John Muter.

A short manual of analytical chemistry, qualitative and quantitative--inorganic and organic online

. (page 28 of 31)
Online LibraryJohn MuterA short manual of analytical chemistry, qualitative and quantitative--inorganic and organic → online text (page 28 of 31)
Font size
QR-code for this ebook


dish, the residue being dried in the water oven to constant weight and
weighed = actual real soap present. The dish and contents are then gently
heated to redness, the residue left being dissolved in water and titrated with
tenth-normal acid, using methyl orange as the indicator. The number of Cc.
used is multiplied by '0031 for hard soda soaps, or by '0047 f r s ft potash
soaps, and the resulting amount of alkali being deducted from the weight of
real soap found the difference x 1*03 = amount of fatty acids. The weights
of real soap and total impurities added together, and deducted from 2, gives the
water present in the sample. Finally, everything is calculated to percentage.

XIII. ANALYSIS OF ESSENTIAL OILS,

i. Physical Constants. The specific gravity and the rotation in the
polariscope, using a tube 100 Mm. long at a temperature of 25 C., are of
importance, although variable within narrow limits. The following are the
average results with the U.S.P. oils :

Sp. Gr. at 25 C. Optical Rotation in 100 Mm. tube at 25 C

(if F.). (77 F.).

inactive.

-2.

+ 95 (not less),
inactive.

2 (not more).
+ 70 to + 80.

inactive or slightly .

5 (not more),
practically inactive ( or + 1.
not constant.

+ 7 to + 14.

25 to 40.
+ 50 (about).

+ 10 (not more).



Oleum Amygdalae Amarae


I '045 to ro6o




Anisi




'975


985




Aurantii .




842


846




Betulae




1-172


ri8o




Cajuputi .




915


925




Cari




'90S


915




Caryophylli




ro4o


ro6o




Chenopodii




965


989




Cinnamoni




i '045


i'055




Copaibce .




895


905




Coriandri.




863


878




Cubebae .




'90S


925




Krigerontis




845


865




, Eucalypti .




'90S


925



216



ANALYSIS OF DRUGS, ETC.





Sp. Gr. at 25 C.


Optical Rotation in 100 Mm. tube at 25 C.




(77 F.).


(77 F.).


Oleum Foeniculi .


'953 to '973


. not constant.


,, Gaultheriae


1-172 ri8o


i (not more).


,, Hedeomas


920 -935


. + 18 to + 22.


Juniper! .
,, Lavandulae


860 -880
880 -892


. not constant, dependent on age.


,, Limonis .


851 -855


. + 60 (not less). The first 10 per cent.



1


Menthse piperitae


. -894


914


- 25 to - 33.


>


,, viridis.


* -914


'934


- 35 to - 48.




Myristicae


. -862


-910 .


+ 14 to + 28.


t


Pimentse .


i '033


1-048 .


not constant, gener;


(


Rosse


. -855


865 .


5> >t


!


Rosmarini


'894


912 .


+ 15 (not more).


>


Sabinae


-903


923 .


+ 40 to + 60.




Santali


. -965


'975


- 1 6 (not less).


J


Sassafras .


. 1-065


1-075


+ 4 (not more).


>


Sinapis . .


. 1-013


i -020 .


inactive.




Terebinthinae .


. -860


, -870 .


not constant, but










dextrogyrate.


),


Thymi .


. -900 ,


. '930 -


3 (not more).



of oil obtained by fractional dis-
tillation should not differ more
than 2 from the original.



American oil is



The boiling point is scarcely ever constant, as these oils are always mixtures,
and therefore require fractional distillation in a proper dephlegmator. The
results depend so much on the apparatus employed, that it is hopeless to get
any agreement in this respect between different operators, until an official
method is definitely laid down. If, however, 50 Cc. of the oil be distilled
from a long-necked Erlenmeyer flask of 100 Cc. capacity, with a thermometer
in the neck, and placed on a piece of wire gauze, to which heat is directly
applied by a Bunsen burner, fairly concordant estimations may be made on
successive quantities. Treated in this way Oleum Terebinthince, U.S. P. should
practically entirely distil over between 155 and 162 C.

