金属离子的硼砂珠测试

用硼砂熔融形成的有色玻璃珠鉴定过渡金属

Qualitative Analysis Intermediate (High School) 45 分钟 ~$8.00

目标

通过过渡金属离子融入硼砂（四硼酸钠）玻璃珠时产生的特征颜色来鉴定过渡金属离子。

背景

The borax bead test is an elegant method for identifying transition metal ions. When borax (Na₂B₄O₇·10H₂O) is heated, it loses water and forms a clear glassy bead of sodium metaborate. When a metal salt is dissolved into this bead, the metal ions become trapped in the glass matrix, producing characteristic colors. The color often differs between the oxidizing flame (outer cone) and reducing flame (inner cone), providing additional diagnostic information.

安全警告

  • Molten borax beads are extremely hot
  • Chromium compounds are irritants — avoid dust inhalation
  • Do not touch hot beads — let cool on a watch glass
  • Cobalt compounds are toxic if ingested

所需PPE

goggles gloves lab_coat

材料

  • Borax (Na₂B₄O₇·10H₂O) (5 g)
    Powdered
  • Metal salt samples (0.5 g each)
    CuSO₄, CoCl₂, NiCl₂, FeCl₃, MnCl₂, Cr₂O₃
  • Unknown metal salt (0.5 g)

设备

Platinum wire loop (or nichrome alternative) Bunsen burner Forceps Watch glasses (7)

步骤

1

Make a small loop at the end of the platinum wire. Heat the loop in the hottest part of the flame until red-hot.

2 分钟 Wire is very hot
2

Dip the hot wire into powdered borax. Return to the flame and heat until a clear, transparent glass bead forms. Repeat dipping and heating if needed to build up the bead.

5 分钟
3

Touch the hot bead to a tiny amount of CuSO₄ powder. Return to the oxidizing flame (outer cone). Observe the color (should be blue-green).

5 分钟
4

Now heat the same bead in the reducing flame (inner cone, blue). The color may change to red (metallic copper).

3 分钟
5

Make fresh beads and repeat for each metal salt. Record colors in both oxidizing and reducing flames, both hot and cold.

20 分钟
6

Test the unknown salt and match the bead colors to your reference chart.

10 分钟

预期结果

Cu: blue-green (oxidizing), red (reducing). Co: deep blue (both). Ni: gray-brown (oxidizing), gray (reducing). Fe: yellow-brown (oxidizing), green (reducing). Mn: violet (oxidizing), colorless (reducing). Cr: green (both, darker in reducing).

清理

Allow all beads to cool completely. Dispose of transition metal waste appropriately. Clean the platinum wire by fusing with fresh borax until clear.

详情

类别
Qualitative Analysis
难度
Intermediate (High School)
时长
45 分钟
预估费用
$8.00
步骤数
6
材料
3

更多实验

pH指示剂彩虹 45 min 卤素的贝尔斯坦测试 25 min 未知物质鉴定挑战 75 min 植物色素的色谱分析 60 min 沉淀法阳离子鉴定 90 min 火焰发射光谱分析 60 min 碳水化合物的淀粉-碘测试 30 min 肥皂液硬水测试 40 min 阴离子鉴定测试 60 min

Frequently Asked Questions

What is the objective of 金属离子的硼砂珠测试?
通过过渡金属离子融入硼砂（四硼酸钠）玻璃珠时产生的特征颜色来鉴定过渡金属离子。
How difficult is 金属离子的硼砂珠测试?
This experiment is rated as Intermediate (High School). It takes approximately 45 minutes to complete.
What safety precautions are needed for 金属离子的硼砂珠测试?
Key safety precautions include: Molten borax beads are extremely hot; Chromium compounds are irritants — avoid dust inhalation; Do not touch hot beads — let cool on a watch glass.
What materials are needed for 金属离子的硼砂珠测试?
The main materials required are: Borax (Na₂B₄O₇·10H₂O), Metal salt samples, Unknown metal salt.
What results should I expect from 金属离子的硼砂珠测试?
Cu: blue-green (oxidizing), red (reducing). Co: deep blue (both). Ni: gray-brown (oxidizing), gray (reducing). Fe: yellow-brown (oxidizing), green (reducing). Mn: violet (oxidizing), colorless (reducing). Cr: green (both, darker in reducing).