[Footnote 1:  A Paper read before the American Chemical Society,
    September 2, 1881.]

BY P. CASAMAJOR.

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 931/2 deg..

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 deg.  Baume, 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 deg.  B. density is stirred with three times its volume of ethylic alcohol of about 931/2 deg. 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 deg.  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 Baume 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 deg.  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 deg.  B., but a mixture of sirup and crystals.  Therefore, if the product is a clear sirup at 40 deg.  B., and it tests 55 per cent., it cannot be straight.