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Kei.ler l\d Heckman

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JKHOM <; H HECKMAN
CHARI }>> M

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iri2 X STREET, N. W

WASIIINCtTON, Tj.C. £0036

TELEPHONE

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David

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2%-aroo

CAJ3LE ADDRESS

February

5,

1971

All Members of the SPI Food, Drug
and Cosmetic Packaging Materials
Committee.

Gentlemen:
Having just received a letter and
the FDA suggested procedure for extraction
testing on pigmented plastics mentioned at our
January 13 meeting, I am writing to supply this
information to you.
At the same time, however,
I thought I would take the opportunity to inform
the Committee on an interim basis about two
other subjects of interest so I hope you will
not mind receiving something of an "omnibus"
report.
Firstly, we are enclosing herewith
a copy of a February 2, 1971 letter from Al
Holtz of the Food and Drug Administration, along
with a copy of the extraction methodology men­
tioned therein.
We would appreciate it if all
of you with an interest in .the pigments situation
would review the methodology and send us any
comments you care to make at your earliest
convenience.
Since the comments are apt to be
technical in nature, it would be helpful if you
could send copies of anything you have to say to
Bill Westveer, the Chairman of our Technical
Information Committee and to George Ingle who
is acting as Chairman pro tern of the Pigments
Task Group.
Depending on the nature of the comments
received, we may well decide to meet with the Food
and Drug Administration staff on this matter some­
time in March, probably on March 25, so that the

ASI-PR 0001173

’ifELMAN"

February 5,
Page Two

1971

entire situation can be discussed with Mr.
Holtz and his associates.
Thus, we do hope
you can review the enclosed and give us your
thoughts by no later than March 10, 1971.
Regarding the minutes of the
January 13 meeting, we had hoped to have them
completed before now but we have been delayed
while we were awaiting one of the liaison
reports expected.
We are now proceeding with
the final typing so the minutes should be in
your hands within the next two weeks, the
additional time being required to accomplish
reproduction and distribution by the SPI office.
Finally, and as what I hope will
be nothing more than an interim report, we did
have a meeting with members of the Food and
Drug Administration staff on the so-called
"Ramsey proposal" on February 3, as scheduled.
You will recall that this meeting was set up
at the suggestion of Tom Brown of the Food and
Drug Administration during our question and
answer session on January 13.
At that time,
Mr. Brown indicated that he thought we could
move the Ramsey proposal ahead if we could
delegate two or three people to work with the
staff promptly.
Thereafter, we cleared the
Frawley-Wulfsberg-Heckman delegation with the
Inter-Industry Committee representing all of the
major packaging association interests and notified
the Food and Drug Administration that we were
prepared to get together on February 3.
At the session with FDA, those in
attendance from the Administration were Les
Ramsey, Lou Buckley, A1 Holtz, and Joe McLaughlin.
To our great surprise--I might even more properly
say shock--although we had lengthy discussions
during which it was generally agreed that the
Ramsey proposal remains, in Mr. Ramsey's opinion,
"scientifically sound" we were told that Mr. Ramsey

ASI-PR 0001174

February 5,
Page Three

1971

did not believe it could be published as
a final amendatory regulation to Section
121.2500, nor even as a proposal at this
time because "it would not be administratively
[or to use my word, politically] advisable
under current general conditions."
As we read
it, what Mr. Ramsey is saying is that he does
not believe the Food and Drug Administration
should have the courage to proceed with a
helpful rules revision despite its scientific
soundness at a time when FDA is under such
fire because of situations like those involving
the GRAS list review.
To put it mildly we were very
disappointed with this advice.
Furthermore,
I am still unable to believe that this result
is what Tom Brown had in mind when he suggested
at our meeting that we work together to further
our mutual interests.
For this reason, and
especially since Mr. Brown was not in attendance
on February 3, I am now planning to be in touch
with him on this very important subject once
again, hopefully when he returns to Washington
on Monday or Tuesday of next week.
All I can
add at the moment is that I hope this effort
to move past Mr. Ramsey will be fruitful.
In
any case, this interim report should serve to
bring all of you completely up to date for the'
time being.
If anyone receiving a copy of this
letter has a question about any of the subjects
discussed before we are in touch once more, please
do not hesitate to call or write.

Enclosure

ASI-PR 0001175

DEPARTMENT OF HEALTH. EDUCATION. AND WELFARE
PUBLIC HEALTH SERVICE
FOOD AND DRUG ADMINISTRATION
WASHINGTON. D.C.

