J. Franklin (John Franklin) Jameson.

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a somewhat similar method would keep a year without fermen-
tation.f

II. Starch solution by heating with glycerinCy according to
Zulkowsky.\

In 70*^"** of pure glycerine 6 grm. of potato starch were
heated at a temperature of 186°-190° C. for half an hour with
constant stirring. The starch dissolved and the solution turned
through yellow to a deep red. The solution was cooled to
120° C. and poured slowly and continuously into 200*="* of
alcohol. The precipitate was thoroughly stirred, settled and
filtered while warm. It filtered readily and was washed with
alcohol until the filtrate came through colorless. The color-
less residue was then dissolved in 500*''"* of water heated to
60^-70° C.

The product is called amorphous amylodextrin. It is
described as non-crystallizable, coloring blue with iodine,
(a)j= 206-8°+.

Ill, Soluble starch by saliva digestion.

In a little cold water 2 grm. of starch were ground with
0-5 grm. of acid potassium carbonate and poured into 200*"** of

♦ PayeD. Coinp. Rend.. Ixi. 512. f Zeitschr. anal. Chem.. 1886, 37.

X Ber. Chem. Ges , xiii, 1395-1398



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Oxidizers in the Hydrolyaiu of Starch and Dextrins. 385

boiling water and boiled a few minutes. The solution was
then allowed to cool to 40^-45° C. Meanwhile lO*''^* of fil-
tered saliva were neutralized with 0*1 per cent hydrochloric
acid. A blue litmus strip, which had been dipped in acetic
acid and w.ished, was used as indicator. The saliva was added
to the starch solution at the proper temperature. In three or
four minutes the solution became entirely clear, and was at
once brought to a boil and boiled for ten minutes.

The addition of the alkali was to hinder the action from
going beyond the first step of digestion. The boiling at the
end destroyed any further action of the saliva. Starch cellu-
lose is said to produce a feeble red or brownish color with
iodine,* hence the possible utility of this method lay in the
absence of cellulose from the starch solution, since the cellu-
lose is digested by the saliva.

Solutions were made up according to each of these formulae.
The amorphous amylodextrin was made from impure starch,
the other two solutions from pure potato starch, specially pro-
cured. Table IV shows the relative sharpness of the different



Table IV.

Volume 125«'»3.

n/lOlsol. Potassium iodide. Starch sol. Color,

drops. cm*.

1

2 faint change

3 decided change

4 light yellow

6 decided yellow

1 Igrm. " *'

1 1 crystal " "

1 1 ordinary pale purplish

2 " stronger faint **

1 1*5 amorphous

amylodextrin flash of blue

2 1-5 " good blue

1 1 crystal 1*5 " " «

I I KI starch " «

2 '* deeper blue

1 1*5 amidulin slight change

3 ** very faint pink

2 3 " no change

3 3 " pale blue

2 5 " stronger " "

* Beilsteiii I, 1082, line 17.



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386 Hale — Initiative Action of Iodine and other

end reactions in blank. It will be noticed that the plain iodine
reading is not sharp unless potassium iodide be present, and
this is true of the starch solutions. The ordinary starch solu-
tion mentioned in this table and in the following table was a
different one from that previously used. It was freshly pre-
pared and hence shows a less amount of the impurity present.
The burette used took four to five drops to make 0*1*^*, or
approximately one drop equaled 0'022""*.

It will be seen that the potassium iodide starch solution gave
the sharpest and best end reaction, that amorphous amylodex-
trin lost one drop of iodine, and amidulin and plain iodine
two drops. However, the presence of a crystal of potassium
iodide rendered them all sharp to a drop, with the exception
of amidulin, which explains the closeness of the results in the
next table. In this tneir delicacy was tested in regular titra-
tion with a fresh arsenite solution, and with a slightly stronger
iodine solution.







Tablb V.








Volume 125«°»«.




n/lO








lOt sol. 1


1/10 I sol.


