FEEDS

159

with distilled water. The prepared material is now to be used as any other
asbestos for forming Gooch filters.

Extraction of Sugars from the Feed.—Place 12 gm of the material in a
250-cc round flask and, if the substance has an acid reaction, add 2 gin of
calcium carbonate. Add 150 cc of 50-pcr cent alcohol (volume) and
boil on the steam bath for one hour, using a reflux condenser. Cool and
allow the mixture to stand for several hours. Rinse into a 250-cc volumetric
flask with 95-per cent alcohol which is not acid to phenolphthalein and
dilute to the murk with this alcohol. Mix thoroughly, allow to settle,
transfer 200 cc to a beaker with a pipette and evaporate on a steam bath to
a volume of about 20 ee. (Do not evaporate to dryncss, a little alcohol
in the residue doing no harm.)

Clarijicatioji.-—Transfer to a 100-ec graduated flask and rinse the beaker
thoroughly with water, adding the rinsings to the contents of the flask.
Add enough Maturated neutral lead acetate solution (c) to produce* a
flocculent precipitate, shake thoroughly and allow to stand for 15 minutes.
Dilute to the mark on the flask, mix thoroughly and filter most of the
solution through a dry paper, rejecting the first 5 ec of filtrate. Add
sufficient anhydrous sodium carbonate to the filtrate to precipitate all of the
lead, again filter through a dry paper and test the filtrate with a little more
sodium carbonate, in order to be sure that all of the lead has been removed.

This solution will serve for the determination of both sucrose and reducing
sugars.

Since the, insoluble material of grain or cattle food occupies some space
in the flask as originally made* up, it is Decennary to correct for this volume*.
Results of a large number of determinations on various materials have
shown the average volume of 12 gm of material to be 9 ee, arid therefore

to obtain the true amount of sugars present all results must be multiplied

(250 — 9\
= "-"orQ""' I* ^ the sample weight wan not 12 gm

(±0.5 gm) the factor should be modified accordingly.

Reducing Sugars.—Measure 25 cc of the copper milphate solution (a)
and 25 cc of the alkaline tartrate solution (6) into a 400-cc beaker. Add
25 cc of water and 20 cc; at the sugar solution already prepared. Cover the
beakers with watch glasses and heat on an asbestos mat at such a rate
that boiling begins in 4 minutes. Continue the boiling for exactly 2 min-
utes. Filter through Gooch crucibles (weighed if method («), below, is to be
followed) immediately after heating and wash thoroughly with hot water
(about 60°.) Front this point proceed by one of the following methods:

(«) Gravimetric Method.—Th® Gooch filters must bo dried, ignited, cooled
and weighed before filtration. After filtration dry the crucible and con-
tents, then place in a muffle furnace which in heated to redness (about 700")
and heat for 15 minutes. Cool and weigh and from the weight of cupric
oxide find that of dextrose from Table VII. Multiply by 0.025(- ().9(H X
100 260N

20 X20()J

and calculate the corresponding per cent of dextrose in the

12-gm feed sample, reporting as " reducing sugars/'