I,YDUSTRIAL A N D ENGINEERIiYG CHEMISTRY
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The sugars had been determined previously on duplicate samples of the fresh juice. The results for starch and sugars are given in Table I.
DISCUSSION The starch content shows a comparatively wide range. Referring for convenience to the column for weight of starch in pounds per 100 gal. of juice, it will be noted that the quantity varies from 1.3 to 7.8. Separating the series arbitrarily into three groups as the starch varies 1.3 to 2.2, 2.3 to 3.2, and 3.3 to 7.8, and averaging the sucrose and reducing sugars of the samples that fall within these groups give the results in Table 11.
Vol. 15, h’o. 7
I n some cases the sirup-manufacturing process involves clarification of the juice with lime, followed by settling and decantation or by filtration, but probably 85 per cent of the sirup produced is made by direct open-pan evaporation of the raw juice, with removal of scums by skimming. That portion of the starch that finds its way into the finished sirup probably has a tendency to retard crystallization. However, there are indications that starch is responsible for the wellknown “jellying” of sorghum sirup, and that juice low in starch will produce sirup which is more satisfactory from the standpoint of consistency and general appearance. Indications also point to starch as the cause of the great difficulty in filtering sorghum juice, especially after i t has been heated.
TABLE I1
.............................. .......... .....................
Group Number of samples in group.. Average sucrose.. Average reducing sugars.. ..............
1.3-2.2 3 7.58 4.49
2.3-3 2 5 10.43 2.40
3.3-7.8 7 13.58 2.03
These figures indicate that a high starch content is accompanied by a high sucrose content and a low reducing sugar content, and vice versa. This is also shown very plainly by the results for Samples 8 and 15 in Table I. Either starch or reducing sugar is always present in considerable quantity, and the low ratios Per cent starch plus per cent reducing sugar per cent sucrose are usually found in samples with a high sucrose content. Willaman, et u Z . , ~ ~ show that as the sorghum approaches maturity there is a rapid increase in the sucrose content and a rapid decrease in the levulose and dextrose content, the dextrose decreasing a t a more rapid rate than the levulose. They consider that the decrease in dextrose is due to a t least three causes: (a)respiration; ( b ) conversion into sucrose; and ( c ) conversion to a slight extent into starch. I n view of the fact that no analyses were made on immature samples, no information is available as to whether or not the metabolism of the plants conformed with Willaman’s observations. I n each case the juice had been obtained from plants which from appearance, hardness of seed, etc., were mature and at the stage of growth ordinarily considered suitable for the manufacture of sirup. It seems probable that the starch-sucrosereducing sugar ratios may be characteristics of the variety. Bulletins of the United States Department of Agriculture, Division of Chemistry (1884 to 1893), dealing with experimental work in connection with the attempted production of sugar from sorghum, show that “gummy” and “mucilaginous” constituents of the juice were responsible for extreme difficulty in clarification and filtration and that these constituents plus reducing sugars were responsible for unsatisfactory crystallization of sucrose. The gummy constituents were investigated but apparently no investigation was made on the quantities of starch present. The repeated failure of numerous attempts forty years ago to produce sugar commercially from sorghum showed quite conclusively that the commonly grown varieties of sorghum are not adapted to the production of sugar and that i t is not practical to attempt to produce sugar from them. The presence in the juice of the quantities of starch and reducing sugars here shown is further evidence of this. I n view of the large areas in the United States that seem to be suited to the production of sugar beets and sugar cane, there appears to be no necessity a t present to consider sorghum for sugar production. It is of great value, however, for the production of sirup, as much as 49,505,000 gal. having been produced in 1920. For this purpose, the presence of reducing sugars is desirable because it retards and, when present in sufficient amount, prevents crystallization of sucrose. 11
Lac. C i t . , p. 25.
A Stirring Device‘ By Henry W.George HARVARD MEDICAL
SCHOOL,
BOSTON,MASS.
I n carrying out a reaction in a narrow-neck, balloonshaped flask i t is difficult to introduce a stirrer with arms long enough to extend close to the walls of the flask. To overcome this difficulty the following piece of apparatus has been developed : A glass T-tube with short arms is sealed to a long glass rod, and another rod of slightly smaller diameter than the tubing is passed through the T. The rod is bent a t right angles close to the arms of the T so that the ends of the rod point in opposite directions. The rod is then flattened a t each end. To insert into the flask the movable glass rod is fixed so that the arms are vertical (Position A). After the stirrer has passed through the neck of the flask, it is jarred sharply and the movable rod falls so that the arms assume a horizontal position. When the stirrer rotates the paddles remain horizontal and cause vigorous agitation throughout the contents of the flask.
POSITION A
Evidently, such an apparatus can be used in any large flask with a small neck. Care should be taken to have the movable rod evenly balanced. 1
Received April 12, 1923.
