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寒劍飄雪木蟲(chóng) (著名寫(xiě)手)
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[求助]
雜多酸制備中pH調(diào)節(jié)問(wèn)題 已有5人參與
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各位蟲(chóng)友,我想合成一個(gè)單取代的磷鎢酸鹽,文獻(xiàn)上說(shuō)是將磷鎢酸和相應(yīng)的硝酸鹽溶液水后,緩緩滴加碳酸氫鈉溶液,在不斷攪拌下使其pH值調(diào)為5后停止滴加,繼續(xù)攪拌5h。我照文獻(xiàn)做的時(shí)候把pH值調(diào)到5以后,然后攪拌一會(huì)兒后ph值又降下來(lái)了,我應(yīng)不應(yīng)該把pH值又調(diào)回5?還是讓它一直降了?我在問(wèn)一下,這個(gè)緩緩滴加,到底是緩到什么程度?是我邊攪拌邊滴加上一會(huì)兒后,然后不滴加讓攪拌一會(huì)兒再加呢,還是我一直攪拌滴加至5呢? 忘各位做過(guò)此類(lèi)雜多酸的大師指導(dǎo)指導(dǎo),謝謝了 |
木蟲(chóng) (著名寫(xiě)手)
金蟲(chóng) (正式寫(xiě)手)
木蟲(chóng) (著名寫(xiě)手)
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謝謝你,那我調(diào)到5以后,攪拌了大概有一小時(shí),我測(cè)ph值得時(shí)候,大概又降到4了,我調(diào)到5,這樣對(duì)嗎? 還有一個(gè)特別棘手的事,我合成出的單缺位的硅鎢酸鹽極易溶于水,怎么重結(jié)晶了,能給我具體指導(dǎo)一下嗎?文獻(xiàn)表述如下: First PW12 (2.88 g) was dissolved in water (10 mL) and the pH of the solution was adjusted to 4.8 using NaHCO3 solution. This resulted in the formation of lacunary heteropoly anion [PW11O39]7. The solution having pH 4.8 was heated to 90 C with constant stirring. Then to it a solution of Co(NO3)26H2O (0.29 g) in water (10 mL) was added. The NaCoPW11 was obtained by solvent evaporation, and recrystallization from water, followed by subsequent drying at 110 C for 12 h |
至尊木蟲(chóng) (知名作家)
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