HOW TO DETECT ADULTERATIONS IN SPICES—THEIR FORMATION AND ANALYSIS
AS far as its practical use to the merchant or consumer of spices is
concerned, it would be as well, perhaps, if this chapter remained
unwritten, and yet this treatise would be far from complete without it,
as much of that which is herein contained is of the utmost importance,
could it be put into practice.
In this chapter I attempt to give ways to detect adulterations, but the
lamentable fact is that the general merchants have neither the time nor
the facilities at hand to discover the foreign substance.
There are two principal ways of detecting adulterations in spices, which
depend upon the difference in the structure of the cells between the
adulterants and the true spice to which they are added, and also on
their proximate composition. The former difference is recognized by the
mechanical separation and by the use of the microscope, and the latter
by chemical analysis. The adulterations found in spices may be classed
in four grades:
_First._ Integuments of grains of seeds, such as bran of wheat and
buckwheat, hulls of mustard seed, flax seed, etc.
_Second._ Farinaceous substances of low price, as spice damaged in
transportation or by long storage, middlings, corn meal, and stale ship
bread.
_Third._ Leguminous seeds, as peas and beans, which contribute largely
to the profit of the mixer.
_Fourth._ Various articles chosen with reference to their suitableness
to bring up the mixtures, as nearly as possible, to the required
standard color of the genuine article; various shades from light colors
to dark brown may be obtained by skillful roasting of the farinaceous
and leguminous substances, and a little tumeric goes a long way to give
a rich yellow color to real mustard made from pale counterfeit of wheat
flour and terra-alba, or the defective paleness of artificial black
pepper is brought to the desired tone by judicious sifting in of a
finely pulverized charcoal.
From what has been said of the different foreign substances used for
adulterations of spices and condiments, the necessity of knowing the
structure and formation of the molecules of both principal and foreign
elements which constitute the principal tissues of the particular
plant-parts used for the adulterations is apparent, while in the
chemical examination the principle of proximate analysis must be
understood and applied.
It is also necessary that the analyst should be thoroughly acquainted
with the application of the microscope, to determine the cellular
structure, to make determinations of proximate principles in the
substances under examination, since a mechanical separation by the
microscope is more expeditious and is more at the command of the
majority of persons searching for adulterations. For a mechanical
analysis of food separations, a powerful microscope of good workmanship
is required. It is better if it is supplied with a substance condenser
and Nical prisms for the use of polarized light. Objectives of an inch
and half inch, and, for some starches, one-fifth inch, equivalent focus,
are sufficient. One eye-piece of medium depth, one-fourth to one-sixth,
adjusted at 160 degrees is enough, with plenty of good light. The
analyst should also have plenty of sieves of 40 to 60 meshes to the inch
to be used for separation, which will furnish means of detecting
adulterants and selecting particles for investigation, and will often
reveal the presence of foreign material without further examination,
since many adulterants are not ground so fine as the spices to which
they are added, and by passing the mixtures through the sieves the
coarser particles remaining will be either recognized at once by an
unaided educated eye or with a pocket lens.
In this way, tumeric is readily separated from mustard and yellow corn
meal; mustard hulls and cayenne, from low-grade pepper. Where a pocket
lens is insufficient, the higher power of the microscope is
confirmatory. It is also desirable to be provided with a dissecting
microscope for selecting particles for examination from large masses of
ground spice, and for this a large Zeiss stand, made for that purpose,
is best, but simpler forms, or even a hand lens, will answer the
purpose. For smaller apparatus, a few beakers, watch crystals, stirring
rods, and specimen tubes, with bottles for reagents, will be sufficient,
in addition to the ordinary glass slides and covers for glasses. The
reagents required for chemical analysis (if no great amount is used) are
as follows:
Strong alcohol,
Ammonia,
Chloral-hydrate solution—8 parts to 5 of water,
Glycerine,
Iodine solution—water 15 parts, iodide of potash 20 parts, iodine 5
parts; water distilled.
Balsam in benzol and glycerine jelly are desirable for mounting media,
and some wax sheets will be needed for making cells. In addition, the
analyst should supply himself with specimens of whole spices, starches,
and known adulterants, which may be used to become acquainted with the
forms and appearances to be expected; it is easier to begin one’s study
in this way on sections prepared with the knife, and afterwards the
powdered substance may be taken up.
