Procedure for DO analysis by Winkler method (manual analysis)

The following is a description of the DO titration method using the Winkler method (manual analysis).

溶存酸素測定の手順Dissolved oxygen measurement procedure　Ⅰ液、Ⅱ液を入れたのち、蓋をしてオーバーフローさせるAfter adding Liquid Ⅰ and Liquid Ⅱ, cover and overflow　上下転倒して良く撹拌Stir well by inverting up and down　静置してよく沈殿させるAllow to stand and settle well　蓋をゆっくり外しRemove the lid slowly.　スポイトで上澄み液を10mlほど吸い上げコニカルビーカーに移すSiphon off about 10 ml of the supernatant liquid with a dropper and transfer to a conical beaker.　上澄み液supernatant fluid　沈殿物sediment　机面でくるくる回転、沈殿を溶解させるSpinning on the desk surface, dissolving sedimentation　コニカルビーカーにすべて移すTransfer all to a conical beaker.　洗瓶の純水でDO瓶を洗い、洗液もコニカルビーカーに移すWash DO bottles with pure water in wash bottle and transfer wash solution also to conical beaker　ビュレットの液面の目盛を記録するRecord the liquid level scale of the burette.　ビューレットからチオ硫酸ナトリウムをコニカルビーカーに滴下Drops of sodium thiosulfate from burette into conical beaker　コニカルビーカーは机面上でクルクル回転Conical beakers spin around on the desk surface　薄黄色になったら、スポイトでデンプン溶液を1ml加えるWhen light yellow, add 1ml of starch solution with a dropper　色が無くなったところを、滴定の終点とする。The endpoint of the titration is the point where the color disappears.　色の有無の判別が難しければ、最後の一滴を滴下する前の目盛を読んでおく。一滴たらしてみて、判断すればよいIf it is difficult to determine the presence or absence of color, read the scale before dropping the last drop. Just try one drop and judge.