260 
ON STARCH. 
objective. Measurements, *0008 to *0002 inch. Pepper starch 
is only distinguished from that of rice by its smaller size and 
uniformity of granule. 
Chemistry of Starch. 
Starch, chemically speaking, belongs to the carbo-hydrates, 
sub-class amyloses, and contains carbon, combined with H and 
O, in the proportion to form water. The carbo-hydrates are 
divided into three classes— 
Glucoses. 
Saccharoses. Amyloses. 
Composition C 6 H 12 0 6 
or Cia (H a 0)i 2 
Grape Sugar 
(dextrose) 
Fruit Sugar 
c l2 H 
22 On 
Oia (H 2 0)n 
Cane Sugar 
(saccharose) 
Milk Sugar 
(lactose) 
C<5 H l0 Og 
Oia (H a 0)10 
Starch 
Dextrin 
Inulin 
Cellulose 
Gum. 
The close connection between starch and the sugars is seen 
from the above table, and will readily explain how starch is 
converted by absorption of one molecule of water to form 
cane sugar and two molecules to form glucose in plants. 
Glucose readily loses water to re-form starch, which becomes 
stored up in the plant as reserve material; when starch is 
acted upon by dilute mineral acids, chloride of zinc, and by 
certain ferments, diastase, saliva, yeast, &c., it is changed 
into sugar. In these reactions starch takes up the elements 
of water, and is resolved into glucose and dextrin. 
H 2 0 -f- 8 C 6 Hi 0 Og— C 6 Hi 2 0 6 2 C 6 Hi 0 Og 
Glucose. Dextrin. 
Hence, glucose, when required in considerable quantity, is 
always prepared from starch. When starch is heated with 
water near to boiling point, the granules burst and disappear, 
producing a thick gelatinous mass, slightly opalescent from 
the shreds of fine membrane—the starch cellulose of the 
granules. By the addition of large quantities of water the 
solution may be made to pass through filter paper. It is 
doubtful whether the starch is really soluble—it is more 
likely to be merely suspended in a swollen, transparent, 
insoluble jelly. Again, when gelatinous starch is boiled with 
a small quantity of hydrochloric, sulphuric, or indeed any 
acid, it speedily loses its consistency and becomes thin and 
limpid from having suffered conversion into a soluble gum¬ 
like substance called dextrin, having the same percentage 
composition as starch. If the boiling is carried on for some 
time a further change is noticed, and dextro-glucose is 
produced. One of the most interesting changes of starch 
into glucose is produced by diastase, a peculiar nitrogenised 
principle found in malt. The gelatinous starch is warmed to 
