194

QUANTITATIVE

\ \ MM'.s'/.S

Newhall states that as little as 5 per rent, of soyboan oil may
be detected in a mixture, by this test. To the limited extent to
which this teat has boon used by the, mil liors if has \m-n found to
be reliable but see also a criticism by Honiuy and Whitescarver.1

Fish and Marine Animal Oils in Mixtures with Vegetable
Oils.— Practically all of these oils have very c'onsi<l«Tul>to
"drying" properties, as shown by their iodine absorption
numbers. They are chameforixod by the prewwe of glyreriden
containing highly unsatuntted acids. The* peculiar "'fishy1''
odor of these oils is probably due to the presence of the glymides
of such acids.

Absorption of bromine by unsatuntted acid* or their Klycc»ridon
produces bromides of limited solubility and high melting point,
Octobromstoarin, obtained! from .such acids, melts at a higher
temperature (above 200°) and has a lower solubility f him liexu-
bromstearin, obtained by bromlnntiug linoleum, and fbis alno
differs in a similar manner from tef.rabrorn?ttearinf obtained from
linolin. Therefore the* separation of oefobrowHtwirm from
brominatcd fish and blubber oils provides a means for detecting
marine animal oils in the. presence of vegetable oil*. The* test in
performed as follows ;

in a tout-tube about 0 gm of the* oil its I'J «•<• f»f u mi^titr** of
equal ]>nrtH of chloroform ami glnc'ial itfrlir add, Add hrninitt*1, drop
by drop, until a Blight, oxccss w imiimtff! by tin* rolor, kf*(*pinfc thf maiutiott
at about 20°. Allow to Htund for 15 minutcM or inc»n* nwl fhou jiliwr flir*
tcHt-tuhd in boiling watr T. If only v<wtnf>Ic <>»!« »ri* pnvMfnf ili»» Noltifion
will hecome porfectly diwr, while fwli uiJn will rmuim rhnirly or «»nf.«Iri a
precipitate of insoluble h

Color Reactions.— A large* ntimlH*r of r|ualitaiivo twin, l>ow»d
upon certain color roactioriH, have* bi«c»n prof)cjHi*il uncl ron»ifif»ral>iy
usod in the pant for thu d<»t(*«tiV)ii of varioii« oil*. ( j»br r«*act,ic «w
produced by adding <wir<»ntrat«'cl nitrir or Htiliilttirir iteiflu
may be montionotl. Almost without c!xw|.)t«.in thrw» havct bwn
found to bo unrdiablo and thoy will not IK* flifHrribfid hwo in
detail.
Hardened Oils.— XJndnr any circumKtnnci'K thc» analytical
investigation of oils anrl fnf« offctrH diffifitlllw that aw often
l,7. IwL Bug. Chew., 13, S7-I H^l).