V O L U M E 2 2 , N O . 12, D E C E M B E R 1 9 5 0
1535
T:ililv I d i o that ~ thc procedure cari be used for the detc~r~iiiiii:itioii of ozoric’ at concentrations at Icast its high as 20.2 w i g h t %. Effect of pH. T h r data i n Tahlr I1 show that p€I has iio c~fioc-tupon the accuracy of thc dctrrniination in thc p H imig(> 2.3 t o 12.3. The “neutral” iocloniotric iiicthoti also givrs rori.rct i ~ w i l t . . Thus, the mnclusion of Rirsc~rif(~ld ( 1 1-13) rqyrdiiig sei~ious(’rror in :ilkalinc solutions appears t o I)(- iiirorrect, as i? also the, c.I:riin f o r error iii boric acid sol~itioiisor acid huffercd solutions. 1 q o r t c d by Ru>-ssen (14, 1.7). Thcs Ion- I - I ’ I Y ) ~with ~ dilute ~ ~ ~ i r t ~ t i t r : i t iofo ialuniinuni is rliloridr : i i i d 1iighi.r vrroi’s ;is the, c o n c ~ ~ ri i~t i t i o nin SCP can he cspl;iinc~d t)y tliv far1 t l m t at t h r ahsoi4)iiig surfnet) thcxrc, is :in alk:iliiie filni pl’cJdUCCd- , 1 tilt' f ~ ~ l l 1 i l t i l ) lOf l pot iuni hydroxitic. Although tht. 1)ulk of the solution nxiy tw :it p I I 3.5, tlir filin at thc surfacr of shvotytion is a t :i hig1ir.r pI1, 1)ecaur;cof the forniatioii of potassium hydi,oside iri tho film. I n ordcai, for t,hc newly foi,iiwtl pot:issiriin hytlro\.itir to diffusct into thc hiilk of t h e solution, a c o n r c ~ i 1r:rtioii gratlitvit must v s i r t , The iwction of potassium iotlidtx ~vitliozon(’ is c:strc~nit3ly ixpid, a s i n c l i c ~ i t c ~by i t,he ohwrvahle giuwth of iodiiir crj-stals a t t h c b interf;ic:cL of 10 w i g h t 70ozn11egas and 0.; .ll potassium ioclidc., :iiid also h y the precipit:ition of aluniiiiuni h y t i i w i d ( ~at f i l i i i ~ v h c ~:ii luniinuin i chloridc is prcseiit. Thv thtv)ry of :it)sorptioii follo\\-c’d hy rapid irrevc~rsihlecheniic:il iwc.tioii i i i thv liquid p1i:iw h:is b w i i thoroughly developed and provcd b>- nuniet’ous espcriInentaI invcvtigations (16). BcC L I U P ( thv ~ film has a high pH, tlics formation of hydrogen pei,osidc is limitrcl ( 2 , 5 , 18). Whcn thc roncentrat~ion of aluminum chloridc is highor tho pH of tlirl film is lo\vrr: the ozone is actually :ihwrhctl u n d ( ~acid t ~ renditions causing greater error. The coiicc,iitiation of aluminum chloriclc givon by Thorp ( 1 7 ) is low enough to produce no error. Thorp, howvc>r, made no attempt t o evaluatc~ the usti of such a I~uffcr a t ozone concentrat,ione greator than O.lyo. I t \vas found n-ith xluminum chloride buffcrs that it is not nercssary t o acidify \vith strong acid hrfore titi~:ition: however, no error \vas found if additional acid were atldctl. In :dl othor i n s t m c w it \\-:is nrcessary t o acidify with strong arid. I.:nlew acid is addtd hrfore titration, up t,o 50% or m o i ~vrror is caused hy failure of iodate, formed dui,ing ahsorption, to react with sodium thio,wlfatr. Possibly t h r rwction is
6KOH
Table 11. L I Hof Ti1 .\haorbant Pollition , . .
2.3 3.4 4.0 4.0 :i, .?I
3.5 3.5 3 5 1 2 4
4
%2
.1
3r& of Ozone per
__ 100 111. of Gas Addeda 18.8 27.0 25.7
Satd. HJ303 Satd HaBOa Satd. HaBOa
Measured27.5 35.5
Relati\ e E ~ 9; 46 +31 +27
+
12.4 9 1 22.1 10.2 20.2 1s . 9 20.0 17.2
38.4 13.0 9.1 21.3 10.7 21 . o 19 4 24.8 21.5
12 f, 17 15 6
12 5 17 7
-1
15 4
+1 -I
+50
-4 +;, 4-3
+22
++21 2.5
KHnPOa-XaOH ’I
12 4
12 3
-1
21 . O 11 . O 18.2 19,O I7 , 6
19.1 11.0 17.4 18.8 17.2
-4
10.2
HaB03-KCI-;2‘aOIIh H3BOa-KC1-SaOHb HaBOn-KCI-KaOH HsBOa-KCl-VaOHh H1BO3-KCI-kaOH
-2
12 3 12 3
0 2 .ti NaOH 0 . 2 M NaOH
22.8 23.9
22.5 23.9
-1 0
Sone Xane
24 8 24.2
24.6 24 2
-1
6+
10 10
*
0 -4
-1
0
tVeight determined from absorption in standard reference britrer ( p H = 6.98). See procedure. analytical method for standardization, and analytical method for effect of pH. Buffers prepared a s given by Clark ( 5 ) .