Starch sol.


Color.


cm*.


cm'.


cm*.




50


49-38


1 KI starch


permanent purplish


49-40




good blue


((


49-40


1 " (4 crystals KI)


good blue


1


49-40


2 ordinary


slow-fading purplish


i


49-42




permanent blue


««


, 49-38


1 -5 amorphous amy lo-


permanent purplish




; 49-40


dextrin


deep blue


«


49-42


5 amidulin


permanent purplish




49-44




deeper purple


u


49-55


25 ordinary


abundant red



While these results are very close and the discrepancies
might be ascribed to manipulation, yet the loss on 25*^* of
ordinary impure starch freshly made, can hardly be over-
looked. Moreover, these titrations were made at a slight dila-
tion, and the slight loss hinted at in the case of amidulin is in
keeping with later experiments. The introduction of con-
siderable potassium iodide made no difference in the sharpness
of the potassium iodide starch, and since this preparation gave
the best blue color it was used in a series of parallel titrations
in which readings were made with the starch blue and then
with plain iodine alternately in order to eliminate accidental
errors. Starch was added subsequently to corroborate the
plain iodine reading, as the yellow is very delicate. The abso-



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Oxidizers in the Hydrolysis of Starch and Dextrins. 887

lute reading were fonnd by snbtracting one drop from the
actual reading. To render the plain i<Mline readings sharp a
crystal of potassium iodide was added in the firet two titra-
tions.

Table VI.

Volume 126«»».
n/10 1 sol. n/lOIsol.



n/10
A8,0,.


n/10 1 sol.

reading
by iodine

color.


reading

by

KI starch

blue.


n/lOIsoL
abs. amt.


n/10 1 sol,
abs. amt.


abs. amt.

calc'd
, from

50cm8


n/10 1 sol.

abs. errors

in A, . . in B.




A


B


A


B




A B


cm*.


cm*.


cm*.


cm*.


cm*.


cm*.


cm*. cm*.


5


. 1 drop*
4-94*


1 drop
4-96


4-92


4-94


4-94


0-02- 0-00 ±


10


9-88


9-90


9-86


9-88


9-88


0-02— 0-00±


16


14-83


14-83


14-81


14-81


14-82


0-01— 0-01 —


20


19-78


19-78


19-76


19-76


19-76


00± 000 ±


30


29-64


29-64


29-62


29-62


29-68


001— 0-01 —


40


39-55


39-65


39-63


39-63


39-61


0-02 4- 0-02 -f


60


49-41


49-41


49-39


49-39


49-39


0-00 ± 0-00 ±



The most noticeable and important fact is that all loss, noted
in the beginning of this paper, has disappeared, and that the
plain iodine and tne starch readings agree exactly except for the
first two titrations, and here there is only a difference of a
drop. The absolute errors are interesting as they show how the
absolute values fluctuate about a standard set by the 50*^* read-
ings. This fluctuation is limited to a drop plus or minus.

The statement has been made that starch from different
sources has a varying power of absorbing iodine, e. g., that

{)otato starch absorbs three times as much as rice starch.f To
earn whether this fact had any bearing upon the question at
issue, and at the same time to learn whether pure starch solu-
tions made in the ordinary way (G. Gastinc) would give as
delicate readings as when boiled with potassium iodide, solu-
tions were made from pure potato starch, pure rice starch,
pure arrow-root starch and a pure soluble, so-called, starch of
unknown origin. The results of titration with these solutions
as indicators are shown in Table VII.

A fresh arsenite solution was made in a slightly different
manner from the former. To assist in dissolving the arsenious
oxide (4*95 grm.), 4 grm. of potassium hydroxide were added,
not enough to entirely form di-potassium hydrogen arseniate,
but more than enough to form potassium di-hydrogen arseniate.
At each titration 5*^*°* of a saturated solution of acid potassium
carbonate were added.

* A crystal of potassium iodide was added.
fGirard., Ann. Chim. Series (6), xii, 275.



