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Circular No. 4.— (To accompany Bulletin No. 46.)

United States Department of Agriculture,

DIVISION OF CHEMISTRY.

Washington, D. C. , December 11, 1897.
All the changes in methods of analysis of the Association of Official Agricul-
tural Chemists, which were made at the annual meetings of 1896 and 1897, have
been incorporated in Circular No. 4. In this circular, the pages in the edition
of Bulletin 46, where the methods described would naturally be found, are indi-
cated. By this arrangement, the expense of entirely reprinting Bulletin 46 has
been avoided without sacrificing, to any appreciable extent, the availability of
the methods.

This circular will be furnished to all members of the Association of Official
Agricultural Chemists and to others in so far as the extent of the edition will
permit.

H. W. Wiley,
Chief of Division, Secretary A. O. A. C.
Approved :

James Wilson, -•

Secretary.

CHANGES IN AND ADDITIONS TO METHODS OF ANALYSIS ADOPTED
AT THE THIRTEENTH AND FOURTEENTH ANNUAL MEETINGS OF
THE ASSOCIATION OF OFFICIAL AGRICULTURAL CHEMISTS.

[In all cases, unless otherwise mentioned, pages and paragraphs cited refer to Bulletin No. 46,
Chemical Division of the United States Department of Agriculture.— H. W. W.]

DETERMINATION OF PHOSPHORIC ACID.

Page 14 (2) (6) {h^), eighth line, omit "six," and insert "from ten to fifteen."
Sixteenth line, omit all after "wash" to end of sentence and insert "from five
to six times with water, using in all from 150 to 250 cc."

5. Determination of Potash.
(Insert instead of methods on pages 22, 23, and 24. )

(a) LINDO-GLADDING METHOD.

(1) Preparation of reagents.

(a) AmTnonium chlorid solution. — Dissolve 100 grams of ammonium chlorid
in 500 cc of water, add from 5 to 10 grams of pulverized potassium platinic
chlorid, and shake at intervals for six or eight hours. The mixture is then
allowed to settle over night and filtered, and the residue is ready for the prepara-
tion of a fresh supply when needed.

(b) Platinum solution. — The platinum solution used contains 1 gram of metal-
lic platinum (2.1 grams of HaPtClg) in every 10 cc.

(2) Methods of making solution.

(a) With potash salts and mixed fertilizers.— Boil 10 grams of the sample with
300 cc of water thirty minutes. In the case of mixed fertilizers, add to the hot
solution a slight excess of ammonia and then sufficient powdered ammonium
oxalate to precipitate all the lime present. Cool, dilute to 500 cc, mix and pass
through a dry filter. In case of muriate and sulfate of potash, sulfate of pot-
ash and magnesia and kainit, dissolve and dilute to 500 cc without the addition
of ammonium and ammonium oxalate.

(h) With organic compounds.— When it is desired to determine the total
amount of potash in organic substances like cotton seed meal, tobacco stems,
etc., saturate 10 grams with strong sulfuric acid, and ignite in a muffle at a low
red heat to destroy organic matter. Add a little strong hydrochloric acid and
warm slightly in order to loosen the mass from the dish, and proceed as directed
under (3) (a).

(3) Determination.

(a) In mixed fertilizers.— ^Y&,]^OTa,te 50 cc of the solution made according to
(2), corresponding to 1 gram of the sample, nearly to dryness, add 1 cc of dilute
sulfuric acid (1 to 1), evaporate to dryness and ignite to whiteness. As all the
potash is in form of sulfate, no loss need be apprehended by volatilization of
potash, and a full red heat must be maintained until the residue is perfectly
white. Dissolve the residue in hot water, using at least 20 cc for each decigram
of K.^0, add a few drops of hydrochloric acid and platinum solution in excess.
Evaporate on a water bath to a thick paste and treat the residue with 80 per cent
alcohol, sp. gr. 0.8645, avoiding the absorption of ammonia. Wash the precipi-
tate thoroughly with 80 per cent alcohol both by decantation and on the filter,
continuing the washing after the filtrate is colorless. Wash finally with 10 cc of
the ammonium chlorid solution (1) (a), to remove impurities from the precipi-
tate and repeat this washing five or six times. Wash again thoroughly with 80
per cent alcohol and dry the precipitate for thirty minutes at 100°. The precipi-
tate should be perfectly soluble in water.

