 /.  ',**//

155ῑῒORP + 

++'() +0 * +* + 0,+!", #$%&+,- () +0 * +, + 0,./ORP Evaluation of the Qualities of Chlorinated
Hot Spring Waters
Shoichi OKOUCHI+, Hideyuki OHNAMI+, Kazuyuki KOHMURA+,
Takuya MORIMOTO, and Shigeo IKEDA++

Faculty of Engineering, Hosei University,
Nippon Onsen Research Institute

Abstract
The ORP (oxidation-reduction potential) and pH measurements have been made on
hot spring waters and their bath waters disinfected with chlorine at various spas
including Dougo spa of Ehime Prefecture and Arima spa of Hyogo Prefecture. Our
comparative analysis of the qualities of non-chlorinated and chlorinated waters revealed
that disinfection with chlorine causes a qualitative change of waters from the reductive
state to the oxidative state. To maintain a predetermined level of disinfection intreatment of hot spring waters, a considerably larger amount of chlorine must be added
than that required for disinfection in treatment of ordinary service waters taken fromrivers and lakes. The oxidative state of hot spring waters disinfected with a large
quantity of chlorine should result in promotion of the oxidation or aging of human skins
contrarily to what is expected to be beneﬁcial in hot spring water bathing.
Key words : ORP, Oxidation-reduction potential, Dougo spa, Arima spa, Chlorinated hotspring water
01213 : ORP 4 5678 9: ;< =>?@+ῌ ῏ ῍ ῐ ῎A* BCDEF GHIJK LMNOPQR SF;TU9: VK=>?@WXUYZ[UN\]^_ `K.a[b\ cdeKSf @Wghi^j[kl ?@Wmnoplq\]^W rs*tK LukpvbR KEGS ?@wxῌyz{S|}lqHj[E~^_  @UE~^ῌKZfUZSf^W jqGSEXU»¼156


 !" #$% &     '()# *  +, 

-./012 % 34  1*ῌ 5678(9 #$"+"1$ :;<= >  ?

 #@A!B

C DE& C FEGH&#"IJ?K> %  LM H&#1A!B
N O +332 +333 ,*** ,**, ,**- ; Okouchi  ,**, & + ORP P
HQRS " pH TU,V (WX YZE([ !\" QR] ^J?  ; M#$"_`abc/defg # H hijkl

aging ; $H m$%4 1$+" n op q&" '(PHn o$H)
% F X E&+uC_vwx@hijrq?s&\1$+"(*tklyz<$  X"&{| PH}1$L|$+" E ,
QR~(# FPH~(-<$MH<$s&\./>$% !&E-<$QR0(12 >03

*.,*.. ppm   (4<$56 Rb#7E( "8  E& ;9
L56"$% + !<$+"& > i0$":;"; i0& <PH> =>$+"> #$ ! '((PH $H(?y<$MH<$+"@>$% F N& &# iN!'(0(A|#$ b "2& "$+"BSeki  ,**- > #$%F+ ORP " pH TU,V  L GHC#D C n o GH./>$E ῏ /¡k(9W¢-F(G"  YZCE£¤!\H¥# H¦<$%, £§& C C D n o-F ¨I (W¢YZ n o> JE ORP, pH n o:K3 @L(z2 % @LMNn o©i.ªOMN& +H¦ O +332 +333 ":P %  £¤  «¬Pd­®¯EQ°(R± ORP ":K3 TU(²X %- -+³ +  C  D  "  JE ORP " pH TU(´<% ³1µ±£S& F¶ ῍ no ῎ 8>$·0k-8,V#E

ORP " pH TU Guenther, +31/ (´<%ORP¸+.,-¹*.*/3 pH῍O,º.Hºº.e¹ῌ,H,O
ORP¸¹*.*/3 pH
,Hºº,e¹ῌH,῎¶ /. · 0,**/4

ORP ´µFij"UVVª¥157

Fig. + Relationship between ORP and pH of the hot spring water with that of its bath water disinfected for Dougo spa (Honkan) of Ehime Prefecture.
 +    ORP pH ῌ  ῍    !"#$%&' !" ()*+,-./ 0123+ +3324 5"67 ORP 0ORPeq489 ῎ :;+'ORPeq<*.2.=*.*.1 pH῎>?@ ῎ A5(ORP B

