The Romance of Modern Chemistry

SUGAR AND STARCH converted into grape sugar. Cane sugar itself is changed into glucose and another similar sugar called “ fructose,” merely by heating a solution with an acid—sulphuric acid, for example; the cane sugar is said to be “ inverted,11 and the resulting mixture of glucose and fructose is known as “ invert sugar.” This product is obtained in the form of a thick syrup, and is extensively employed in brewing. This reminds one that it was the use of sulphuric acid in the manufacture of glucose and invert sugar which led to the “arsenic in beer” scare of 1900. In Manchester during that year a number of cases of arsenical poisoning occurred, and were ultimately traced to the beer drunk by the patients. Arsenic was found also in the glucose and invert sugar from which the beer had been brewed, having got into these materials from the sulphuric acid employed in their manufacture. It must be remembered that the sulphur required for making sulphuric acid is generally in the form of iron pyrites, a natural product which is invariably contaminated with arsenic. Unless, therefore, submitted to special purification, commercial sulphuric acid is liable to contain arsenic; and it was the use of such an impure acid in the manufacture of glucose and invert sugar that was at the bottom of the “ arsenic in beer ” trouble. The conversion of other carbohydrates into glucose can be brought about by certain ferments without the aid of acids at all. When moist bailey, for instance, is allowed to germinate, a ferment called “ diastase ” is pro- duced. This subtle agent upsets the equilibrium of the starch molecules in the barley. Under its influence they are converted into sugar molecules, and the latter, unlike starch, can be fermented by yeast, and so produce alcohol. 233