To study the physiological structure in the spices and their adulterants
is quite difficult, as the vegetable tissues which make up the structure
of the spices and the materials of a vegetable origin which are added as
adulterations consist of cells of different forms and thickness; those
which are most prominent and common are the parenchyma, the sclerenchyma
fibrous tissue, and the fibro-vascular bundles. Spiral and dotted
vessels are also common in several of the adulterants, and in the
epidermis are other forms of tissue which it is necessary to be well
acquainted with, though not physiologically. The parenchyma is the most
abundant tissue in all material of vegetable origin, making up the
largest proportion of the main part of the plant. It is composed of thin
wall cells which may be recognized in the potato and in the interior of
the stems of maize. In the latter plant, also, the fibro-vascular system
is well exemplified, running as scattered bundles between the nodes or
joints. Fibrous tissue consists of elongated thick-walled cells of
fibers which are very common in the vegetable kingdom and are well
illustrated in flax, but they are not so commonly used for adulterating
purposes. They are optically active, and in the shorter forms they
somewhat resemble the cells next described. They are seen in one of the
coats of buckwheat hulls and in the outer husks of the cocoanut.
The sclerenchyma is found in the shells of many nuts and in one or two
of the spices, the cells being known as stone cells, from the great
thickening of their walls. To them is due the hardness of the shell of
the cocoanut, the pits of the olive, etc. (See Fig. 1.) Spiral and
dotted vessels are common in woody tissue and are readily recognized.
All these forms an analyst should make himself familiar with.
In pepper and mustard the parenchyma cells are prominent in the interior
of the berry, while those constituting the outer coats are indistinct in
the pepper, because of their deep color; but in the mustard are
characteristics of this particular species. In fact, in many of the
spices, and especially those which are seeds, the forms of the epidermal
cells are very striking, and, if no attempt is made to classify them
their peculiarities must be carefully noted, as the recognition of the
presence of foreign husky matter depends upon a knowledge of the normal
appearance in any spice.
The fibro-vascular bundles are most prominent in ginger and in the
barks, while in the powdered spices they are found as stringy particles.
The sclerenchyma, or stone cells, as shown in Fig. 1, are common in the
adulterant, especially in cocoanut shells, where may also be seen
numerous spiral cells, and in the exterior coats of fibrous tissue. As
to aids to distinguish these structures, the following peculiarities may
be cited:
[Illustration:
Fig. 1. STONE CELLS
Fig. 2. STARCH STAINED WITH IODINE
Fig. 3. _Starch, plain_
Fig. 4. POTATO STARCH
Fig. 5. _Potato_]
The stone cells and fibrous tissue are optically active, and are,
therefore, readily detected with polarized light, shining out in the
dark field of the microscope as silver-white or yellowish bodies.
The fibro-vascular bundles are stained deep orange brown with iodine,
owing to the nitrogenous matter which they contain, while parenchyma is
not affected by this reagent, aside from the cell contents, nor has it
any action on polarized light, remaining quite invisible in the field
with crossed prisms.
Next to cellular tissue, starch is the most important element for
consideration in the plant, which possesses an organized structure and
is distinguished by its reaction with iodine solution, which gives it a
deep blue or blackish-blue color, varying somewhat with different kinds
of starch and with the strength of the reagent, and its absence is
marked by no blue color under the same circumstances.
Heat, however, as in the process of baking, so alters starches,
converting them into dextrine and related bodies, that they give a brown
color with iodine, instead of a blue-black; they are no longer starch,
however; their form, not being essentially changed, permits of their
identification, with a study of the size and shape of the granules of
the hilum, or central depressions of nucleus, and the prominence and
position of the rings. By polarized light and selenite, the starches of
tubers showed a more varied play of colors than the cereal and
leguminous starches which are produced above ground. The starches we are
to consider are those of a limited number to be met with in spices and
their adulterants, and one must be able readily to recognize the
following:
STARCH NATURAL TO SPICES AND CONDIMENTS
Ginger,
Pepper,
Nutmegs,
Cassia,
Pimento,
Cinnamon,
Cayenne.
STARCHES OF ADMIXTURES
Wheat and other Cereals:
Corn,
Oats,
Barley,
Potato.
Maranata and other arrowroots:
Rice,
Beans,
Peas,
Sago,
Buckwheat.