(6) Muriate of potash. — Dilute 25 cc of the solution, prepared according to (2)
(a), with 25 cc of water, acidify with a few drops of hydrochloric acid, add 10 cc
of platinum solution and evaporate to a thick paste. Treat the residue as under
(3) (a).

(c) Sulfate of potash, sulfate of potash and magnesia, and kainit. — Dilute
25 cc of the solution, prepared according to (2) (a), with 25 cc of water, acidify
with a few drops of hydrochloric acid and add 15 cc Of platinum solution. Evap-
orate the mixture and proceed as directed under (3) (a), except that 25 cc por-
tions of ammonium chlorid solution should be used.

(b) Optional Method.*

(1) Preparation of reagent.

Platinum solution.— The platinum solution used is the same as that described
Tinder the Lindo-Gladding method.

(2) Method of making solution.

The solution is prepared as directed under the Lindo-Gladding method, omit-
ting in all cases the addition of ammonia and ammonium oxalate.

♦ The Lindo-Gladding method is preferable in the presence of soluble sulfates.

(3) Determination.

Dilute 25 cc of the solution made as directed under (2), (50 cc, if less than 10
per cent of potassium oxid be present) to 150 cc, heat to 100", and add, drop by
drop with constant stirring, a slight excess of barium chlorid solution. With-
out filtering, in the same manner add barium hydrate in slight excess. Filter
while hot and wash until the precipitate is free from chlorids. Add to the fil-
trate 1 cc of strong ammonium hydrate, and then a saturated solution of ammo-
nium carbonate until the excess of barium is precipitated. Heat and add, in
fine powder, 0.5 gram of pure oxalic acid or 0.75 gram of ammonium oxalate.
Filter and wash free from chlorids, evaporate the filtrate to dryness in a plati-
num dish, and ignite carefully over the free flame below a red heat until all vol-
atile matter is driven off. Digest the residue with hot water, filter through a
small filter and dilute the filtrate, if necessary, so that for each decigram of KgO
there will be at least 20 cc of liquid. Acidify with a few drops of hydrochloric
acid and add platinum solution in excess. Evaporate on a water bath to a thick
sirup and treat the residue with 80 per cent alcohol (specific gravity 0.8645).
Wash the precipitate thoroughly with 80 per cent alcohol both by decantation
and after collecting on a Gooch crucible or other form of filter. Dry for thirty
minutes at 100° and weigh.

It is desirable, if there be an appearance of foreign matter in the double salt,
that it should be washed according to the previous method with several portions
of the ammonium chlorid solution of 10 cc each.

(c) Factors.

For the conversion of potassium platinichlorid to KCl use the factor 0.3069,
to K,S04 use 0.3587, and to KjO, 0.1939.

METHODS FOR THE ANALYSIS OF DAIRY PRODUCTS.

Provisional Method of Saponification.

Insert on page 28, after (b^), the following:

Using the same amounts of alkali and alcohol as described above, the saponifi-
cation may be conducted on a steam or water bath, the flask being connected
with a reflux condenser consisting of a glass tube of not less than one meter in
length, or of a shorter condenser cooled by a current of water.

Page 36, under 2, Milk Analysis; omit first and second sentences and insert :

1. Heat to constant weight at the temperature of boiling water from 1 to 2
grams of milk in a tared flat dish of not less than 5 cc diameter. If desired,
from 15 to 20 grams of pure dry sand may be previously placed in the dish.

Insert 2 before " Babcock Asbestus Method."

Page 36 (c). Determination of Total Nitrogen.

Add at end of paragraph the following :

1. Provisional method for determination of casein in cow's milk.— The determi-
nation of casein in milk should be made when the milk is fresh, or nearly so.
When it is not practicable to make this determination within twenty-four hours,
add 1 part of formaldehyd to 2,500 parts of milk, and keep in a cool place.
Weigh about 10 grams of milk, dilute in a beaker with about 90 cc of water at
40°-42°, and add at once 1.5 cc of a solution containing 10 per cent of acetic
acid by weight. Stir with a glass rod, and let stand from three to five minutes
longer. Then decant on filter, wash two or three times with cold water by decan-
tation, and transfer precipitate completely to filter. Wash once or twice on
filter. The filtrate should be clear, or very nearly so. If it be not clear when

it first runs through, it can generally be made so by two or three repeated
filtrations, after which the washing of the precipitate can be completed. The
washed precipitate and filter paper are digested as in the regular Kjeldahl
method for the determination of nitrogen, and the process is completed as usual.
To calculate the nitrogen into an equivalent amount of casein, multiply by 6.25.
In working with milk which has been kept with preservatives, the acetic acid
should be added in small proportions, a few drops at a time, with stirring and
the addition continued until the liquid above the precipitate becomes clear, or
very nearly so.

