A simple method of detecting sulphured barley and oats


Material Information

A simple method of detecting sulphured barley and oats
Series Title:
Circular / U.S. Dept. of Agriculture, Bureau of Plant Industry ;
Running title:
Method of detecting sulphured barley and oats
Physical Description:
8 p. : ill. ; 24 cm.
Carroll, W. P
United States -- Bureau of Plant Industry
U.S. Dept. of Agriculture, Bureau of Plant Industry :
Place of Publication:
Washington D.C.
Publication Date:


Subjects / Keywords:
Barley -- Postharvest losses -- Prevention   ( lcsh )
Oats -- Postharvest losses -- Prevention   ( lcsh )
Sulfuric acid   ( lcsh )
Bleaching   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Cover title.
General Note:
"Issued November 30, 1909."
Statement of Responsibility:
by W.P. Carroll.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029629496
oclc - 48872599
System ID:

Full Text


B. It. T, \LAL. AV AY, (lirf Bi rtl.


[ 1lirrr



I '' '. -- ~ -

I _;* ,n^


Chil,f RImtn u, BIEVRIY T. (i LLOWAY.
A1siltnft 'hi(f of li;01,1t, ALBEIVT F. \VODS.
',1idor, ,j. i. ROC(KWI:I.I,.
(i'hif Clrk, JAMES t. JNEE .
[Cir. 410]

IB P. I.-*:*i




l or Years it I hais; beeni he. )1 l(immo practice inlk me 'rlw in c toi rlee'it
suIIect staie 1 )r (I isc olo e ad ta lHe amd ()ats to i I) a prtwe't' fleachi '
ior 'der to rellmove, or it lealt pr iall rel oe, thil diso'loreat io, adli
to a certailn extolnt improve til' apieiaranie of ikernriels otherwise dalii-
;,i,'.1. Tthe ctlio on :lrtii i th o accoi p liit" h lhie result it sulphur in lthe'
folrml (of I'ulpIhlIrois acid. mid the pr'oess itselt its(l,\ kn iown 1iv diflerent
names, ai oiiii,- wlich iai e the leiit i isulpht i ili .'" "h bleacl hin ," allid
Tile ,L,,.11-a: a1 iiap earance. especially tie color of balrleY alld oats.
has all important heail iln determining ". their l *coml" llliercial l'rades :1n1d
vahlc-s, and ill view oif the fact tlat tilie Ille:lIiii,-` Of these ,rains i as
become iii,,i,, and 1 becalise it is o ftiettimes1- dilt.icllt to dis'crimliinlae
between, ri'iiti that lias been 'leached and orainll that is liaturall\v
bri-ht in aippearanallce, it was deehlled expedient to 11se a1 simple qnali,,uta-
tive niethod )yv mllealls of which tile l'raili lierchalit om ii illspector
coul determille whether or not. (ymini has beeli suliphured. I lereto-
fore tie senlse ,If sniell or tile p sol' juldo'ilie t lias eell the (onI)
ea nsi avtilabile to practical o'l-aill mIlen (of dtl'ereiiti;itiin between n thle
natural and tlhe hleahead/'lails.


Sulplihur burned in lir m, inll the pre.sleince of ox\'cn ,,(.lbeomles sulphulr
dioxin. a codloleshs, t ranis'p.lr larint "*,as with :a Alarp, piliTenit odo" similar
to that found in billnIi'i silpl]thulr illatclhcs. This l-as is \er\ soluble
ill water, f(,rllinli" sulphurlolus acid. whilh 1s tIle bleachillc.- aIllent for
ba rhv and o)ats4.
In actual practice, tiw slielphtilr is, li.,,,-d to sulplhur dioxide t, v t burn-
ill,- in all () vell. fIom()ll which lie fuiile's arle,( conducted (o a receptacle o(
bleachilln" tower, frolll the ilt, tollm to the t)p oIf which thle ;is circl-
lates, (c-,l1ii.ir-" in coltact with tlhe, i'ai1 thliat is constatliill\ | Svi
tin ,,'' till tetower. \Wiater mlut he Supplied too cihanle thle dihxid into
sulphulous acid. Is sulphilur ldioxid is not a bleachint)] aIielllt. This i-
1(,'i,. 1''!