The combination of fractional distillation and specific gravity or optical
rotation is often very useful in detecting mixtures of essential oils with
turpentine, etc. This method is employed by the U.S. P. in the examination
of certain oils as follows :

Oleum Limonis and Oleum Rosmarini should respectively rotate the plane of a ray of
polarized light not les? than 60 and not more than 15 to the right in a tube 100 millimeters
long; and if 100 volumes be fractionally distilled, the 10 volumes first collected should not
produce a rotation differing by more than 2 from that produced by the original oil in the
former case, and should also be dextrogyrate in the latter.

Oleum Sinapis Volatile should distil between 148 C. and 152 C., and the first and last
portions of the distillate should have the same specific gravity as the original oil (absence of
ethylic alcohol and petroleum).

In the case of Oleum Aurantii Cortex fractional distillation is resorted to, and any oil
passing over under 170 C. may be limonene, but, should the oil be adulterated with
turpentine, pinene may also come over, and therefore the U.S. P. applies the following test
to this fraction :

Dissolve 5 Cc. of the fraction to be tested in half its volume of glacial acetic acid, add
5 Cc. of amyl nitrite, cool thoroughly in a freezing mixture, and add, very gradually, 5 Cc.
of a mixture of equal volumes of hydrochloric acid and glacial acetic acid. Collect any
crystals which separate upon standing, on a force filter, and wash them with a little alcohol.
Transfer the crystals to a flask, add 5 Cc. of alcoholic KHO, and heat on a water-bath
fifteen minutes. Pour into cold water, collect the precipitate, and wash it with cold water.
Recrystallize the dried precipitate from alcohol, and determine the melting point of the
crystals. Nitrosopinene melts at 132 C., whereas nitrosolimonene melts at 72 C.

The determination of the congealing or crystallizing point of an oil is also
occasionally of value. This method is applied to the following oils by the
U.S. P. as under :

Oleum Anisi. Transfer 10 Cc. of the oil to a test-tube placed in water cooled by ice ;
insert a thermometer at once into the oil, and allow it to remain undisturbed until its



ANALYSIS OF ESSENTIAL OILS.



217



temperature has fallen to about 6 C. Induce crystallization either by rubbing the inner
wall of the test-tube with the thermometer or by the addition of a particle of solid anethol,
and stir continuously during the solidification of the oil. The highest temperature reached
during the crystallization is regarded as the congealing point, and this should not be
below 15 C.

Oleum Fceniculi. Is similarly done, but a freezing mixture must be used to bring the
temperature down to 5 C., and the congealing point should not be below 5 C.
Oleum Rosa should congeal between 18 and 22 C. when tested as follows :
Introduce about 10 Cc. of oil into a test-tube of about 15 Mm. diameter; insert a
thermometer so that it touches neither the bottom nor the sides of the tube. Raise the
temperature of the oil in the tube from 4 to 5 above the saturation point by grasping it in
the hand, and shake the tube gently. Allow the oil to cool, and when the first crystals
appear, note the temperature. This is regarded as the congealing point ; a second test
should be made for confirmation.

2. Solubility. The presence of turpentine and various adulterants is
frequently made manifest by the use of a definite volume of alcohol, and on
this point the U.S.P. lays down the following standards :

Name. Standard of Solubility.

Oleum Amygd. Amane equal vols. of 70 per cent, alcohol.

Anisi 5 ,,9

Cajuputi I ,, 80

Cari equal ,, 92*3

Caryophylli . . . . .2 ,, 70

Chenopodii . . . . .5 ,,70

Cinnamoni 2 7

Copaike ...... 2 ,, 92-3

Coriandri 3 ,,70

Eucalypti 3 ,,70

Fceniculi . . . . . . 10 (or less) ,, 80

Hedeomae 2 ,,70

Juniperi ...... 10 , } 90

Lavandulse. ..... 3 7

Menthae piperitse . . . .4 ,,70

,, viridis ..... equal ,, 80

Myristicse , . . . . .3 ,, 90

3. Chemical Analysis. Qualitative tests are, as a rule, unnecessary, because
each oil has a perfectly characteristic odor, but some are useful to detect
impurities, such as :

(a) Alcohol in essential oils may be detected by shaking up a measured
quantity with water in a burette, when the bulk will diminish owing to the
alcohol dissolving out.