No one of these is complete in itself, but from the characters given,
and with the aid of illustrations, the starches which commonly occur in
substances which are here considered may usually be identified without
difficulty.
For the benefit of those who have had no experience with the microscope,
I will give the following directions:
Take a small portion of the starch or spice to be examined upon a clean
camel’s hair brush and dust it upon a common slide, blow the excess away
and moisten that retained with a drop of a mixture of equal parts of
glycerine and water, or with glycerine and camphor water, and cover with
a glass. It is well to have a small supply of the common starches in a
series of tubes which can be mounted at any moment and used for
comparison. They may be permanently mounted by making with cork borers,
of two sizes, a wax cell ring equal to the diameter of the cover glass
and, after cementing the cell to the slide with copal varnish thinned
with turpentine and introducing the starch and glycerine mixture, fixing
the cover glass on after running some of the cement over the top of the
ring. A little experience will enable one to put the right amount of
liquid in the cell and to make a preparation that will keep for some
time. After several months, however, it is hard to distinguish the rings
which mark the development of the granule, and it is better to keep it
fresh.
For other purposes, the starches should be mounted in prepared Canada
Balsam, or by well-known methods in which they may be preserved
indefinitely, but they are scarcely visible with ordinary illumination
and must be viewed by polarized light, which will bring out distinctive
characters not seen as well, or not at all, in the other mounts. When
mounted in the manner described, in glycerine and water, or in water
alone, if for temporary use, under a microscope with one objective of
equivalent focus of one-half to one-fifth inch, and with means for
oblique illumination, the starches will display characteristics which
are illustrated in Figs. 2, 3, and 4. The illustrations have been drawn
from Nature; Fig. 2 gives starch stained with iodine; Fig. 3 gives shape
and size of plain starch, and presence or absence of a nucleus, or
hilum, and of the rings and their arrangements which can be made out.
The starch is classed in its proper place.
If mounted in balsam, their appearance is scarcely visible under any
form of illumination with ordinary light, the index refraction of the
granules and the balsam being so similar, but when polarized light is
used the effect is a striking one. (See plates of ginger, where it is
easy to distinguish all the characteristics, except the rings, the
center of the cross being at the nucleus of the granule.)
The principal starches which are met with may be described as follows in
connection with illustrations given, beginning with those of the
arrowroot class, including potato, ginger, and tumeric.
[Illustration:
Fig. 6. & Fig. 7. POTATO STARCH
Fig. 8. MARUNTA STARCH
Fig. 9. & Fig. 10. _Marunta_]
POTATO STARCH
Potato starch grains are very variable in size, being found from .05 to
.10 millimeter in length, and in shape from oval and allied forms to
irregular, and even round in the smallest; these variations are
illustrated in Fig. 4, but the frequency of the smaller granules is not
as evident as in Figs. 5 and 6. The layers in some granules are very
plain and in others are hardly visible. They are rather more prominent
in the starch obtained from a freshly cut surface. The rings are more
distinct near the hilum, or nucleus, which in this, as in all tuberous
starches, is eccentric, shading off toward the broader or more expanded
portion of the granules.
The hilum appears as a shadowy depression (Fig. 4) and, with polarized
light, its position is well marked by the junction of the arms of the
cross. It will be found by comparison of Fig. 6 and Fig. 7, that in the
potato it is more often at the smaller end of the granules, and that in
the arrowroot it is at the larger. With polarized light and a selenite
plate a beautiful play of colors is obtained.
The smaller granules, by their nearly round shape, may be confused with
other starches, but their presence at once serves to distinguish them
from Maranta or Bermuda arrowroot starch. Rarely, compound granules are
found composed of two or three single ones each within its own nucleus.
Of the same type as the potato starch are various arrowroots. The only
ones commonly met with in this country are the Bermuda, the starch of
the rhizome of Maranta arundinacea, and the starch of tumeric.
MARANTA STARCH
The granules are not usually so varied in size or shape as those of the
potato, as may be seen in Figs. 8, 9, and 10. They average about .07
millimeters in length. They are about the same size as the average of
those of the potato, but are never found as large or as small. This
fact, together with the fact that the end at which the nucleus appears
is broader in the Maranta and more pointed in the potato, enables one to
distinguish the starches without difficulty. With polarized light, the
results are similar to those seen with potato starch, and, by this
means, the two varieties may be readily distinguished by displaying, in
a striking way, the forms of the granule and the position of the hilum,
as is illustrated in Figs. 8 and 9.
