FEEDS

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trated sulphuric acid. Heat gently until frothing ceases, then boil the
mixture briskly and continue the digestion until the solution ia colorless or
nearly so or until oxidation i« complete. Cool, dilute with about 200 ce of
water, and add .50 ec of potassium sulphide solution. Make basic and distill
as in the Kjeldahl method.
Non-protein (Amid) Nitrogen.—The non-protein forms of
nitrogen compounds arc usually soluble in water and they are not
precipitated by copper hydroxide. This fact is utilized in effect-
ing a separation of the arnids from true proteins as the latter
form an insoluble compound with copper hydroxide, which
may be separated from the amid by filtration. The amount of
protein nitrogen in the residue is determined by the Kjeldahl
method. This per cent, subtracted from that of total nitrogen,
gives the amid nitrogen.
Determination of Protein Nitrogen.—Prepare cupric hydroxide an follows:
Dissolve 100 gin of pure cupric sulphate in 15 liters of water, add 2.5 ee
of glyeerol and then 10-per cent sodium hydroxide until the liquid "m just
basic. Allow the precipitate of cupric hydroxide*, to settle and decant off the
supernatant liquid. Add distilled water containing 5 per cent of glyeerol,
decant and continue to wash the precipitate by decantatkm with thin
glycerol solution until the washings are no longer basic to phenolphthaleiri.
Rub the cupric hydroxide precipitate in a mortar with enough water con-
taining 10 per cent of glyeerol to make a uniform gelatinous mass capable
of being measured with a pipette. Calculate the weight of cupric hydroxides
in 1 cc of the mixture.
Places a 1-grn sample of the feed in a beaker arid add 100 cc of water.
If the feed is high in alkaline phosphates (an are seeds and oil meals) 'i cc
of a pure Maturated potassium alunx solution (free from ammonia) should be
added to avoid any solution of the protein-copper precipitate. Heat slowly
to boiling and add sufficient cupric, hydroxide reagent to contain about 1 gm
of cupric hydroxide. Stir thoroughly and filter after the. liquid has cooled.
Wash with cold water, place the paper and washed residue in a Kjeldahl
digestion flask and determine the amount of protein nitrogen, an already
directed for nitrogen of crude protein.
Amid Nitrogen.—-Calculate the per cent of amid nitrogen by deducting
the protein nitrogen from the total nitrogen of the* sample.
Carbohydrates.—Carbohydrates are found in vegetable feeds
in variable quantities. In corn, they range, from 70 per eent
in the grain to 16 per cent in the stalks. Their food value
depends to a considerable extent upon the degree of solubility
as a result of mild hydrolysis and enssyme action. The ones
that are immediately soluble in water are the most readily