CD G #$

G #$

67CDA E 67 ORP DF CDH' >?@ pH1 GK JLMNOPJ QR LST ῎ H67 ORP GIJIJKCC QR' E ELG 123+ 0+3324 UVWVXYZ67 ORP B
G[XC\EL UV]^_`abcD defgGUVWVK

-67 ORP BhijELk+ ῏ H67 ORP L l\XmnD UV5]^_`aop 0AI op ; Aging Index4 L-qB Drs"'
AI<ORPeq=ORP> ῌ k+ ῏ ῏

ORP B XYZ ,/t pu

x + k+y+k>z {|UV}~ WV

vwDH' ῎ H( 67 ORP BG[XCDH"'  5"   L-} *., k+ *.. ppm

K5-XK d  *.*0 ppm L[Zkk?+Yy+k ORP BCGC"DH"'A +  6 +/ UV "{|UV DH' !" x ,  6
1  ῌ ¡¢£L 6 +/ UVῌ ¡¢£K "¤|  ¥k>z 6 1 L +/ ¦§DH 0UV ,**-4' x , k+y+ ¦§ ¨ 2 fg|Z  ©>Vª¥ K«+

>XELK k'!" ¬­¤| ® ¦§Z UVῌ ¡¢£ ¬­¤|  ¥ ¯°R± Z L²³5" 0x ,4' {|UV z>A/ JK158
Table +Chemical composition of Dougo spa (Honkan water) of Ehime Prefecture +  

Cationcomponents

mg/kg

Anioncomponents

mg/kg

Nondissociation
components

mg/kg

NaH

1,4*FI+,4/H, SiO-.*4-

*41

ClI

--42

HBO,.43+4-SO.

,I+04,I-

0-4/

Total

mg/kg

I-+240HK

Mg
Ca,H,H
H.

NH-43*4+

HCO
CO,0142

Fig. , Comparison of chemical compositions of the hot spring water and its bath water disinfected
for Dougo spa (Honkan) of Ehime Prefecture.
,    +    !"#!

$ %&'() *+* ORP ,- .+/ 0123 3456*7) 89: / ;<=->?#/8# =->?#8#@. 123AB >$CD

BE1233*7$FG)Q /.  ",**/#
Table ,ORP lmXk V W8159

Chemical composition of Arima spa (Kinnoyu water) of Hyogo Prefecture ,  Cationcomponents

mg/kg

Anion
components

mg/kg

Nondissociation
components

mg/kg

Li,.42Cl

,,***H, SiO-+.1+****

Br



-24,

HBO,,+2,*2*SO.

Total

mg/kg

NaK
Mg

,+/4-,+3,*

Mn,,.4,,+*,

Cu,*4+2,*4+1CaFeZn,

+34+
-+,14*HCO-02**Fig. - Relationship between ORP and pH of the hot spring water and its bath water disinfected forArima spa (Kinnoyu) in Hyogo Prefecture.
-   ORP  pH   ,   ! "ῌ# $%&'()* +,- . ")/ + 0, 0 12  '!῎34567῎89:;

# <=>? @ A BCDE/FGH IJKLMHN O  ! "ῌ#$%&PQR8LMSTUVR8! "῍# W8XYZ? ORP [\]M^ _`X abcdefghicjXk? XX lmXknoVFA O VR8! "῍#
<C>H pq rsqtuvw *.*3 ppmxvw\ydz { - =>O|

noVAabcd /dR8c} W8Xk? Ld pH \O R~4Xk? ]M )* FAlmO  /dW8NH pq  V~\R8c01¹º160

Fig. . Relationship between ORP and pH of the hot spring waters and their bath waters disinfected
for various spas.
 .  ORP pH  $   ῍   !"#pH ῎ %&'()*+,-.

