352 



GLUCOSE. 



it is any less wholesome than cane or maple 

 sugar. It has been objected that the substance 

 when not properly made contains impurities, 

 one of which, tree sulphuric acid, is poisonous; 

 and Dr. R. C. Kedzie, of the Michigan State 

 Board of Health, states that he has found in one 

 sample 71 '83 grains of free sulphuric acid, -28 

 grain of sulphate of iron, and 363 grains of lime 

 to the gallon. Professor Haines has shown, 

 however, that it is to the direct interest of man- 

 ufacturers, for the sake cf the preservation of 

 their apparatus and the salability of their prod- 

 uct, to prevent the possibility of any free acid 

 remaining after manufacture, and that for that 

 reason they are accustomed to use much more 

 marble-dust than is necessary to neutralize the 

 acid. Professor Wiley says that a properly 

 made glucose contains only a very little sul- 

 phuric acid and lime, "not much more than 

 good spring-water, and perhaps an almost in- 

 finitesimal trace of copper, so slight as only 

 to be detected in large quantities of the sub- 

 stance." He does not doubt, however, that 

 glucoses " have been sold which contain large 

 quantities of free sulphuric acid, and likewise 

 other injurious ingredients. But these are due 

 to carelessness in manufacture, and are not 

 constituents of the genuine article. I have 

 never found a glucose of this kind." A more 

 valid objection to the use of glucose is, that it 

 is employed as an adulterant, and is sold to 

 consumers under the representation that it is 

 a better and more valuable article than it is, 

 and for several times its actual value. Ac- 

 cording to Dr. Kedzie, one gallon of sirup 

 made from sugar-cane has more sweetening 

 power than four gallons of glucose-sirup ; con- 

 sequently, if cane-sirup is worth one dollar a 

 gallon, glucose-sirup should be sold for not 

 more than twenty-five cents a gallon. 



Glucose presents several anomalies when ex- 

 amined with polarized light. Its highest rotato- 

 ry power is found when it is made with the least 

 possible amount of conversion ; continued boil- 

 ing with dilute acid causes a gradual decrease 

 of rotatory power; and a constant rotatory 

 power, equivalent to about one half the max- 

 imum power exhibited by the substance, is 

 reached only after from six to eight hours' 

 heating at a temperature of 104 C., or 219 

 Fahr. The minimum rotatory power is, how- 

 ever, greater than that possessed by cane-sugar. 

 Glucose has the property, which always acts 

 inversely as the rotating power, of reducing a 

 hot alkaline copper solution and separating the 

 metal as a red sub-oxide. 



The ordinary chemical tests for glucose are 

 based upon the following reactions : 1. It is 

 colored a dark brown by potash-lye, while 

 cane-sugar is not so colored ; 2. Basic nitrate 

 of bismuth gives a black-brown coloration to 

 the solution of glucose mixed with carbonate 

 of sodium, and causes a grayish-brown precipi- 

 tate from it; 3. Glucose reduces cupric salts 

 immediately, whereas the reduction takes place 

 more slowly with cane-sugar ; 4. It produces a 



decoloration of the alkaline solution of ferro- 

 cyanide of potassium, while cane-sugar does 

 not; 5. The non-production of a violet-blue 

 precipitate with nitrate of cobalt and caustic 

 alkali indicates the presence of glucose in a so- 

 lution previously known to contain cane-sugar ; 

 G. Glucose alone in the solid state, or as a strong 

 sirup, dissolves in strong sulphuric acid with- 

 out coloration, while cane-sugar, if present, is 

 blackened and decomposed. 



Mr. P. Casamajor has described some easy 

 processes for the detection of starch-glucose in 

 commercial refined sugar and in sugar-house 

 molasses. "When the adulterant is present in 

 sugar, in large enough quantities to make its 

 use profitable, it may be readily detected with 

 the optical saccharometer. It is a dextro-gy- 

 rate substance, and the only substance of that 

 character that can be used in so large quanti- 

 ties to adulterate sugar. Somewhat less than 

 its own weight of water is added to the sus- 

 pected sugar, and the mixture is stirred for a 

 few seconds. If starch sugar is present, it will 

 be seen floating in the solution as white specks 

 resembling crushed wheat. The appearance is 

 due to the comparative insolubility of starch- 

 glucose in cold water, and to the fact that as 

 the cane-sugar present is crystalline, and its 

 refrangibility is not very different from that of 

 a sugar solution, the part of it which remains 

 undissolved is not so distinctly seen as are the 

 specks of starch-sugar. The specks are best 

 seen by using a beaker glass and putting in only 

 as much sugar and as muh water as will allow 

 the light to show through the flat bottom of 

 the glass. If a flat-bottomed glass is not at 

 hand, the observation may be made on a flat 

 pane of glass. Another process is based on 

 the fact that the taste of sugar has a tendency 

 to dull the perception of the taste of other sub- 

 stances that may be mixed with it. In order 

 to neutralize this effect we may, before tasting 

 a suspected sample, put a pinch of pure sugar 

 into the mouth. If, after this sugar is dis- 

 solved, but while its sweet taste is still per- 

 ceived, we put on the tongue a pinch of sugar 

 containing starch-glucose, we may distinctly 

 perceive the bitterish taste of the glucose. The 

 presence of chloride of tin in molasses and 

 sugars, even when it is used in very small 

 quantities, can be likewise easily detected by 

 its unpleasant bitter taste, if, before tasting 

 the suspected products, the mouth is filled 

 with the pure sweet taste of refined cane-sugar. 

 The adulteration of sugar-house molasses may 

 be detected by the use of strong methylic alco- 

 hol. A straight sugar-house sirup mixed with 

 three times its volume of this spirit will dis- 

 solve by stirring, except for a very slight tur- 

 bidity, which remains suspended ; while sirups 

 containing the usual admixture of starch-sugar 

 give a very turbid liquid, which separates 

 w r hen left at rest into two layers, of which the 

 lower one is a thick, viscous deposit containing 

 the glucose-sirup. A thin sirnp (about 32 

 Baume), in which the proportion of sugar to 