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388 Hale — Initiative Action of Iodine and other

Tablb VIL

No extra dilution. Volume about 110«"^
n/10
AsaO,. n/IOIsoI. KHCO,. Starch sol! Color.

cm*. cm^. cm^. cm^.

-^ J49M1 5 1 ordinary pure potato pale blae

" 14913 deep blue

" 49-1:^ " " ordinary pure rice blue, slightly

purplish
" 49*14 ** " ordinary pure soluble blue, slightly

purplish
** 49-15 " " ordinary pure arrow-
root deep blue
" 4915 '' " KI pure starch good blue
" 49-13 *' " yellow

It is at once seen that these values are coincident within a
drop and that all the starch solutions are within the limits set
by a plain iodine reading on the one hand and a potassinin
iodide starch reading on the other, though there was no dilu-
tion of the standard solutions.

To test the action of pure starch further some titrations
were made with pure potato starch in varying amounts, and
again with increasing amounts of acid potassium carbonate.
As the loss of iodine, previously noticed, had been almost
complete when 10*^"' of arsenite solution had been titrated,
this quantity was used. Again there was no dilution.











Table VIII.










No extra dilution.




n/IO












A8,0,.


w/lOIsol.


KHCO,


. Starch sol.


Color.


cm^


cm^.


cm^.


cra^.






10


9-82


5


1-5


ordinary pure potato deep blue,












purplish


(<


9-82


4(


5


((


** deep blue


«


j 9-82
( 9-84


l<


10


i(


" pale blue, purplish










deep blue





9-82


((


15


u


" deep blue


u


9-84


((


20


((


" deep blue


if.


9-85


({


25


i(


" deep blue


50


4915


((


25


((


" medium blue


u


49-35


((


25


ordinary inn


ipure abundant red



The last experiment was made to see if the conditions were
the same as in the preceding experiments save for the starch,
and a loss of 0-20'""' of iodine solution seems to prove that
there were similar conditions. There appears to be no loss
with any amount of pure starch solution, even when 50"°" of



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Oxidizers in the Hydrolysis of Starch and Dexirins. 389

arsenite solution is titrated. Especially noticeable is the fine
blue color, with only a tinge of purple twice. The same thing
is noticeable in the next series, by which it is seen that no
reasonable excess of acid potassium carbonate causes any loss.









Table IX.










No extra dilution.




n/lO












A8,0,.


n/lO I 8ol.


KHCO,


. Starch solution.


Color.


cm'.


cm'.


cm*.


cm*.


ordinary pure potato.


10


9-82


5


1-5




deep blue


10


9-82


10


((




deep blue


10


9-83


15


C(




deep blue


10


9-82


20


((




deep blue, purplish


10


9-81


25


«




deep blue



As still further corroborative proof a solution of tartar
emetic was made up as follows.* Tartar emetic was recrystal-
lized, dried by exposure to the air and pulverized; 16 grm.
were weighed out and dissolved in 200-300^* of water ; 20
grm. of tartaric acid, dissolved in a little water and filtered,
were added and also 1*"" of strong hydrochloric acid. The
solution was diluted to one liter. The significant fact about
the following titrations is the absence of any red colors, such
as are historically connected with antimony titrations. Indeed,
Freseniusf speaks of the red as giving the closer reading.









Table X.






n/10 Tartar








Volume.


emetic.


n/lO I sol.


Starch sol


KHCO,. Color.


cm'.


cm'.


cm"*.


cm', pure potato.


cm'.


100


10


9-58


1-5


1 blue, no red


100


10


9-58


15


10 blue


75


10


9-56




10 yellow


125


50


. 47-75


1-5


25 blue,

(purplish tinge)


125


50


47-75




25 yellow



The average of the 10^™' readings (absolute) multiplied by
five equals 47*73. The absolute 50^™* reading (47-75-0-02)
equals 47*73. Evidently even tartar emetic causes no loss on
pure starch, for the 50*='"* reading agrees with the plain iodine
reading for the same amount and with the 10*^™' titrations.