CIRCUMA
Circuma, or tumeric starch (Fig. 11), though of the arrowroot class, is
quite distinct in appearance from these we have described, being most
irregular in outline, so that it is impossible to define its shape or to
do more than to refer to the illustration. Many of the granules are long
and narrow and drawn out to quite a point. The rings are distinct in the
larger, and the size is about that of Maranta.
Ginger starch (Figs. 12, 13, and 14) is of the same class as potato and
Maranta and several others which are of underground origin. In outline,
it is not oval like those named, but is more rectangular, having more
obtuse angles in the larger granules and being cylindrical or circular
in outline in the smaller; its average size is nearly the same as
Maranta starch, but it is much more variable in size and form, the rings
being scarcely visible even with most favorable illuminations. Fig. 12
shows ginger adulterated.
------------------------------------------------------------------------
[Illustration:
Fig. 15. BEANS
Fig. 16. _Beans_
Fig. 17. PEAS
Fig. 18. _Peas_.
Fig. 46. CINNAMON ADULTERATED]
[Illustration:
Fig. 21. _Pepper_
Fig. 27. RICE STARCH
Fig. 28. RICE STARCH
Fig. 29. _Rice_
Fig. 42. P. D. PEPPER
Fig. 43. PEPPER ADULTERATED]
LEGUMINOUS STARCHES
Such as those of beans and peas (Figs. 15, 16, 17, and 18), produce but
a slight effect under polarized light; the rings are scarcely visible,
and the hilum is stellate or much cracked along a median line. This
characteristic is more marked in the bean than in the pea. In the latter
it resembles fresh dough kneaded again into the center as in making
rolls, and in the former the shape assumed by the same after baking. In
both it varies in size from .025 to .10 millimeter in length.
NUTMEG STARCH
Fig. 19 has rings scarcely visible and not iridescent with polarized
light. It is smaller in size than the preceding, which it resembles,
being at times as long as .05 millimeter down to smaller than .005
millimeter, and of extremely irregular form, having angular depressions
and angular outlines. It is distinguished by a budded appearance caused
by the adherence of small granules to the larger.
CAPSICUM STARCH
Fig. 20 is nearly circular or rounded polyhedral in forms with scarcely
visible rings, and in most cases a depressed hilum, resembling in size
and shape corn starch, but having peculiar irregularities which
distinguish it, such as rosette-like formation on a flattened granule,
or a round depression at one end. It does not polarize as actively as
maize starch and can be distinguished from rice by the greater
angularity of the latter.
PEPPER STARCH
Fig. 21 is the most minute starch which is usually met with, not
averaging over .001 millimeter nor exceeding .005. It is irregularly
polyhedral and polarizes very well, but requires a high power to
discover any detail when a hilum is found. It cannot be confused with
other starches.
CINNAMON STARCH
Figs. 22 and 23 have an extremely irregular polyhedral or distorted
granules, often united in groups with smaller granules and adherent to
the larger ones. In size, it varies from .001 to .025 millimeter,
averaging nearly the latter size. In some granules the hilum can be
distinguished, but no rings; it is readily detected with polarized
light.
BUCKWHEAT STARCH
Fig. 24 is very characteristic. It consists of a chain or groups of
angular granules with a not very evident circular nucleus and without
rings. The outline is strikingly angular and the size not very variable,
being about .01 to .015 millimeter.
MAIZE OR CORN STARCH
Figs. 25 and 26 have granules largely of the same size from .02 to .03
millimeter in diameter, with now and then a few which are much smaller;
they are mostly circular in shape or, rather, polyhedral with rounded
angles. They form very brilliant objects with polarized light, but with
ordinary illumination show but the faintest signs of rings and a
well-developed hilum, at times star-shaped and at others more like a
circular depression.
RICE STARCH
Figs. 27, 28, and 29, is very similar to corn starch, and is easily
confused with it, being about the same size. It is, however,
distinguished from it by its polygonal form and its well-defined angles.
The hilum is more prominent and more often stellate, or linear, and
several grains are at times united.