. / 0123456

7189:;<=>6ORP  pH?@ABCDE -F*G*FH >I+ 712 ORP J ῌ KLDEMNO PQR 01< STLR,UVWCDE"X .+*71%Y)*+:;<L ORP J
>I+2MNZ PQR*.. ppm

W,ABCD :;< [\]^ *., F*_`%ab]^c6>,%, op qrlL *.*0d:e fghYXijklmnEs]^F* ,., ppmt]^ _`Rc% >I+289

 UVW 71F* W :;< 1uCv5,ABCw
x H W:;< d: ELye*%z{ |}~* +333 ,**- ; |}~ ,**- H 

ORP JCZv5 C   CE,01< STLR,UVW  ,1u, .+ 71F :;L 
ChYE,x E6 01 STC 45,xῌ%,-,  AI-/0171 < A B 01  <CO

ORP-pH ?@CD  < O% ,=+6. 

ORP Z UVW ῌ KLDE ORP C)6 W
- 0  - /  ¡>6[\]^ . KLDE ORP ORPeq  ¢L£¤¥¦§¨© AI Aging Index  ?@CDE - 0 F*G*FH O%ªE=+6 AI J«v  E4¬0171 <  v+6 ORP JCZv5 ­WAI®* ¯E, . ° [\]^±²³´L"rL v*

O AI  W µ¶ Jc ·¸ abv+,[\]^%*., F* *.. ppm L G*F01< Wc [\]^ ORP J AI®* C

` /. a W,**/X

ORP YZ[\H23>]^_161

Fig. / ORP and pH changes of the hot spring waters by adding chlorine (sodium hypochlorite).
P Q : Original hot spring water of A and B spas, respectively.
R S : Adding of chlorine (NaOCl) to the A and B spas.
 /   ORP  pH P Q : A T9U B N
R S : A T9U B NV WX I

Fig. 0 Relationship between AI (Aging Index) and residual chlorine concentration in the hotspring waters.
 0  AI     !"#$ %$&'()* +,-./01#$ 23/45#$
9 23:;<=:

6 7 %$8>? <@6ABC DE 9FG

HI /JK 6 7 L 0  , MN* *.- ppm +,-.<OM>?



162

 / 0     !"# $%&'!
 ()*+,-.

+*"#/-.0/1 023!()  4 4*+ 56*7 89: ;< = > ?@ABC7+D-E

%!F  G HIJKLGMIῌN =O+ ,**.>-E 56*7 8 PQ 4DRS 0T!:&UVWB !XYD! Z : N[\ ]^_`a@9b -.cd e. fgh iUS'!

.ῌ ῎ ῍ ῏+>

ORP j-k pHl-. cmnA0opq!S&?@-. "#/*+0/r  1 0AstSu!
?@-.

,>v S ORP Aw !x7SVo pH Jyz 0&V%1uo 023!&'!
?@ {|}~  1 +*0/ 0->!0/"o#| !
;< = > ?@AB$7+D-E%!F  6*7 PQ WBu.>%
ῑῐOc % &   B '() =+332> :  ^*0"#+  .2 ,3ῌ-/.
Oc %4u , -. '() /  =+333> : j-k !
ORP =0"#+>  pHN[  .3 /3ῌ0..

Oc %4u -. '() =,***> : 001

ORP  pHN[  /* 3.ῌ+*+.
Oc 23 4 56 789: m;<  6 =,**,> : 001
-!=ῌ¡ ¢,,#y0£%  /, +,ῌ+3.

Oc 23 4  6 '() 789: =,**-> : +¤"#/ ¥¦£%  /- +ῌ3.
Oc =,**-> : gu%!§*¨g©J2%g©ª%«¬ !¨ oR­
2®> ?¯Oc 4 °@A =,**.> : ORP =0"#+> -! 56*7 8  ±BC²¨³D´µ =+>ῌN¨ ¶E - e;<¶F·¸ ,0ῌ,3.
¹´µº =,**-> : G»¼r

,-!1 0£% ¹´µº

Guenther, W.B. (+31/) : Chemical equilibrium, Plenum, New York, ,*1.
Okouchi, S., Suzuki, M., Sugano, K., Kagamimori, S. and Ikeda, S. (,**,) : Water desirable forthe human body in terms of oxidation-reduction potential (ORP) to pH relationship, J.
Food Sci., 01, +/3.ῌ+/32.
Seki, T., Morimatu, S., Nagahori, H. and Morohashi, M. (,**-) : Free residual chlorine inbathing water reduces the water-holding capacity of the stratum corneum in atopic skin,J. Dermatology, -*, +30ῌ,*,.