done b)y dampening the grain either with steam or small sprays of
water playing upon the grain as it enters the tower.
The ble:t-lhiii:- is supposedly bruglit about by the acid abstracting
oxygen from the coloring matter of the grain. Complete 1,h:i'ling'is
not immediate, and the grain is therefore conveyed in a damp condition
from the bleaching apparatus to moderately air-tight bins, where it is
allowed to remain long enough to finish the process. To prevent heat-
ing" and to put the grain in a proper condition for shipping, it is moved
about after some time in such a manner as will permit the air to pass
freely through it, which to a certain extent will remove thile acid odor
but will not completely remove all of the sulphurous acid, the presence
of which will always betray the fact that the grain has been '"sul-
The method outlined in this circular for the detection of sulphur-
ous acid has been one of the standard methods of ascertainin' the
presence of sulphurous acid in grain for several years, and a more
detailed description of the chemical reactions that take place may be
found in any of the later standard text-books on qualitative chemistry.
The principle upon which the method is based is to change sulphurous
acid into hylrlgri sulphid, which in the presence of lead salt will
give a brownish black precipitate. This method has been used in
Germany for some years in detecting sulphurous acid in bleached
seeds, and in modified forms by chemniists in this country for similar
purposes. In order to accelerate thle test and at the same time reduce
the possibility of error to a mnnnimum, so that it can be used by per-
sons other tlian those familiar with chemical reactions, it has been
(leemned advisable to make a few cli, i,,_.. in the apparatus commonly

For the detection of sulplhuired grain a supply of chemically pure
zinc, hydrochloric acid, lead acetate, ferric or platinic chlorid, and
distilled water should always be on hand. The hydrochloric acid
should be diluted to about 20 per cent of its normal strength by add-
in-,. 4 parts of distilled water to 1 part of acid. The lead acetate
must be dissolved in water, and to give the best results the solution is
prepared by ;iddlithg 2 gramins of the acetate for every 98 cubic centi-
meters of distilled water, which makes practically a 2 per cent solution.
If the operator desires to make several tests, stock solutions of the
proper -tr, iigth should be made up in quantity. Imi.% or, if the
stock solution of lead acetate is allowed to stand very l,1ng it will
become scummy and flakes will adhere to the sides of the container.
Therefore, it will be necessary to filter it occasionally so that a .lear,
transparent liquid may always be ready for use when needed.
[fir. 40]



To perform the test, 1) -1-:11am's o4 e.hmiclly a lIv p'r. mot ss\. i:-ailltilirl.
or .Shot yinc an' dist-rributad over tihet' )ttolll of ;ol |iss contailir '\\ ith
a capacity of at lea:it o (.l) ciiic centtiliters. I'p1 the, ziunc :rin pi:ld
about Ill) "i ,r.'-. of the mraini to he tested. Into tilht lla-k is Ipioidi
1no01.L.- dilutte hYdro'hhlol ie acid to cover tliet(, nraill. approximaintelY li",,
clinic c'tltiliilcr'-. Till. llas-l is tlh tn clho, d with a cork stopper plio,,
vid('l with an i ,nv rtid -' I'" la:. ti>he arlu t 7 milliljlter's in intetlrnal
diantiter. Thle shirt :taril of tiltl hlass tubt slould prjec! tl apir)loi-
iiateiv oiiu-halft itnclh 1ihelo ti, bott oiit f ti titl stopipeir. \\ hliih tilte Iot.
i Sl'lll sliould extenld I llyi+V to the bottom ofi { o (' tilt lt1,4t ltlb c tllt:1iltiil", a1
2 per c'nlit Isoluttion of lead acctatt. S. (t ti,. I.) A ost4 tutbe of aoutit
15 cubtic conltinetesv capacity is l'i (no,,,l, lo,,. tlislt purpoM' amlt
should not boe over twxo-hirds full; otherxi'e tihe coi'tllents \I I ill spill

....- ~--, ~ ~ --- --
,.. ... -
00ap 1 jolll- "' -

FI;. 1.-Cl-( ih icaNi s wAlln !ippiar;il- usi>'tl i'n *-u] h ) g/Ih r ill.