2. Provisional method for determining albumin in milk. — The filtrate obtained
in the above operation is neutralized with caustic alkali, three- tenths cc of a 10
per cent solution of acetic acid added and the mixture heated to the temperature
of boiling water for from ten to fifteen minutes. The precipitate is collected on
a filter, washed, and the nitrogen therein determined. Nitrogen multiplied by
6.25 equals albumin.

3. Provisional optional method for determining casein in milk. — To 5 grams of
milk, 50 cc of a solution of magnesium sulfate saturated at from 40° to 45"
are added and the mixture heated to about 45°, until the precipitate separates
and subsides, leaving the supernatant liquid clear. The precipitate is collected
on a filter, washed two or three times with the solution of magnesium sulfate
prepared as above and at the same temperature, viz, about 45°, and the nitrogen
therein determined.

4. Provisional optional method for determining albumin in milk. — To the
filtrate, obtained by the above process, are added three-tenths cc of a 10 per cent
solution of acetic acid and the mixture boiled until the albumin is completely
precipitated. The precipitate is collected on a filter, washed as above described,
and the nitrogen therein determined.

Page 37, "3. Cheese Analysis (Provisional Methods), "omit "(Provisional
Methods)."
Page 37, omit all of (a) save caption and insert the following :
When the cheese can be cut, a narrow wedge-shaped segment reaching from
the outer edge to the center of the cheese is taken. This is to be cut into strips
and passed through a sausage-grinding machine three times. When the cheese
can not be cut, samples are taken by a cheese trier. If only one plug can be
obtained, this should be taken perpendicular to the surface at a point one-third
of the distance from the edge to the center of the cheese. The plug should reach
either entirely through or only halfway through the cheese. When possible,
draw three plugs — one from the center, one from a point near the outer edge,
and one from a point halfway between the other two. For inspection purposes,
the rind may be rejected; but for investigations requiring the absolute amount
of fat in the cheese the rind is included in the sample. It is preferable to grind
the plugs in a sausage machine, but when this is not done they are cut very fine
and carefully mixed.

Page 37, under (b), omit first and second lines and ''tus" of the third line
and insert :

From 2 to 5 grams of cheese should be placed in a weighed platinum or porce-
lain dish which contains a small quantity of material like freshly ignited asbestus,
sand, etc.

Page 37, omit under (c) the whole paragraph and insert:

The extraction tube is prepared as follows:

Cover the perforations in the bottom of the tube with asbestus, and on this
place a mixture containing equal parts of anhydrous copper sulfate and pure,
dry sand to the depth of about 5 cm, packing loosely. Cover the upper surface

of this material with a film of asbestus. On this are placed from 2 to 5 grams
of the sample of cheese. The tube is placed in a continuous extraction appara-
tus and treated for five hours with anhydrous ether. The cheese is removed and
ground to a fine powder with pure sand in a mortar. The mixed cheese and
sand are replaced in the extraction tube, the mortar washed free of all matters
with ether, the washings being added to the tube, and the extraction is continued
for ten hours.

Page 37, add: (g) Provisional method for the determination of acidity in
cheese. — Add water, at a temperature of 40°, to 10 grams of finely divided cheese
until the volume equals 105 cc ; agitate vigorously and filter. Titrate portions
of 25 cc of filtrate, corresponding to 2.5 grams of cheese, with a standardized
solution of sodium hydroxid, preferably one-tenth normal. Use phenolphtalein
as indicator. Express amount of acid as lactic acid.

OPTIONAL METHOD OF DETERMINING PHOSPHORIC ACID IN SOILS.

