Rensselaer Union, Volume 8, Number 43, Rensselaer, Jasper County, 13 July 1876 — The Manufacture of Glucose. [ARTICLE]

The Manufacture of Glucose.

As there is just now much inquiry as to the process of making glucose, or grape sugar directly from (starch or other vegetable matter, the following will be oi interest: Dilute sulphuric acid, and the feeula of the potato are the active agents in the production of grape sugar from starch. The principal processes are the following:The boiling of starch meal with dilute sulKric acid is effected on a small scale m en pans; but in an extensive preparation, iron pans are employed. The requisite quantity of water Is first heated tome boiling point, and to this is added, the sulphuric acid diluted with three parts by weight of water: The starch b also brought, by the addition of water, to a milky consistence. The liquids so prepared are mixed, and -the boiling continued until all the starch is converted into sugar. An intermediate stage, not usually noticed by the manufacturer, is the conversion of the starch into dextrin, which, in its turn, suffers conversion into sugar. The entire conversion of the dextrin into grape sugar cannot be with certainty ascertained by the iodine test, as sometimes a purple-red tint is produced, while in others there is no change. The most reliable test is that with alcohol, founded on the well-known insolubility of dextrin in* an alcoholic menstruum. If no precipi- ‘ tate is thrown down there is no dextrin remaining, and the conversion has been entire. The proportions of materials are,"' generally, to 200 pounds of starch, fours pounds of ordinary sulphuric acid of sixty degrees Baume, and from eighty to one hundred gallons of water. The conversion of the starch and grape sugar is hastened by the addition of a. small quantity of nitric acid. The separation of the sulphuric acid from the sugar solution is a most important operation, for the color, purity and flavor all depend upon success in this stage of the process. The acid is neutralized with baiyta or lime, with either of which it forms an insoluble salt, deposited at the bottom of the neutralization vessels, and leaving a clear supernatant sirup. The baryta can be emaed as a carbonate (witherite), and is, out doubt, the better neutralizing agent, sulphate of baryta being very insoluble. Lime, although ordinarily used, forms with the sulphuric acid a sulphate (gypsum) that is not perfectly insoluble in water. It can be employed as marble dust, chalk, or caustic lime. The neutralization is completed in the boiling pan while the sirup is still hot. For every pound of sulphuric acid so much pulverized marble is required as the varying strength of the acid may demand, about pound to pound. After the addition of the marble powder, and when the effervescence has subsided, the liquid must be tested with litmus paper, or better, with tincture of litmus; if the sugar solution be neutralized when at twenty-six degrees Baume density, the following evaporation will concentrate even the smallest quantity of sulphuric acid which may have remained, and rendered another neutralization necesstuy. To insure perfect neutralization, it is useful to add an excess of carbonate of baryta in the proportion of five to ten ounces to every ten pounds of sulphuric acid. The evaporation and purification are similar to those employed for other sugars.— Scientific American.