The severest test of all was then made on the pure potato
starch solution. With it were tried the two oxidizing experi-
ments with hydrogen dioxide and potassium permanganate.

I. Into an Erlenmeyer flask 100"°* of water, 10*^"* of acid
potassium carbonate, 4"^"' of the starch solution and 5*^"* of

♦Gruener, this Journal, vol. xlvi, Sept., 1893.
f Freseuiu", Quaut. Anal., 6»« Aufl., II, 818.



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890 Haie — Initiative Action of Iodine and othet*

hydrogen dioxide were poured, brought to a boil and boiled
five minutes. The solution was cool^ and iodine was added.
A few drops brought out a fine blue with perhaps the barest
trace of purple.

II. Into an Erlenmeyer flask 100*^* of water, 10*"' of acid
potassium carbonate, 4*^* of the starch solution and 1*°*" of
potassium permanganate were poured, broueht to a boil and
boiled five minutes. The permanganate laded to a light
brownish yellow. The solution was made acid and the excess
of permanganate was faded with a few drops of very dilate
sulphurous' acid. The solution was then cooled, made alkaline,
ana iodine was added. A few drops produced a blue. There
was not a trace of red.

These facts substantiate the statement that pure starch causes
no red color, nor loss of iodine, in alkaline titration of arsenite
solution or of tartar emetic. If any purplish tinge occasion-
ally occurs it is no hindrance to the reading and it causes no
appreciable loss of iodine, since under most advantageous con-
ditions the loss is but slight, even with an impure starch.

With an impure starch the reading from the first permanent
color, whether red or blue, is nearest to the correct value.
The readings with impure starch may be compared with plain
iodine readings and a correction applied, since the loss for a
constant quantity of starch is constant in the titration of 20-50*=™*
of arsenite solution. It is* better to titrate with considerable
dilution, e. g., 150-200*^'"*, and to add a crystal of potassium
iodide if necessary, since the production of red is at a mini-
mum and less troublesome, and the loss of iodine is hardly
appreciable. With impure starch fresh solutions should be
frequently made.

Experiments showing the Cause of the Trouble,

The foregoing experiments have shown that pure starch is
not attacked by iodine, hydrogen dioxide, or potassium per-
manganate in the presence of acid potassium carbonate, and
that impure starch is attacked. There were found in the
impure starch employed two impurities, one of which colors
red with iodine, and the other under the influence of nascent
oxygen and acid potassium carbonate is changed to a body
which colors red with iodine. These two impurities were sepa-
rated from the starch in the following manner. A solution
was made of the impure starch. To two separate portions
iodine was added.

I. Iodine was run in to excess, and the resulting starch blue
was precipitated by dilute sulphuric acid and filtered. The
excess of iodine was shown by its action on the filter paper



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Oxidizers in the Hydrolyds of Starch and Dextrine. 391

and by the color of the filtrate, which was yellow. This latter
fact showed that the dextrins present, if such they were, had
been included in the starch blue. An attempt to wash them
out with water completely failed. The principle suff^esting
this and the following experiment was the greater solubility of
the dextrin iodide than of the starch iodide, and the fact that
it is not precipitated by dilute sulphuric acid, when alone.

!!• With care iodine was run in just sufficiently to use up
the starch present with but the barest excess, so as to include
no dextrin iodides if possible. The starch iodide was then
precipitated with dilute sulphuric acid and filtered. That
there was no excess of free iodine was shown by the lack of
action on the filter paper and by the color of the filtrate, which
at first came through of a pale blue color and finally came
colorless. The precipitate was well washed. To a few cubic
centimeters of the filtrate a drop of iodine was added, and at
once a red color was produced with no trace of blue. Enough
dextrin was present to completely hide the pale blue of the
earlier portions of the filtrate.