OV0p" :Is s0ool 1:4 tIt(e o'as g. ills to pa,1-- frlv fromn th in" ;Anc tmid1
h dri-ociloric acid. If thie Zinc is vr t ) iipr' tli:lt is to s:t1v. fi't're Il.tIl
all forei"+n stilst;ianc(, tlhe action t etwenll tle ziltc amid the livdrf,
thilrhic actid will Ie retahrded, lhut it n:iv the cosider:thlIv Ihasteneid h-
the auldhitioll of :a few dlrps oif fterric l'ihhrid. On ti le, Ift inl ti tt"ire I
a In Bulletin 107 (r-vi\ ji l;Iurean u" ('RfiC minstrtv, I. S. I)e tt. tof A\ ri'ullirv. p,.
1-, the u -e ot a Iradl .alt in a lit til difflk r-it tiL m i r'oii 'lnticidi dI ftr th li letoltiti
of s-ulIp uiiroug :acidl it veL_ etablt,+-. ThIis It-st i tulii inilv klniou n as the h*ti lat ,tir
test and diif!ers frtim i ll e solutitnm t.t iiesriii. ll this circula r in that .1 piect ff
Itilhublos iiater is saturattl \61hith a solution )f a hlead s:alt and is thet- placedt u hnd +r-
nteatih tlihe stopper of lite tla-k ill which tit hylidro.. ii gie-eirtated itcea d 44 u -i -
tlhe a:l id solution ill a se[Iar;ate i')o om e clhie ists for thlt detet1 ion of Siliphurins a thle Bureau of I'Plant Indlustry for the sa-it purposlu, Rit dttir repeLatted Iriadl it ;s
not deitiilI ad\'isal-l< too rec llilmm iend its tli- I p persons ,nIurfilitam iliar with l.ialic d
react i },11s.


are shown two flasks with connections to the test tubes. This figure
fully demonstrates how the apparatus is to be adjusted.
When the hydrochloric acid comes inll contact with the zinc in tilhe
bottom of the flask, hydrogen is liberated and bubbles may be noticed
pa--igi up through the gaini and then through the lead acetate in the
test tube. As soon as the air has been expelled from the flask, these
bubbles are either hydrogen or hlir,'gii sulphid, conditional upon
whether thle grain is natural or sulphured. With unbleached grain
the gas is II .lr,_.'ii and thie bubbles passing thrii:- the lead acetate
solution will leave the liquid in the tube clear, colorless, and trans-
parent. but with sulphured grain these bubbles will be hI ilrg,.ii sul-
phlid gas, which produces a brownish black, tlocculent precipitate in
thlie lead acetate. This precipitate is lead sulphid, caused by the
breaking up of the hydrg-,ii sulphid and the lead acetate, thle lead
of the latter unitiiig with the sulphur of the former.
Occasionally fine granules will be seen held in suspension in the lead
acetate should the gr:ii i be very dusty, and tle same conditions will
exist if the acid is too strong, because -tr iiig acid produces violent
action in the flask, which may cause to be carried over some line parti-
cles of dust or zinc. These granules must not be mistaken for lead
sulphid. After the operator hias had a little experience he can readily
distinguish the granules from thle black, flocculent precipitate. It is
easy to test these granules by adding a few drops of ferric clilorid
(one part of ferric chlorid dissolved in ten parts of distilled water) to
the precipitate in thie test tube. If the precipitate is lead sulphid it
will readily dissolve in thle ferric clilorid, whereas the zinc particles
andl dust will remain practically un g. These particles and their
consequent annoyance mav be obviated to a r:it extent by screening
thle grain before it is put into the flask. A still better way, however,
to circumnivent this difficulty is to place a piece of clean absorbent
cotton ini the nieck of thle flask just below the outlet in the stopper,
which will serve as a tilter and allow thlie gas to pass through freely,
bit will retain any '.solid( impurities that may (collme illn contact with it.
In all cases ii ii:- pans. l:i:-sware, and all other apparatus should
1be (cean, anld1 no chenlmicals sh(uldl be iused that are not chemically pure.
These precautions cani not lie urged or impl)ressed( too strgy upon
thle operator, because other substances Iiig'ht be present in the glass-
ware 'and ciheniceals that would perhaps give a reaction similar to that
of sullphurous acid. Rubber stoppers contain sulpthur in their coru-
position, altl,1,,-, not in such a form that it is readily changed to
hydI (rogen sulphid; still, it is a(dvisalble to uise cork stoppers to avoid
av polssibility of (touh1t or c(mtr(oversy. Flasks with ground-glass
st(oplers, p)r()vided with special conductimeng tubes, are to be preferred
in all cases where they are procurable.
S'i r. I ..


