铂金——定义、发生、属性、应用
铂及其合金在化学实验室中是必不可少的,用于电极、坩埚和可以将材料加热到高温的盘子。铂是最普遍的铂金属之一。因为铂可以抵抗高温和电弧的化学侵蚀,所以它被用于电触点和火花点。它的大部分应用是在珠宝和牙科合金中;铂铱用于手术针。
直到 50 年后,人们才知道在南美洲发现了铂,许多法国、德国、瑞典和英国科学家对其特性进行了早期分析,他们正在研究的原生铂还含有其他元素。
什么是铂金?
铂存在于一些镍和铜矿石以及一些原生矿床中,主要在占全球产量 80% 的南非。由于其在地壳中的稀缺性,每年仅生产数百吨,鉴于其重要的应用,它是一种极具价值的重要贵金属商品。
Platinum has the chemical symbol Pt and the atomic number 78. It is a silverish-white transition metal that is dense, malleable, ductile, and highly unreactive.
铂属于元素周期表的铂族和第 10 族。它有六种天然存在的同位素。它是在地壳中发现的较为稀有的元素之一。
铂金的出现
铂是一种极其稀有的金属,存在于地壳中,浓度仅为 0.005 ppm。有时会与银混淆。经常发现铂在化学上未结合为天然铂和与其他铂族金属(主要是铁)的合金。原生铂通常存在于冲积矿床的次生矿床中。哥伦比亚是铂族金属的重要来源。另一个大型冲积矿床位于俄罗斯的乌拉尔山脉,目前仍在开采。
铂族金属以硫化物、碲化物和镍或铜端合金形式存在于镍和铜矿床中。在加拿大,砷化铂是与镍矿石相关的铂的主要来源。
铂在月球和陨石中的含量更高。铂可以经济地开采,在地球上的火流星撞击地点发现的丰度略高,这与撞击后的火山活动有关。
铂金的特性
- 铂金是一种柔软而有光泽的银色金属。
- 它具有高密度、延展性和延展性。
- 它还耐腐蚀,沸点高。
- 铂是自然界中发现的化学性质最稳定的元素之一。由于其高稳定性,它经常被称为贵金属。
- 它对硝酸和盐酸有抵抗力,但它可以在高温下被王水溶解。
- 铂是一种贵金属,这意味着它具有化学稳定性。
- 它不会在空气中失去光泽,因为它不会与存在的氧气发生反应。
- 它也不受酸侵蚀。
- 卤素、氰化物、硫和碱会腐蚀它。
- 铂在高温下会吸收大量氢气,就像海绵吸收水一样,这是铂不寻常的特性。
- 铂具有很强的形成络合离子的倾向。 Pt(I) 是最常见的平面结构,具有抗磁性。
What are some Environmental Effects of Platinum?
Platinum is emitted into the atmosphere by the exhausts of vehicles that run on leaded gasoline. As a result, platinum levels in the air may be higher in certain locations, such as garages, tunnels, and trucking company terrains.
Platinum accumulates in the roots of plants after absorption, but it is unclear whether it can harm animals or humans.
In soils, microorganisms may be able to convert platinum substances to more dangerous substances, but we also know very little about this.
铂金的用途和应用
- 它的耐磨和抗变色特性使其成为制作精美珠宝的理想之选。
- 铂及其合金用于手术器械、实验室设备、电阻丝和电触点。
- 它在催化转化器中用作催化剂(30%),催化转化器是汽油动力汽车排气系统的可选组件。
- 化学、电气、玻璃和飞机工业每年使用约 10 吨铂,占其使用量的大部分(50%)。
- 铂在玻璃工业中用于光纤和液晶显示器玻璃,特别是笔记本电脑。
- 它还存在于实验室设备、电触点和电极、铂电阻温度计、牙科设备和珠宝中。
- 由于它是一种重金属,因此接触其盐类会导致健康问题;然而,由于其耐腐蚀性,金属铂与对健康的不利影响无关。
铂的化合物
- 卤化物:六氯铂酸是最重要的铂化合物,因为它是许多其他铂化合物的前体。它用于摄影、锌蚀刻、不褪色墨水、电镀、镜子、瓷器着色和作为催化剂。
- 氧化物: PtO 2或氧化铂(IV)是一种黑色粉末,可溶于氢氧化钾溶液和浓酸中。
示例问题
问题一:铂金是如何提取的?
回答:
After crushing the ore, the Froth-Flotation process is completed. During Flotation, air is passed through an ore-water mixture known as Slurry. The platinum particle is chemically attached to the oxygen that rises to the surface in a froth and is then skimmed off for further refining. It is then dried and heated to 1500° C in an electric furnace before being blown through with air to remove iron and sulphur impurities. After that, aqua regia is used to dissolve platinum metal from the mineral concentrate by producing chlorine, which binds to platinum to form chloroplatinic acid.
Finally, ammonium chloride is used to convert chloroplatinic acid to ammonium hexachloroplatinate, which is then burned to produce pure platinum metal.
问题2:什么是白金大块头?
回答:
Platinum and platinum alloys are used to create platinum hunk, which serves as an international standard for weighing a kilogram.
问题 3:我们可以在王水中溶解铂吗?
回答:
Platinum is not attacked by acids due to its chemical inertness. However, platinum is easily soluble in Aqua Regia, a 1:3 mixture of concentrated nitric and hydrochloric acid. As both acids are concentrated, the mixture is extremely volatile. The main cause of noble metal dissolution is its volatile nature. Noble metals such as gold, palladium, and platinum are soluble in Aqua Regia but not in either acid alone. Aqua regia dissolves metals by oxidising them first.
问题 4:已知最不活泼的金属是什么?
回答:
Platinum is the most unreactive metal.
问题 5:定义王水。
回答:
Aqua regia is a 3:1 mixture of concentrated hydrochloric acid and nitric acid. It is extremely corrosive and can dissolve precious metals such as gold and platinum.