2023*

February 2, 1971

Mr. Jerome H. Heckman
1712 N Street, N.W.
Washington, D.C. 20036
Dear Jerry:
Attached is a copy of our suggested procedure for extraction testing
on pigmented plastics which yon requested (1/15/71).
This is the method
which was mentioned at the recent SPI meeting and is essentially the one
which Eastman evaluated for their petition.
This version includes some
modifications introduced to answer some of Eastman's questions and which
they considered desirable.
Our interest in submitting the above through you to several other
interested parties is to derive the benefit of varied trials and/or view­
points towards providing a standard acceptable procedure.
Our August 1966 Guidelines should also be consulted for any pertinent
information relating to this special extraction subject.
If any questions arise concerning this tentative method we will be glad
to discuss them.
Thank you for your help and cooperation.
Sincerely yours

Attachment

A. Holtz, Chemist
Food Additives Petition
Evaluation Branch
Division of Food Chemistry
and Technology

ASI-PR 0001176

:cttq-;

color

A.

teet for

roi/rr-'mc i:\TniAT"

Extraction of rigid or semi-rigid food-contact containers,
(i) Equips 2111
(1)
(2)
(5)

CCC :.l bunkers with watch glass covers
Tarc.d 250 ml beak or
2-1/2 inch square stainless steel screening sufficient
for the replicates needed.
(4)
Paper clip or other clipping device to hold screen
and cample sandwich together.
(5)
Suspending wire to hold sample sandwich in beaker.
(6)
longs
(7)
Hot air oven
(8)
Thermostatically controlled waterbath to - 1.0° F.,
variable from 80° F. to 135* F., capable of holding
800 ml beakers.
(9)
Hood and hot plate, facilities
(10) Analytical balance of suitable sensitivity (0.1 mg) and
capable of handling the 250 ml beaker.
(11) Desiccator
(ii)

Reagents.
(1)
(2)
(3)

(4)

Freshly deionized distilled water
Freshly redistilled, reagent grade n-heptane b. pt. 208° F.
95 percent (by volume) ethyl alcohol, diluted with
deionized distilled water to 8 percent and 50 percent
by volume,
Freshly distilled acetic acid diluted to 3 percent
(by volume) with deionized distilled water.

0001177
asi~pr

•Y*

Page 2.

L. Buckley, ¥,7-i20

(iii)

Test mater,'.ala
Select a sufficient number of rigid nr semirigid containers
so ;u, to be able accurately to cut eight 2-1/2 inch square
samples or other desirable samples from the formed products
for the test material.

(iv)

Procedure
(a)

Total nrn-volatile extractives
(1)

(2)(a)

(b)

Determine the appropriate solvents and oxtractabili t.y
conditions for the intended uses as described in
section 121.2526(d) Tables 1 and 2.
For the nqrmnl
packaging of thermoplastics we consider 120-30® F
a suit-limiting temperature.
Using the tongs, carefully prepare two sandwiches
consisting of screen, sample, screen, sample, screen,
sample, screen, sample, screen.
Clip each sandwich
together by moans of the clipping device.
Introduce 100 ml o.f the appropriate food simulating
solvent in an LOO ml beaker* usinu each of the four
food J ii..ul,;Li:. solvents u:.;..uJ ..Love (wat^r, 2%
acetic acid, alcohol (8,1 or 60,1) and n-heptanc,
cove:; with a watch glass, and place in the constant
temperature hath and condition at the desired
temperature.

(c) After conditioning, carefully introduce the sample
sandwich into the appropriate extracting liquid.
(d) Extract using the appropriate solvents and timetemperature conditions.
(3) If tie procedure under (2) is not readily applicable
then use the following immersion method.
E>tract the samples as necessary (by film or
plaque immersion etc.) with proper aliquot
sampling at optimum intervals until equilibrium
(i.e. no change in extraction level) as gauged
hy at least 3 periodic tests at the same tem­
perature covering at least 72 hours for aqueous
and 6 hours for heptane.

ASI-PR 0001178

Page 3.

L. Buckley, IiP-320
(4)

At the conclusion of the extraction period, carefully suspend
the sandwiches by the wire to drain into the beaker.

(5)

After draining, pour the food simulating solvent
solution into the fared beaker.
Rinse the 800 ml
beaker three times with the required solvent, using
a total of not more than 50 ml.