There seems to a ditllere ci(e f o pinioni :;i1 .m1j- pari'oi I ,, ,n e
in thle (rain trade as- to whether the pr[ ci[itatet o4 hbad -Ullplid is pro-
cured onl] froill 'rlaill that lias Iwell sulphti'ed. S ome co ted that
lhe natu1 -:1l sulphur t'ouiilt inl barlev rhli ill protein will give tht( '- ri
priciplitate :as that foilld ill sultll iuredl lb:ilt. y ai l tanll hiel molru that
ditterenlt s' ils will produ e arhley somie f (It li.ch \\ ill s omw a* silphiill
reaction. It- wnav lbo ,aid, lomwi've r, in thisw coil .cthio t11a then ttiiral
suilp ilih r found ill tho protein 44 "ill or :; 'i 0 ? ,1 I I t' o arlehv i- ltoo small
to iniia ife't itself iln such a test. luIu.el' the Idiilitp aid iha1: liahrdlv
s itlicient, tilin( too pl i 'n rate li tlt, interior of tit, kernell. lorcv,',
fact, (do not bear out th'e ucollti itmiiti,. a-, will Ii1w deiI istra-:itd.
To astc ltain howv ltali v ^I+rI in oln (11di]tirellt ils a i i l] i l'ercitz .a c-
tions of the conulit rv ouhlY rIspoiol when w-ii>t|l'di 0h (Ioli "t, I -'crihoed

j _._.___ _+ .. -_.. .

L A -

(A ) an d ofril l-' | It ) g -ul hur-, o l bmrl',y v (B) r "cc eiv I iroin t iitiricultuir l +.|>rin('ct :i.t wt ioti n( .
4' isul 'O i N4. ini.ka t o\e a, \'i\ijitii t'l, or1ah e K il-(-. itll te tidi tanl.

in this circlilar, reqlasta s were ;\ ( il t oiae o i :tih lptiiral expcri[lienlt
stations of 1linnoesota, N{ebi'aska. Iowax:i. WVisconsxin. I'alh, anIsla,. andi
Indiana for arly salimplesl l that were known to he uiniuiplnilured. F'acl
of these stations forwl'arded samlpltesi and ait qualitative tast of t'ach wia
iilad e. Foiur oult'n es of leaI ctate were Ilwe sedi ii.tead of I0 ctitiaa
Ientiii(tri' (iot rals of batlleyv were s bstittilda for lai ol'tain ae inl
vtacli case. and tlhe acid and zillc W0ere ilnc'reaVse4d ill the salle proportion.
Ill i,,iire "2 tih solution in tlie bottle oil lhe left is of ink\ blackness
in color, i,, itlu,, a heavy plecipitate of( lead sulphid. The :arley
which lausedl this discoloraition wais known to he stilphured. The
hI di y ,i .i wh iIN ,h I cIpasse thII,.' _II the sIo ltioI I i s t o f the I 'I ll- ai i-( seVe(I
bottles was gellyerated ill the preselnce (d the liatural harley, v from
Minne-ota. Nebraska, Iowa, Wi-consin, I'tali. Kansa-, and Iidiala.
respectively, but the liquidI remained clear and transparent.


The bottle marked A on the left in figure 3 shows the result obtained ^ -_
by generatingv hL,1r',,'', in the presence of commercially sulphured 0 1_=
barley iid allowing- the gas to pass through a solution of l1.;vl acetate, ?__o
as in the (quialitative test herein described. The bottles marked B', --
('. and showhmw the results of similar tests with natural barley from >w
thlie, agricultural experiment stations of Nebraska, Wisconsin, and ____,
Kais:ias, respectively, while those marked B, (6 and D are from the _
same stations, but have, respectively, 50 per cent, 25 per cent, and 21
)per( cent of sulp)hured barlev added.
Tlie I contrast between the precipitate in the two bottles of each pair
is i-ad(lilv ail)pparent. The lead sulphid is so abundant in A, which
represents a commercially sulphured sample, that the whole solution


A B B" C C' D D'

Fji(;. 3.-Seven I)ottics tillid witl sli itions, showing the results of tests of sMmtphls containing differ-
et ieree(i ag(es of sulphiiir-d barl ey andl of slunplk,, (of niaturil, or unsulphure.d, barley. front tile
Inrieltiiit url e xperilnient stations of Ntebrniaska. Wisconsit, and Kainsais.
is black and o)aque. TIlie solutions in (C, and 1) vary fro 1ni black
tulrbidity v to dull transliicency, depending upon the pir, n.it:iL'. of
sulplhured 1);iilev. ('ont rasted with the natural barley in each ease,
thlie turbidity v is very evident, and it is plainly seen that this turbidity
decreases froim right to left. or as the 1prr'.iita.,, of sulp)hured a(hnix-
ture decreases. Numerous other trials were made with sulphured
111and iinsttill)phured r:iii. and in each case tihe sIame results were
A approvedd:
<'<'ret, )/ (_f" Aq l c1'H l/,,1r',.

WVASHING(TON, I). (., ()<'1)o(1 12. /,909.
[Cir. 10]