This pale blue compound, though separated in less quantity,
proved to be the more interesting body, for to it was due the
loss of iodine in titration. No method was found, however, of
separating it from the erythrodextrin, though its distinct char-
acter is shown by the following experiments. A few cubic
centimeters of the filtrate above mentioned were colored deep
red with iodine, and separate portions were shaken with chloro-
form, carbon disnlphide, and amyl alcohol. At once these sol-
vents became colored with free iodine respectively purple,
purplish red, and yellow, and the watery solution of the dex-
trins was left of a pale blue color, proving that the dextrin
coloring blue had a stronger affinity for the iodine than the
dextrin coloring red. A drop of iodine added to the water,
without shaking, colored it red, showing that the erythrodex-
trin was still present in the water, i.e. the blue-coloring dextrin
held the iodine from the erythrodextrin.

The next noticeable and interesting feature about this blue-
coloring dextrin is its difference from starch in that its iodide is
not precipitated either by dilute or concentrated sulphuric acid.
Hence this body seems to be intermediate between starch and
erythrodextrin ; first, because its iodide is more stable than
erythrodextrin iodide ; and second, because its iodide is more
soluble than starch iodide.

Examination was made of the amorphous amylodextrin solu-
tion, and of the amidulin solution, since these were bodies
coloring blue with iodine and probably intermediate between
pure starch and erythrodextrin.

The amylodextrin iodide blue was readily precipitated by



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392 Hale — Initiative Action of Iodine and other

dilute sulphuric acid. The amidulin iodide blue was not precip-
itated by dilute sulphuric acid nor bj concentrated sulphuric
acid. Both aniylodextrin and amidulin were tried with perman-
ganate and acid potassium carbonate with the following results.

I. In an Erlenmeyer flask 100°"' of water, 10^' of add
potassium carbonate, 1^* of potassium permanganate and 25""*
of amylodextrin were boiled five minutes. The permanganate
faded to a yellow color. The solution was made acid and the
excess of permanganate was faded by a few drops of dilute
sulphurous acid. The solution was then cooled, made alkaline,
and iodine solution was added. Two drops brought out a blue
with a trace of purple, due possibly to the presence of a trace
of impurity, since the amylodextrin was made from impure
starch.

II. In an Erlenmeyer flask lOO""' of water, lO*^' of acid
potassium carbonate, 1^* of potassium permanganate and 25*"'
of amidulin were boiled five minutes. A brown precipitate
formed and was filtered off. The filtrate was clear and color-
less. It was cooled and iodine was added. A deep red color
was produced, equal to and identical with the color given by
erythrodextrin with iodine. There was a loss of about two
drops of iodine.

Tests were made with amidulin in regular titration.

Table XI.
A
Volume, n/10 A 8,0,. w/lO Isol. KaCO,. Amidulin. Color,

cm*. cm'*. cm*. cm*. cm*.

125 50 49-29 5 pale yellow

135 50 49'40 5 25 deep red, to deep

purple

100 2 drops * 25 good deep blue

100 2 drops . (Igrm. KI)25 purplish

Sb,0, B

125 50 4'7'75 25 very pale yellow

160 50 47-82 25 25 deep red, to deep

purple
The two experiments in A in blank show that two drops are
necessary for a reading in any case. One gram of potassium
iodide, the amount present in an ordinary titration, tended to
give a purplish hue to the blue. This is probably analagous
to the action of an excess of potassium iodide upon the starch
iodide.f Both phenomena seem to be distinct from the
hydrolytic action.

Though the titrations were at a fair dilution, yet the table
shows a loss of about 0*08°'°* of iodine Solution. Allowing

* On addition of acid potassium carbonate the solution turned purplish, and ihe
blue showed a tendency to fade,
t See Table I.



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Oxidizers in the Hydrolysis of Starch and Dextrina. 893

two drops for the amidulin reading and one drop for the iodine
reading, the absolute values in A are 49*86 and 49'28 with a
difference of 0*08^* of iodine solution. The abundant pro-
duction of a red color is as important as the loss of iodine.

