328 
ber of the globules to burst. At this temperature, 
however,some grains of fecula are observed, which 
do not appear to have yet attained their maxi- 
mum of enlargement, and whose contents conse- 
quently are not yet diffused through the liquid. 
It is only between 161:6° and 212° Fahr. that the 
| maximum of expansion becomes general and that 
the solution acquires its greatest consistency. 
The remarkable property possessed by starch of 
making a glutinous solution or thick paste with 
water under the influence of heat, led M. Payen 
to conjecture that a contrary effect would be pro- 
duced by lowering the temperature,—that the 
starch might be recovered in its original state of 
distinct globules by suitable management; and 
this he in fact accomplished by an ingenious 
procedure. Starch appears to suffer no actual 
change when diffused in water by exposure to a 
temperature of 212° Fahr.; the granules have 
only swollen to about thirty times their original 
dimensions by the imbibition of a large quantity. 
of water. 
“Formerly, the starch of commerce was uni- 
versally obtained from grain,—wheat; at pre- 
sent, the potato furnishes a still larger quantity 
than grain. In the equatorial regions of South 
America, starch is abundantly prepared from the 
Jatropha manihot, and from several species of 
palm. To obtain starch from wheat, the grain 
is either coarsely ground and mixed with water 
in large tubs, or it is put to steep in sacks until 
it is so soft that a process of kneading suffices to 
-set the starch at liberty. To obtain it from po- 
tatoes, the tubers are grated after having been 
well washed, and the pulp being thrown on a 
sieve, the starch is carried off by the water and 
deposited in suitable vessels. The washings in 
the manufacture of potato starch soon become 
putrid by reason of the azotised matter which 
they contain, and until lately occasioned much 
annoyance, until M. Dailly conceived the happy 
-idea of turning them to account as liquid man- 
-ure. None of the amylaceous principles or fecu- 
las obtained by the ordinary processes are abso- 
lutely pure; even supposing all the soluble sub- 
stances to have been removed by washing, they 
still retain fatty matters, azotised principles, and 
colouring substances. Starch is purified’ by fol- 
lowing up the water washings by the action of 
alcohol, of acetic acid, and of ammonia. Starch 
in its state of greatest purity, and dried at 212° 
Fahr. contains, according to the analysis of M. 
Jacquelain, 44:9 per cent. of carbon, 6:3 of hy- 
drogen, and 48°8 of oxygen. 
“By slight roasting, amylaceous feculas un- 
dergo considerable changes; they become soluble 
in water, and then present the properties of gum. 
Starch thus roasted, supplies the place of gum in 
various manufacturing processes ; still it should 
not be confounded with gum in a chemical 
point of view. The acids act with more or 
less energy on starch, and give rise to different 
products. Nitric acid, when it is diluted with 
a 
— 
STARCH. 
water, merely dissolves fecula; but at a certain 
degree of concentration, it exerts a destructive | 
action. In this reaction several acids are formed, | 
among others oxalic acid. By employing very | 
i} 
ae 
a 
itt 
ult 
thi 
dilute sulphuric acid, Kirchhoff succeeded in | 
changing starch into a saccharine substance.simi- | 
The operation | 
lar to the sugar of the grape. 
may be performed in a leaden or silver pan, or, | 
what is preferable, especially when the process — 
is carried on upon the great scale, in wooden 
vessels, in which the liquid mass is heated by | 
steam. According to M. Couverchel, several or- | 
ganic acids are capable of changing fecula into |, 
sugar ina similar manner; such are oxalic, tar-— 
taric, and malic acids. 
factorily accounted for. 
not seem to undergo any change; it is found in 
its original state and quantity after the opera- 
tion. M.de Saussure thinks that the effect of 
the reaction is the fixation of water; thus 100 
parts of fecula yielded him 110°40 parts of sugar. 
M. Couverchel and M. Guérin, on. the contrary, 
state that the quantity of sugar obtained was 
less than that of the starch they employed. 
Gluten exerts a reaction on starch similar te- 
that produced by acids; Kirchhoff discovered, 
that.under the influence of the azotised matters 
which are met with in flour, the fecula is con- 
verted into sugar. Two parts of starch being 
mixed with four parts of cold water, on adding 
twenty parts of boiling water, a thick paste is 
produced ; if into this one part of dry, powdered 
gluten:be introduced, and the mixture be kept 
at the temperature of 140° Fahr., the paste be- 
The artificial conversion | 
of starch into grape sugar has not yet been satis- | 
The acid employed does — 
comes more and more liquid, so that the mix- 
ture may be filtered at the end of from six to. 
By concentration a syrup is ob- 
tained,.in which small crystals of sugar-are per- | 
eight hours. 
ceived. It is well known that during the act of 
germination, fermentable saccharine matter is 
produced. 
ments, that this production of sugar in germina- 
tion is attributable to the reaction of the: gluten 
on the starch. Germinating grain, barley-malt 
for instance, reacts rapidly and powerfully on 
any fecula with which it is brought into contact, 
—a fact well known to, and constantly taken 
advantage.of, by manufacturers of spirits from 
potatoes and raw grain, large mashes of which 
are rapidly converted into sweet fermentable 
liquids under the action of a little malt. These 
facts, it is evident, cannot be explained by Kirch-. 
hoff’s experiment; in the fermentation of the 
potato, the mass of fecula to be converted into 
sugar is too great compared with the quantity 
of gluten which exists in the malted barley. Fur-. 
ther, the gluten in grain which has not germi-| 
nated, scarcely exerts any appreciable action. 
The principle which, in the preceding operations, 
converts the starch into sugar must therefore 
become developed during germination. This 
important point in the art of the distiller has 
Kirchhoff concluded from his experi-. 
