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一、引言硝酸銨法測定三氧化鎢,滤液中微量的鎢用甲基紫—丹宁溶液收回,已证明鎢能沉淀完全。有些厂矿对此曾提出意見,主要是有大量铁、錳及硝酸銨存在,鎢是否沉淀完全(因第一次报告中未加铁、錳等杂质),有的将甲基紫—丹产沉淀鎢过滤后的滤液,再以硫酸冒烟法比色,认为尚有万分之几的鎢,因之,部分厂矿分別采用了下列三种方法回收微量的鎢。即 1.将滤液加热蒸发至近干时,用滤紙擦下,并入主要残渣內灼燒比色。 2.将滤液加热蒸发至近干时,用1∶1氫氧化铵中和,并入主要殘渣溶液內比色。 3.于滤液内加入1∶1硫酸8毫升,加热蒸发至冒烟,
First, the introduction of ammonium nitrate method for the determination of tungsten trioxide, the filtrate trace tungsten with methyl violet - tannin solution recovered, it has been proved that tungsten can precipitate completely. Some factories and mines have made comments on this, mainly a large number of iron, manganese and ammonium nitrate exist, tungsten is completely precipitated (because the first report did not add iron, manganese and other impurities), and some methyl violet - Dan precipitate Tungsten filtered filtrate, and then sulfur smoke colorimetric method, that there are still very few of the tungsten, therefore, some mines were used in the following three ways to recover traces of tungsten. Namely 1. When the filtrate is heated to near dry, wipe with filter paper, and incorporated into the main residue burning color. 2. When the filtrate is heated to near dryness, neutralize with 1: 1 ammonium hydroxide and incorporate colorimetric solution into the main residue. 3 in the filtrate by adding 1 ml sulfuric acid 8 ml, heated to smoke,