Note. — The following method, devised by Mr. Goss, was recommended as an
optional method by the association in 1895, but was not ordered printed with the
official methods. A synopsis of it is printed here for the convenience of analysts :

Page 41, after (g), insert the following:

"Ten grams of the air-dried soil, passed through a sieve of one millimeter
mesh, are placed in a small Kjeldahl flask marked at 250 cc. From 20 to 30 cc
concentrated sulfuric acid and approximately 0. 7 gram yellow oxid of mercury
are added, the contents of the flask well mixed by shaking, and oxidized over
the open flame, as in the determination of nitrogen, for an hour. After cooling,
about 100 cc of water, 5 cc of concentrated hydrochloric acid and 2 cc of concen-
trated nitric acid are added, and the mixture reboiled to oxidize the iron, cooled,
the volume completed to one-fourth of a liter with water, and the contents of
the flask filtered through a dry, folded filter paper. One hundred cubic centi-
meters of the filtrate are placed in a flask of about 450 cc capacity, strong ammo-
nia added until a permanent precipitate is formed, which is dissolved by the
addition of about 7 cc of nitric acid, and the mixture boiled until clear. The
flask is removed from the flame and cooled at room temperature for exactly two
minutes, 75 cc molybdate solution added, and the flask placed in a water bath
kept at 80° for 15 minutes, shaking vigorously four or five times meanwhile.
After removing from the bath, the flask is allowed to stand for ten minutes until
the precipitate has settled, and the supernatant liquid is poured on to the filter
paper under pressure, the precipitate being partially brought upon the paper.
The fiask and precipitate are thoroughly washed with ammonium-nitrate solu-
tion, the precipitate either by decantation or in the filter paper. The flask is
then placed under the fllter, the precipitate is dissolved in ammonia, and the
phosphoric acid estimated by the usual processes. Details of the manipulation
are given in Bulletin No. 43 of the Division of Chemistry, pp. 58-60. "

Page 42, omit all of 8 and insert :

From 7 to 14 grams of the soil are placed in a small Kjeldahl digesting flask,
about 250 cc capacity, with 30 cc of strong sulfuric acid, or more, if necessary,
and 0. 7 gram yellow oxid of mercury, and boiled for an hour. The residue is
oxidized with potassium permanganate in the usual way. After cooling, the
flask is half filled with water, vigorously shaken, the heavy matters allowed to
subside and the supernatant liquid poured into a flask of from 1,000 to 1,200 cc
capacity. This operation is repeated until the ammonium sulfate is practically

6

all removed and the large flask is a little more than half full and the ammonia
distilled in the usual manner. If a sample be known to contain a considerable
amount of nitrate, use method p. 17 (c).
Page 54, first line, read pages " 55-57," instead of page 55.

METHODS FOR THE ANALYSIS OF FOODS AND FEEDING STUFFS.

Page 63. Read caption in (c) Determination of Starch in Commercial
Starches.
Omit 3 in first line of (c) and insert 2.5.
Add after section (c), page 62, the following:

(cj) Diastase Method for Starch.

Extract from 2 to 5 grams of the finely powdered substance with ether, bring
the extracted residue on to a filter, or into a Gooch crucible, and wash with
150 cc of 10 per cent alcohol, and then with a little strong alcohol. Place the
residue in a beaker with 50 cc of water, immerse the beaker in a boiling water
bath, and stir constantly until all the starch is gelatinized, cool to 55°, add
from 20 to 40 cc of malt extract and maintain at this temperature until the solu-
tion no longer gives the starch reaction with iodin : Cool and make up directly
to 250 cc, filter, bring 200 cc of the filtrate into a ten ounce flask with 20 cc of
25 per cent hydrochloric acid (sp. gr. 1.125), connect with a reflux condenser and
boil for two hours and a half, exactly neutralize while hot vnth. sodium car-
bonate, avoiding excess, cool and make up to 500 cc. Mix the solution well, pour
through a dry filter, and determine the dextrose in an aliquot part by Allihn's
method, pages 52-57. Convert thei starcn\iatQjtlextroselby the factor .90.

Add on page 62, after (Cj), the following :

(C2) Method for Estimating Galactan.

