Prueba de Perla de Bórax para Iones Metálicos

Identificación de metales de transición por las perlas de vidrio coloreadas formadas en una fusión de bórax

Qualitative Analysis Intermediate (High School) 45 min ~$8,00

Objetivo

Identificar iones de metales de transición por los colores característicos que producen cuando se fusionan en una perla de vidrio de bórax (tetraborato de sodio).

Antecedentes

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.

Advertencias de seguridad

  • 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

EPP requerido

goggles gloves lab_coat

Materiales

  • 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)

Equipamiento

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

Procedimiento

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 min 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 min
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 min
4

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

3 min
5

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

20 min
6

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

10 min

Resultados esperados

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).

Limpieza

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

Detalles

Categoría
Qualitative Analysis
Dificultad
Intermediate (High School)
Duración
45 min
Costo estimado
$8,00
Pasos
6
Materiales
3

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Frequently Asked Questions

What is the objective of Prueba de Perla de Bórax para Iones Metálicos?
Identificar iones de metales de transición por los colores característicos que producen cuando se fusionan en una perla de vidrio de bórax (tetraborato de sodio).
How difficult is Prueba de Perla de Bórax para Iones Metálicos?
This experiment is rated as Intermediate (High School). It takes approximately 45 minutes to complete.
What safety precautions are needed for Prueba de Perla de Bórax para Iones Metálicos?
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 Prueba de Perla de Bórax para Iones Metálicos?
The main materials required are: Borax (Na₂B₄O₇·10H₂O), Metal salt samples, Unknown metal salt.
What results should I expect from Prueba de Perla de Bórax para Iones Metálicos?
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).