[Illustration:
Fig. 22. PURE CINNAMON
Fig. 23 _Cinnamon_
Fig. 25. MAIZE STARCH
Fig. 26 _Corn_
Fig. 41. PURE CASSIA]
[Illustration:
Fig. 30. WHEAT STARCH
Fig. 31 _Wheat_
Fig. 32. BARLEY STARCH
Fig. 33 _Barley_]
WHEAT STARCH
Figs. 30 and 31 are quite variable in size, varying from .05 to .012
millimeter in diameter, and this starch belongs to the same class as
barley and rye; the hilum is invisible and the rings are not prominent;
the granules are circular disks in form, and there are now and then
contorted depressions, resembling those in the pea starch; it is the
least regular of the three starches and does not polarize actively.
BARLEY STARCH
Figs. 32 and 33 are quite similar to that of wheat, but barley starch
does not vary so much in size, averaging .05 millimeter. It has rings
more distinct and very small granules adhering to the largest in
bud-like forms.
RYE STARCH
Fig. 34 is more variable in size, many of the granules not exceeding .02
millimeter while the largest reach .06 to .07 millimeter. It lacks
distinctive characteristics entirely, and is the most simple in form of
all starches described.
OAT STARCH
Figs. 35 and 36, is unique, being composed of large compound masses of
polyhedral granules from .12 to .02 millimeter in length, the single
granules averaging .02 to .015 millimeter. It does not polarize
actively, as may be seen in the figures, and displays neither rings nor
hilum.
The first sign of maize or corn meal as an adulterant is the thin outer
coat which becomes detached in milling and is not readily crushed. In
yellow corn it has a pinkish color, and simple, longitudinal cells.
Broken rice is sometimes used as a dilutant; it may be recognized by the
brilliant appearance of the hard white particles which may be picked out
of the spice under a hand lens.
The two cereals named (broken rice and maize corn) are the only ones
which are commonly met with that introduce starch.
Wheat bran (Fig. 37) is occasionally added, which can be recognized by
its distinctive structural character and is better understood from an
authentic specimen, which should be soaked in chloral-hydrate.
As modified cereals, we find refuse bread, cracker dust, and stale ship
bread, in which the wheat starch is much changed from its original form
by the heat and moisture, so that at times it might be confused with
leguminous starch, but the softness of the particles and the ease with
which they fall to pieces in water reveal their true name. Oil seed, oil
cake, and husk (Figs. 38, 39, and 40) are very commonly used and are
readily recognized by the peculiar structure of the outer coats of the
seed. The particles, which can be usually found and selected with a
dissecting microscope, should be examined in alcohol or glycerine, or a
mixture of the two, as the outer coats of some seeds, such as mustard,
are swollen by water and become indistinct. Many varieties of the
cruciferous seeds resemble it very much, so that it is difficult to
distinguish them, but it is generally recognized by the outer layer of
hexagonal cells and a middle and inner coating, which consists of
peculiar angular cells, the latter being much larger than the former,
which are the most characteristic feature, and should be compared with
seeds of known origin. After soaking in chloral-hydrate, the remaining
interior layers are, perhaps, more easily made out, in some cases, after
moderate bleaching with nitric acid and chlorate; the interior of this
seed is not blued by iodine.
Peanut, or ground nut cake, is recognized by the characteristic
structure of the red-brownish coat, which surrounds the seed, and
consists of polygonal cells with peculiar saw-toothed thickening of the
walls. The seed itself consists of polygonal cells full of oil and
starch granules, which are globular in form and not easily confused with
pepper starch. The structure of the brown membrane is best made out in
chloral-hydrate, which removes the red color and leaves the fragments of
a bright yellow.
Linseed cake is distinguished by the fact that its husk is made up of
one or two characteristic elements. The outer coat, or epidermis, is
colorless and swells up in water, forming a mucilage, like the mustard
seed. Beneath this is a layer of thin, round, yellow cells, while the
third is very characteristic and consists of narrow and very
thick-walled dotted vessels; next to these is an inner layer of compact
polygonal cells, with fairly thin, but still thickly dotted, white walls
and dark-brown contents containing tumeric. The endogen and embryo are
free from starch and will not color yellow by potash, as is the case
with mustard and rape seed cake.
[Illustration:
Fig. 35. OAT STARCH
Fig. 36. _Oats_
Fig. 37. WHEAT BRAN
Fig. 46. POWDERED ALLSPICE SHOWING PORT WINE CELLS. (A) STARCH]
Cocoanut shells are often used, and have numerous, both long and short,
stone cells and spiral vessels from this fibrous tissue; the long stone
cells having thinner walls than the shorter cells, all of which are
readily seen after bleaching. When the shells are roasted, they refuse
to bleach, and it is then only possible to class the particles, on which
the reagents do not act, as roasted shells or charcoal, which are
frequently used in pepper to give desired color to material rendered too
light by white adulterants.
