniscus is on the etched line. The delivery time is recorded and a mark made upon the gummed paper at the lowest
T
1
Received December 7, 1928.
point of the water meniscus. The mark is then permanently etched. Burets and Mohr pipets are calibrated in the same fashion. The method has been used to check calibrations etched by the manufacturers. When the water delivered from a pipet is weighed and the mark ascertained by trial and error according to the usual method, 1 hour is required to calibrate each pipet. The first time the above method was used, with no effort to attain speed, twelve pipets were calibrated in 1 hour. The correct weights are at once placed upon the balance. The mercury is poured out after each determination and leaves the flask dry and clean. This eliminates re-weighing the flask, or cleaning and drying it between determinations. Further, since the exact weight is already on the balance pan, the calibration is correct at the first trial. If too much mercury is delivered, a few drops can be withdrawn from the weighing flask with a hypodermic syringe and needle and returned quantitatively to the apparatus. The accuracy of the method was tested by the weight of
,
