W/W463
L. C. Laporte, E4q.*
Imprial Thbacco Go*
P.O. D= 65W,
IMIWA6
Daar Leo,
((:or") Ltd.
26 th January, 19W
Thank you for your Lfter of 19th JammWp dealing
turftr
with filtration afficlencle*. I soy not have 0w40
It clear that
the graphical v*thod for the d1ract dttendmtton of
f Utratim
coafficient is only &A alternative nothodt largely
evolved In
ordcr to permit rapid w*ke d*naltmotry. go agm
idth you in
still Prefoidng an absolute oneur* of filtration
afflelv=y.
Tho direct method do*3 involve the asvmptlors that
each cigaretto
;re:ent3 essontially the came swunt of woke to the
filter, but
as You X=ark laterp In o= case we rwed war vakt
the esvmptlon
for each filtration rAluation separately, and our
problms of
standardisation ari correopmWingly less smre tbars
yours. For
this purpo" W fim that our rA=A1 selection RMUNJUS
rage
weight :t 23 mg. and th*n average pro"=* drop + 4)
tire quite
sufficient. ' L%vry point on &Ar Uro 1e the iqrsga
of at least
five daterfainations, and by drawSM the best
otrelght line through
thete points (using Statistical vwthWsp If
necessary - they soldom
an) in apin then avexago the lioms.
Ile aro mw workiN on the problem of using owke
donsitomtry
to provide an absolute mosswe of filtration
officUncy. Our Idea
hare Is to razz= swkt deiaLties before " aftor the
filter, and
to put the urftlancW oloctrical output fm
photocells Into a direct
Wasure of filtration efficiencyl, usiW *=*
=bIrAtIon of elec:Wcal
integreMrs. At MaWt. We art in the Wry early $taps
of
recogaising the expaAwntal difficulties to be
onrcow# and we do
not 0~qxct an early cor4lusion to the VIA*.
/tonUm*d
BATCo document for Province of British Columbia 3
November 1999


Le Co Laport*9 bqo 2- 26th J*MaM, 196')
W9, tw, a" considering Opt*-fju=-&try of smoke as
On-the-T
wthod -ftr tax outinatiom As you say tUs Wjuld
avurcome the
expe.-joentgi difiLadtles " to plasticiawy althmO
an pvtoPs
you know, wo hm rimm foaW this as VaTims *0
ObJ&ctl&n As YOu
do. In any ownt v, the u" of rdeotim as an Wax
caterial
vudcea6fully ovcrwws this difficulty.
We havo also invo3tigated sawvlut, spora&cally the
colourimtric
cothod detailed hv DobzvA*y in rjM= 19D9, March
27th pp. 11-14,,
AMU 3rd, pp-p- 11 - 14. rMs'apln Is an absolute
m*thod. Ratbox
to my turprise It 860= to hold TZ'=188 &W to give
results Its
agroommat idth our athn cathodat but these
zose=J-as an Aot yet
I horA thtt I havu convinced you that wo, are Iq
no w*y t=ning
back on the absolute mathod of dotendnirn
filtratten officlemyt
a-Leh still remains our standard "Ference mpthDd.
7ha &!tqm-tive
procedure has Its user, *nd Into-"*stop howeva.
Thank yo,3 for t1te-ganerour of for to lot us have
half ymm stock
of thoce oxperl=ntal Ultors Usted. ir. your
letter. While I a,;r"
that a Alargart number %sould b* profor&blo for
dotalled crientitative
voD.-K., Vwsa filters posseas som novel footurosj,
e.g. additiverp etc.
arLi we sl;ould ba wry grateful If you co;jld sond
uts such samples es.
you have lodicated you om Opere.
Lastly# thare is a wall, but nevortholessp hlUhly
1,rportant
paint WhIch I might mantion hem You will ramw-ber
tiot in S,:--
0 =1ss's calculatIvas. of cooko and wxt-Ung
A,&z.449rs, he vokes tho
&s6wptioA that the obsprption coefficient (is)
varies Inversely with.
Uhs puff wl"- . Z3 hava lookad into this and-tho
conclunion is
Uat thad variation is less rapid than the asmaAlon
tupasted. An
wpirical curva ralatin3. absorption coefficlenES
to air flof has been
oamputod oi the basis of axpQrlmantal rasultsp
#jY1 Urst indications
am that thL3 1-41da In differoat types of filter
pliqr This Will be
icittan up in duo ccurse &Ad r4 doubt you w111 V=
receive a cM.
Kindaet. roga-Maj,
yours, sincerely'R
Do 0. FEUMN
c. D. & F. Nobson * -Ovq*
sLr Charlos ElUs
C::)
U1
Ln
(-n
BATCo document for Province of British Columbia 3
November 1999