(6)

Evaporate the liquid to a few milliliters on a low
temperature hot plate, transfer to an oven at 2^f 1° F.
and evaporate to dryness.
Allow to cool in a
'
desiccator to room temperature and weigh the residue
to the nearest 0.1 mgrn.
Calculate the total ex­
tractives in milligrams per square inch of container
surface.
.

(7)

Whan running the acidic and alcoholic extractions, the
sampling and analyses on these need not be started
until the point where the. water extraction reaches
equilibrium.
If those extractives are of the same
type and equal or less than the voter value level
then wo can consider these at equilibrium.
If
however, Luulr ranges are 10-137* greater, then the
acidic and/or alcoholic extractions should be
eontinuna ro emitii.hH.tim.

(b)

Amount of colorant extracted.

^

Dissolve Mil? '’cighad residue in deionised water or
requires, concuntrati-ch -o£ reagent grade nitric acid,
if necessary, neutralizing the acid with reagent
grade sodium hydroxide solution after the residue
is dissolved.
Proceed as described for flexible surfaces.
B.

Extraction of flexible polymeric food-contact surfaces.
(!)

Equipment
(1)

Extraction test cells described in Methods of Analysis,
AOAC, sec. 7,035, 7,037.

(2)

Oven rack for extraction test cells

(3)

Hot air oven

(4)

Graduated cylinder

(5)

Fritted glass filter

/ O/1

ASI-PR 0001179

Page 4.

L. Buckley, RF-320

(6)

PL-.Uir.um evaporating dish

(7)

Stearn bath

(8)

Desiccator

(9)

Analytical balance of appropriate sensitivity (0.1 mg)

(ii)

Reagents
(1)

Freshly del onized distilled water

(2)

Freshly redistilled, reagent grade n-heptane, b.pt.
208° F.
95 percent (by volume) ethyl alcohol, diluted wi.tln
deionized distilled water to '8 percent and 50 percent
by volume.
Freshly distilled acetic acid diluted to 3 percent
(by volume) with deionised distilled water,

(3)

(4)

(iii) Test materials
Select samples of flexible food-contact films and protect from
exposure to liquids nr contact v;ith other materials and
from wrinlfling or -b’-n ;ior.,
Cut in rectangle,; equal m ul
exceeding thu dimensions of the extraction cell with 1
dimension at least equal to or greater than the S" width,
of the cell, and Sufficient for 2 rectangles to each cell
and
for 2 cells por determination.
(iv) Procedure
(a) (1)
(1)

Total non-volatile extractives:
Determine the appropriate solvents and extractability
conditions for the intended use(s) as described in section
121.2526(d) Tables 1 and 2.
For normal packaging of thermoplastics we consider
120-130° F a self-limiting temperature

(2)a.

(b)

Follow the test procedures set forth in Official Methods
of Analysis of the AOAC 7.037, 7.033, and 7.039, using
the appropriate solvents and temperature conditions.

If the procedure under (2)(a) is not readily applicable then
use the following immersion method.

ASI-PR 0001180

Page 5.

L. Buckley, BF-320

Extract the samples as necessity (by film nr plaque
immersion etc.) with proper aliquot sampling at optimum
intervals until equilibrium (i.e. no change in extraction
level) as gauged by at least 3 periodic tests at the same
temperature covering at least 72 hours for aqueous and
6 hours for heptane.
(3)

When running the acidic and alcoholic extractions, the sampling
and analyses on these need not be started until the point
where the water extraction reaches equilibrium.
If these,
extractives are of the sane type end equal or less than the
water value level then we can consider these at equilibrium.
If however, their ranges are 10-157, greater, then the
acidic and/or alcoholic extractions should be continued to
equilibrium.

(4) (a) Calculate the total extractives in milligrams per square
inch of container surface.
(b) In calculating migrations of milligraw.s per square inch,
the. area of the- exposure used 'is only that of one side
if the film used is less than 5 mils.
(b)

rti.iounc of colorant extracted.
Dissolve the weighed residue in deionised water or required
concentration of reagent grade nitric acid, if necessary,
neutralining the acid with reagent grade sodium hydroxide
solution after the residue is dissolved.