(b) Metals (chiefly copper and lead) are detected by shaking up the oil with
a little very dilute acid, and then applying the usual tests to the acid liquid.

(c) Petroleum products are detected by the action of sulphuric acid, which
will combine with the oil, but not with paraffins. The U.S.P. applies this
method to the detection of petroleum in oil of turpentine as follows :

If 5 Cc. of oil of turpentine be placed in a small beaker, and 20 Cc. of sulphuric acid be
gradually added, with agitation, while the beaker is cooled by immersion in cold water, and
the contents, after cooling and renewed agitation, be transferred to a burette, graduated in
tenths, the clear layer which forms after the dark mass has settled should not measure more
than o - 35 Cc. (absence of petroleum, benzzn, kerosene, or similar hydrocarbons).

Quantitative Analysis to ascertain the amount of the active odoriferous
principle is now being more and more applied to essential oils. When these
active constituents are not simple mixtures of terpenes, they are capable of
chemical determination, and may be divided into six classes as follows :
(a) Esters (compound ethers) ; (b) Phenols or phenolic ethers ; (c) Aldehyds ;
(d) Ketones; (e) Alcohols; (/) Isothiocyanates. They may be respectively
tested for and estimated as follows :

(a) Estimation of Esters (compound ethers). These bodies are capable of
sapomncation by boiling with alcoholic KHO, and the amount of alkali
unconsumed having been ascertained by residual titration with acid, the



2i 8 ANALYSIS OF DRUGS, ETC.

difference gives the means of calculating the amount of ester. Taking, for
example, bornyl acetate (existing in OL Ros?narini\ the equation would be :

C 10 H J7 O . C 2 H 3 O + KHO = C 10 H 17 . HO + KC.H 3 O,,

and therefore each Cc. of \ KHO consumed would equal '09734 bornyl
acetate. For the menthyl acetate (in Ol. Menth. pip.) the similar equivalent
would be '09834. The U.S. P. directions are :

Introduce 10 Cc. of oil into a tared flask, and note the exact weight ; add 25 Cc. of
alcoholic KHO, connect with a reflux condenser, and boil the mixture during one hour.
After cooling titrate the residual alkali with HJ5O 4 , using phenol-phthalein as indicator.
Subtract the number of Cc. of H 2 SO 4 required from the 25 Cc. of KHO taken, multiply
the difference by 9734 (or 9*834), and divide the product by the weight of the oil taken to
find the percentage.

Ol. Rosmarini should contain not less than 5 per cent., and OL Menth.
pip. not less than 8 per cent., of their respective esters. The esters in Ol.
Roses not having as yet been properly studied, the U.S. P. takes an empirical
saponification factor founded on experience, thus :

Place about 2 Cc. of the oil in a weighing-bottle, and weigh accurately. Transfer it, with
the aid of a little alcohol, to a 100 Cc. flask, and add 20 Cc. of alcoholic KHO. Connect
the flask with a reflux condenser, and boil the mixture during thirty minutes on a water-bath.
When cool, add 50 Cc. of distilled water and a few drops of phenol-phthalein, and titrate
with H 2 SO 4 . Subtract the number of Cc. of H 2 SO 4 required, from 20, multiply the
difference by 27^87, and divide by the weight of the oil to obtain the saponification value,
which should be between 10 and 17.

(b) Estimation of Phenols and Phenolic Ethers. Such bodies are met
with in anethol CsH 5 . CeH 4 . OCH 3 (in oil of anise) and eugenol
C 6 H 3 . OCH 3 . OH . C 3 H 5 (in oils of clove, pimento, etc.). The U.S.P. does
not make any estimation of the former, relying on the other constants for OL
Anisi, especially the congealing point (see supra), but it assays the oils of
clove, pimento, and thyme for the latter by taking advantage of the fact that
such bodies combine with and dissolve in solutions of alkaline hydroxides,
and can be so extracted from a bulk of oil, and the unacted-upon portion
read off thus :

Introduce into a flask with a long neck (graduated in tenths) 10 Cc. of the oil of pimenta
and loo Cc. of 5 per cent, solution of KHO, and shake the mixture for five minutes. When
the liquids have separated completely, add sufficient KHO solution to raise the lower limit
of the oily layer to the zero mark of the scale, and note the volume of residual liquid.