*
ACKNOWLEI)(:\lEVT
Tht, authors arc iiidehtcd to Res J . Itoliin,wn and R. W. SIoulton for valuablt: suggestions in prcp:iration of manuscri1)t. LITER.ZTURE CITED
Effect of pII on lodometric Method
Concentration of pH-Controlling iipent. 1 v HCl 0 1 .V HCI 0 1 A’ HCI 0 01 s HCI 0 028 .v AlCli 0 028 ’V AlCll 0 028 .v AlCla 0 05*5S AlCla 0 100 .\‘ .41Cli 0 166 S AlCli 0 166 JV .1ICI$
(5 . 1
6-+
(:O3(; LII S I O Y s
I’otassiuin iodide a l w r h a n t P in the pH r:iiipt. 2.3 t o 12.3 gi\o correct results for concentrations of ozoiie up t o 20 w i g h t 70, if the solution is acidified with i t i ~ i i i gacid hrforc titration ivith sodium thiosulftite. .Iddition of aluminurn chloritlr to ttie absorption solutioii iri concentrations u p to 0.055 .Y c a u s ( ~no rrror. Strongly acidified potassium iodide absortxitits give high riisults. The conceiitriitiori of the acid affwts t,hc degrre of rrror.
+ 37, .&KIO:: + 5Ie rc:i products condeiised in water mi.-t. T1ii.q a p p r ~ r sto hr iricoi iiiasmuch as the sinoke was alsu prodiicc,tl undvi imhytlrou$ c ~ ) i i t l i tions when an oxygen-ozoiic inistui,c, \\.us paswcl ovvr iwuI)linird iodine at room tenipctraturr. Tlii,. .c.trd iv:is .wIut)k in watrr :tnd l i b r r i r t d i w l i w fro111 acidified pot:i+ sium iodide ~oiutioiis. To prc~-eiit( ~ i ~ i ~t)y or1 ~ 0 ~ sof these ositlt,s, nioiPtened glass-xool plugs n - c . 1 ~ uscd i r i t t i r g:rs lines to r o l l ( ~ ~ t t h c smoke formed during ;ihmrptiori. T h c h plugs iv(’r(> w i s h i d with distilled water and this \\-nshings f i , o i i i t ties(>plugs \vorv t h r i i :iddvd to the solution t)vEoi.e :icidific,:itiori a n d titration i v i t l i sodium thiosulfate.
~
~
Allen, 5 . .I s u . I < s ( ; , (‘HEM., .ix.ar.. En., 2, 55 (1930). Brndie. B. C . , Phil.Tram.. 162,435-85 (187’4). (‘lark. TV. 11.. “Determination of Hydrogen Ions,” 3l.d rd.. Baltimore. n’illiams & Wilkins Co.. 1928. Furniaii, ?;. H.. ”Scott’s Standard Xethoris of Analysis.“ 5th ed., Tol. 11.p. 2370, SeivYork, D. Van Snstrand Po., 1980. Ladenherg. A . . and Quasig. R., Rer.. 34,1184 (1901). Lechner. G.. Z. Elelitrochc7n.. 17, 412-14 (1411). Maslan, F. D., ‘‘IYet Oxidation of Sulfur Dioxide Promotrd b y Ozone.” 116th Meeting, A M , ( I H E x . Sor,.,Ahstrarts, p. 11 K, September 1949. llellnr, J . IV.,“Conipiehensivc Treatise o n Iiinrgaiiir and Theoretical (‘hemistry.” Tol. I, p. 905, Y e w York. Longmans, Green and Co.. 1922. Putnam, G. L., and Hahn, V, A , , 7 ’ w , ~Electrorhrvr. . ,%w., 93, (1948). discussion. ~ 355-7‘ , Putnam, G.L.,Moulton. K. IV., E’il1nioi.c.\V.\V.,and (‘lark, I,. H., J . Electrochem. SOC.. 93,211-21 (1948). Riesenfeld, E. H., A u g e w . Chem., 45,309 (1932). Riesenfeld, E. H . , and Benker, F.,%. 1r71orq. Chem., 98, 167 PO1 (1916). Riesenfeld, E. H., and Sehwib. G. 11.. Ber., 55, 2088 (1922). Ruyssen, R., ;Ynfzrurzc. Tijdaehr., 14, 245-53 (1932). Ihl’d., 15, 125-30 (1933). Sherwood, T. K., “.%bsorptioti and I