Bring three grams of the substance into a beaker about 5.5 cm in diameter
and 7 cm deep, together with 60 cc of nitric acid of 1.15 specific gravity and
evaporate the solution to exactly one -third of its volume on a water bath at a
temperature of 94 to 96°. After standing twenty-four hours, add 10 cc of water
to the precipitate, and allow it to stand another twenty-four hours. The mucic
acid has in the meantime crystallized, but is mixed with considerable material
only partially oxidized by the nitric acid. The solution is therefore filtered
through filter paper, washed with 30 cc of water, to remove as much of the
nitric acid as possible, and the filter and contents brought back into the beaker.
Thirty cc of ammonium carbonate solution consisting of one part ammonium
carbonate, 19 parts water, and 1 part strong ammonia, are added, and the beaker
brought onto a water bath and heated gently for fifteen minutes. The ammo-
nium carbonate takes up the mucic acid, forming the soluble muciate of ammo-
nia. The solution is filtered into a platinum or porcelain dish, and the residue
thoroughly washed with water to remove all of the muciate of ammonia. The
filtrate is evaporated to dryness over a water bath, 5 cc of nitric acid of 1.15
specific gravity are added, and the mixture thoroughly stirred and allowed
to stand for thirty minutes. The nitric acid decomposes the ammonium muci-
ate, precipitating the mucic acid, which is collected on a tared filter or Gooch
crucible, washed with from 10 to 15 cc of water, then with 60 cc of alcohol and
quite a number of times with ether, dried at 100° for a short time, and weighed.
The mucic acid multiplied by 1.33 gives galactose, and the product multiplied
by .9 gives galactan.

Page 63, omit at end of (d) all relating to factors and insert:
The weight of hydrazone X 0.516 -{- 0.0104 -r- weight of sample used = percent-
age furfurol.
Furfurol X 1.84 = pentosans.
Pentosans -r- 0. 88 = pentoses.
Furfurol x 1.65 = xylan.
Furfurol X 2.03 = araban.

Determination of Pentosans by means of Phloroglucin.

On page 63, at the conclusion of (d) add the following:— (dj) Three grams
of the material are brought into a ten-ounce flask, together with 100 cc of 12 per
cent hydrochloric acid (sp. gr. 1.06) and several pieces of recently heated pumice
stone. The flask, placed upon wire-gauze, is connected with a Liebig condenser,
and heat applied, rather gently at first, using a gauze top to distribute the flame,
and so regulated as to distill over 30 cc in about ten minutes. The 30 cc driven
over are replaced by a like quantity of the dilute acid by means of a separatory
funnel, and the process continued as long as the distillate gives a pronounced
reaction with aniline acetate on filter paper. To the completed distillate is grad-
ually added a quantity of pholoroglucin dissolved in 12 per cent hydrochloric
acid, and the resulting mixture thoroughly stirred. The amount of phloroglucin
used should be about double that of the furfurol expected. The solution first
turns yellow, then green ; and very soon an amorphous greenish precipitate ap-
pears, which grows rapidly darker, till it finally becomes almost black. The solu-
tion is made up to 500 cc with 12 per cent hydrochloric acid, and allowed to stand
over night. In case there is very little furfurol in the substance tested, and the
resulting distillate consequently small, it is best to add sufficient 12 per cent
hydrochloric acid to the distillate before adding the phloroglucin solution, so
that, upon the addition of the latter solution, the resulting mixture will contain
approximately 500 cc.

The amorphous black precipitate is filtered into a tared Gooch crucible through
an asbestus felt, washed with 100 cc of water, dried to constant weight by heat-
ing from three to four hours at 100°, cooled and weighed, the increase in weight
being reckoned as phloroglucid. To calculate the furfurol from the phloroglu-
cid, use the following table :

Weight of phloroglucid :

f. 20 gram ^

r 1.8201

1 .22 '

1.839

.24 '

1.856

.26 '

'

1.871

.28 '

1.884

.30 '

1.895

.32 '

> _i_ .

1.904 V

.34 '

1.911

.36 '

1.916

.38 '

1.919

.40 '

1.920

.45 '

1.927

.50-1- '

' ^

1.930 J

furfurol.

METHODS FOR THE ANALYSIS OF FERMENTED AND DISTILLED

LIQUORS.

Add on page 77, after 18 :

"19. Determination of Fusel Oil.

"The apparatus recommended for this determination is Brom well's modifica-
tion of Roese's fusel-oil apparatus.

8

"This apparatus consists of a pear-shaped bulb holding about 200 cc, stoppered
at the upper end and sealed at the lower to a graduated stem about 4 mm in
internal diameter. To the lower end of this graduated stem is sealed a bulb of
20 cc capacity, the lower end of which bears a stopcock tube. The apparatus is
graduated to 0.02 cc, from 20 cc to 22.5 cc.

