Determination of Halates in Sodium Hypochlorite SI DYEY I T K I X l , Analytical Section, Process Derelopmen t D e p c i r t r t w n / . General 4 n i l i n e & Film Corporation. Grassrlli, S. J .
s
Sodium thiosulfatt, solution, 0.1 . \ , Sodium hypochloi,itc sulut ion, al)out 6.0' ,. *tarc*h-iodide test papvi' ( 1 : .
.:
ODII-11 li\ poclrloi,ite caii 1)e determined qu:iirtitatively 1 ) ~ ~ . reaction with :i stuiidard solution of sodium benzene 5111-
finate. The resultant sodium benzene sulfonate solution ill tlir presence of sodium chloride can be treated n.ith concentr:ited hydrochloric acid, pottissium l)romide, and pot:issium iodide arid the total hdates (as sodium chlorate) determind. Using tliir ~)i,ocedure both components can tie determined iii one sample, arid the iinalysis completed in approximately 0.5 hour. Several methods for the quantitative detetminntion of chlorates i n Iiypochlorite have been described. (iaukhnian and Stt~fanovski12, dcteimined chlonitcss in hypochlorite by using thc ratalyat osmium tcstrositie. Results wtw, usually loiv. Hernandez (S) recommended determining chlorates in hypochlorite bv decomoosinv with hvdrochloric acid and distilling tht, solution i&o potakiumTodide solution. The arsenite methodwas used for the determination of the hypochlorite. Kolthoff (4) determined chlorates in hypochlorite by boiling gently with hydrochloric acid and a known amount of 0.1 -Y sodium arsenite and then titrating the excess arsenite with 0.1 .I' potassium bromate, using indigo as the indicator. Ackerman ( 1 ) found t'hat sodium benzene sulfinate react;. quantitatively with sodium hypochlorite according to thc following reaction
S'I'iYD.iRD17. I'l'lOY O Y SOI)IU\I I % E \ \ % E Y ESULFI\IATE
l ' i l x s t t\vo 25-ml. aliquots of thtt Sodium Irypochlorittl solutioii
into 200 nil. of ivater. Titratc' one aliquot ivith 0.1 S sodiuni arscxnit t i solution, using starch iodidc tmt papt~r. Titrate a second :iliquot with the sodium twnzenc. sulfinat t s solution, using this starch-iodide test paper. Calculate normality of the sodiuni bcnztnne sulfinate. Procedure. Dilute about 10 grams ol thcs sodium hypochloritt~ t o l)c analyzed to 260 ml. in a volumetric flajk. Pipet a 25-1111. aliquot into a 300-ml. Erlenmeyer flask with a ground-glass stopper. Titrate n i t h 0.1 S sodium benzene sulfinate, until a bluca spot no longer appears on starch-iodide test paper, taking caw not to add an excess of the reagent. A = ml. of 0.1 S sodium benzene sulfinate. Then add 3 grams of potassium bromide antl concentrated hydrochloric acid, so that the resultant acid solution is approximately 8 S (20 ml. of concentrated hydrochloric acid for each 10 ml. of solution). Place stopper in flask and lct stand for 5 minutes. Add 10 ml. of potassium iodide (105) antl titrate the liberated iodine Tvith 0.1 :Y sodium thiosulfatr. R = nil. of 0.1 3' sodium thiosulfatc
3 725 -1 Vright of sample = C;SaOCl
+ SaOCI +CoHsSOnSa+ NaCl
-+--
CeftaSOnSa
\\*eight 1775 B = of saniplc
and does not affect the chlorate present. This has been verified by t,he author, who used this reaction for the determination of thts hypochlorite. The total halates (as sodium chlorate) were then determined in the presence of the sulfonate, as prescribed by Kolthoff and Furman ( 6 ) , with slight modification for esisting conditions.
cL total hahtes as r\'aC'lO1
Table 11. Comparison of >lethods $:iiupleh
SaOC1 by Sodium Arsenite
TaOCl by Sodium Benzene Sulfinate
15.44 14.56 14,23 14.28 13.83
15,48 14.70 14.24 14.24 13.88
The latter procedure i h recommended because (1) the possibility of low results obtained in an acid solution is eliminated b!. titrating in a neutral or alkaline solution, (2) no distillation is required, reducing possible sources of error due to loss of vapors, (3) both chlorate and hypochlorite can be determined on the snnw sample, and (4)the method is rapid and :iccur:ite.
EXPERIWEYTAL
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Tlie standard d i u m benzene sulfinate was found to be very stable. Tests were run to determine whether any chlorate was affected tiy the sodium benzene sulfinate. Known amounts of sodium chlorate were added to a hypochlorite solution containing 0.5y0 sodium chlorate as determined by the proposed procedure. The sodium chlorate found in Table I represents the chlorate after O.jC;, in the sample was deducted. h comparison of the sodium benzene sulfinate and the arsenite methods for determining sodium hypochlorite is shown in Table 11.
Table I. Effect of Sodium Benzene Sulfinate SaClOa Found
KaClOs Added M g
M g
10
11.0 10.3 10.2 21.3 19.8 20.2 25.0 24.8 24.9
20 25
50.0 49.1 49.7
50
ACKNOWLEDGMENTS
.\ppreciation is esprehsed to Leo hckerman, whose suggebtions and advice resulted in the completion of this work. The author also thanks P. Nawiasky, F. Ebersole, IT-. C. Wilhelm, and L. T. Hallett for cooperation and proofreading.
REAGENTS
Sodium benzene sulfinate, 0.1 Y. A good technical grade can be used. Dissolve 8.5 grams in 500 ml. of water, add 50 ml. of barium chloride (lo%), and digest on a steam bath for one hour (the sulfites and the sulfates are precipitated). Filter the solution, wash with water. cool the filtrate, and dilute to 1 liter with water. Sulfuric acid, 50%. Potassium iodide solution, 10%. Sodium arsenitr solution, 0.1 -V. 1
LITERATURE CITED
(1) Ackerman, L.. IND.Esc. CHEM, A x u . ED.,18, 2 4 3 4 (1946). (2) Gaukhman, M. S., and Stefanovuki. V. F.,Zavodakaya Lab., 9, 493-7 (1940). (3) Heinandez, F., Quim. e i n d . , 7,177-8 (1930). (4) Kolthoff, I. hi., Pharm. Weekblad, 55, 1289-95 (1918). (5) Kolthoff, I. M., and Furman, N. H., "Volumetric .hial>sis," Vol. 11,p. 388,New YOIk. John Wile> & Sona. 1929.
Present rtddrem, Pilot Plant, Chemical Construction Corp., Linden, S . J.
RErt1rF.D
816
December 23, 1946