This should not exceed 2 Cc., 3*5 Cc., and 8 Cc. respectively in oils of
clove, pimento, and thyme, thus proving them to contain respectively 80, 65,
and 20 per cent, of phenolic bodies.

(c) Estimation of Aldehyds. Such bodies are met with as cinnamic aldehyd
C6H 5 .C2H 2 . CHO (in oils of cinnamon and cassia), benzoic aldehyd (in oil
of bitter almonds), citral CioHi 6 O (in oil of lemon), etc., and to estimate them
advantage is taken of the well-known reaction of aldehyds with sodium or
potassium bisulphite, whereby a crystalline compound is produced which is
soluble in water, and thus the aldehyd can be removed and the rest of the
oil left and measured. The U.S.P. directs for OL Cinnamoni :

Introduce into a flask with a long graduated neck (in 5 V Cc.), by means of a measuring-
pipette, 10 Cc. of the oil of cinnamon, add IO Cc. of a 30 per cent, solution of sodium
Bisulphite, shake the flask, and heat it in a water-bath containing boiling water until the
contents are liquefied; add successive portions (10 Cc. each) of the bisulphite solution,
shaking and heating as before, after each addition, until the flask is three-fourths filled.
Continue to heat it in the water-bath until the odor of cinnamic aldehyd is no longer per-
ceptible, cool the flask to about 25 C., and add enough of the bisulphite solution to raise
the lower limit of the oily layer to the zero mark of the scale. The residual liquid should
not measure more than 2 '5 Cc., corresponding to at least 75 per cent., by volume, of
cinnamic aldehyd.

For the estimation of benzaldehyd in OL Amygd. Amarcz, and of citral in



ANALYSIS OF ESSENTIAL OILS. 219

OL Limonis, this rough process is not sufficiently delicate, therefore the U.S. P.
directs as follows :

(1) Benzaldehyd. Introduce into a tared 150 Cc. flask 10 Cc. of purified kerosene, note
the exact weight, add 12 drops of the oil, and again note the weight; add 20 Cc. of dis-
tilled water with 6 drops of phenol-phthalein, and then neutralize the solution exactly by
the addition of ^ NaHO, agitating the flask thoroughly. Add from a burette, gradually,
a solution of sodium sulphite (i in 5), alternating with HC1 from ^ second burette, until
10 Cc. of the sodium sulphite solution have been added, and enough HC1 to maintain the
neutrality of the mixture ; after adding a few drops of phenol-phthalein, and agitating the
flask frequently, allow it to stand two hours to insure a permanent condition of neutrality, and
then note the number of Cc. of the HC1 used. Carry out a blank test, identical with the
foregoing, without the oil, and note the amount of ^ HC1 consumed. Subtract the number
of Cc. required in the blank test from the number required in the original test ; each Cc. of this
difference corresponds to 0-0526 Gm. of benzaldehyd. To find the percentage, multiply the
above difference by 0-0526, and this product by 100, and divide by the weight of the oil taken.

This process is also applicable to the assay of artificial benzaldehyd, which
should show 84 per cent., while the natural Ol. Amygd. Am. should contain
85 per cent. The same process is also applicable to artificial cinnamic
aldehyd, except that the equivalent for each Cc. ^ HC1 is 0*033, an d the
article should show 95 per cent.

(2) Citral. Introduce about 15 Cc. of oil of lemon into a counterpoised 150 Cc. flask, and
note the exact weight ; add 5 Cc. of distilled water and a few drops of phenol-phthalein, and
then neutralize the liquid exactly by the cautious addition of ^ NaHO. Add 25 Cc. of a
neutral solution of sodium sulphite (i in 5), and immerse the flask in a water-bath containing
boiling water. From a burette add, as needed, just sufficient HC1 to maintain the neutrality
of the mixture, keeping the flask continuously heated and frequently agitated, and adding a
drop or two of phenol-phthaleiri. When a permanent condition of neutrality is reached, note
the number of Cc. of the HC1 consumed. Carry out a blank test, identical with the tore-
going, without the oil, and note the amount of HC1 consumed. Subtract the number of
Cc. required in the blank test from the number required in the original test ; each Cc. of this
difference corresponds to 0-03802 Gm. of citral. To find the percentage, multiply the above
difference by 0*03802, and this product by 100, and divide by the weight of the oil of lemon
taken. The oil should not show less than 4 per cent.