,-l'-

If the colorant is a metallic compound carefully evaporate
the solution to about three drops and examine for the
metal by means of suitable quantitative techniques with
a maximum detection limit of about 0.05 micrograms of the
metal.
Calculate amount extracted per square inch of contact
surface.
: If the colorant Is an organic substance, the residue solution
j should be made up to a standard volume with deionised dis­
tilled water or other appropriate solvent and the concentration
of colorant determined chromatcgraphic.ally or spectrophotomatrically by comparing the results from an uncolored
film under test.
The sensitivity of the technique use should
be shown.
,,
—X

/

Or
ASI-

PR 0001181

Pa-e

b.

L. Buckley, BF-320

The results of the total extractive determination are to be
used as a check on the equilibrium conditions and v;here
appropriate to determine the compliance of the base film
with the existing regulations.
Our suggested general analytical procedures are not necessarily binding.
Any satisfactory validated method and sensitivity will be accepted.

cc:

BF-100, BF-112, BF-301, BF-117, BF-143,

BF-350(Mr.

Spilier).

AHoltz:mas 9/23/70
D/Init: MTrochazka 9/23/70

■rs..~e
Tf.m. *

*y~<■*

y -

✓'***'
~t~~‘ *'

.A

ASI-PR 0001182

»
« Additives

Food Additives

123

.before using, at rate of 15 ml
tide soln for washing.__
.iot <2.5% NH, by wt.
A RATION OF SOLUTION

e with little Mg(NO,), soln,
lissolve in HC1 (1 +2.5), and
In aliquot of soln det. P,0, as

stermination

prepd loin into 250 ml beaker;
ftht excess and barely dissolve
■w drops HNOi, stirring vigorjSO, has been used as solvent,
, NH4NOi or soln contg that
oln add 70 ml molybdate soln,
100 mg P,0, present. Digest 1
it for complete pptn of P,0, by
ulate soln to clear supernatant,
ith cold H,0 or preferably with
. Dissolve ppt on filter with
nd hot HiO, and wash into
> 100 ml. Neutralise with HCI,
r or bromothymol blue as indiFrom buret add slowly (ca I
. vigorously, 15 ml of the mag*
g PiOi present. After 15 min.
H and let stand until super*
tally 2 hr); filter, wash ppt with
il washings are practically Cl*
heat, and ignite to constant
•nace at 950-1000°; cool
w,.
as MgjPjO,. Report as

4

'alive Test—Official,
Final Action
) to 1-2 g sample in 150 ml
t acid with HNO», filter, take
e and NHi molybdate soln,
m at 40-50®. Yellow ppt indiihosphate.
[10)—Official, Final Action
1.5 hr with mixt. of 300 ml HaO
Iter, wash filter thoroly with hot
d filtrate and washings, and dil.
3. Det. sulfate in 100 ml aliquot
lia—Official, Final Action
in distn flask add 300-400 ml
>f NaOH soln (1+1), connect
id distill into measured vol. ltd
»cid in distillate with std alkali,

Arsenic—Official, Final Action

FOOD ADDITIVES

Place 5 g sample directly in generator,
24.007(a); add 10 ml HtO, little at time to prevent
foaming over, and then 15 ml As-free HCI, adding
it dropwise until foaming ceases. Heat on steam
hath until drop of mixt., when dild and treated
•iih I soln, does not show blue. Then dil. to ca
10 ml with HtO and continue as in 24.010, begin­
ning "add 5 ml of the KI reagent. .. ” Prep,
blank and stda for comparison, using As-free HCI
of sane concn as that used in detn.

Exposing Flexible Barrier Materials
for Extraction

7.0JI

7.012

Vlnorine—Official, Final Action—
See 24.029-24.035

ASTM-AOAC Method (11)—Official, First Action
7.034

7.033
7.011

Lead—Official, Final Action—
See 24.041-24.031

principles

Method provides std liquid extn method for
flexible barrier materials, singly, coated, or com­
bined, including extns thru flexible barrier mate­
rials of surface coating ingredients by food-simu­
lating solvents. Specimens of flexible barrier mate­
rials are exposed to extg liquids in test cell and
amount of nonvolatile extractives remaining after
exposure is measured.
APPARATUS

(a) Test cell.—See Fig. 7:2. Consists of two
SXllixr No. 310 stainless steel plates, de-