Buckwheat, after bleaching, shows a preponderance of tissue made up of
long, slender, and pointed sclerenchyma cells and a smaller amount of
reticulated tissue, resembling the cereals somewhat and cayenne pepper.
Portions of the interior of the seed are also visible and consist of an
agglomeration of small hexagonal cells which originally contained
starch. The starch is readily recognized by its peculiar
characteristics. The sclerenchyma is, of course, optically active and
forms a beautiful and distinctive object with polarized light. Sawdust
of various woods may be recognized by the fragments of various spiral
and dotted vessels and fibrous material which are not found in spices or
in other adulterants.
Rice bran is made up prominently of two series of cells at right angles
to each other, which make up the outer coats of grain, the structure
being best made out after soaking in chloral-hydrate; the cells of one
series are long, small, and thin-walled, and are arranged in parallel
bundles; the others have very much thicker walls and are only two or
three times as long as they are broad.
Clove stems are distinguished by their peculiar yellow dotted vessels
and their large and quite numerous cells, neither of which is seen
prominently in the substances which are adulterated. The peculiarities
of adulterants should be carefully confirmed and the eye trained by
practice so as to become accustomed to recognizing their structure by a
study of the actual substance.
Take one gram of powdered spice which will pass a 60-mesh sieve and dry
at 150 degrees to 110 degrees C. in an air bath provided with a
regulator, until a successive weighing shows a gain, which denotes that
oxidization has begun, which takes about 12 hours, or over night; the
loss is water, together with the largest part of volatile oil. Deduction
of the volatile oil, as determined in the ether extract, will give a
close approximation of water. The ash portion is determined by
incineration at a very low temperature, such as may be attained in a gas
muffle, which is the most convenient arrangement for work of this kind.
The proportion of ash insoluble in acid may be determined where there is
a reason to believe that sand is present.
To find the amount of volatile oil by ether extract: Two grains of
substance are extracted for twenty-four hours in a siphoning extraction
apparatus, being first placed in a test tube, which is inserted into a
continuous extraction apparatus of the intermittent siphon class, the
tube used being an ordinary test tube, the bottom of which has been
blown out. A wad of washed cotton of sufficient thickness is put in the
lower end of the tubes to prevent any solid particles of the sample from
finding their way into the receiving flask; another wad of cotton is
packed on top of the sample, and the apparatus is then so adjusted that
the condensed ether drops into the tube and percolates through the
sample siphons into the receiving flask. In this way the operation is
continued the length of time named. The best ether should be used to
avoid extracting substances other than oil soluble in alcohol, and to
continue the extraction for at least the time named, as piperine and
several other proximate principles are not extremely soluble in ether.
On stopping the extraction, the extract is washed into a light, weighed,
glass dish, and the ether is allowed to evaporate spontaneously, but not
too rapidly, for the reason that water, which is difficult to remove,
might be condensed into the dish. In a short time the ether will
disappear, and the dish is placed in a dessicator with pumice and
sulphuric acid, not with chloride of calcium, which has been shown to be
useless. It is allowed to remain over night to remove any moisture; the
loss of oil by this process is scarcely appreciable. The dish is next
weighed and afterward heated to 110 degrees C. for some hours, to drive
off the volatile oil, beginning at a low temperature, as the oil is
easily oxidized, and then is not volatile oil. The residue is weighed,
the difference being calculated to volatile oil and examined as to its
composition of purity.
[Illustration:
Fig. 11. _Tumeric_
Fig. 12. GINGER ADULTERATED
Fig. 13. PURE GINGER
Fig. 14. _Ginger_
Fig. 19. _Nutmeg_
Fig. 24. _Buckwheat_
Fig. 34. _Rye_]
Alcohol extract is made in the same manner as the ether extract, using,
of course, the substance extracted. The solvent may be either absolute
alcohol—that of 95 per cent. by volume, or 80 per cent. by weight, the
latter being preferable in most cases, as there is no definite point
with the stronger spirit at which the extraction is completed.