(d) Estimation of Ketones or organic oxides. These bodies, such as carvol
(in oils of carraway, dill, and green mint) and cineol (in oils of cajuput and
eucalyptus), combine with phosphoric acid to form a precipitate which is
insoluble, but is decomposed by the action of warm water. The U.S. P. only
employs the process for cineol, and directs as follows :

Introduce into a beaker a solution prepared by dissolving 10 Cc. of oil in 50 Cc. of purified
petroleum benzin ; immerse the beaker in a freezing mixture and add phosphoric acid, drop
by drop, with constant stirring, until the white magma of cineol phosphate formed begins to
assume a yellowish or pinkish tint ; then transfer the magma to a force filter, wash it with
cold purified petroleum benzin, and then dry it by pressure between two porous plates.
Transfer the precipitate to a narrow graduated cylinder, and add warm water, which will
cause separation of the cineol. The volume, in Cc., of the separated oil, multiplied by 10,
represents the volume per cent, of cineol. Thus tested, 01. Cajuputi should show 55 per cent.,
and Ol. Eucalypti 50 per cent.

(e) Estimation of alcoholic bodies. These bodies, such as borneol CioHigO
(in oil of rosemary), menthol CioH 2 oO (in oil of peppermint), and santalol
CisHgcO (in santal oil), may all be estimated by first converting them into
their acetic ester, and then titrating that as already directed under Esters
(see (a) supra). The following is the method of acetylization :

Introduce 10 Cc. of the oil into a flask provided with a ground-glass tube-condenser
(acetylization flask), add 10 Cc. of acetic acid anhydride and about I Gm. of anhydrous
sodium acetate, and boil gently during one hour. Allow it to cool, wash the acetylized oil with
distilled water, and afterwards with 5 per cent, solution of NaHO. until the mixture is slightly-
alkaline to phenol-phthalein, and then dry it with the aid of fused calcium chloride, and filler.

In dealing with Ol. Santali this process is applied directly, but in the oils
of rosemary and peppermint it is performed on the residual oil left after esti-
mation of the respective esters in 10 Cc. of the original oil (see (a) supra).



220



ANALYSIS OF DRUGS, E1C.




Having thus obtained the acetic ester, we then proceed to estimate it by
residual titration. For santal oil the U.S.P. instructs as follows :

Transfer to a tared 100 Cc. flask 3 Cc. of the dry acetylized oil, note the exact weight, add
50 Cc. of alcoholic KHO, connect with a reflux condenser, and boil gently during one
hour. After cooling, titrate the residual alkali with H 2 SO 4 , using phenol-phthalein as
indicator. Subtract the number of Cc. of H 2 SO, required from the 50 Cc. of alcoholic
KHO taken, multiply the difference by 1 1 -026, and divide by the weight of the dry acetylized
oil taken, less the above difference multiplied by 0*021 ; the quotient will represent the
percentage of santalol in the oil of santal, which should amount to 90 per cent.



ANALYSIS OF ESSENTIAL OILS.



221




/4 2&r*f,

2 -. &^<nf*t-



For Ol. Menth. pip. the U.S. P. directs to take 5 Cc. of the acetylized oil
and then proceed exactly as above, except that the difference is to be
multiplied by 7749, and the product divided by the weight taken, less the
above difference multiplied by 0*021 ; the quotient will represent the per-
centage of menthol in the oil of peppermint.

For OL Rosmarini the procedure is the same as for peppermint, except
that the two factors are 7*649 and 0*021 respectively.

It will be observed that the oils of peppermint and rosemary are doubly



222 ANALYSIS OF DRUGS, ETC.

assayed, and the standards are respectively not less that 8 of menthyl acetate
and 50 of total (menthol + menthyl acetate), and 5 of bornyl acetate and
15 of total (borneol 4- bornyl acetate).

