GLUCOSE AND GRAPE-SUGAR. 255 



half the price of cane-sugar, this adulteration proves immensely profit- 

 able. The presence of grape-sugar in table-sugars can be approxi- 

 mately determined by several simple tests. When placed on the 

 tongue, the bitter after-taste, already spoken of, may be detected. If 

 spread in a thin layer on a piece of glass, and treated with a little 

 water, the cane-sugar granules dissolve first, and the grape-sugar is 

 left as a flocculent mass. With the microscope, its particles can be 

 detected by the absence of all crystalline structure. Its exact quan- 

 tity can only be determined by the polariscope. This is hardly a 

 proper place to describe how this is done. 



From the best information I can obtain, it appears that the cost of 

 manufacture of glucose and grape-sugar is about one cent a pound. 

 From twenty-six to thirty-two pounds are made from a bushel of 

 corn. It is sold by the manufactories at three to four cents per 

 pound. In the West the price of corn during the last year has 

 averaged a little over thirty cents per bushel. It thus appears that 

 the manufacture of glucose is a profitable industry. 



I shall attempt here no detailed statement of the method of 

 manufacture, but give only such an outline as may interest those 

 who like to know how the things on their tables are prepared. The 

 corn is first soaked for two or three days in warm water, and is then 

 ground on specially prepared stones with a stream of water. The 

 meal is next passed into a trough, the bottom of which is made of 

 fine . bolting-cloth. Here the starch is washed through, and led to 

 large tanks, where it is allowed to settle. It is next beaten up with 

 caustic soda to separate the gluten, and the starch is again allowed 

 to settle in long, shallow troughs. The starch, washed from all ad- 

 hering alkali, is next beaten up with water into a cream, and con- 

 ducted into the converting-tubs. These tubs are supplied with coils 

 of copper steam-piping and are made of wood. Here the starch- 

 cream is treated with dilute sulphuric acid, and steam is allowed to 

 bubble up through the mixture from small holes in the copper pipes. 

 This process of conversion, which is called " open conversion," is com- 

 pleted in about two hours. 



Another method is called " close conversion." The substances are 

 inclosed in stout copper cylinders, and subjected to the action of super- 

 heated steam. This process occupies about fifteen minutes. 



The conversion is also accomplished sometimes by fermentation. 

 This requires a much longer time. The greater part of it, however, 

 is carried on by the method first named. 



After conversion the acid is neutralized by marble-dust and animal 

 charcoal. Since the sulphate of calcium, which is formed in this oper- 

 ation, is slightly soluble in water, carbonate of barium has been used 

 instead of marble-dust. Its use, however, has not become general. 



After neutralization the liquid is filtered through cloth and animal 

 charcoal, and is then conveyed to the vacuum-pan. Here it is evapo- 



