PROBLEM TO BE SOLVED: To provide means for stably reducing nitrous acid in a vessel containing brine in a short time without making brine cloudy, because solutes are deposited making the brine cloudy and pH and nitrous acid concentration remain unstable for a long time when an aqueous solution saturated with magnesium hydroxide or calcium hydroxide is added to the brine.SOLUTION: Warm salt water having a salt concentration near the concentration of brine in a vessel dissolves calcium hydroxide and is cooled to ordinary temperature to obtain a saturated aqueous solution. The obtained saturated aqueous solution is poured into the vessel to prevent solutes from being deposited and the brine in the vessel from getting cloudy, and thus stable pH and nitrous acid ion concentration are obtained.COPYRIGHT: (C)2015,JPO&INPIT【課題】塩水に水酸化マグネシウムや水酸化カルシウム飽和水溶液を入れると溶質が析出して塩水が白濁し、長時間pHが安定せず、亜硝酸濃度も不安定となる。そこで、塩水を入れた容器内の亜硝酸を、水を濁らすことなく短時間で安定して減少させる手段が求められている。【解決手段】容器内塩水濃度付近の濃度の温塩水に水酸化カルシウムを溶解させ、常温まで冷却して得られた飽和水溶液を容器内に注ぐことで溶質の析出を防止することができ、容器内の塩水の白濁を防止することができるとともに、安定したpH及び亜硝酸イオン濃度が得られる。【選択図】図1