(f) Estimation of Allyl isothiocyanate. P'or the assay of volatile oil of
mustard, the U.S. P. employs combination with silver and residual titration
as follows :

Weigh accurately about 2 Gm. of volatile oil of mustard, and dilute this with sufficient
alcohol to make 50 Cc. of the solution represent I Gm. of the oil ; of this solution, 5 Cc. are
transferred to a 100 Cc. measuring flask, and 30 Cc. of ^ AqNO 3 and 5 Cc. of ammonia
water are added. The flask is well-stoppered and set aside in a dark place for twenty-four
hours. The contents of the flask are diluted with water to the 100 Cc. mark and filtered.
To 50 Cc. of the filtrate, 4 Cc. of nitric acid and a few drops of ferric ammonium sulpuate
are added, and finally sufficient ^ KCNS to produce a permanent red color ; not more than
5*6 Cc. of the latter reagent should be required (each Cc. of ^ AqNO g consumed corre-
sponding to o '00492 gramme of allyl isothiocyanate).

DIVISION II. ANALYSIS OF URINE.

A sample of urine taken for analysis should be that first passed by the
patient in the morning, or, better, a portion taken from the total twenty-four
hours' urine.

The following are the chief points on which information is usually required
by the physician who submits urine for examination to an analyst :

1. Take the specific gravity, which should range from roi5 to 1-025 at
60 F. For every i F. above 60 add 'oooi to the observed specific gravity.
By multiplying the last two decimals of specific gravity by 2*33 we have the
grammes per litre of total solid matter. Make, a note also of the daily
quantity, which should be 1200 to 1500 c.c. (40 50 fl. oz.). On standing
some time urine undergoes ammonic fermentation, and becomes alkaline in
reaction.

Note. In diabetes the gravity is too high, sometimes reaching 1*060, while in albuminuria
it is abnormally low, even occasionally falling to I '005.

2. Examine the reaction, which should be very faintly acid.

3. Set a portion to settle in a long glass, and examine the deposit under
the microscope for calcium oxalate or phosphate, uric acid or urates, pus,
casts or kidney tubes, etc., etc. (See pages 212 and 213, and fig. 50, p. 218.)

Note. The nature of the deposit may also be confirmed chemically as follows :

(a) Warm the urine containing the sediment, when, if the latter should dissolve, it
consists entirely of urates. In this case let it once more crystallise out, and
examine it by the ordinary course for Ca, Na, and NH 4 , to ascertain the
bases.

(J>) If the deposit be not dissolved by heating, let it settle, wash once by decantation
with cold water, and warm with acetic acid. Phosphates will dissolve, and
may be reprecipitatecl from the solution by excess of NII 4 HO filtered out,
well washed with boiling H 2 O, dissolved in HC 2 H 3 O.>, and examined for Ca
or Mg by the usual course for these metals in presence of PO 4 .

(c) If the deposit be insoluble in acetic acid, warm it with HC1. Any soluble

portion is calcium oxalate, which may be precipitated by NH 4 HO.

(d) If the deposit be insoluble in HC1, it is probably uric acid. In this case apply

the murexid test as follows : Place it in a small white dish, remove moi ture
by means of a piece of bibulous paper, add a drop or two of strong HNO 3 ,
and evaporate to dry ness at a gentle heat. When cold add a drop of
NH 4 HO, which will produce a purple colour, deepened to violet by a drop
of KHO.

4. Test for albumin, as follows :

(a) Boiling test. Filter the urine, place 10 c.c. in a narrow test tube,
and add one drop of acetic or nitric acid. Heat the tube



ANALYSIS OF URINE.



221



over a small flame in such a way that the upper portion of
the liquid only shall be heated. Coagulation will take place,
and the presence of albumin will be evident from the formation
of a turbidity ranging from a faint cloud to a dense coagulum,
but always strongly contrasted with the clear liquid beneath,
which was not heated. Mucin also precipitates with this test.



Online LibraryJohn MuterA short manual of analytical chemistry, qualitative and quantitative--inorganic and organic → online text (page 28 of 31)