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When ceric iodate is precipitated from acid solution by the addition of asoluble iodate,a gelatinous precipitate is obtained,which is difficult to filterand wash.The precipitate must be redissolved and reprecipitated as oxalatefor final ignition to ceric oxide.A method has been deviced to improve the form of the ceric iodateprecipitate by slow precipitation in homogeneous solution.Advantage is takenof the fact that cerium exists in two distinct valence states,the cerous and theceric.Cerous iodate is soluble...

When ceric iodate is precipitated from acid solution by the addition of asoluble iodate,a gelatinous precipitate is obtained,which is difficult to filterand wash.The precipitate must be redissolved and reprecipitated as oxalatefor final ignition to ceric oxide.A method has been deviced to improve the form of the ceric iodateprecipitate by slow precipitation in homogeneous solution.Advantage is takenof the fact that cerium exists in two distinct valence states,the cerous and theceric.Cerous iodate is soluble in dilute acid solution,while ceric iodate isinsoluble.Cerium is first reduced to the cerous state by hydrogen peroxide innitric acid solution.Ammonium iodate is added and no precipitation occurs atthis moment.The precipitation is brought about by the slow formation ofceric ion in the iodate solution by ammonium persulfate.Thus a denseprecipitate is formed slowly.This compact volume of the precipitate facilitatesfiltration and washing.The precipitate is ignited directly to ceric oxide,part of which is always stained with a brown color.This is remedied by evapora-tion of the ignited precipitate to dryness with a few drops of concentratedsulfuric acid and ignition to ceric oxide for final weighing.For samples containing 10-50 mg of ceric oxide,a total volume of 300-400 ml gives best results.The optimum concentration of the nitric acid presentis 0.4-0.5 N.A starting temperature of 40-60℃ favors the denseness of theprecipitate.Precipitation is continued at an elevated temperature(70-80℃ )on a hot plate.Stirring not only improves the crystallinity of the precipitateand may decrease the occlusion of impurities,but also shortens the time forcomplete precipitation.Dilute iodic acid solution(1-2%)is used as washsolution.This method is good for samples containing 2.5-250 mg of cericoxide.The composition of the precipitate is not reproducible.The precipitate is abasic iodate and the ratio of IO_3~-found/IO_3~- theoretical for Ce(IO_3)_4 increaseswith the concentration of the nitric acid present(up to 0.5 N)to a maximumvalue of about 0.92.The ratio never reaches unity.An analysis of the pre-cipitate dried at 40-45℃ for 2-3 days shows a fairly constant ratio of IO_3~- found/IO_3 theoretical for Ce(IO_3)_4 From the ratio of Ce:IO_3,an approximate formulaCe_2(IO_3)_7(OH)·XH_2O has been proposed for the precipitate obtained under theconditions described.The number of water molecules in the formula is in-definite,varying from 3 to 5.

1.在均匀溶液中沉淀的碘酸铈,性质紧密,便利于过滤和洗涤。烧灼成为氧化铈后,适合于作为铈的定量分析。2.利用碘酸亚铈能溶解于稀酸溶液而碘酸铈则不溶的区别,先用过氧化氢把全部铈离子还原,再加入碘酸铵,然后进行氧化,使碘酸铈在均匀溶液中沉淀出来。3.本方法适用于含氧化铈2.5—250毫克的样品。4.所得沉淀的分子式经初步测定为 C_(e2)(IO_3)_7(OH)·x H_2O,其中 x 的数值不定,涨落在3与5之间。

Mu-feng-chin has been used as a diuretic and dropsic, etc. in Chinese medicine for many years. Four substances have been isolated by the author from a sample of Mu-fong-chi brought in Shanghai, and the details of the isolation and chemical properties of two of them, viz. Mu-fong-chin A and B, have been reported in previous papers of this series elsewhere. The present paper deals with Mu-fong-chin C, which has the molecular formula C_(18)H_(21)O_(10) and a melting point 180-181℃. Mu-fong-chin C was shown to be...

Mu-feng-chin has been used as a diuretic and dropsic, etc. in Chinese medicine for many years. Four substances have been isolated by the author from a sample of Mu-fong-chi brought in Shanghai, and the details of the isolation and chemical properties of two of them, viz. Mu-fong-chin A and B, have been reported in previous papers of this series elsewhere. The present paper deals with Mu-fong-chin C, which has the molecular formula C_(18)H_(21)O_(10) and a melting point 180-181℃. Mu-fong-chin C was shown to be a phenolic substance, it probably contains phenolic OH, methylenedioxy, aldehyde and methoxy groups.

提去木防巳甲乙二素的母液以醚去油、脂、蠟及色素等後,母液濃縮,以熟戊醇及热水交互處理,分離得一種棕黄色結晶。融點180—181℃,定名為木防巳丙素。分子式為C_(18)H_(21)O_(10)。其分子中可能含有酚性羟基、甲二氧基、醛基及甲氧基等,其初步暫定構造式為

Aureomycin (Ⅰ) on reduction with zinc-acetic acid gives desdimethylaminoaureomycin (Ⅱ) under mild conditions and desdimethylaminodesoxyaureomycin (Ⅲ) under more drastic conditions. Ⅱ can be converted into Ⅲ by further reduction. Treatment of Ⅰ, Ⅱ or Ⅲ with concentrated hydrochloric acid or methanolic HCl produces anhydroaureomycin (Ⅳ), desdimethylaminoanhydroaureomycin (Ⅴ) or desdimethylaminodes- oxyanhydroaureomycin (Ⅵ) respectively. Compound (Ⅴ) can be obtained from Ⅳ by hydrogenolysis, and, similarly, Ⅵ...

Aureomycin (Ⅰ) on reduction with zinc-acetic acid gives desdimethylaminoaureomycin (Ⅱ) under mild conditions and desdimethylaminodesoxyaureomycin (Ⅲ) under more drastic conditions. Ⅱ can be converted into Ⅲ by further reduction. Treatment of Ⅰ, Ⅱ or Ⅲ with concentrated hydrochloric acid or methanolic HCl produces anhydroaureomycin (Ⅳ), desdimethylaminoanhydroaureomycin (Ⅴ) or desdimethylaminodes- oxyanhydroaureomycin (Ⅵ) respectively. Compound (Ⅴ) can be obtained from Ⅳ by hydrogenolysis, and, similarly, Ⅵ from either IV or V. All the above compounds, (Ⅰ), (Ⅱ), (Ⅲ), (Ⅳ), (Ⅴ) and (Ⅵ), when subjected to zinc dust distillation, form naphthacene. A comparison of the ultra-violet absorption spectra of Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ and Ⅵ affords a supplementary evidence for the location of the angular-OH group in the structure of aureomycin.

金黴素(I)在冰醋酸與甲醇溶液中,用鋅粉氫解,在温和條件下,產生脫二甲胺金黴素(II);較劇烈條件下,則生成脫二甲胺脫羥金黴素(III)。III從II經鋅粉醋酸氫解得到。 I,II,III分別與濃鹽酸或甲醇鹽酸處理相應地得到脫水金黴素(IV),脫二甲胺脫水金黴素(V)及脫二甲胺脫羥脫水金黴素(VI)。脫水金黴素(IV)經鋅粉醋酸氫解亦產生V與VI。VI亦可從V製成。 I,II,III,IV,V或VI和鋅粉共同蒸餾,皆得到并四苯。 從紫外吸收光譜測定,對金黴素結構中二甲胺基及角羥基的位置有補充的說明。

 
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