"The reagents required are fusel-free alcohol that has been prepared by frac-
tional distillation over caustic soda or caustic potash, and diluted to exactly 30
per cent by volume (sp. gr., 0.96541), chloroform freed from water and redistilled,
and sulfuric acid (sp. gr., 1.2857 at 15.6°).

'• Distill slowly 200 cc of the sample under examination till about 175 cc have
passed over, allow the distilling flask to cool, add 25 cc of water, and distill again
till the total distillate measures 200 cc. Dilute the distillate to exactly 30 per
cent by volume (sp. gr., 0.96541 at 15.6°).

"The following is an accurate method for diluting any given alcohol solution
to a weaker solution of definite percentage : Designate the volume percentage of
the stronger alcohol by V, and that of the weaker alcohol by v. Mix v volumes
of the stronger alcohol with water to make V volumes of the product. Allow
the mixture to stand till full contraction has taken place, and till it has reached
the temperature of the original alcohol and water, and make up any deficiency
in the V volumes with water.

'* Example. — It is desired to dilute a distillate containing 50 per cent of alcohol
by volume until it contains 30 per cent. To 30 volumes of the 50 per cent alcohol
add enough water to make 50 volumes, or place 150 cc of the distillate in a 250 cc
flask, fill to the mark with water, mix, cool, and fill to the mark again.

"Prepare a water bath, the contents of which are kept at exactly 15°, and place
in it the apparatus (covering the end of the tube with a rubber cap to prevent
wetting the inside of the tube), and flasks containing the 30 per cent fusel-free
alcohol, chloroform, sulfuric acid, and the distillate diluted to 30 per cent by
volume. When the solutions have all attained the temperature of 15°, fill the
apparatus to the 20 cc mark with the chloroform, drawing it through the lower
tube by means of suction, add 100 cc of the 30 per cent fusel-free alcohol and 1 cc
of the sulfuric acid, invert the apparatus, and shake vigorously for two or three
minutes, interrupting once or twice to open the stopcock for the purpose of
equalizing pressure. Allow the apparatus to stand ten or fifteen minutes in
water that is kept at the temperature of 15°, turning occasionally to hasten the
separation of the reagents, and note the volume of the chloroform. After thor-
oughly cleansing and drying the apparatus, repeat this operation, using the
diluted distillate from the sample under examination in place of the fusel -free
alcohol. The increase in the chloroform volume with the sample under exami-
nation over that with the fusel-free alcohol is due to fusel oil, and this difference
(expressed in cubic centimeters), multiplied by the factor 0.663, gives the volume
of fusel oil in 100 cc, which is equal to the percentage of fusel oil by volume in
the 30 per cent distillate. This must be calculated to the percentage of fusel oil
by volume in the original liquor.

"Example. — A sample of liquor contains 50 per cent of alcohol by volume.
The increase in the chloroform volume with the 30 per cent fusel-free alcohol is
1.42 cc; the increase in the chloroform volume with the distillate from the
liquor under examination, diluted to 30 per cent, is 1.62 cc: difference, 0.20 cc.
The volume of fusel oil in 100 cc of the 30 per cent distillate then is 0.20x0.663=
0.1326 cc, and by the proportion 30 :50 : -.0.1326 : 0.221, we obtain the percentage
of fusel oil by volume in the original liquor.

"20. Determination of Aldehyds.

' ' (a) Preparation of reagent. — Eighty cubic centimeters of a saturated solution
of sodium disulfite are mixed with a solution of 0, 12 gram of fuchsin in about
800 cc of water, 12 cc of sulfuric acid added, the solution thoroughly mixed,
and diluted with water to 1 liter.

"(b) Determination. — A portion of the sample is diluted with water, or strength-
ened with aldehyd-f ree alcohol until it contains 50 per cent of alcohol by volume,
and 25 cc of this solution are treated with 10 cc of the reagent, and allowed to
stand twenty minutes. At the same time 25 cc of a solution of 0.05 gram of
acetic aldehyd in 1,000 cc of 50 per cent alcohol are treated in the same manner
and allowed to stand the same length of time. The relative intensity of the
colors of the two solutions is then determined by means of a colorimeter, and
from the figure thus obtained the weight of aldehyd is estimated as acetic alde-
hyd, and calculated to percentage of the original liquor.

"21. Determination of Ethereal Salts.

