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567 89:; <=>? @ABC +3  ++  ,,   ,*  +  2 ORP-pH Relationship of Bath Additives Composedof Calcium PolysulﬁdeHideyuki OHNAMI, Kuniyasu ASAI, Shigeo IKEDA and Shoichi OKOUCHI
Department of Materials Chemistry, Faculty of Engineering, Hosei University

Abstract
In ,**., the mass media reported that some inns at Shirahone spa, highly popular for
its milky white spring waters, were using a certain amount of additive in bathwaters
without disclosure in order to compensate for the insu$cient milky turbidity of source
spring waters. This a#air became one of the big issue of public concern as a “fake” spa.
Regarding the additive (0+* HAP/Kusatsu onsen HAP) composed mainly of calcium
polysulﬁde (CaS/), which was used for artiﬁcial whitening of Shirahone apa, we have conducted ORP-pH measurements on its actual bathwaters by adding the calcium polysulﬁde additive thereto as was the case with the above-mentioned a#air. The results ofour experiments show that the calcium polysulﬁde additive can improve chlorinated tap
water that is oxidative in a bath - through the process of producing milky turbidity(colloidal suspension of sulfur particles) - to develop a reductive characteristic that is oneof the favorable features of natural hot spring waters. Besides, the minimum requirement
for a total sulfur concentration of + ppm, which is deﬁned by the Japanese law concerning
natural hot springs, can be fully satisﬁed by using the calcium polysulﬁde additive in thequantities recommended in its prescription. Thus, the calcium polysulﬁde additive hassuch excellent properties that are not found in the other commercial additives examinedby us. Through the preset study, it can be presumed that the scandalously reported inclusion of the calcium polysulﬁde additive in bathwaters at Shirahone spa must have resulted in enhancement with respect to milky turbidity and sulfuric water quality, though
to a slight extent, at that time also.
Key wards : Calcium polysulﬁde, ORP-pH, Reductive Characteristic, Shirahone spa

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 ,**. "#$%r&s0_t&"u)*  !"#$"%& :C9 J678!Gvw07 <_'u"F '
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  +,-./-./ 012  'I=&;<P9 ^ 0& *I0C(0:<0= '012 @=&, C :Q) * 2& :;<ῌ Q+=0u3* 2 _  +,-./ -./  2 %& << .*

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/)  %& D<678¬j­ED<012 C ®*  ¯FI +332
+333 0°%&- -+  ORP-pH ±²³´GQR <0=µ¶H C?aIC CaS/  +,-./C'gh* ῌ ·0¸ 7r0=<* J_vw JKLMN<I´ " CaS/,H,OCaOH,H,S.Sῌ-.

228
Fig. + 567(89:;<:=>&?5@AB 8CD:=> 5 E῍BFGH

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N+ r>de 5V>8= ῌ+!"#5]C= NV>N Q/ ¡¢X+῍£¤¥¦§¨]©ªr>o ῍£8«¬­C>®_]ῑ8¯9 ORP-pH ST®_῎°±²¦
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 : Tap water,  : After addition of 0+* HAP,  : After addition of Kusatsu onsen HAP,
: 0+* HAP,  : Kusatsu onsen HAP,  : Carbonic acid additive,: Mineral salt additive,  : Herbal essence additive,: Sinter (mineral deposit) additive +  ORP-pH  :   : ῑ  : : ῑ: $%&ῐ !"  :   :  !"#: +,
#  : '()* !"#6 /1 7 3,**24

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 : Wellhead water at Shirahone,  : Open-air bath,  : Men’s indoorbath,  : Ladies’ indoor bath,  : After addition of 0+* HAP ,    !"#! ORP-pH $%!&  :  :  :   :  : 230   %&'()   *!"#$+ *$, - ./%01!

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j k]^_ f  lmno pqr^ st +332 : fuvwxyz
{"|  .2 ,3ῌ-/.
]^_ }A~) 

! st "  +333 : f0 #$ ORP {"|  pH +  .3 /3ῌ0..
]^_ }A~)

! st ,*** : %{"&X ORP  pH +  /* 3.ῌ+*+.
]^_ '( ) * st +,-. ,**- : 
 #@  /- +ῌ3.
]^_ ) / 01 +,-. ,**/a : ORP 2 2Xf 3"  /. +//ῌ+0,.
]^_ ) 45  +,-. * 6q78

! 9 ,**/b :f#$0 : ;7  // //ῌ0-.
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.
Ohnami, H., Koumura, K., Ikeda, S. and Okouchi, S. (,**-) : ORP (Oxidation-Reduction Potential) pH Relationship between Hot Spring Waters and Human Body Fluids, Proceedingsof The -2th Conference of Societe Internationale des Techniques Hydrothermales (Beppu,Ohita, Japan), -,*ῌ-,/.

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