192	QUANTITATIVE AGRICULTURAL ANALYSIS
of error.    These " constants" will be of use chiefly in the detec-
tion of drying oils, all of which show high values.
Determination of Matimene Number.—Place a beaker, about 5 by 1.5
inches, inside a somewhat larger one and pack the open space between with
wool, asbestos or cotton. Cover the beakers with a piece of cardboard
through which passes a thermometer. Weigh into the inner beaker 50 gm of
oil. Bring concentrated sulphuric acid to the same temperature as that of
the oil, and then add, under a hood, 10 cc of this acid, stirring thoroughly
with the thermometer. When the acid is all in, place the thermometer in the
center of the oil-acid mixture and note the highest point attained by the
mercury. The total rise in temperature is the Maumene* number.
Determine also the specific temperature reaction as follows: Clean the
inner beaker and introduce 50 cc of water. Add 10 cc of acid as before
and note the rise in temperature. The Maumene* number divided by this
rise is the specific temperature reaction.
The drying oils often develop so much heat that active foaming results.
Such oils should be first diluted with petroleum oils or olive oil and the
proper correction made in the temperature rise.
Qualitative Reactions.—If simple and reliable qualitative
tests were known for all of the oils, it is not likely that the work
outlined in the preceding pages would often be carried out. It
has already been explained that comparatively few such tests
are known because of the similarity in the composition of the
various animal and vegetable oils. Aside from the mere varia-
tion in the proportion of the various glycerides, free alcohols and
free acids, there are certain constituents of certain oils that will
give color reactions which are characteristic. A few of those
that are reliable will be described. In most cases these tests
should accompany the determination of the analytical constants,
rather than be substituted for them.
Resin Oil.—Polarize the oil in a 200-mm tube. If the oil is too dark
in color for this purpose it may be diluted with petroleum ether and the
proper correction made in the reading. Resin oil has a polarization in
a 200-mm tube of from +30° to 40° on the International sugar scale (see
page 130) while other oils read between +1° and —1°
Cotton Seed Oil: ffalphen Test.—Mix carbon disulphide containing about
1 per cent of sulphur in solution, with an equal volume of amyl alcohol. Mix
equal volumes of this reagent and the oil in a test tube and heat in a bath
of boiling, saturated solution of sodium chloride for about an hour. In
the presence of as little as 1 per cent of cotton seed oil a characteristic
red color is produced. Lard and lard oil from animals fed on cotton seed
meal will give a faint reaction for cotton seed oil. The unknown con-