"After the determination of the volatile acids, the neutralized distillate is
transferred to a flask connected with a reflux condenser, treated with 25 cc of
tenth normal sodium hydroxid, and boiled one-half hour. The flask and contents
are then cooled, 25 cc of tenth normal hydrochloric acid added, and the excess of
acid titrated with sodium hydroxid, using phenolphtalein as indicator. The
number of cubic centimeters of tenth normal alkali used in this titration, multi-
plied by 0.0088, is equal to the weight in grams of ethereal salts (calculated as
ethyl acetate) in the volume of liquor taken for the determination."

METHODS OF TANNIN ANALYSIS.

Page 78. — Omit all of 2 and insert the following:

{a) Shake 10 grams of the hide powder with 250 cc of water for five minutes;
filter through muslin or linen ; squeeze out thoroughly by hand ; collect the hide
powder, and repeat the operation three times with the same quantity of water.
Pass the last filtrate through paper until a perfectly clear liquid is obtained.
Evaporate 100 cc of the final filtrate in a weighed dish ; dry at 100° until the
weight is constant. If the residue amount to more than 10 mg, the sample
should be rejected. The hide powder must be kept in a dry place and tested
once a month.

(b) Prepare a solution of pure gallotannic acid by dissolving 5 grams in 1 liter
of water. Determine the total solids by evaporating 100 cc of this solution and
drying to constant weight. Treat 200 cc of the solution with hide powder exactly
as described in paragraph 6. The hide powder must absorb at least 95 per cent
of the total solids present. The gallotannic acid must be completely soluble in
water, alcohol, acetone, and acetic ether, and should contain not more than 1 per
cent of substances not removed by digesting with excess of yellow mercuric oxid
on the steam bath for two hours.

Omit all of 3 and insert the following :

Dry 3 grams of the sample, if it be an extract, in a flat-bottomed dish not less
than two and one-half inches in diameter, to constant weight. Of barks and
similar substances take two grams.

Omit all of 4 and insert the following :

In the case of barks, woods, leaves, etc., use such an amount of the material
as to give about 1 gram of total solids per 100 cc of solution, and extract in a
Soxhlet or similar apparatus. In the case of extracts, use 20 grams, dissolve in
900 cc of water at 80°, let stand for twelve hours and dilute to 1,000 cc.

10

Under 5 first line after "and " insert: "without filtering."
Omit all of 6 and insert the following :

6. Determination of Soluble Solids.

Filter about 125 cc of the solution through a double folded filter (S. and S.
No. 590, 15 cm) returning the filtrate through the filter once. Evaporate 100 cc
as before.

Page 78, omit all of 7 and insert the following :

7. Determination of Tanning Substances.

Prepare 20 grams of hide powder by shaking for five minutes with 250 cc
of water and straining through linen. Repeat the ojieration three times. Finally,
remove as much water as possible by squeezing in a press. Transfer the pressed
hide powder to a covered dish, and weigh. Dry a portion approximately equal to
one-fourth of the whole to constant weight at 100°. Add the remainder of the
hide powder to 200 cc of the original unfiltered solution and shake for ten min-
utes. Squeeze through linen, collect the filtrate, add 5 grams of kaolin free
from soluble salts, stir well, and filter through a folded filter (S. & S. No. 590,
15 cm), returning the first 25 cc. Evaporate 100 cc as before. The weight of
the residue must be corrected for the dilution caused by the water contained in
the hide powder. The shaking must be done in some form of mechanical shaker.
The simple machine used by druggists, and known as the "milk shake " is rec-
ommended.

Page 78, at the end of VIII-1, insert:

"Extracts must be heated to 50°, well shaken, and allowed to cool slowly to
room temperature. "

METHODS OF TANNIN ANALYSIS.

Add on page 78, after 7 :

"8. Testing the Nontannin Filtrate.

" (a) For tannin.— Test a small portion of the clear nontannin filtrate with a
few drops of a 1 per cent solution of gelatin. A cloudiness indicates the pres-
ence of tannin, in which case the determination must be repeated, using 25
grams of hide powder instead of 20 grams.

" (b) For soluble hide. — To a small portion of the clear nontannin filtrate add
a few drops of the original solution, previously filtered to remove reds. A cloudi-
ness indicates the presence of soluble hide due to incomplete washing of the hide
powder. In this case, repeat the determination with perfectly washed hide
powder."

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