In the manufacture of coloured glass, adding which metallic oxide to the glass mixture produces a deep blue colour?

Introduction / Context:
Coloured glass is widely used in bottles, decorative objects, stained glass windows and laboratory equipment. The colour arises when specific metal oxides are added to the glass forming mixture, which change how the glass absorbs and transmits light. Knowing which oxide produces which colour is a common general knowledge and chemistry question that connects inorganic chemistry to everyday materials. Here you are asked which oxide, when added to glass, gives it a characteristic deep blue colour.

Given Data / Assumptions:

• The options include manganese oxide, cobalt oxide, chromium oxide, iron oxide and copper oxide.
• Each oxide can impart characteristic colours to glass or other materials.
• The question is specifically about a deep blue colour in glass, not about purple, green or brown shades.
• We assume typical soda lime glass formulations used in commercial practice.

Concept / Approach:
Different metal ions in glass absorb specific wavelengths of visible light based on their electronic transitions. Cobalt compounds, particularly the Co2 plus ion, strongly absorb in the yellow part of the spectrum, so the transmitted light appears deep blue. This is why cobalt oxide is used as a colouring agent to produce rich blue glasses. Chromium compounds more often produce green colours, iron oxides give brownish or greenish tints and manganese oxides can be used to decolourise or give purple shades, not vivid blue. Therefore, the approach is to recall the colour associations and select cobalt oxide for blue glass.

Step-by-Step Solution:
Step 1: Consider cobalt oxide, which contains cobalt ions known for producing intense blue colours in glass and ceramics. Step 2: Recognise that cobalt blue pigments and cobalt glass are famous for their deep blue appearance. Step 3: Chromium oxide typically imparts a green colour to glass, as seen in many green bottles and art glass items. Step 4: Iron oxide in glass can give brown, amber or greenish tints, depending on its oxidation state and concentration. Step 5: Manganese oxide has been used both to remove the green tint from glass and to produce purple colours at higher concentrations. Step 6: Copper oxides may produce blue green colours, but the classic deep cobalt blue in glass is specifically associated with cobalt oxide. Step 7: Therefore, among the options given, cobalt oxide is the correct choice for producing deep blue glass.

Verification / Alternative check:
Historical and industrial references to glassmaking repeatedly refer to cobalt compounds as the source of blue glass. Well known products such as cobalt blue bottles and laboratory glassware use cobalt oxide or cobalt carbonate as colouring agents. Glassmakers can control shade and intensity by adjusting the amount of cobalt oxide added to the batch. In contrast, chromium oxide is used when a green colour is desired and iron impurities are partly responsible for the natural green tint of many unrefined glasses. These consistent uses across industries confirm cobalt oxide as the blue producing agent.

Why Other Options Are Wrong:
Option A, manganese oxide, does not primarily give deep blue glass; it is more associated with purple or decolourising effects. Option C, chromium oxide, leads to green glass, not blue. Option D, iron oxide, gives brown, amber or green tints and is often an impurity rather than a deliberate blue colourant. Option E, copper oxide, can contribute to blue green colours but does not produce the characteristic intense cobalt blue that the question refers to. Only option B, cobalt oxide, correctly matches the deep blue colour of coloured glass.

Common Pitfalls:
Students sometimes confuse cobalt and copper when thinking of blue colours because both can form blue coloured compounds. However, copper in glass generally gives more greenish tones, while cobalt gives a pure, intense blue. Another pitfall is to think of chromium oxide as blue because chromium compounds can show multiple colours in other contexts. To avoid these errors, remember the strong association cobalt equals blue glass, chromium equals green glass and manganese equals purple or decolourising glass. This mental picture helps in quickly answering colour related inorganic chemistry questions.

Final Answer:
Adding Cobalt oxide (CoO or Co2O3) to the glass mixture produces a characteristic deep blue coloured glass.