The amount of reducing material produced by boiling the spices with
dilute acids serves with several as an index of purity. In the case of
pepper, which contains a large amount of starch, the addition of fibrous
adulterants reduces the equivalent of reducing sugar, which are
indicated in the solution after boiling with acid. Tumeric is always
found in spices, such as cloves and pimento of good quality.
It has been said that preliminary extractions of the material with the
best ether is necessary to remove oil and other substances, not tannin
on which permanganate may act; ordinary ether will not answer, as it
contains so much alcohol and water as to dissolve some of the tannin.
The substance freed from ether should be extracted with boiling water
and the extract made up to such dilution that 10 CC. is equal to about
10 CC. of the thirtieth normal,—permanganate solution used. The
titration must be performed slowly to insure accuracy, the permanganate
being run in at the rate of not more than a drop in a second, or three
drops in two seconds. The eye must become accustomed to the bleaching of
the indigo used, and select some one tint of yellow, as the end of
reaction is then possible to duplicate. That part of the material
analyzed, which is insoluble in acid and alkali of certain strength
after treatment for a definite length of time, at a definite
temperature, is called _crude fiber_, and it may be described as
follows: Select two grains of substance 200 CC. of 5 per cent.
hydrochloric acid; steam bath two hours, raising the liquid to a
temperature of 90 degrees to 95 degrees C. filtration on linen cloth,
washing back into beaker with 200 CC. 5 per cent. sodic-hydrate; steam
bath two hours, filtration on asbestos, washing with hot water, alcohol,
and ether, drying at 120 degrees, weighing, ignition and crude fiber
from loss in weight.
REAGENTS AND APPARATUS
(1). Hydrochloric acid whose absolute strength has been determined.
(a). By precipitating with silver nitrate and weighing the silver
chloride.
(b). By sodium carbonate, as described in Fresenius Quantitative
Analysis, second American edition, page 680.
(c). by determining the amount neutralized by the distillate from a
weighed quantity of pure ammonium-chloride boiled with an excess of
sodium-hydrate.
(2). Standard ammonia whose strength relative to the acid has been
accurately determined.
(3). C. P. sulphuric acid specific gravity 1.83, free from nitrates, and
also from ammonium sulphates, which are sometimes added in the process
of manufacture to destroy oxides of nitrogen.
(4). Mercuric-oxide, HgO, prepared in the wet way. That prepared from
mercury nitrate cannot safely be used.
(5). Potassium permanganate tolerably finely pulverized.
(6). Granulated zinc.
(7). A solution of 40 grams of commercial potassium-sulphide in one
liter of water.
(8). A saturated solution of sodium-hydrate, free from nitrates which
are sometimes added in the process of manufacture to destroy organic
matter and improve the color of the product.
(9). Solution of cochineal, prepared according to Fresenius Quantitative
Analysis, second American edition, page 679.
(10). Burettes should be calibrated in all cases by the user.
(11). Digestion flasks of hard, and moderately thick, well-annealed
glass, which should be about 9 inches long, with a round, pear-shaped
bottom, having a maximum diameter of 2½ inches and tapering out
gradually in a long neck, which is three-fourths of an inch in diameter
at the narrowest part and flared a little at the edge. The total
capacity is 225 to 250 cubic centimeters.
(12). Distillation flasks of ordinary shape, 550 cubic centimeters
capacity, and fitted with rubber stoppers, and a bulb tube above to
prevent the possibility of sodium-hydrate being carried over
mechanically during distillation; this is adjusted to the tube of the
condenser by a rubber tube.
(13). A condenser with tube of block tin is best, as glass is decomposed
by steam and ammonia vapor, and will give up alkali enough to impair
accuracy; the tank should be made of copper, supported by wooden frame,
so that its bottom is 11 inches above the workbench on which it stands.
It should be about 16 inches high, 32 inches long, and 3 inches wide,
gradually widening 6 inches toward the top; the water-supply tube should
extend to the bottom, and there should be a larger overflow pipe above.