In B with antimony there is a similar lofs of iodine and
production of a red color, but it is no more striking than with
arsenic, and the loss is no greater. It is noticeable, however,
that toward the end the tartar emetic fades the iodine some-
what more slowlj than arsenious acid and hence the red some-
times appears a little sooner and lingers somewhat longer.

Titrations without dilution and with increasing amounts of
amidulin present were now made. The colors mentioned were
all permanent, and the last color mentioned was as nearly as
possible of the same shade of purple.







Table XII.








No extra dilution.




n/lO A8,0,.


n/10 I sol.


KHCO,


Amidulin.


Color.


cm*.


cm^


cm''.


cm*.




10


9-85


5


.. -


yellow


in


j 9-86
( 9-88


((


5


deep purplish red


XV






deep blue, purplish




9-91


cc


10


deep red


10


. 9-94
9-96






deep reddish purple
deep blue, purplish


10


] 9 89
( 9-91


<(


15


deep purplish red
deep blue, purplish






10


] 9-90
\ 9-93


a


20


deep red






deep blue, purplish




( 9-94


u


25


very deep red


10


\ 9-96
( 9-98






deep purplish red
deep blue, purplish



There is apparent in this table a loss of iodine increasing
very slightly with the increase of amidulin, somewhat irregular
because of possibly much varied conditions, such as volume,
rapidity of running in the iodine, amount of stirring, etc.
The conditions with 10*^' of amidulin present seem to have
been exceedingly favorable for the development of the phe-
nomena under consideration, as the red produced was very
abundant and the loss of iodine was nearly as much as with
25^* of amidulin present.

That the erythrodextrin of the impure starch is identical
with the erythrodextrin of saliva digestion of starch was
proven in the following manner. A solution of impure starch
was dialyzed for twelve days. The product which came
through became colored a faint brown upon adding iodine.
This was due to its extreme dilution. On concentration it
gave a rich red with iodine.



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394 Hale —Initiative Action of Iodine cmd other

Some pure erythrodextrin was made as follows : To 200*"'
of a 1 per cent pure starch solution at a temperature of 40*^ C
was added 0*25 ffrm. of acid potassium carbonate and lO*^' of
filtered saliva. I^^ot a trace of erythrodextrin, as shown by
testing with iodine every few minutes, appeared for twenty
minutes, and in thirty minutes the last traces of amidulin, as
shown by the iodine test, had disappeared. The solution was
at once boiled to stop further action of the saliva, and the
erythrodextrin was precipitated with three to four times its
volume of alcohol and filtered. The precipitation was only
partial and filtration was very slow. The erythrodextrin,
washed with alcohol, was redissolved in 200°°** of warm water.

Both of these solutions were tested by the polariscope for
rotation of polarized light. Of each solution ten readipgs were
made with the sodium flame and the average was taken. The
percentage strength of the solution was determined in two dif-
ferent ways. In the case of the erythrodextrin by saliva diges-
tion, 25*™" portions were drawn from a burette into weighed
beakers and evaporated to dryness over sulphuric acid in a
vacuum dessicator. Duplicates gave 0*0422 and 0*0424 grm.
of dextrin. Hence 100*^* contained 0*1692 grm. of erythro-
dextrin. The readings with the polariscope were all very close
and gave a result of 0*26°+. As a 1^^ tube was used

('»>- = :001692=l^^-^^°+- ...

A previous attempt was made to precipitate the dextrin by
alcohol and ether and to filter on a Gooch crucible, but it failed
of complete precipitation.

A slightly different course was taken with the dialyzed
erythrodextrin, as the above method was rather long and
tedious. As a preliminary test, portions of the erythrodextrins,



Online LibraryJ. Franklin (John Franklin) JamesonThe American journal of science → online text (page 41 of 52)