GR.AMS OF
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0.21 0.12
0.10
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DEPARTMENT OF ~ I E T A L L U R G \ OHIO STATE UNIVERSITY COLUXBUS
TVeight of starch taken Grams
Reading in 200 mm. tube Degrees Ventzke
5 I) R 85 11
x
17 5 23 7 28 9
201.3 200 I 199 4
0.2 0 3 0.4
2 4
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3 .O 3 6 4 2
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A POLARIMETRIC METHOD FOR THE DETERMINATION O F STARCH I N PAPER B y CHRISTIANE. G. PORSTA N D H A R R Y.iCx0n.s Received January 7 , 1913
The work described in this paper is supplementary t o t h a t given in a paper under the same title, which was submitted to the Eighth International Congress of Applied Chemistry, b u t too late for publication, and also t o t h e authors’ paper, “Research on Lintner’s Polarimetric Method for the Determination of Starch,” which was published among the original communications t o the Congress. I n our previous work, we found t h a t the ,method could be applied t o the determination of starch in paper with reliable results. But i t was found necessary t o determine the value of the specific rotatory power for small amounts of starch, as this value varies from t h a t found and given in our paper on Lintner’s method, depending on the amount of starch taken in work. Therefore, the object of the present work was t o determine t h e specific rotatory power of starch for low concentrations, similar t o those encountered when working with j grams of paper and t o test the method more fully on a large number of samples of paper. When weights of starch below one gram were taken, t h e value for [ a ] g varied considerably, duplicates not checking well. This discrepancy seemed due t o t h e precipitation of some of the starch by the phosphotungstic acid. I t s use was then omitted as i t is not necessary t o precipitate the protein which is low in the pure starch and does not affect the reading. But when the phosphotungstic acid was not used, the starch solutions obtained were cloudy, due to the small amount of fat which is present in the starch, and the polarimetric readings could not be made with sufficient accuracy. It was then decided to add some paper pulp to the starch solution, this producing the same conditions as when samples of paper which give clear solutions are worked upon. The result was satisfactory, the pulp absorbing the fat and giving a perfectly clear filtrate. Pure Swedish paper pulp was used and the solutions obtained were clear, even when as much as five grams of starch mere dissolved. Blank tests
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0 3 0 9 1.n 1. S 2 0 3.0
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4 8
5 35
were run on the paper pulp which was found to be free from starch. Working with pure corn starch, the preceding values for the specific rotatory power were obtained. The method by which these values were obtained is as follows: The pure starch of known weight is mixed with 20 cc. of distilled water in a mortar, which is cooled in ice-water. To this is added 40 cc. concentrated HC1 previously cooled down in a freezing mixture, stirring with the pestle until all the starch is dissolved., and then the solution is kept a t z o o C. for half a n hour. The contents of the mortar are then transferred t o a zoo cc. flask to which had been added about one gram of pure paper pulp, disintegrated by rubbing in a mortar with HC1 of 1 . 1 2 5 specific gravity, and t h t flask is filled t o the mark a t 2 0 ’ C. with HC1 of 1 . 1 2 j specific gravity. The flask is kept for half an hour in a water bath a t 2 0 ’ C. and then the solution is filtered, first with suction through a Buchner funnel, the paper pulp acting as a filtering medium and then through a Munktell washed filter. Just fifteen minutes after the first filtration is begun, the reading is taken a t 2 0 ’ C. in a 2 0 0 mm. tube. About sixty samples of paper were now tested by the above method, for starch retained, the addition of paper pulp being omitted, but the other details followed as above. The value 2 0 7 . 0 for [a]:’ was used in all computations since the maximum reading obtained was 1 . 5 V. ~ I n all the samples tested, the percentage of starch retained varied from o to as high as 4.7 per cent. Two or three samples contained coloring matter which imparted a dark red color t o the HC1 solution, making i t impossible t o obtain a polarimetric reading. Some papers gave yellow solutions but this color did not affect the readings. Results in duplicate checked well and on the whole, the method worked satisfactorily. CORN PRODUCTS REPININGCO EDGEWATER. i%. J.
LABORATORY AND PLANT ~
CHEMICAL ENGINEERING AND THE NEW LABORATORIES AT COLUMBIA UNIVERSITY l B y M. C. WHITAKERAND R. K . MURPHY
The development of the manufacturing industries Paper presented a t t h e New York Section of the American Chemical Society, Chemists’ Club, New York. March 7 , 1913.
[ a ]E Degree 207 0 207 .o 207 0 207 0 207 . O 207 . O 207 n 207 n 205. I 203 6 203 5 203.5
0 6 1.2 1 5
0 1
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produces a n ever-increasing demand for men trained in the fundamental sciences and their applications. Manufacturing processes based upon chemical principles are advancing in importance a t a most astounding rate. To supply properly trained men who c a n
