(c) Sodium bicarbonate and alum.—These constitute the most reprehensible forms of baking powder. The sanitary effects of alum have been referred to under Flour. It may be present either as potash or ammonia alum. The following is a fair example of an alum powder:—
| Per cent. | |
| Alum | 26·45 |
| Sodium bicarbonate | 24·17 |
| Ammonium sesquicarbonate | 2·31 |
| Cream of tartar | None |
| Starch | 47·07 |
From an exhaustive investigation of baking powders made by Dr. Henry A. Mott, it was found that about 50 per cent. of these preparations were impure, alum being the chief admixture. Of 280 samples of cream of tartar lately examined by various American Health Boards, 100 were adulterated; of 95 baking powders tested, 16 were adulterated.
SUGAR.
The sugars of commerce may be conveniently classified into two varieties, viz., sucrose (cane sugar or saccharose) and dextrose (grape sugar or glucose). The former, which is the kind almost exclusively employed for domestic uses, is chiefly obtained from the sugar cane of the West Indies and American Southern States (Saccharum officinarum), and, in continental Europe, from the sugar beet (Beta vulgaris). A comparatively small quantity is manufactured in the United States from the sugar maple (Acer saccharinum), and from sorghum (Sorghum saccharatus).
Cane Sugar (C12 H22 O11).—Among the more important chemical properties of cane sugar are the following:—It dissolves in about one-third its weight of cold water—much more readily in hot water—and is insoluble in cold absolute alcohol. From a concentrated aqueous solution it is deposited in monoclinic prisms, which possess a specific gravity of 1·580. Cane sugar is characterised by its property of rotating the plane of a ray of polarised light to the right; the rotary power is 66°·6. Upon heating its solution with dilute mineral acids, it is converted into a mixture termed “invert sugar,” which consists of equal parts of dextrose and levulose. The former turns the plane of polarised light to the right, the latter to the left; but owing to the stronger rotation exerted by the levulose, the combined rotary effect of invert sugar is to the left, i. e., opposite to that possessed by cane sugar. Invert sugar exhibits the important property of reducing solutions of the salts of copper, which is not possessed by pure cane sugar. Cane sugar melts at 160°; at a higher temperature (210°) it is converted into a reddish-brown substance termed caramel. When subjected to the action of ferments, cane sugar is first transformed into invert sugar, then into alcohol and carbonic acid, according to the reactions:—
(a) C12 H22 O11 + H2O = 2 C6 H12 O6.
(b) C6 H12 O6 = 2 CO2 + 2 C2 H6O.
The varieties of cane sugar usually met with in commerce are the following:—
1. Loaf sugar, consisting either of irregular fragments, or (more often) of cut cubes.