ASI-PR 0001183

124

7. Baring Powders, Baking Chemicals, and Food Additives

greased; one JX J1" U-shaped virgin TFE-fluorocarbon (Teflon) gasket, grooved on both sides os
shown; twelve 1X1' stainless steel bolts with
wing nuts; one J X1X 8* TFE-lluorocarbon gasket
plug tapered to provide tight fit. (Available from
Scientific Products, Inc., Div. of American Hos­
pital Supply, Evanston, 111., No. 6200.) To prep,
app. for use, wash plates and gaskets in aq. de­
tergent soln. Rinse with HjO and dry at 1008.
Wash with n-heptane and redistd acetone. Im­
merse new gaskets in n-heptane overnight. Rinse
gaskets with fresh n-heptane and dry at 100s.
(b) Own rack—Set Fig, 7:3. To hold oxtn tost
cells.
(c) Hoi air oven.—With safety provisions for
flammable solvents. Vac. oven or autoclave is
suitable.
7.030

REAGENTS

Use solvents (usually HtO, dil. alcohol, and nheptane) specified in regulations (Cods of Federal
Regulations, Title 21, Sec. 121.2514(d)(2);
121.2526(d)). Solvent for blanks and detn should
be from same container.
7.037

■ i

preparation op cells

Select samples of flexible barrier material and
protect from exposure to liquids or contamination
by migration from contact with other materials,
and from wrinkling or abrasion. Samples shall
equal or exceed dimensions of cell where possible.

and shall in all coses have 1 dimension equal to or
greater than width (8*) of coll.
Place 1 stainless steel plate of cell on flat surface
with bolts protruding up thru holes in plate. Place
prepunched specimen (side to contact liquid up)
on plate with 1 edge aligned with bottom of plate,
2 edges aligned with sides of plate, and bolts pass­
ing thru prepunched holes. Place gasket on speci­
men with outer edges of gasket aligned with cell
bottom and sides. If desired, place second pre­
punched specimen (side to contact liquid down)
on top of gasket. If only 1 sheet is used for test,
place inert barrier sheet sueh as Teflon or electro*

lytically cleaned tinfoil in place of second sheet.
Place second stainless steel plate on top of assem­
bly. Place wing nuts on bolts and tighten.
Preheat assembly (including TFE-fluorocarbon
gasket plug) to test temp, and retighten nute so
that assembly is liquid-tight.
7.038

determination

Place measured vol., A, of extg liquid, pre­
heated to test temp., into assembly. Use vol. of
liquid such that top of liquid is 0.5' below top of
specimen. In no case should vol. of extg liquid be
>200 ml. Insert gasket plug in top of cell. Expose
eeJl in rock in oven to conditions of time and
temp, specified by regulations. If roc. oven is
used, operate it at atmospheric pressure. Align
cells in rack in oven parallel with air flow.

i

\

tm

mmsmmm

ASI-pr 0001184

s.

t

OniTIVl!#

ive 1 dimension equal to or
|of cell.

I

I'
i of cell on flat surface
it
j holes in plate. Place
(side to contact liquid up)
igned with bottom of plate,
les of plate, and bolts passolcs. Place gasket on speciof gasket aligned with cell
desired, place second pree to contact liquid down)
ly 1 sheet is used for test,
t such a» Teflon or eleetroI in place of second sheet,
itecl plate on top of aesemi bolts and tighten,
chiding TFE-fluorocarbon
mp. and retighten nuts so
tight.
brmination

, A, of extg liquid, prento assembly. Use vol. of
liquid is 0.5' below top of
ould vol. of extg liquid be
plug in top of cell. Expose
) conditions of time and
ulations. If vac, oven is
noepberic pressure. Align
alls! with air flow.

Nmim
After exposure, remove cell from rack, remove
gasket plug, and immediately pour out extg liquid
into graduate. (If solids flake from specimen and
it is desired to det. only sol. materials, filter thru
fritted glass filter from ceil into graduate.) If vol.
of extg liquid is <90% of original vol., investigate
cause.
Det. total nonvolatile extractives by evapg total
vol. extg liquid to apparent dryness in weighed Pt
evapg dish on steam bath. Dry in oven 30 min. at
100°. Cool 30 min. in desiccator and weigh.
Perform at least 2 blank detns with 200 ml extg
liquid each and glassware that will bs used in
detn. Preclean glassware with chromic acid soln
followed by H,0 rinse. Place equal vol. extg liquid
into each of blank-receiving containers. If filter is
used on extg liquid from exposed samples, include
contact of solvent of blank with filter. Wt blank
must be <2.0 mg/200 ml and <30% of wt ex­
tractives.
7.039

calculation

With 2 sheets in cell, ratio of exposure area to
vol. extg liquid used to fill cell is 2 ml/sq. in. Calc,
mg extractives/sq. in. exposed sample =» (mg ex­
tractives—mg blank) /sq. in. exposed sample.
Acetone Peroxides {It)—Official, Final Action
7.040

