The selling price of beets naturally depends upon their yield in
sugar, and what gives potatoes their value is their yield in fecula or
starch, a product that serves to nourish man and animals and that is
also used in the manufacture of alcohol and glucose. No account,
however, is taken of this important coefficient in business
transactions, potatoes containing proportions of starch varying from
13 to 23 per cent. being sold at the same price. Nevertheless, it is
of the greatest interest to cultivators to make such measurements,
since, in order to increase the value of their product, they might
thereby be led to make a judicious selection in their planting.
[Illustration: THE FECULOMETER.]
Mr. A. Allard, starting from the fact that the richness in starch
increases along with the density, has constructed a simple apparatus
that gives both these data at once, with sufficient precision, and
without calculations, tables, etc. It is, upon the whole, a large
areometer with constant weight and variable volume that is plunged
into a cylindrical vessel 0.5 m. in depth and 0.3 m. in diameter,
filled with water. The instrument itself consists of three parts: (1)
A lower receptacle in which is placed a weight to assure the
equilibrium; (2) a central float into which is put a kilogramme of
very clean and very dry potatoes; and (3) a rod graduated for density
and feculometric richness. The deeper the apparatus sinks, the more
valuable is the potato. How much more?
The degree to which the rod sinks shows this. The same principle and
the same instrument might be applied to the determination of the
density of various agricultural products, such as beets, cider fruits,
grain, etc. It would suffice to graduate a special scale each time.
For each variation of a thousandth in density, the areometer sinks
about 5 millimeters--that is to say, it presents a sensitiveness that
is more than sufficient in practice.--Le Monde Illustré.
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