In previous communications I have given processes for detecting the
adulteration of cane-sugar by starch-sugar. The adulteration of
sugar-house sirups by starch glucose is still more extensively
practiced than that of sugar, and a great portion of sirups sold by
retailers in this market is adulterated with starch glucose. This form
of adulteration may be very easily detected by the use of strong
methylic alcohol, in which the alcoholometer of Tralles or of Gay
Lussac will indicate about 93½°.
A straight sugar-house sirup when mixed with three times its volume of
this strong methylic alcohol will dissolve by stirring, giving a very
slight turbidity, which remains suspended; while sirups containing the
usual admixture of starch sugar give a very turbid liquid, which
separates, when left at rest, into two layers, the lower being a thick
viscous deposit containing the glucose sirup.
Considerable quantities are sold of a thin sirup, of about 32° Baumé,
in which the proportion of sugar to the impurities is greater than in
common sugar-house molasses. When a sirup of this kind is stirred with
three times its volume of methylic alcohol, a marked turbidity and
deposition will take place, which consists of pure sugar. The crystals
are hard and gritty. They adhere to the sides of the glass, and are
deposited on the bottom. There is no resemblance between this
precipitate and that due to starch sugar sirup.
It may not be useless to mention that if a straight sugar-house sirup
of about 40° B. density is stirred with three times its volume of
_ethylic_ alcohol of about 93½° the sirup will not dissolve. Hence
ethylic alcohol of this strength is not suitable for distinguishing a
sirup mixed with starch glucose from a _straight_ sugar-house sirup.
The presence of starch glucose in sugar-house molasses may be easily
detected by the optical saccharometer when the sirup has the usual
density of about 40° B., and when starch sugar has been added in the
usual quantities.
For making the test the usual weight should be taken (16.35 grammes
for Duboscq's saccharometer, and 26.048 grammes for Ventzke's
instrument). The direct test should show a percentage of sugar not
higher than the number of Baumé degrees indicating the density, and it
may be from 2 to 3 per cent. lower. To understand this, we must refer
to the composition of cane-sugar molasses of 40° B.:
Sugar.......................................37.5
Insoluble impurities........................37.5
Water.......................................25
If the direct test should indicate 55 per cent. of sugar, and if the
molasses were straight, the composition would be--
Sugar...........................................55
Soluble impurities..............................20
Water...........................................25
Now, a product of this composition would not be a clear sirup at 40°
B., but a mixture of sirup and crystals. Therefore, if the product is
a clear sirup at 40° B., and it tests 55 per cent., it cannot be
_straight_.
The presence of starch glucose in sugar-house molasses may also be
detected by the copper test. The possibility of applying this test, as
well as those already indicated, rests on the fact that starch glucose
is always added in very large quantities for the purposes of
adulteration. A very small addition could not be satisfactorily
detected.
The detection by the copper test rests on the observation that very
nearly one-half of the soluble impurities in sugar-house molasses
consists of glucose in the shape of inverted sugar. We have seen above
that for a molasses of 40° B. the soluble impurities amount to about
37½ per cent. We may, then, lay down the rule: that the percentage of
glucose shown by the copper test cannot, in a straight sugar-house
molasses, be much greater than one-half of the number expressing the
density in Baumé degrees. The reason is obvious from what has been
said of the test by the optical saccharometer.
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FALSE VERMILION.--A curious case has been noticed in Germany,
where a small cargo of vermilion was purchased, and, upon being
analyzed, turned out to be red oxide of lead colored by eosine. This
is an entirely novel sophistication. The eosine was separated from the
oxide of lead by digesting the product for twenty-four hours in very
strong alcohol. A much shorter time is sufficient to color the spirit
enough to enable an expert chemist to detect the presence of this
splendid organic coloring matter. Another kind of "vermilion" consists
entirely of peroxide of iron, prepared especially to imitate the
brilliant and costly sulphide of mercury, which it does very well, and
is largely used in England, France, and America.
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