In Baking Premize*

Weigh accurately ca 8 g sample into flat-bot­
tom centrifuge bottle, pipet 100 ml H,0 onto
sample, and stir 10 min. after making sure no
lumps remain. Centrifuge at ca 1500 rpm ca 10
min. Pipet 25 ml supernatant into erienmeyer,
add 25 ml H1SO4 (1 -4-4), and let stand at least 3
min., swirling occasionally. Titr. to light pink that
lasts >20 see, with std 0. IN KMnO« soln,
42.023~42.024.
Total peroxides in g H1O1 equiv./lOO g premix
— ml KMnO4XnormalityX0.0170Xl00/0.25Xg
sample.
7.041
In Milling Premize*
Weigh accurately ca 200 mg sample into erien­
meyer, add ftO ml H1SO4 (1+9), let stand >3
min., stirring occasionally, and titr. with std 0.1 AT
KMnCh, 42.023-42.024, to light pink that persists
>20 sec.
Total peroxides in g H,0, equiv./lOO g pre­
mix - ml KMnO,X normality X0.0170X 100/g
sample.
Qualitative Teet
(Acetone peroxides are extremely expioeive. Do
not ext. more org. peroxides from adsorbents than
necessary for test.)
7.042
APPARATUS
(a) Recording infrared epectropkotometer.—Suit­
able for work from 2 to 10 a.

13ft

(b) Rock tall plate.—Or other support stable to
acetone and acetone peroxides and transparent in
2-16 it region.
7.043

TEST

Weigh sample contg ca 10 mg H1O1 equiv. of
acetone peroxides into g-s. flask. Add ca 1 g anhyd.
NaiSO, and 10 ml acetone for every g adsorbate.
Shake 3 min., filter (Whatman No. 12 paper has
been found satisfactory) or centrifuge (for baking
premix), and carefully evap. clear soln to ca 1
ml under vac. at room temp.
Under wgrm light and gentle current of dry
warm air, add coned acetone ext. dropwise to rock
salt plate. When film of viscous liquid is visible
on plate, place it in infrared light path and, with­
out recording, check transmittance of peak at ca
12.1 it. If necessary, add enough addnl portions of
ext. to give 20-25% transmittance. Set spectro­
photometer at acetone peak at ca 9.2 44. Let radia­
tion pass thru sample on plate until raised pen
reaches max. transmittance (acetone has evapd).
Then record spectrum of film on salt plate from 2
to lft ».
Compare curve to one obtained from reference
acetone peroxides treated in same manner.
Nitrites {13)—Official, First Action
(Applicable to dry cure mix or curing pickle)
7.044

APPARATUS

Bend piece of glass tubing 250 mm long, 0 mm
o.d,, to form right angle ca 60-70 mm from one
end. Connect short end with rubber tube to outlet
of pressure regulator on COi tank.
7.045

PREPARATION OP SAMPLE

(a) Dry cur* mix.—Weigh 50.0 g sample and
dissolve in 1 L HtO. Transfer 25 ml aliquot to 250
ml erienmeyer.
(b) Pickle eoln.—Filter thru dry paper. Weigh
60.0 g filtrate into 260 ml erienmeyer.
7.046

DETRBMINATION

To soln in flask, add 20 ml colorless 15% KI
soln and ca 2 ml starch soln, 17.001 (g). Insert long
end of gas inlet tube and adjust flow of COi to ca
5 bubbles/sec. Continue flow of COi thruout
detn.
After ca 5 min., add 20 ml HtSO, (1 +7) from
buret, and mix thoroly. Titr. with stdxd 0.0725N
NatStOt to first complete disappearance of atarchI color. 1 mi 0.0725W NnStO, = 0.0050 g NaNOt.
SELECTED REFERENCES
(/) J. Aseoo. Offio. An. Chemiete6,463(1923).
(t) Ibid. 10, 30(1927).
(3) Ibid. 31,278(1948); 32, 83, 269(1949); 33.
77(19601.

ASI-PR 0001185