The block tin condensing tubes should be about ⅜ of an inch inner
measure and seven in number, entering the tank through holes in the
front side of it near the top above the level of the overflow, and pass
down perpendicularly through the tank and out through the rubber
stoppers, tightly fitted into holes in the bottom; they should project
1½ inches below the bottom of the tank, and connect by short rubber
tubes, with glass bulb tubes, of the usual shape, which dip into glass
precipitating beakers. These beakers should project about 6½ inches high
by 3 inches in diameter below, gradually narrowing above, and should be
about 500 cubic centimeters capacity. The titration can be made directly
in them. The seven distillation flasks should be supported on a
sheet-iron shelf attached to the wooden frame which supports the tank at
the front; where each flask is to stand, a circular hole should be cut
with three projecting lips to support the wire gauze under the flask,
and three other lips to hold the flask in place, and to prevent its
moving laterally out of place while distillation is going on. Below the
sheet-iron shelf should be a metal tube carrying seven Bunsen burners,
each with a stopcock like those of a gas combustion furnace. These
burners are of larger diameter at the top, which prevents smoking when
covered with fine gauze to prevent the flame from striking back.
(14). The stand for holding the digestion flask should consist of a pan
of sheet iron, 29 inches long by 8 inches wide, on the front of which is
fastened a shelf of sheet iron as long as the pan, 5 inches wide and 4
inches high. In this are cut six holes 1⅝ inches in diameter. At the
back of the pan is a stout wire running lengthwise of the stand, 8
inches high, with a bend or depression opposite each hole in the shelf.
The digestion flask rests with its lower part over a hole in the shelf
and its neck in one of the depressions in the wire frame, which holds it
securely in position, and heat should be supplied with Bunsen burners
below the shelf.
THE DETERMINATION
One gram of the substance to be analyzed is brought into a digestion
flask with approximately 0.7 grams of mercuric-oxide, and 20 cubic
centimeters of sulphuric acid, and the flask is placed on the frame
described in an inclined position, and heated below the boiling point of
the acid for from five to fifteen minutes, or until frothing has ceased.
The heat is then raised until it boils briskly. No further attention is
required until the contents of the flask have become a clear liquor,
which is colorless, or, at least, has only a very pale straw color. The
flask is then removed from the flame, held upright, and, while yet hot,
potassium permanganate is dropped in carefully and in small quantities
at a time until, after shaking, the liquid remains of a green or purple
color.
After cooling, the contents of the flask are then transferred to the
distilling flask with water, and to this 25 cubic centimeters of
potassium-sulphide solution are added, 50 cubic centimeters of the soda
solution, or sufficient to make the reaction strongly alkaline, and with
a few pieces of granulated zinc.
The flask is at once connected with the condenser and the contents of
the flask are distilled until all of the ammonia has passed over into
the standard acid contained in the precipitating flask previously
described and the concentrated solution can no longer be safely boiled.
This operation usually requires from 20 to 40 minutes. The distillate is
then titrated with standard ammonia. The use of the mercuric-oxide in
this operation greatly shortens the time necessary for digestion, which
is rarely over an hour and a half in the case of substances most
difficult to oxidize, and is more commonly less than an hour.
In most cases the use of potassium permanganate is quite unnecessary,
but it is believed that in exceptional cases it is required for complete
oxidation, and, in view of the uncertainty, it is always used.
Potassium-sulphide removes all mercury from solutions and so prevents
the formation of mercuro-ammonium compounds which are not completely
decomposed by soda solution.
The addition of zinc gives rise to an evolution of hydrogen and prevents
violent bumping. Previous to use, the reagents should be tested by a
blank experiment with sugar, which will partially reduce any nitrates
that are present which might otherwise escape notice.
This method cannot be used for the determination of nitrogen substances
which contain nitrate or certain albumenoids.
These methods of analysis are suitable to all spices and have been used
with them. They are but a general process, however, and are dependent
for their value on uniformity in the way they are carried out and the
manner in which peculiarities of proximate composition in different
spices are considered in drawing conclusions; determinations of
particular substances, such as piperine, require, however,
modifications, which must be described when discussing the analysis of
each separate spice.
The chemical composition of olive stones and cocoanut shells is about as
follows:
Water, 5.63 6.15
Ash, 4.28 2.15
Fiber, 41.33 37.15
Albumenoids, 1.56 1.25
Nitrogen, .25 .20
------------------------------------------------------------------------
[Illustration: BLACK PEPPER (Piper Nigrum)
1 Malabar
2 Acheen or Sumatra
3 Mangalore
4 Singapore
5 White, from Penang, with all three coats removed
6 White, with one coat removed
7, 8 Parts of spikes
9, 10 Fruit
12 Ovary with stamens
13 Stamens
14 Portion of spike
15 A flowering twig]